Memoirs Of A Mouse Trapper
A Twenty-five Year Field Study Of Small Mammal Populations
Lowell L. Getz
Those Who Have And Those Who Don’t
There are those who have sophisticated analytical minds, who can
conceptualize large sets of information and develop complex predictive
mathematical models. Then, there are those whose minds cannot get
around the mathematical aspects of conceptualizing. Early on in my
academic career it became patently obvious where my abilities lie. I
have neither the ability for mathematics nor a brain that is wired for
conceptualizing. But, I discovered that I did have the perseverance and
stamina to carry out demanding field research programs. Being in the
field, studying plants and animals in their natural setting was what got
me interested in biology in the first place. I also saw that few of those
interested in theoretical modeling had the interest or wherewithal to
carry out the long-term field programs necessary to provided sufficient
data on which to base their modeling efforts.
In the late 1950s there began a flurry of research activity into the
causation of presumed “cyclic” fluctuations of many species of small
mammals, especially microtine rodents. In part, this was stimulated by
the intrigue of such potential phenomena and the recent application of
mathematical tools in the study of biological systems. By applying
sophisticated mathematics to analyses of demographic data, field
biologists also gained prestige in the eyes of their physical science
colleagues. They were now “real scientists”, not merely descriptive
natural history biologists, or as some were wont to say, “running around
chasing butterflies.” Granting agencies also became enamored by the
application of mathematical modeling to biological systems. As a result,
grants for demographic studies were easy to come by. In order to take
advantage of the funding availability, a high percentage of field
mammalogists were lured into demographic studies of small mammals,
with the objective of finding the “silver bullet” controlling presumed
cyclic phenomena.
Acknowledging my shortcomings, however, my first mammalian
research programs involved primarily field and laboratory studies of
physiological adaptations involved in habitat utilization of small
mammals. I conducted only short-term field studies to provide habitat
distribution information from free-living populations. The analyses of
these data were straight forward, with no need to conceptualize. Three
of the studies required that I follow population fluctuations of small
mammals, including voles, for up to four years. This work tempted me
to consider changing my research to the study of population
fluctuations, as it was one of the most active areas of small mammal
research. As my last study was winding down, I had to make a decision
as to which way to go—pure physiological studies of adaptations of
small mammals or focus on field studies. The latter tempted me, but I
still realized my shortcomings regarding an inability to utilize
“sophisticated” statistical and modeling programs such as are required
to analyze adequately data in testing the prevailing hypotheses driving
periodic (“cyclic”) population fluctuations.
Giving In To Temptation
In 1967, while at the University of Connecticut, I was eligible for a
sabbatical leave. I decided to let NSF decide my fate. I put in a grant
request to begin studying population fluctuations of the meadow vole,
with the idea it would be for the long term. Not being confident I would
be funded, I made arrangements to become proficient in the current
physiological techniques for studying water balance and energy
requirements of small mammals, should the grant request be denied.
Both Knut Schmidt-Nielson at Duke University and Bill Dawson at the
University of Michigan offered to let me work in their labs for the year
to obtain the necessary techniques. Support for my stays at those
universities was also available so that I could spend the entire year in
their labs. But, NSF funded my request in full, so it was going to be longterm studies of periodic population fluctuations of voles. As I had
proposed in my grant request, I spent my sabbatic at the University of
Wisconsin, the region where I best could expect to find a population of
meadow voles in sufficient numbers to work out field techniques I
would need in the long-term study. (This, by the way, shows how easy it
was to get funding for demographic studies in those days. The theme of
my request was to initiate a “long-term study of population cycles”, yet I
was going to spend the first year of the three-year grant period in
Wisconsin, putting off initiating the long-term study for another year.) I
found such a population near Madison and worked out a potential field
protocol. The field data also provided an insight into social behavior of
the meadow vole. Because I previously had done a few studies of intraand inter-specific social behavior of voles, I decided to add an
investigation of social behavior to my research program.
When I returned to Connecticut in September 1968 I began
identifying potential study sites for a long-term study. Before I had
determined the sites to use in the study, I received an offer from the
University of Illinois and moved there in September 1969, as a full
professor. A number of experimental rooms were promised me for my
research and modest start-up funds for equipment were provided.
Given the facilities available, I decided that it would be more realistic for
me to follow up on my social behavioral interests and work on social
interactions of the prairie vole. However, when I arrived on campus,
there was a problem in gaining access the rooms. The Department Head
had promised me rooms that did not belong to the department. I spent
a year and a half trying to get permission to use the rooms. The rooms
were not being used, but the faculty member to whom they were
assigned, would not release them to me. Finally, I decided enough was
enough and returned to my earlier plan, that of conducting a long-term
study of periodic fluctuations of small mammals.
Thus, after ten years into my career I finally fell under the
influence of the “in studies”, testing for the reality and causation of
“cyclic” population fluctuations of small mammals. Going into this field
I, of course, realized I could not hope to apply sophisticated analyses to
my data. It had been obvious for some time, however, that there was no
long-term detailed data set available sufficient to test the various
hypotheses proposed to explain “cyclic” population fluctuations of small
mammals. Only short-term studies, of 3-5 years, of demographic data
were available, essentially involving only one fluctuation. These data
sets were not adequate to test what drove 3-4 year population “cycles”,
let alone determining if such cycles were realities. Knowing I had the
ability to conduct field research, I felt this perhaps was where I could
make my contribution, a long-term collection of detailed demographic
data of sufficient duration and intensity to test for cyclic phenomena.
Others could use these data in testing their pet hypotheses. Perhaps I
could at least publish descriptive results from the study.
The Beginning
The University recently had purchased the Philips Farm, adjacent
to its Trelease Prairie research area, 15 minutes from campus. The farm
had adequate sites for my study: three bluegrass sites (2 ha, 0.8 ha and
0.5 ha), two adjacent alfalfa fields, 1 ha, each (most times only one site
was planted to alfalfa, the other planted when alfalfa plants in the
original site were becoming replaced by grasses and other forbs) and a
restored 1.5 ha tall grass prairie site (suitable for two 0.5 ha sites at
opposite ends, with 0.5 ha buffer in between). A 2.5 ha portion of the
Trelease tall grass prairie, adjacent to the farm was also available to me.
Three species of small mammals (prairie vole, Microtus ochrogaster;
meadow vole, M. pennsylvanicus; Short-tailed shrew, Blarina
brevicauda) were common in all three habitat types.
I was 40 years old, so a 25-year study seemed doable. The
nearness of the available study sites meant that, with rearrangement of
my teaching and administrative schedules, I could do the trapping with
minimal conflict. That there were three different habitats (bluegrass,
alfalfa and tall grass prairie) within the available study sites and three
species of small mammals, each with different food and cover
requirements, presented an ideal situation to study population
fluctuations of small mammals. There were multiple sites of bluegrass
and tall grass prairie, which allowed for manipulative studies of effects
interspecific interactions between the two vole species (removal of one
species from each of two sites) and effects of supplemental feeding in
marginal food availability habitats, with controls for both studies.
During the summer and autumn of 1971, I established trapping
grids, with a 10 m interval between stations in the three bluegrass sites
225, 81 and 60 stations, each), in one of the alfalfa sites (100 stations),
in Trelease prairie (250 stations) and two 0.5 ha areas in opposite ends
of the Philips tall grass site (49 stations, each). A 6-foot iron stake, with
an attached station number tag, was placed at each station. We first
started trapping the large bluegrass area in October 1971 so as to work
out our trapping protocol; data collection began January 1972. In March
1972 we began trapping the Trelease tall grass prairie site and the
alfalfa site in June 1972, continuing through May 1997. We trapped the
0.5 ha supplemental-fed bluegrass site from June 1977-December 1983
and the 0.8 ha site, serving as a control for the supplemental feeding and
interspecific studies, from March 1977-June 1987. In March 1979 we
stopped trapping the Trelease site and initiated trapping in the two
Phillips Farm tall grass prairie sites in September, continuing through
May 1997. Part of the Trelease site was trapped again from June 1981November 1986.
