ACUB Project Progress Report
1. Project Title: Captive rearing methods test for mardon skipper (Polites mardon)
2. Project Lead: Mary Linders, Washington Department of Fish and Wildlife, 600 Capitol Way N.
Olympia, WA 98501-1091; 360-902-8135; lindemjl@dfw.wa.gov
3. Project Site (if appropriate): Oregon Zoo, Portland, Oregon
4. Executive Summary
Mardon skipper is an endangered species in Washington State, and a federal candidate for listing
under the Endangered Species Act. It remains at only two locations in south Puget Sound, with
likely only a few hundred adults at either location. Captive rearing can play an instrumental role
in amassing sufficient animals for reintroduction at unoccupied sites, while providing insight into
key aspects of life history that may be difficult to observe in the wild. Captive rearing grass
skippers is known to be challenging. Due to poor weather in spring 2008, we were only able to
obtain two female mardon skippers from south Puget Sound. These were taken to the Oregon
Zoo and placed on netted 2-gallon pots of Roemer’s fescue, its larval host plant. It appears we
were unable to obtain eggs from these females in spite of the addition of artificial heat and light.
Consistent failure to obtain eggs from south Puget Sound mardon skippers leads us to believe
there may be significant differences in oviposition strategies and cues between south Puget
Sound skippers and those from the South Cascades in Washington that will require a controlled
side-by-side study with females from both populations.
5. Project Goals and Objectives
The goal of this project is to acquire and refine essential information that will increase the
success of mardon skipper captive rearing efforts for Polites mardon in south Puget Sound. The
objectives are to:
1) Obtain eggs from wild females at the capture site and release females back into the wild.
2) Test captive rearing protocols for mardon skipper from egg to adult.
3) Document the over-wintering stage of mardon skipper in captivity under ambient outdoor
rearing conditions.
4) Compare adult emergence times to known emergence times of wild populations in south Puget
Sound.
5) Increase our understanding of the behavior, physiology, and husbandry requirements of
mardon skipper in captivity.
6) Use adult mardon skippers emerging in the lab for a test of hand-mating techniques.
6. Methods
Our original plan was to obtain up to 10 female mardon skippers from south Puget Sound
populations to provide eggs for a captive rearing methods test. Weather in the spring of 2008
was unusually cloudy, cool and wet. This delayed the flight period and limited opportunities for
locating females. For the same reason, plans to hold females in captivity in the field were
abandoned. Instead we opted to capture fewer females and transport them to the Oregon Zoo,
where staff could provide better care and more appropriate conditions with respect to heat and
light. Ultimately, just 2 female mardon skippers showing slight wing wear were captured and
sent to the Zoo.
Female skippers were held in netted flight cages (12.5” W x 12.5”L x 40”H) containing a 2gallon potted Roemer’s fescue plant (larval host). The fescue grasses were tall enough that either
leaves or seed heads were close to the top of the box and available to the females regardless of
their position in the box. Blooming nectar plants and a small vase of cut flowers were also
placed provided. Nectar plants and flowers included yarrow, fleabane, eroduim and other
flowers with good nectaring structure. The favored nectar plant was the fleabane, Erigeron
karvinskianas. Each box also contained a small moist water sponge and a tiny vial with a honey
and water mixture on a small cotton swab. The butterflies were allowed free flight inside the
boxes.
These flight cages were placed inside the greenhouse at the Oregon Zoo to provide them with
enough warmth to induce oviposition. For the first several days after arrival, the weather was
cloudy and the greenhouse reached a maximum temperature of 66 degrees F. Subsequently,
lights were put on a timer to increase the light and temperature. Potted plants were moved out of
the boxes and put into mesh sleeves to force the butterflies into direct contact with the plants.
Butterflies were checked daily. Nectar plants and cut flowers were watered and/or replaced as
needed. The activity levels of the butterflies were monitored and they were offered honey water
mixture on a cotton swab. They were not held or forced to nectar, but within a day or two, the
females unrolled their proboscis and climbed onto the sweetened swab when offered. During
hot, sunny periods the fescue plants were watered from below and misted with water. Females
remained in the netted fescue plants until they died.
The fescue plants were moved out of the greenhouse on 1 July 2008. They were moved to the
conservation plant area. The netted pots are inside the skipper boxes and the skipper boxes are
inside the mesh/sun tent between the two new hoop houses. Both plants were inspected for signs
of larvae, including frass, leaf eating, and larval “nests.”
7. Results and Discussion
Poor weather and a late spring in 2008 made working with butterflies very challenging, as they
were often active for only very short spells and at unpredictable times. Capture of only 2
females severely limited our ability to obtain eggs. Even at the Zoo butterflies were mostly
inactive during periods of cloudy weather in spite of artificially increasing temperature and light.
On 6 June 2008, butterfly #2 was found dead at the base of the fescue plant, after only 3 days in
captivity. The weather during this time was cool and cloudy. She was largely inactive and it is
unlikely that she laid any eggs.
After 6 June 2008, the weather was warm and sunny for many days. The temperature inside the
greenhouse ranged from a low of 49 to a high of 120 degrees F. Butterfly #1 was active on many
checks. For the most part, she was observed near the top of the plant, fluttering against the
netting. On 23 June 2008 she was found dead, having lived 20 days in captivity.
The results of this year’s work are disappointing. While weather can be blamed for our limited
success in obtaining adults, the very slow pace of progress in captive rearing this species is of
great concern. No sign of eggs or larvae have been found during checks of the two host plants,
and while these will continue to be monitored until spring 2009 it is unlikely that we obtained
any eggs. Consistent failure to obtain eggs from south Puget Sound mardon skippers leads us to
believe there may be significant differences in oviposition strategies and cues between south
Puget Sound skippers and those from the South Cascades in Washington that will require a
controlled side-by-side study with females from both populations.
8. Future Plans
Oviposition plants will continue to be monitored until May 2009. Partial funding has been
secured for the 2009-2010 rearing season, however a new project strategy is needed. It may be
that differences in life history traits and oviposition cues for mardon skippers in south Puget
Sound and the South Cascades in Washington State differ to the extent that a more controlled
study between these populations is needed. The proposal and funding level for 2009-2010 does
not consider the need to include animals from the South Cascades or significantly expand current
objectives.
9. Further Information Available
None at this time.
10. Questions for Further Research
Do female mardon skippers from different regions in Washington exhibit significant differences
in oviposition strategies and cues?
Do mardon skippers from different regions in Washington diapause at the same life stage (i.e.,
larvae or pupae)?