Ben Lundquist
Biology Lab
Professor Galvez
Wednesday 7-9:50
Demographic Effects of Canine parvovirus on Free-Ranging Wolf Populations over 30 years
Introduction:
The Canine Parvovirus is a highly contagious virus that typically only affects dogs, but has been
linked to cats as well. The virus is spread by direct and indirect contact with animal feces. The
virus is even more contagious in puppies that have not been provided with maternal antibodies
which would protect the pup against the disease. This disease although highly contagious, is not
able to infect humans. The existence of CPV was first discovered in wild wolves. Samples were
taken from wolves in the Northern Minnesota area in 1973. The group hypothesized that the
CPV virus correlates to the declining wolf population in Minnesota. However, domestic animals
are not affected by this virus because they carry the maternal antibodies which help protect them
from CPV.
Materials and Methods:
The team used many materials and methods in order to test their hypothesis. To collect data the
team used a 6 step process. 1) Annual antibody prevalence of CPV taken from wolves 19732004. 2) An index of annual wolf pup survival to 4 months of age was collected in the ISA
(Intensive Study Area) 3) Annual winter census of wolves 1972-2004. 4) Intermittent CPV
antibody prevalence estimates in wolves in the total Minnesota wolf range 1974-2004. 5) Index
of annual pup survival to 4mo of age from the entire wolf pop range in Minnesota. 6) Histories
of CPV antibody states in wolves sampled multiple times in the ISA. The ISA that was chosen to
be the main area for the study is a 2,060km study area in the superior National Forest because
this is where the largest wolf population in Minnesota was located. Radio collars were used and
airplanes were used in addition to the radio collars so they could track the wolves from the air.
Results:
From 1973 to 2004 720 samples were taken from wolves and tested for CPV antibodies (which
helps protect wolves from the Disease) also some wolves might have been caught more than
once. In 1973 five of 9 caught wolves tested positive for CPV, in 1974 five of 11 tested positive.
Since wolves travel large areas they tested nine wolves from 2-3 different packs in 1973 that
were within 18km, four wolves tested positive and five were negative for CPV. As previously
stated they attained 720 samples from the ISA area over a period of 30 years. 335 wolves were
negative and 385 were positive for CPV. Of the 350 males tested, 183 were positive and 167
were negative. Of the 370 females tested, 201 were positive and 169 were negative. Fifty-four
pups tested positive and 165 negative versus 330 adults positive and 171 adults negative.
Between pups and adults, nearly equal proportions were positive. During the course of this study
it was found that some wolves went from positive to negative and back to positive with the CPV,
and vice versa over the years. However some wolves were not found to switch from positive to
negative and vice versa during the study. The primary effect of CPV in the ISA wolf population
could have been due to death in young pups less than 3 months old, because of most of these
deaths, these animals obviously would not have been able to be tested, which removed them
from the study. In the ISA adult wolves tested for antibody prevalence from 1985 through 2004
averaged 81%. Wolf pups aged 3-7 months CPV averaged 43% from 1973-82.
Discussion:
Though CPV was primarily studied in the Greater Minnesota area, it has since been found in
Texas and all across the world. The results led scientists to believe that the primary effect of
CPV is due to death of pups. CPV related mortality mostly occurred in 1-12wk old animals. The
Wolf pups that did not have maternal antibodies became susceptible to CPV at 3wk's of age.
Wolf pups that had maternal antibodies became vulnerable to CPV at 6 wks. of age. Additional
data showed that wolf pup population in the ISA had decreased 70% from pre CPV times.
Additionally in the entire Minnesota are numbers dropped 40-60%. However even with this
decline in population their data suggests that enough wolves are able to survive, which helps to
maintain the overall population. Their data ultimately suggest that CPV caused the demographic
changes they observed during this study. This study is believed to be the first study to gather
compelling data relating to the long term effects of CPV on a wolf population. This test also
followed the disease for 30 years, which seems to be one of the only studies that have followed a
disease for so long. In conclusion the data this test reported concluded that there is compelling
enough evidence to conclude that CPV could be a major factor in the declining of rate of wolf
population in the Greater Minnesota area.