So as to cover all sites as concurrently as possible, it was
necessary to trap the three habitat types in as short a period of time as
feasible. Other studies had shown that three days of trapping, with
traps checked morning and afternoon, were adequate to capture most of
the trappable animals in a study site. A two-day prebaiting period also
was necessary for maximum capture efficiency. After considering the
options, and taking into account what would best facilitate scheduling, it
was seen that all areas could be covered in three weeks time. We started
each monthly trapping regime as close to the first of the month as
possible so that the intervals between trapping of each habitat type
would be approximately one month throughout the study. The
sequence of coverage of habitat types each month throughout the study
was: bluegrass, alfalfa and tall grass. The following schedule was
followed through the first 20 years of the study. Prebait, Sunday 1500;
set traps, Tuesday 1500; check traps, Wednesday-Friday 0800 and
1500. This schedule allowed those involved in the field work to have
Monday and mid day to attend or teach classes, as well as one week
each month to attend to more lengthy obligations.
Over the years we observed that rarely did we catch new animals
on the Friday 1500 check. Thus, to provide more time for me to attend
to administrative and other tasks, beginning the 21st year, we dropped
the afternoon check on the third day. And, to free up more of the
weekends for family activities, we rearranged the schedule to: prebait,
bluegrass Monday 1500; set bluegrass, Wednesday 1500; check
bluegrass, Thursday-Friday 0800 and 1500 and Saturday 0800; prebait,
alfalfa, Thursday 1500; set alfalfa, Saturday 1500; check alfalfa, SundayMonday 0800 and 1500 and Tuesday 0800; prebait tall grass, Sunday
1500; set tall grass, Tuesday 1500; check tall grass, WednesdayThursday 0800 and 1500 and Friday 0800.
Manipulative studies involved supplemental feeding the 0.5
bluegrass site from June 1977-December 1983 and a 0.5 ha tall grass
site from September 1977-May 1987. A feeding station consisting of a
0.5 liter glass bottle was placed at each trapping station. Purina rabbit
chow was placed in the bottles and, refilled, twice a week to ensure
there was food in the bottles and in good condition at all times. For the
effects of interspecific interactions, we removed all prairie voles from
half of the 2.0 ha bluegrass site June 1977-June 1987; meadow voles
were removed from the other half of this bluegrass site, June 1977-May
1997. Finally, meadow voles were removed from one of the 0.5 ha tall
grass sites September 1987-May 1997. The individuals to be removed
were placed in a plastic bag at each trap check and released 1 kilometer
from the study sites, across an Interstate highway.
Field Protocol
We used 2.5 x 2.5 x 8.0 inch, inside dimensions, live traps made of
½ inch redwood, with and a metal sliding door at the back. The animals
entered the trap by lifting a 1.0-inch wide metal one-way, gravity
dependent, sloping door in a 2.0-inch long chute at the front of the trap.
The rest of the front was covered by ¼ hardware cloth. A small flange
prevented the voles from lifting the door. Some of the shrews used their
pointed noses to lift the door and escape. This was an advantage owing
to high mortality of shrews (27%), minimizing adverse trapping effects
on population dynamics while giving us a relatively accurate estimate of
population densities.
When an animal was in the trap, another could interact with the
“occupant” through the hardware cloth. If seemed OK to enter, the new
animal would lift the door and enter. This could keep on going so long
as new animals were there to enter. Routinely, when population
densities were high, it was not unusual to catch 4-5 animals in a trap.
The record was 21 prairie voles! Seldom was there mortality in
multiple captures of voles. When more than one shrew was in the trap,
most times only one was alive.
For the first 15 years we simply pulled grasses and other plants to
cover the traps in summer in order to protect the animals from
becoming overheated. We did not place bedding in the traps in winter
owing to the insulation provided by the wooden traps. Seldom did
adults die in the traps and only a few juveniles, even when temperatures
were subzero. The main problem we encountered in winter was ice
freezing on the traps, often turning them into blocks of ice. We would
have to use sharp putty knives to chip the ice off the traps and clear the
groves for the back door. Later, we placed aluminum shields to protect
the traps from sun, rain, snow, and ice.
Except for when there was potential for snow, we placed the traps
in the most logical place to catch an animal, within a meter of the station
stake, typically in a runway or at least where there was dense
vegetation. In winter, we placed the traps at the base of the stake. After
learning the hard way, we placed the traps on the north side of the
stake, with the shield touching the base of the stake. When we had deep
snow, especially when there was a crust on the snow, we found that
invariably we had to stomp down through the snow on three sides
before we found the trap (someone’s law?). When snow was very deep
(up to two feet or more), we would take snow shovels to dig down to
the traps.
Raccoons would often go out in the study areas from the adjacent
University Trelease Woods and roll traps to get at the animals.
Although not all that wandered into the areas rolled traps, once one
began doing so, it created a major disturbance by killing trapped mice
and preventing others from being trapped. Feral and domestic cats
from nearby houses also would “run” our traps. We routinely set
several large raccoon-size live traps in the study sites. At first, when a
cat or raccoon was caught, we removed and released them to the
southwest side of Champaign-Urbana, 6 miles from the study sites.
Unfortunately, we found that the cats would return when released that
close to the study area. We then took the cats 20 miles away. This was
an onerous task, setting the traps and carrying a heavy raccoon or cat,
that was trying to scratch or bite (all too often, successfully) us through
the wire cage, a couple hundred yards to the car. And then the extra
driving to release the animals. As succession in the area to the west
(which was being allowed to undergo succession to a tree stage) of our
bluegrass and alfalfa sites progressed into the tree stage, raccoons
began moving between Trelease Woods and that area. Thus, more and
more raccoons began moving through the study sites, resulting in more
frequent episodes of traps being rolled over and more raccoons to haul
out. This soon became a rather tiring adventure, plus resulted in losing
excessive numbers of animals to predation. To complicate matters
white-tailed deer (which were abundant in the area) found that by
kicking off the shields and rolling the traps, cracked corn would fall out
to be licked up. We tried putting heavy wire hoops over the aluminum
shields to anchor the shield to the ground such that the deer could not
roll them. Not to be outdone, the deer learned to spread out their front
legs and reach under the shield with their snout and pull out the trap.
Trap disturbance became a major problem and had to be reduced.
George Batzli and I had designed a trap shelter to avoid raccoon
disturbance when trapping white-footed mice in a flood plain forest in
the early 1970s. This involved a hardware cloth “cage” with a wooden
floor in which to place the trap. I had assumed voles and shrews would
not walk readily to the trap across the open wooden bottom of the
shelter, so did not use them in our study. Because of the increased
disturbance, I decided we had no other choice. I nailed the aluminum
shields to a wood base to form an open-ended “Quonset” hut. We
enclosed the front of the shelter with ½ inch hardware cloth in which
we cut four, 1-inch openings to allow the animals to enter. On the back,
we added a drop-down door of ½ inch hardware cloth. We staked down
the shelters with small iron rods. The voles and shrew entered the traps
just as effectively as they had when the trap was sitting in the
vegetation. The shelters solved our disturbance problems. You can
imagine my disgust for not trying the shelters at the beginning of the
study. The time we could have saved from setting raccoon traps,
carrying the raccoons and cats out of the area and driving to release
them.
In checking the small mammal live traps, we picked up the trap
and peered inside the trap through the hardware front. When occupied,
we would place a plastic bag over the back and slide out the door,
dumping the animals into the bag. One at a time, we would pin an
animal against the side of the bag and reach in and pull the animal out.
