Results of the Spring 2025 Snake Survey
- Sheila Leary
- May 14
- 6 min read
by Stephen Davis
Snake Survey at Cherokee Marsh-North Unit
Conducted April 22nd to May 7th, 2025 for the Friends of Cherokee Marsh by Stephen Davis
Purpose of Survey The purpose of the Spring 2025 snake survey was to obtain an estimate of snake species and their respective numbers present in Cherokee Marsh North Unit. Survey results will be shared with interested parties such as Friends of Cherokee Marsh, City of Madison Parks, and the Wisconsin Department of Natural Resources. In addition, snakes captured were examined for Snake Fungal Disease (SFD), measured, and photographed. Any snake suspected of infection with SFD was reported to the Wisconsin DNR.
Survey Design The survey involved placing four 2' x 4' plywood sheets and one 2' x 3' plywood sheet in various habitats deemed likely to harbor snakes. I chose areas that were recently burned or cleared for sheet placement. My rationale was the plywood sheets would provide cover in an area of cover scarcity. Cleared or burned areas chosen were in close proximity to woodland, marshland, or grassland.
I planned to return to inspect under each plywood sheet 3–4 days after placement and capture any snake(s) present. Snakes were to be photographed and measured. Data would be recorded and snakes released unharmed. The survey would last two weeks and involve four visits to inspect beneath the plywood sheets. At the conclusion of the survey, plywood would be removed and findings summarized in this report.
The Survey The survey commenced on Earth Day, April 22. The temperature was 51ºF, weather mostly cloudy, and ground wet from recent rain. Plywood sheets were placed in the following areas:
recently burned area adjacent to the Frog Pond
recently burned prairie area enclosed by the Bluebird Trail
recently cleared area on edge of elevated woodlands north of Bluebird Trail
the Oak Savanna just off the trail from South parking lot to Woodpecker Trail
recently burned elevated grassland bordering Woodlands off of South Hill Trail
On my way to place the Frog Pond plywood, I encountered a Garter Snake on the edge of the Overlook Trail. The snake was sunning itself, trying to warm up, and was still sluggish. Upon return from Frog Pond, I also encountered what I believed to be a DeKay’s Brown Snake. It was also on Overlook Trail’s edge and quite sluggish. Since I did not have disposable gloves or measuring tape, I did not capture or handle either snake. I did photograph both snakes, with my 13" shoe included as a size reference. I subsequently received much appreciated feedback that the DeKay’s Snake was, in fact, a Red-Bellied Snake.
On April 25 at 8:40 AM, I returned to inspect each plywood sheet. Temperature was 48ºF, overcast with recent rain. No snakes were observed under plywood or on the trails. The next return visit occurred on April 28 at 8 AM. Temperature was 58ºF, partly sunny with hazy overcast skies. No snakes observed under plywood sheets. However, I did observe a snake elsewhere in the park. I captured, measured, examined, and photographed an approximately 22-inch Fox Snake. The snake had lesions under its chin and neck areas that suggested the presence of Fungal Snake Disease. I forwarded photographs to the DNR and received confirmation of SFD.
April 30, 9:20 AM. Temperature was 48ºF, with a high overcast and light wind. No snakes observed under plywood or on trails. Upon departure at 10:50 AM, temperature was 50ºF with partly sunny skies and a moderate breeze.
May 4, 10:05 AM. Temperature was 55ºF, mostly sunny and breezy. The North parking lot was full, and there were many visitors on the trails on a Sunday. Therefore, I had low expectations of finding snakes along the trails. No snakes were observed under plywood sheets. I captured, examined, photographed, and attempted to measure a very active Fox Snake, 24-26", partially concealed in grass along the Overlook Trail. This snake also had lesions suggesting SFD infection. Photographs were sent to DNR staff, who confirmed snake as having SFD. I also captured, examined, photographed, and measured a beautiful Red-Bellied Snake, approximately 9", that was in short grass bordering the South parking lot. I observed a Garter Snake on the lower portion of the South Hill Trail, but it was too quick for me so it was not captured. The visit concluded at 11:45 AM. Temperature was 60ºF.
May 7, 2 PM. Temperature was 71ºF, partly cloudy and breezy. No snakes were observed under plywood sheets. A pair of mice were found under sheet off of South Hill Trail. A small, dark snake was observed by the Overlook Trail. No capture attempted. All plywood sheets were removed and loaded into my car by 3:15 PM. This marked the end of the survey.