Voles, we grasped by the nape of the neck so they could not bite us. The
skin of shrews, however, was so loose that, if you grabbed one by the
nape of the neck, it simply turned in its skin and bit you (which by the
way, because their needle-sharp teeth, hurt like H. . .). We pinched the
skin between the eyes and the tip of the snout, letting the shrew twist in
the air, defecating and peeing all over our hands. When combined with
release of potent musk from scent glands, handling shrews was nasty.
During the first part of the study, we worked the animals with our bare
hands in winter, with hand warmers in our pockets or simply warmed
the hands in our pockets between stations. Our hands would become
very red and numb. Often our fingertips became so numb we had to
hold the animals by squeezing them between the sides of the thumb and
knuckle of the second finger. Later, flexible ski glove became available
and I bought pairs for the field workers to use in winter. I also
scavenged lost gloves on campus to use in the field. Use of gloves did
not keep our fingers from becoming excessively cold when
temperatures were subzero. (Our feet also came to feel like frozen
stumps when temperatures were very low, even when we wore
insulated boots, and for one session of -20 F, electric socks.)
When first captured, all animals were individually marked by
clipping a combination of toes, no more than two toes per foot (which at
that time was an “approved” method of marking individuals). At all
captures the following information was recorded: station number,
animal number, sex, reproductive condition, new or recaptured, and
body mass.
I had available for the program four Ph. D. students who were
investigating different hypotheses to explain periodic population
fluctuations—food availability, aggressive behavior, emigration, and
social stress. These students helped me get the study off the ground.
The first three students each trapped one of three habitats as their
contribution to the field work. The fourth assisted in the field work and
collected habitat data as needed by the others. At that time my teaching
schedule prevented me from covering all the main trapping effort. I
assisted the field workers, as my scheduled permitted. By the fourth
year, I had rearranged my teaching and administrative schedules such
that I could be in the field for almost all the trapping sessions each
month. Only when something came up that I simply could not get out of,
did I have someone substitute for me. I estimated that I was in the field
for 85% of the trapping sessions over the 25 years.
An Added Time-consuming Field Behavioral Program
During the first seven years of the study, I noticed that we were
seeing a lot more adult male/female prairie vole multiple captures than
we did for the meadow vole. Further, we often caught the same “pair” of
prairie voles together more than once in a weekly trapping session,
some in subsequent months. We seldom captured adult male and
female meadow voles together in the same trap and none of the “pair”
captures was repeated. When I compiled the data for those seven years,
13.2 % of all adult male and female prairie vole captures involved a
male and female together in a trap; 1.8 % of the male and female
meadow vole captures were of a male and female together in a trap.
Although the difference was not as great as I had perceived, it did
suggest a possible difference in social behavior of the two species.
Several workers, including me, had presented evidence that
meadow voles were polygamous, with the female rearing the young
alone and the male wandering around his home range, mating with
several females. The prairie vole records suggested a more intimate
relationship between males and females, perhaps monogamy. Because
monogamy occurs in only about 5% of mammalian species, this implied
something unique regarding social interactions of prairie voles. To
check if prairie voles do display monogamy, I acquired hand-held
directional radios and miniature transmitters and asked Joyce Hofmann,
a post-doc in the program, to radio track “pairs” from given traps to see
where they were residing. When she did this, she found that 11 of the
12 “pairs” she tracked were cohabiting an underground nest and
sharing a common home range. Live trapping at the nests of the other
two animals revealed the female was sharing a nest with a male and the
male with a female.
I then started conducting a series of observational laboratory
studies to test for monogamous behavior. In this research, I began
collaborating with Dr. Sue Carter. Because I was not trained in
behavioral techniques and knowing behaviorists are notorious for
worrying about controls, I would call Sue telling her what I wanted to
test and asked what kinds of controls were needed. She would tell me
and I would conduct the experiment. Then, I would need additional
tests and would again call Sue. This went on for a couple of months.
Finally, Sue asked me to bring over some prairie voles for her to work
with so as to see what I was “excited” about. She soon found that prairie
voles were better research tools for her interests than were the
hamsters she was working with. Thus, started a long and rewarding
collaboration. Results of Sue’s studies provided additional evidence for
behavioral monogamy. Using these observations as evidence, I applied
to both NSF and NIH for funding to test for monogamous behavior and
was awarded a two-year grant from NSF. NIH wanted visual proof I was
onto something before they would fund me. After a site visit, during
which the NIH team observed examples of interactions of adult male
and female prairie voles, I was funded for two years. By the time the
NIH funding became available and with one year to go in the NSF grant,
we had concluded all the laboratory work outlined in the original
requests. I, therefore, combined the two grants and started an intensive
field study of social behavior of the prairie vole. Using the results of this
study, I applied to NIH for additional funding and was funded for five
more years to continue the social behavior field study.
The field social behavior study was conducted from October
1980-May 1987, concurrent with the demographic study. Because
population densities consistently were highest in alfalfa, the social
behavior study was conducted in this habitat. Starting with our grid
trapping, we dusted all adult females with UV reflective powder by
putting a small amount of powder in a plastic bag, dropping the female
in the bag and shaking vigorously (“shake and bake” technique). We
released the female at the station where captured and that night, using a
UV lamp, followed the resulting traces of powder to a burrow leading to
their underground nests. We used different colors of UV reflective
powder to keep the trails separate. We set five multiple capture traps
around the openings to the underground nest or in the runways near
the openings to the underground nest or to a surface nest, those times
such were used. If the capture data indicated a social group was using
the nest, we continued to trap at the nest. We kept trapping a nest for
two weeks after there did not appear to be any animals using the nest.
Whenever we captured an unmarked adult female, or one for which we
did not know her nest, in both the grid and burrow trapping, she would
be dusted and her nest located. In this manner, we were able to monitor
almost all the social groups present in the study site.
The schedule for this project was: Monday, set traps at 0630
(because of the frequency of trapping, prebaiting was not necessary),
check traps at 0900, 1200, 1500, 2000, and 2230 and again at 0630 and
0900 on Tuesday. This regime was repeated Thursday through Friday.
We also had to go to the field at night to trace powder trails of the newly
dusted females, sometimes three nights a week. When population
densities were high, we spent lengthy periods in the field checking the
traps. Not only did we have a large number of social groups to check
(one period, late October-early December 1985, we were checking over
two hundred social group nests), but also social groups were large. I
had to add assistants so as to maintain the trapping schedule, up to four
“teams” (two trap checkers and a recorder, each). Even then, there
were times we would end one trap check barely in time to begin the
next. Many times we did not leave the field until well after midnight,
sometimes after 0100.
On the week of demographic grid trapping of alfalfa, we did not
trap at the nests on Thursday-Friday, when the grid traps were checked.
When grid trapping the alfalfa site, in addition to the 0800 and 1500
checks, we also checked the traps at 2030 each night to reduce stress on
the voles. Half way between the monthly grid trapping of alfalfa, we set
grid traps at all stations at least 20 m from known nests and checked
these while checking the nest traps Monday and Tuesday to help locate
unknown females that were not visiting nests that were being trapped.
In September 1989, I received a small Research Board grant to
support a follow-up study comparing social behavior of the prairie vole
in alfalfa and bluegrass habitats. For this study, we identified the nests
of the voles as in the previous study. This time we set traps a 1500 and
checked them at 2000, 0800 and 1500 for next six days. We skipped a
day and then started the sequence over again, continuing this schedule
from mid September to mid November. The protocol was the same as
for the original study. We traced UV trails after the 2000 trap check. In
the spring semester, 1990, I conducted a similar study in the tall grass
sites by myself, with the help of Mouseketeers (see next section). We
set traps at 1500 on Monday and checked them Tuesday-Friday at 2000,
0800 and 1500 for the next five weeks from early February through
April.
Mouseketeer Program
From the beginning it was obvious that, if we were to maintain the
trapping schedule in so many and such large study sites, we would need
a number of extra hands to help in checking traps and handling the
animals. I, therefore, initiated a program to obtain the help of
undergraduate students, “Mouseketeers”, that would assist the field
workers. Because I was teaching advanced courses at the beginning of
the study, I gave descriptive announcements of the Mouseketeer
program to grad students who were TAs in basic courses to hand out in
their classes. The TAs received a can of beer for each Mousketeer they
recruited, two for each female. A few even got a 6-pack! In 1974 I
started teaching a general biology course, Environmental Biology, for
non-majors. The course soon enrolled several hundred to a thousand
students each semester. I began recruiting Mouseketeers from each
class. The week before advanced registration began, I dressed up in a
Mickey Mouse uniform at the beginning of a lecture and explained the
program. I asked anyone interested in doing something off the wall, at
the same time seeing what field biologists do for a living, to sign up.
Once the Mouseketeer program got underway, a lot of the students also
came to the program through word of mouth. We got lot of friends and
roommates of Mouseketeers.
The Mouseketeers received 2 hours of credit (Ungraded,
satisfactory/unsatisfactory. None was given an unsatisfactory; if the
student was not able to do the work, he or she was asked to drop) for 15
trips (totaling at least 30 hours) to the field--“no exams, no reports, and
all the dead shrews you can eat.” I met with the group before we started
the first monthly session to explain what we were doing and why. I
showed them the way we handled the animals (they learned the actual
handling in the field), explained our toe-clip marking system. After a
few years into the study, I showed them graphs of what we had
observed up then.
There were a total of 1,063 undergraduate Mouseketeers during
the 25 years. Only about half of these were biology majors. The others
were from all sorts of majors, English, physics, chemistry, political
science, economics, finance, psychology, and history, among others. A
number of football players and men from the baseball team worked in
the program. Approximately half of the Mouseketeers were female.
Although there were exceptions, by and large the females were more
effective in handling the small mammals, and in tolerating (without
complaints) the weather extremes. As I look back, it amazes me to no
end, the tenacity of the Mouseketeers, especially the non-biology
majors, in meeting their scheduled times irrespective of how miserable
were the weather conditions. That they kept going in driving rain,
blizzards, sub-sub zero temperatures, and blistering heat, all for a
different experience and two hours of non-graded elective credit,
continues to amaze me. They made the program possible.
Research Assistants
During the study, I had three grant-paid post-doctoral Research
Associates involved in the study. Forty-six paid Research Assistants
helped in the field work. A few were master’s students, but most were
undergraduates. I got almost all the undergraduate Research Assistants
from the Mousketeer program. When I identified especially proficient
students that I knew were working to help put their way through
school, I would offer them a job. For most, I was able to give a quarter
time assistantship, which in addition to paying a stipend, also provided
a tuition and fee waiver. A few I placed on an hourly payroll.
Among my administrative duties, I was Chair of the University
Committee on Natural Areas, responsible for all the ecological field
research areas owned by the University of Illinois. The Committee had
assigned to it a full-time line, to help in the necessary maintenance and
other day-to-day needs of the research areas. In addition, the person
was tasked, as time allowed, to assist those conducting research in the
Natural Areas. Given there were few other research demands for this
person’s time, I was able to utilize the five men filling this position for
help when I needed someone to assist me, or the other paid a assistants,
with the live trapping.
In addition to the line assigned to the Committee on Natural
Areas, the Dean of the Graduate School gave me a full-time line for a
Research Associate to compensate for the amount of my time the
Committee took (I was Department Head and editor of a small journal at
the time). The women filling this position helped me with the editorial
duties and assisted in the field work when I needed extra help. The
position was available from 1975 through 1980.
Those Who Made It All Possible
Obviously, one person could not do a study of this magnitude and
intensity. As I indicated earlier, there were a large number of
participants, especially the Mousketeers, without whom the study could
not have been carried out.
I have not identified any of the
Mouseketeers by name, but in the “Reminiscences”, I have included a
number of those whose actions I especially remember. I cannot name
all the research assistants who were involved, but do want to recognize
those who went above and beyond to ensure successful completion of
the study. Hopefully, I have not left out anyone who had a major impact
on success of the study. If I have, I apologize to them.
The four Ph.D. students testing four hypotheses explaining what
drives population fluctuations made a major contribution during the
early years of the study, both in covering much of the field work and in
perfecting the field protocol. Lou Verner (emigration) was responsible
for routine trapping of the bluegrass sites, Russ Cole (food availability)
covered the alfalfa site and Joyce Hoffmann (aggressive behavior) the
tall grass sites. Jim Hauffe (social stress) did the vegetation sampling of
the various sites and assisted in some of the trapping. The first three
went on to complete their Ph. D.s in the program. Jim Hauffe, decided
there was more potential as a medical doctor than with a Ph.D. in
reproductive physiology. He went on to medical school and came back
to become one of the more popular pediatricians in Champaign,
especially among young mothers. Brian Klatt joined the study in the
early 1980s to investigate the competitive interactions between prairie
and meadow voles involved in habitat usage by the two species.
Because he used demographic data from all three habitats, he assisted in
the routine trapping for several years. One of George Batzli’s students,
Rick Lindroth, also used data from our demographic study as a part of
his doctoral research. He, too, participated in the live trapping and
supervision of Mouseketeers.
The three postdoctoral Researcher Associates all played critical
roles in keeping the study going. After finishing her Ph. D. and a year at
Fresno State, Joyce Hoffmann rejoined the program as a post-doc in the
field social behavior study. Joyce was the one who did the radio
telemetry that confirmed male and female prairie voles cohabited a nest
and shared a common home range.
Joyce was instrumental in
perfecting the field protocol. Barbara Frase coordinated the social
behavior study and wrote the computer program that allowed us to
follow individual social groups through time, as well as the dynamics of
the social groups. Betty McGuire coordinated the social behavior study
for two years, during which we had exceptionally high population
densities, keeping her in the field for extensive periods of time, early
morning and late evenings. Her perceptiveness in differentiating
residents of nests from those only “visiting” was instrumental in our
maintaining control of the study during the times of extremely high
densities and large numbers of social groups. In addition, she carried
out laboratory and field studies testing observations from the basic field
study. It was not until after she had left the program, did I learn that she
was allergic to voles and dust. Betty went to health every other week
for a shot to allow her to keep going. She continued to be involved in
the study by being the one who collaborated, often being the primary
author, on papers resulting from the demographic and behavioral
studies. This collaboration still continues, 28 years later (yes, we are
still milking papers from the study, in 2015).
Nancy Solomon asked me in the spring of 1985, if I had any funds
to support her during the summer. I did not have such funds, but
applied to the University Research Board and was given sufficient funds
to test the effects of snake predation on nestling survival of prairie
voles. We constructed a 15 x 20 m “snake proof” exclosure that allowed
movement of voles, shrews and least weasels in and out of the
exclosure, but prevented snakes from entering (the Research Assistants
obviously named the exclosure “The Snake Pit”). I felt we would be
lucky to have a couple social groups form inside the exclosure.
However, population densities that summer and autumn became very
high, with 11 social groups in the exclosure. Nancy was able to show
rather clearly that snake predation was the primary source of nestling
mortality and a determining factor in the size of social groups and, in
turn, population growth.