Results and Study Limitations A total of seven snakes were observed on trails. Five of the seven snakes were observed close to the intersection of the Overlook Trail and the 0.1 mile shortcut to the Overlook.
My finger is pointing at this apparent “hot spot”. A known hibernaculum is nearby, marked with an X. The grasslands on either side of this area were unburned, providing ample hiding places.
This portion of the trail faces South-Southeast, which provides for excellent morning sun exposure that helps snakes bask and warm up. No plywood sheets were placed in this area due to extensive grassy vegetation.
No snakes were observed under any plywood boards. Possible reasons for this include:
minuscule chance of snakes finding small number of plywood sheets for cover. Cherokee Marsh North is about 946 acres, one acre equals 43,560 square feet. Total area of plywood sheets equals 38 square feet or 0.087% of one acre.
cool, rainy days on April 25, May 1, and May 3 may have affected snake activity. No snakes were observed under plywood or on trails when the temperature was under 50ºF (48ºF on 4/25 and 4/30 visits).
several plywood sheets became infested with ants, spiders, and—under one sheet—mice, as the study progressed. I am unsure if their presence repelled any visiting snakes.
I conducted an online search of snake surveys and discovered alternatives to plywood sheets. A three year survey of herptiles in Cook County, Illinois, conducted by Allison Sacerdote-Valet, Chicago Academy of Sciences, used arrays of drift fencing placed along habitat borders plus funnel traps (35x50cm minnow traps). Traps were recessed into the ground, covered with grass/leaf litter to conceal traps. A Recommended Standard Survey Protocol for the Eastern Massasauga (Casper, Anton, et.al., 2001) used a combination of methods including funnel traps and visual surveys. Their protocol also stressed conducting surveys with temperature 50–80ºF and cloud cover greater than 50%.
Future snake surveys at Cherokee Marsh North could consider using drift fencing and funnel traps along with visual surveys. I would consider focusing on the fenced-in area adjacent to the hibernaculum and have the survey materials set up prior to snakes emerging from hibernation. Recruitment of trained herpetologists and field biologists to conduct the survey could be considered.
Snake Fungal Disease Snake Fungal Disease (SFD) infections have been found on some snakes in the City of Madison's North Unit of the Cherokee Marsh Conservation Park. SFD was first noted in the Eastern United States and Illinois in the early 2000s and has since spread to areas in Wisconsin and surrounding states. The fungus causes lumps, skin blisters, or scabby areas on the face, neck, and body of affected snakes. SFD may cause snakes to become unable to feed or drink, which has the potential to cause great harm to local snake populations. For more information, please visit the Wisconsin Department of Natural Resources webpages on Snake Fungal Disease.
How to Limit the Spread of Snake Fungal Disease at Cherokee Marsh
All visitors are encouraged to
avoid handling any snake they encounter
take photographs and report snakes observed with signs of SFD to the Wisconsin DNR as outlined on the DNR SFD webpage
use footwear brushes to clean footwear before leaving Cherokee Marsh. Brushes are located by the kiosks in both North Unit parking lots.
SFD Considerations for Snake Surveys The following guidelines are a reference for disinfecting field gear when working with any reptile species. The guidelines are designed with Ophidiomyces ophiodiicola (suspected SFD pathogen) in mind, but there could be other pathogens we are currently unaware of, so the greatest precautions should be taken.
Sampling Gear: any gear that physically touches animals, including snake tongs, nets, hooks, holding bags, tubes, buckets, gender probes, PIT tag injectors, etc.
Disinfect hiking/rubber boots between sites. Repeated spraying of boots will likely compromise quality of the boots, so this may be impractical. Some field Biologists use different boots for each site.
Use disposable latex gloves when processing animals; change gloves between animals, and use hand sanitizer between animals.
Wipe down all equipment that has touched the snake using 70% isopropyl alcohol wipes, including buckets and tape measures
If working only a few sites, it may be more practical to have designated tubes, nets, hooks, etc for each site. Inanimate objects may be disinfected with either 70% isopropyl alcohol or 10% bleach in water solution.
(Information provided by WisDNR).
I wish to thank the following individuals for their assistance and advice they provided that made this survey possible:
Sheila Leary, Board President, Friends of Cherokee Marsh
Paul Quinlan, Conservation Supervisor, Madison Parks
Richard Staffen, Conservation Biologist, Wisconsin DNR
Becky Sapper, Director of the Wisconsin Master Naturalist Program, UW Madison Extension
Eric Roscoe, Madison Area Herpetological Society
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