Several assistants played major roles in the study. Terry Pizzuto
saved the field behavior study. Terry had been a Mouseketeer, who I
immediately saw had exceptional abilities for field work. I gave her an
undergrad assistantship to help me with the night trapping of the social
behavior study. In early summer 1985, the post-doc, Barb Frase,
received an offer from Bradley University and had to leave the program
in late July. I needed to release Barb from field work so that she could
complete writing the program to analyze the field capture data. Her
replacement, Betty McGuire, was not available to come to Illinois until
late October.
I placed Terry in charge of coordinating the social behavior study
until Betty arrived and became familiar with the field protocol.
Population densities were on the rise, adding complexity to determining
to which group individuals belonged. By July, population densities were
approaching 100/ha and we were losing control over the study. A
number of unmarked adult females were appearing, indicating there
were social groups we had not located. Terry had the study under
control within two weeks time and maintained such as the population
rose to over 500/ha before Betty was able to take over. Had it not been
for Terry’s abilities and dedication to the program, the entire social
behavior program would have failed.
There were other assistants that went above and beyond in their
contribution to the study. Katherine Gubista covered the social
behavior trapping schedule at 0630 and 0900 Monday, Tuesday,
Thursday and Friday for four years. Patti Katusic met the 0630 and
0900 schedules for one year. Patti was conducting a bird study in
adjacent Trelease Woods. She set her mist nets at 0430, finishing just in
time to set or check the live traps at 0630. Then, she ran the mist nets,
finishing in time for the 0900 trap checks, after which she made her last
check of the mist nets. Thus, it was a win-win for both of us. Patti had
to be in the field for her own work from 0430 through until late
morning and was able easily to fit in the vole trapping, at the same time
being paid for her time in the field. Sadly, Patti was killed in an auto
accident when only 48 years old.
The spring semester, 1985, Maria Snarski, a political science
major, signed up as a Mouseketeer. She was one of the most proficient
field workers I had encountered. And, one of the most delightful
persons I have ever known (I would say “the most”, except that my wife
may read this). Maria was working long hours busing tables to help
cover her college expenses. Her scheduled field time was 0800
Wednesday. She would look so tired as she sat on the front steps of the
Vivarium Building as we waited for the rest of the Mouseketeers. I
remember asking her why she did not waitress where she could make
much more money and not have to work such long hours. She said that
first question she would be asked was if she had waitressed before. She
had never waitressed and would not say she had, just to get a job. I
wished I could hire her, but had no addition resources at the time.
When Barb Frase told me she had an offer and would be leaving in July,
that meant I was going to have some extra salary funds available from
the time she left and until Betty McGuire would arrive. I could use those
funds to put extra assistants in the field for the rest of the year. The first
thing I did was pick up the phone and called Maria, who was in summer
school, and offered her a job. She accepted and went on to work for me
in the field for several years and later as a TA in my Environmental
Biology Course, teaching a section for students who needed additional
help, mainly athletes. Maria did not know what she wanted to do after
getting her undergraduate degree. I kept her employed until such time
she decided on a career in Teaching English as a Second Language. The
program would not admit her, but let her take their courses. After she
had completed most of their requirements with high grades, she was
admitted. Maria has gone on to highly successful career as a Foreign
Services Officer.
I still feel badly about what I did to one of the assistants, Wendy
Shulk (now Holgrem). In the fall of 1981 we were still perfecting the
protocol of the behavior study. I wanted to monitor the nests until the
end of the semester, hoping these data would determine what we
needed to modify to ensure accuracy in locating and following social
groups. We would then be able to start the main study in February. I
hired Wendy to do the night trapping. We were checking the traps
every two hours through the day and until 2330. I told Wendy she
would be done by midnight. Population densities in August were 66/ha,
with about 10-12 captures at each check. Because of the frequency of
trap checks, she had to remain at the study site between trap checks. I
hired a male undergraduate, Bob Berg, to assist her and so she would
not be in the field by herself. At first this seemed to work as I had said.
But, as voles are wont to do, they “decided” to give us a lot of data, and
began rapidly increasing in numbers, reaching 169/ha by November.
Wendy and Bob were soon catching up to 50 voles at each trap check.
Some nights they would not get back to campus until 0130. But, she did
not complain. In January when I was setting the assistants’ schedules
for the spring, Wendy asked for the morning checks. Seems she was not
a night person. Bob Berg then told me that Wendy would fall asleep as
soon as they got back into the car and would sleep until time for the
next trap check. I feel badly about putting her through that, but it is
another indication of how so many went above and beyond in seeing
that the study ran so smoothly.
At the beginning of the summer session in 1985 a student, Sheila
Vanthernout, who had taken my Environmental Biology course the
previous spring semester, came to my office to see if she could be a
Mouseketeer that summer. She was an Economics major making her
own way, as a single parent, through school. She was short two hours of
science for her requirements and had been told by her advisor that my
Mouseketeer course would satisfy those two hours. I accepted her. The
first time we went out Sheila almost immediately was able to
differentiate between prairie and meadow voles, something often
difficult for me, after 30 years of working with the two species, and to
determine sex and reproductive condition, also difficult to discern. The
second time out, when we caught an unmarked animal, I asked Sheila if
she wanted to clip the toes. She said, “Sure.” I gave her the scissors and
told her the numbers. Zip-zip, zip-zip, zip-zip, she went, with no
hesitation. My next question, “Do you want a job?” She said Yes.” I
could not give her a quarter time RA as I did the other undergrad RAs.
She had a Pell Grant, and if I gave her the RA, her tuition and fee waiver
would be canceled. To make certain she received the effective amount
of money, as did the others, I hired her as an hourly student and inflated
her hours in the field such that she received the equivalent of a tuition
and fee waiver in addition to the base salary stipend. Sheila was an
exceptional field worker. She had missed her calling, but went on to a
successful career as an Actuarial with a major insurance company.
The five Committee on Natural Area men were exceptionally
helpful in manipulating the study sites, including mowing the bluegrass
areas 20 cm above the surface at least once a year to control invading
broadleaf plants that would have shaded out the bluegrass, mowing
closely sequential strips of the alfalfa field to slow down crowding out of
the alfalfa by other plants and in periodic burning of the tall grass sites.
They also plowed, worked the ground and planted alfalfa to establish
the new alfalfa sites. All assisted in the field trapping when densities
were high and I needed another trained person to make certain we
could maintain the trapping schedule. John Edgington and Merle
Schmierbach provided valuable support during in the early years of the
study by providing an extra experienced trapper to work with the
Mouseketeers. Dave Tazik helped with the routine trapping and
conducted a special study of interspecific territorial behavior of
male/female pairs of prairie voles and female meadow voles. Phil
Mankin assisted in the demographic study and in the early morning trap
checks for the behavioral study. He also made foam casts of the
underground nest arrays. Steve Buck provided exceptionally valuable
assistance in maintaining the demographic study through the final ten
years. This was a time when I had insufficient funds to hire a full-time
assistant. Steve went to the field to during each trap check so that there
were two of us recording data and supervising Mouseketeers.
Diane Avalos was the first of the Committee on Natural Areas
Research Associates. She had been in a Mouseketeer the first semester
of the program and was exceptionally proficient in the field. Diane had
finished her undergraduate degree and was in the MS program at
Eastern Illinois University when I was given the Research Associate line.
I called her to see if it would be possible for her to come back and work
for me while she was finishing her MS. It was and she did. Diane
compiled the field schedules for the Mouseketeers and went to the field
to help with the trapping when we needed additional experienced
hands. Diane also helped the “diversity” report regarding employees of
the Committee on Natural Areas. John Edgington, who was the CNA
employee at the time, was one sixteenth Native American, which
satisfied the designation as a minority.
At that time one of the
categories of minorities was “Spanish speaking/surname.” Diane’s Dad
was Latin American. Her Mom had met him while working in Central
America. They married and moved to Illinois. Diane also spoke Spanish.
Where she had learned it (in school in the States) was not asked. She
had a Spanish surname and spoke Spanish. Thus, I could fill out the
form that both my employees were minorities. But, then Diane married
Mike Dummit. In one fell swoop, I lost half of my minorities. Spanish
speaking/German surname did not count.
The next to fill the Research Associate position was Pat Prather.
Pat had a degree in French, but soon picked up the field protocol. The
second day she was on the job, we were installing vole exclosures in
some of the areas. We used a 4-inch trencher to dig the trench into
which we buried the hardware cloth walls of the exclosure. To avoid as
much disturbance to the vegetation as possible, we parted the grasses
and forbs ahead of the auger. As Pat was doing this, the trencher was
churning large flows of soil right on top of her head. She looked up at
me and asked “where was this in the job description?”
The last person to fill the Research Associate position was Linda
Shiller. Linda assisted in trapping mice more often than had the other
two women. Even though working in the field definitely was not her
first choice for “fun”, Linda was a trooper. One of the days the two of us
were in the field finishing a monthly trapping session. It started
freezing rain as soon as we arrived at the study site that afternoon. It
kept increasing in intensity as the afternoon wore on. Our raincoats
became frozen, with a thick layer of ice and our hands were losing all
sense of feeling and mobility. As we went to the last site to check the
traps, Linda was about at the end of effectiveness and I was getting
close. John Edgington, who knew were checking traps, came out to the
field to help us finish. Not sure we could have done so, had John not
come to help us. I had on an Arctic parka, with a heavy hood. The ice on
the hood was so thick that, even though we drove back to town (25 min,
as the roads were iced over, with trees and tree limbs coming down
alongside and on the roads) with the heater going full blast, when I got
to my office, I lifted the ice off the hood in the shape of a thick helmet.
That day proved to be one of the worst ice storms in several decades.
Although he did not participate in the field work, results of the
study most likely would never have seen the light of day, were it not for
the contribution of Dr. Madam K. Oli of the University of Florida. I first
analyzed the demographic data using standard statistical analyses and
attempted to publish the results in eight papers. All papers were
rejected for the want of modern, “sophisticated” analyses. That I could
not do. I met Madam at an American Society of Mammalogist annual
meeting and told him my plight. He agreed to do the analyses. Thus
began a 17-year collaboration of publishing the results of the study. His
efforts resulted in 19 papers from the study, on which he obviously was
a co-author. By the way, the “sophisticated” analyses arrived at exactly
the same conclusions as had my “antiquated” analyses. Go figure! And,
where my analyses could be presented in eight papers, owing to the
need for much larger tables and graphs (and, so many we had to place
several as appendices in the University of Illinois Electronic Archives) to
support the “sophisticated analyses”, we had to resort to the 19 papers.
Finally, I need to acknowledge the support of my wife, Mary Ruth,
who had to give up summer vacations, weekend out-of-town family
visits and any number of other social and entertainment events, because
of the need to meet the field schedule. For six years, she was at home
alone until at least 12:30 to 1:30 AM for a minimum of 3 nights a week.
During the period of the follow-up behavioral study, I was in the field 6
of every 7 nights from mid September until Thanksgiving weekend.
Were it not for her tolerance, I could not have completed the study.
Maintaining The Field Schedule
It was essential that I be at the front of Shelford Vivarium at least
five minutes before we were to leave for the field at 0800 and 1500.
Because our studies relied on assistance from the Mouseketeers, I could
not be late or they would not be inclined to remain in the program,
especially if they had dragged themselves out of bed and got to the
Vivarium in subzero temperatures only for me to show up 15-20
minutes late. The word would soon get around that I was not reliable,
thus cutting off all our word of mouth recruits. Likewise, I had to leave
the house at precisely 1945 the nights of trapping for the field behavior
study. I picked up my field assistant(s) at 2000. Often they met me at a
given place on the street. I could not leave them waiting for me,
especially when temperatures were low and/or it was raining or
snowing.
We maintained the field schedule year-round, with minimal
deviation from the schedule. We went irrespective of temperature or
precipitation. The only time we would not go was if the roads were
impassible. There were numerous days the temps were well below 0 F,
the lowest -22 F. The coldest wind chill we encountered was -69 F (and
we caught a large number of animals). One week, the highest chill factor
we had all times we were in the field, day and night, including both the
grid and social behavior study, was -40 F. We conducted trapping in
blizzards and driving downpours at close to freezing temperatures. I
provided rain pants, parkas and boots for rainy times and insulated
boots during cold periods. Unfortunately, it appeared the rainier and
cold was the day or night, the more active were the animals.
Fortunately, when summer temperatures were high, up to 105 F, the
small mammals were relatively inactive.
Snow was so deep the roads were all closed during only two grid
trapping sessions. The traps were already set and the mice survived the
day and a half we could not reach them. We had to skip the entire
monthly trapping session for January 1980 because of heavy rains that
flooded all our study areas, which then suddenly froze, freezing almost
all of our traps in solid ice. We did not conduct the behavior live
trapping for only a few sessions each year. A few times I would cancel
one two-day session in June so that I could attend the meetings of the
American Society of Mammalogists. Typically, we canceled the
Thursday-Friday session for Thanksgiving and the entire week at
Christmas.
How Did I Manage It?
Although I entered the study feeling I knew what I was in for, it
soon became evident it was going to be a long 25 years. As time went
on, and we had laid on the social behavior study in addition to the
routine demographic protocol, it became even more of a bear. The only
way to cope was simply not to think about how much longer we had to
maintain the all-encompassing schedule. Rather, simply “do the chores”
day after day, recognizing only that each day’s work added to our data
base. I was Department Head for exactly half, twelve and a half years, of
the study. It took considerable juggling of my schedule to ensure I could
make the trapping schedule. Fortunately, the Director of the School of
Life Sciences was tolerate of my schedule and accommodated me
regarding many of the School administrative meetings. The schedule
took its toll on the personal life. For the first 20 years, I had to go to the
field at 1500 three Sundays out of the month. This meant restricting our
family social events, including visits to out-of-town relatives to the one
free weekend a month. Compressing the schedule for the last five years
relieved little of this problem. As might be expected, the one activity of
the month the wife wanted to do, fell on that weekend more times than
you want to know (another someone’s law?).
Financial Support
Although both NSF and NIH were funding applications for studies
of population cycles, my attempt to obtain start-up funding for the
program from NSF was rightly was rejected with the suggestion to
reapply when I had established that the study was feasible and we had
some preliminary results to support my request. By 1974 we had
sufficient field data and evidence I could maintain the trapping schedule
to apply again for federal support. This time I received, a four year
grant from NIH for the study of population fluctuations of prairie,
meadow voles and short-tailed shrews. I also was awarded three years
of funding from NSF, but had to turn it down because of the funding by
NIH. I requested a small additional three years of funding from NIH for
my summer salary, which also was funded. When I discovered potential
for behavioral monogamy in prairie voles, I applied for and received
support from both NIH and NSF for a two year laboratory/field study of
prairie vole social behavior. Following that I was awarded a five-year
grant from NIH for an intensive field study of prairie vole social
behavior. Thus, I had continuous grant support from from1975 through
1987. I also obtained several small University Research grants to
support special projects associated with the main program. In 1988 I
became Department Head again (I had been Head from 1975-1980). To
help compensate for detraction from our research, all department heads
were given $20,000 per year by the director of the School of Life
Sciences. This was adequate to hire the few field assistants I needed to
finish the study and to enter all the data for analysis.
Some Numbers.
We made 11,300 trips to the study sites, for a total of 158, 200
miles. We knelt down, picked up and put back down traps and
estimated 2,320,300 times. And, we handled voles and shrews
approximately 236,700 times. I cannot calculate the total number of
different individuals we captured. I had only three major health issues
during the 25 years. The days of field work missed were: hernia
operation, 14 days; rotator cuff surgery, 10 days; heart attack, with
cardiac artery angioplasty/insertion of two steel stents, 0 days.
Reminiscences
Most of the field work over the years involved more drudgery
than exhilaration--cold, wet, hand numbing days and nights, trudging
through deep snow, burning up in the summer sun, and knees aching
from kneeling down and standing up a hundred times or more a day.
And, going to the field when I had headaches, rheumatism flair-ups, a
bad cold, the flu, or intestinal problems. The one thing that did add
interest to the study, however, was the interaction with the
Mousketeers. Because none of the students had handled wild small
mammals in the field, it was a challenge both for the Mouseketeers and
for me to see that they became proficient at processing the animals in
the field. Each Mouseketeer had her or his own idiosyncrasies. A
number of reminiscences of these students have stayed with me all
these years, even though the names no longer can be associated with the
events. I will relate a few of the incidents that have stuck in my mind.
By and large the female students were much less squeamish in
handling the animals. I felt that perhaps the women who learned of the
program thought about what was involved and only if they believed
they could do it, did they sign up. And, when they were asked to take a
vole or shrew out of the bag with their bare hands, they did not freak
out, quickly acquiring the “touch.” The men, on the other hand, most
likely did not think about handling the animals and signed up as
something off the wall to do. When first confronted with a biting shrew
or vole, many lost it, having a difficult time acquiring the skills. When,
however, a female student did freak out, it was a sight to behold.
One student got the vole by the nape of the neck, pulling the skin
up so tightly it would choke the vole and then she would freeze. I would
yell at her to loosen the grip, but she froze her fingers so tightly, I barely
could pry them loose before she strangled the animal. This occurred
each time she went to the field. Eventually, I had to assign her the
duties of recording the data from the animals as I handled them.
Another female student would eventually get the animal out of the bag,
but screamed, stomped her feet and danced around all the time she was
handling the animal. She was petrified of the animals. Each time she
went to the field, up to the very last day, she would beg me to let her not
have to handle the animals. I told her we were “building character.” She
did her required sessions and did not kill or drop an animal.
One year we had two roommates in the Mousketeer group, both
English majors. At that time we identified students who could handle
and record the data themselves. One of the girls did not mind handling
the animals and determining animal number, sex and taking
reproductive information; but she could not bring herself to clip toes.
The other one was afraid to touch the animals, but did not mind clipping
toes. So, one got the voles and shrews out and read off the data from
them, which the other one recorded. When they caught an unmarked
animal, one read off the data, the other recorded the data and clipped
the toes. Worked perfectly.
One morning when the absolute temperature was -10 F, one of the
girls, a history major, was handling the voles barehanded. She caught a
very large male meadow vole. As she was holding it so I could get the
reproductive information, he peed all over her hand. As it ran down
over her fingers she said, “Ahh, that feels good.” Told her she was now a
“biologist.” Another, a freshman, with me in the field one afternoon held
the bag as I dumped the voles from the trap into it. In one trap there
were two adults. As she was working the bag around to get one from
the bag, the voles were scrambling around over each other. She looked
up at me with sort of an embarrassed wide-eyed look and asked,
“Doctor Getz, are they doing something intimate in the bag?” Had to
keep a straight face when I told her, “Nope, just scrambling.”
One snowy January Sunday afternoon I went to the Trelease tall
grass site to prebait the 250 grid traps. The temperature was near zero
and a foot and a half of snow, with a 3-4 inch thick frozen crust on top,
covered the area. I was really struggling and was going to run out of
daylight at the rate it was taking me to find the traps and to clear them
so I could put in the cracked corn. I looked up and saw a Mouseketeer
from the previous fall group coming into the field. He lived about 2
miles from the site and had picked up the trapping schedule from Diane
before Christmas. He had looked at it and saw that I most likely was
prebaiting by myself since the students were not on campus yet. He
took it upon himself to walk the two miles in the snow to help me, even
though he no longer was in the course. This is an example of how many
of the students went the “extra mile” to ensure success of the program.
There was one guy who would get the animal out of the trap into
the bag and out of the bag by the nape of the neck as he was supposed to
do. But, when the animal wiggled ever so slightly, he would stare at it
with an alarmed look for a couple of seconds and then either “spiked”
the animal or tossed it about 5 meters. No matter how much I yelled at
him, he would not keep hold, even though he was never at risk of being
bitten. Another guy was concerned one day that it might be muddy
(was not, as we were trapping in a bluegrass site, where there was only
dense grass) and get mud on his brand new white running shoes (not
sure why he wore them to the field in the first place; was not his first
trip to the field). When handling one large meadow vole, the vole nailed
in him in a finger and his teeth became stuck in his finger. He grabbed
the vole with his other hand, with the same result. He repeated this
twice more, ending up with four big-time bites (the record number of
bites during one handling of an animal) and bled all over his white
shoes. Then, he really was upset. But, he did not let the vole get away.
And, there was the attractive blonde who, at the spring advanced
registration for the next fall, had visited with me about the Mouseketeer
program and had signed up for the fall semester. After the Biology
graduation ceremonies in May, at which I had given out the diploma
covers to the departmental graduates, I was walking out through the
foyer when I saw her. She was there for her sister’s graduation. When
she saw me, she came running up squealing excitedly how happy she
was to see me and how much she was looking forward to working with
me in the field the next fall. I thought to myself, “Heaven help me from
this, a stereotypic hyper blonde.” That fall, she turned out to be a
serious, excellent worker in the field. The next spring semester, she
helped with a short field study, that unfortunately did not give us
enough data (too much raccoon and cat disturbance of the traps) to
publish. The following year we designed a complex, intense laboratory
study testing if young female prairie voles were first reproductively
activated equally by paired and unpaired males. They were not. Over
three times as many were activated by unpaired as by paired males.
This was an exceptionally demanding study. She maintained at least a
couple dozen breeding pairs and their offspring and had six
experimental pens running all the time. Each week she spent hours
upon hours maintaining breeding pairs, setting up experimental groups,
and recording data. Data from this study was published and added
another piece of the puzzle of our understanding of social behavior of
the prairie vole. Sheila went on to get a Ph.D. in botany and a successful
career in academia. An example of an ill-conceived sexist response
regarding stereotypic impressions of attractive blondes.
So What Did We Find And Was It Worth The Effort?
First, we were not able to show evidence supporting presence of
“cyclic” fluctuations in either species of vole. Both species displayed
high amplitude erratic fluctuations. Blarina bevicauda displayed
obvious annual fluctuations. Neither were we able to identify a single,
nor even a limited array of factors involved in generating and stopping
population growth. By elimination of other factors, we proposed that
unpredictable fluctuations in the array of predators resulting in
relaxation of and increase in predation pressure, triggered increases
and declines in abundance. We obviously could not document changes
in the abundance of the array of mammalian and avian predators that
impacted vole populations.
The most important result of the demographic study was the
generation of extensive data sets, which are now available for other
researchers wanting to test more sophisticated models regarding
population fluctuations of small mammals. Both the monthly data from
the 25-year study and the twice-weekly data from five years of the field
behavior study are available to and have been and are being used by
other workers. The data sets are available on line in the University of
Illinois electronic archives to anyone wanting access to them.
The most important contribution of the over all study involves
obtaining evidence of behavioral monogamy in the prairie vole. This
obviously was not one of the original hypotheses we proposed to test.
While conducting the routine trapping, I made a simple observation of
the potential for monogamous behavior in the prairie vole. Laboratory
experiments and field studies provided additional evidence for such
behavior. Dr. Sue Carter began collaborating in the study of social
behavior of the prairie vole.
Specifically, she investigated the
hormonal/behavioral interactions related to affiliation of the males and
females.
These studies provided addition evidence supporting
behavioral monogamy.
When, Sue moved to the University of Maryland, where she
continued her research into the hormonal/behavioral aspects of pair
formation in prairie voles. She began collaborating with Dr. Tom Insel
at the National Institutes of Mental Health. Tom was working with
human affiliative behavioral problems, including autism and
schizophrenia. He saw that many aspects of human behaviors and
changes in such were similar to those observed in prairie voles. Tom
began working with prairie voles.
Dr. Insel later moved to Emory University in Atlanta and set up a
lab emphasizing studies of monogamous behavior in prairie voles and
potential application to human affilitative behavioral problems. Several
of his graduate students, Larry Young in particular, have continued
investigations of human social behavior using the prairie vole as the
experimental animal, after Tom returned as Director of NIMH. As a
result, the prairie vole has now become a major experimental animal for
research into human behavioral problems, including autism,
schizophrenia and alcoholism, among others. The application of
evidence from prairie voles to humans is not simple and will require
much more work before it is determined whether the prairie vole
results really are applicable. But, there is the potential for such. Those
studying human romantic interactions also use the prairie vole to
explain the neuroendocrine basis of “romantic love.” A British
sex/marital counselor, Andrew G. Marshall has published a book
entitled, “Make Love Like A Prairie Vole.” Invariably, articles regarding
male-female relationships, as well as those dealing with potential
treatment
for
human
behavioral
problems
refer
to
hormonal/behavioral aspects of prairie vole brains. As a result, prairie
vole colonies are maintained at twenty-five research laboratories
throughout the US and two in Japan. Larry Young has said of the prairie
vole “research on the animal’s genetic makeup is uncovering more
about human behavior than does the study of just about any other
species.” Thus, what was essentially an esoteric basic study of factors
driving population fluctuations ended up making a major contribution
to research into human behavioral problems. So, the study was worth
the effort.
Will Such A Study Be Repeated?
Most likely not. Granting agencies have such demand for funding
that they can support only a very limited percentage of requests. Given
that results of the previous extensive funding of studies of population
“cycles” were inconclusive, the limited funds have to be channeled to
studies with greater potential for success. As I have shown, a number of
situations have to come together to conduct such a long-term study:
ability to obtain at least minimal grant support to cover times the
investigator cannot meet the trapping schedule; availability of study
sites near enough to campus so that the necessary trapping schedule
can be conducted concurrent with normal teaching/administrative
duties; flexibility of the teaching/administrative schedule to provide
time to facilitate the trapping schedule; availability of sufficient
numbers of trained assistants to cover times the principle investigator
cannot go to the field; availability of volunteers to assist in the trapping;
finally, the principle investigator must already have attained rank of full
professor so that no longer needs to be publishing frequently. Longterm studies, by definition do not generate many papers during the
course of the study.
Demands of the University, family and health problems may make
it impossible to continue the study, and greater career potentials may
result in moving before the study is completed. Few research
universities own research sites within less than a half hour driving time
from campus. Longer driving time would not allow a person to conduct
the trapping within the daily teaching/administrative schedule. Few
faculty members have such control over their schedules to have all their
duties met during the middle of the day, allowing time in the field early
morning and late afternoon. If Federal funding is not available for
trained assistants to cover emergencies and provide addition help
during times of exceedingly high population densities, because of
limited university budgets, few researchers will be able to get local
funding for such help. Even if one were able to establish a program to
supply undergraduate volunteers, because of paranoia regarding
zoonotic diseases, especially hanta virus, universities have put in place
so many restrictions on students handling wild animals that most would
simply not bother, especially non-biology majors. In the present day
academic environment, with few tenure track positions available, most
researchers have to spend several years in temporary post-doctoral
research positions. Even after obtaining a tenure track position, the
evaluation times for being promoted to tenure and to full professor are
lengthy. As a result, most investigators would be too old to be able to
see through such a long-term study. I had attained full professor by the
time I was 36 years old and was 40, when starting the program. Starting
any later than this would decrease the probability of having the stamina
to complete at least a 25 year study.
There is also the question, would even another 25-year study be
worth doing? Given we did not find any evidence of cyclic periodicity in
population fluctuations, suggests that a longer study is required. If 25
years did not provide supportive evidence for such phenomena, is there
any hope that a longer study would be more productive? That a longer
study would be even more difficult to complete, with no guarantee of
better results, it is doubtful anyone would be willing to attempt such a
study.
Would I Do It Again?
This is a question that I have asked myself a number of times,
mostly while still in the throes of the study, especially times when snow
was above our knees and the chill factor -20 F or there was a torrential
downpour. Others have asked me the same question. Before the end of
the study, I was ambivalent.
As I look back on the degree of effort, the conditions under which
we maintained the field protocol and the disruption of my
administrative and teaching duties and family matters, I really cannot
fathom how we pulled it off. And, again, I want to emphasize that it
would not have been accomplished without the help of all those who
participated in the field work. That we did pulled it off successfully and
having seen the results, especially those from the field behavioral study,
gives me a good feeling of accomplishment. I was able to add basic
information regarding population fluctuations of small mammals and,
more importantly, provided a tool for medical research into human
behavioral problems. So, I guess the answer is, “Yes, I would do it
again.” But, I would not want to know what lay ahead of me when I
started the program. That would be awful hard to get my mind around.
Acknowledgement
I thank Don Miller for suggesting I put together this account of
what was involved in doing such an intensive long-term study of small
mammal population fluctuations. Had Don not done so, I most likely
would not have gotten around to putting down my “story.” Don was my
first Ph.D student, at the University of Connecticut. He is the most
perceptive field biologist I have encountered during my career. I wish
Don could have been involved in the long-term study. He would have
added greater dimensions to the project.
Me, leaving the house at 1945 the winter of 1984 to pick up my
assistants on the way to check traps for the field behavior study. I
bought the Arctic parka from my Ph. D. advisor, Bill Burt, in 1957 when
doing my doctoral research at the University of Michigan. I used it every
year until the winter of 1985, when I gave in and bought a ski mobile
winter suit. I had provided new ones for the RAs and they insisted I get
one, too. Note the smudges of UV reflective powder used in tracing adult
females to their nests. The patch has slots for the scales used to weigh
the animals, a pencil and the scissors used to clip toes in marking the
animals.
Areal view of the study sites, taken just after the end of the study.
See the following figure of the study sites to identify the specific sites in
the photograph.
Map of study sites used in the study.
A field record sheet taken from the demographic study showing the data
recorded for each capture. This sheet was filled out during trapping of
the meadow vole (Mp) bluegrass site, from which prairie voles (Mo)
were being removed. Bb represent captures of short-tailed shrews. We
also indicated the condition of the shrews; “Good” if they were
apparently were in good condition.
A field record sheet taken from the field social behavior study. A list of
the nests, which were being trapped, is on the right side of the data
sheet. This list was placed on the first page of the
new data sheets by the coordinator, the night before we started a twoday trapping session. The “station number” column records the nest at
which the animal was caught. When there were too many nests for one
column, a separate sheet of nests to be checked was attached to the data
sheets for that trapping session.
Population fluctuations of the prairie vole during the 25 years of the
study.
Population fluctuations of the meadow vole during the 25 years of the
study.
Number Per Hectare
60
50
40
30
20
10
0
60
50
40
30
20
10
0
Bluegrass
Alfalfa
Tallgrass
72 73 74 75 76 77 78 79 80 81
85 86 87 88 89 90 91 92 93 94
Year
Population fluctuations of the short-tailed shrew during the 25 years of
the study.