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Herpetofaunal Survey Using Drift Fence, Pitfall, and Funnel Traps at Melody Site
Tiffany Barnett, Tam Nguyen, Anna Odaini
Lake Forest College
Lake Forest, Illinois 60045
The positioning of the North American continent on the globe makes it susceptible to a uniquely diverse variety of atmospheric conditions, creating an equally diverse variety of ecosystems. As such, North America can be divided into 15 broad Level I ecoregions, 50 more detailed Level II ecoregions, and still 182 more specific Level III ecoregions (EPA, 2016). Each ecoregion may play host to a number of species of herpetofauna, some of which may be more particular to their regions than others. In North America, the two main Level I ecoregions of the Midwestern United States are the Great Plains and Eastern Temperate Forests; of those two, Illinois has been entirely placed in the Eastern Temperate Forests Level I ecoregion (EPA, 2016). Illinois is a large centrally-located state, measuring 385 miles from north to south and 215 miles from east to west (Barten, 2013). At Level III, it is split into two more ecoregions: the Central Corn Belt Plains and Interior River Valleys and Hills (EPA, 2016). A study by Smith (1961) divided the two main ecosystems into seven defined herpetological sub-areas: grand prairie, outlier prairie, sand prairie, northeastern mesic forest, western division, southern division, and river borders.
Unfortunately, much of the original habitats found in Illinois have been domesticated, destroyed by man. The Chicago Herpetological Society reports that within the last century nearly all of the indigenous prairie was turned into agricultural land (Barten, 2013). Rapidly increasing populations and urbanization continue to mar remaining natural habitats. Nevertheless, a robust range of reptile and amphibian species are distributed throughout the state, having evolved to live efficiently in almost complete hiding. Of particular interest are the sand prairie subareas - well-defined areas located along the eastern borders of the Mississippi and Illinois Rivers, and the northeastern mesic forest sub-areas - found in just the northeastern most corner of the state lining Lake Michigan (Barten, 2013). Among the quickly developing society in this part of the state lay a few pockets of land that have yet to be charted, such as the well-preserved Melody Site in northeastern Illinois.
Reptiles and amphibians are native to every continent on Earth excluding Antarctica. However, due, to their ectothermic nature and reliance on their external environments for body temperature regulation, most species are reported to be found between the latitudes of 40°N and 40°S (Barten, 2013). The Melody Site is very near the 40°N border, making it an ideal field to observe herpetofauna that may be more adapted to the lower end of temperatures.
Material and Methods
This survey was done at the Melody site in Lake Forest, IL 60045. This private site included an almost pristine ecosystem, adjacent to Middlefork Savanna Forest Preserve, including a wide variety of natural habitats to survey. The site included habitats such as savanna, wet savanna, wet prairies, mesic prairies, aquatic, and shoreline. The wide variety of habitats should have allowed for a wide variety of herpetofauna. Surveys started September 10, 2018 and lasted until October 15, 2018. Each survey was conducted by the group on Monday around afternoon and checked throughout the week by Rob Carmichael.
There were multiple parts to this survey, including three different types of traps and meandering surveys. A drift fence was placed in Quadrant 23 along a mesic prairie and savanna edge, hoping to cut off herpetofauna making their way to or from the pond. The fence was made of mesh material and six wooden stakes. The six stakes were placed 4 ft apart, creating a fence 24 ft long. The fence was dug into the ground to keep small herpetofauna from going under instead of around. Pitfall traps, made of coffee cans placed flush with the ground, were placed at both ends of the drift fence and one in the middle on the west side. Making the trap flush with the ground was important for catching herpetofauna. The purpose of the pitfall traps was to catch herpetofauna that got stopped by the drift fence. Each can was filled with a small amount of water, a wet sponge, and some vegetation to ensure the safety of the animals, allowing them access to water and shade. The pitfall traps were numbered (1, 2, and 3) for our records. Along the east side of the fence, a funnel trap was placed (a funnel leading into a mesh bag). Inside the bag was a wet sponge, and vegetation was used to cover it. This trap was intended mostly for snakes, which could easily go through the funnel into the bag but could not get back out.
Although not a part of the personal survey, other surveying groups also set out traps; these include aquatic traps and coverboards. Aquatic traps included turtle traps and minnow traps, placed in the water. The traps were mesh netting or metal traps, each baited with a can of sardines. The sardines baited aquatic animals into the traps where it was easy for them to enter but hard to escape. Cover boards were also placed out various places on the site. Coverboards consisted of large pieces of wood that provided snakes a good place for shade and hiding. This allowed them to rest in a nice and shaded area. Although useful, they may take up to a few weeks or months to be fully utilized by enough snakes to yield results. All three traps were checked every day that they were out, either by the groups or Rob Carmichael, to ensure the safety of the animals caught. Data sheets were also created and used to record the findings.
A meandering survey was done by each of the groups by picking a section of the land and slowly walking through it, searching for herpetofauna. The group walked as a transect through the area, looking for any sign of wildlife. Materials brought along were nets, snake bags, snake hooks, identification cards, and data recording sheets. The group made sure to be as quiet as possible to avoid scaring off any potential animals and walked slowly, stopping every few steps to survey the area around. If a reptile or amphibian was spotted, an attempt would be made to catch the animal. If successful in catching, data including age, weight, length, and gender would be included. If not successful, an identification would be made using visual characteristics and identification cards. GPS coordinates were taken of each animal sighted and each was released in the same spot. Along with coordinates, other data recorded included time, weather, humidity, behavior, and habitat.
Using the drift fence method with pitfall and funnel traps, seven different animals were caught, including five different species (Table 1.1). The first week, two Chelydra serpentina (Common Snapping Turtle) were caught in Pitfall Trap #1. The two were juveniles, not even a week old. One of them had a tooth for breaking out of the egg still visible. Also found this week was the shed skin of Thamnophis sirtalis (Common Garter Snake), found in Pitfall Trap #2, and Faxonius virilus (Northern Crayfish) was found in an unspecified pitfall trap by Rob Carmichael. In the second week, Ambystoma tigrinum (Tiger Salamander) was found in Pitfall Trap #3. The salamander was a very large 140 grams and an adult male with a very golden underbelly. On the third week, Anaxyrus americanus (American Toad) was found in Pitfall Trap #3 and was a juvenile, no more than a year old.
Using the meandering method, seven individuals were spotted with four different species (Table 1.2). The first week included three sightings. Along the shoreline path, two Rana catesbianus (American Bullfrog) were spotted and Lithobates pipiens (Northern Leopard Frog) was spotted in a prairie. The following week, Anaxyrus americanus (American Toad) was spotted on the prairie trail. The third week, two Thamnophis sirtalis (Common Garter Snake) were sighted, one at a prairie/savanna edge and one in the mowed lawn. Lithobates pipiens (Northern Leopard Frog) also was spotted along a path in the prairie.
Not included in Table 1.2 were non-herp species found when meandering. One included an unidentified gray-transparent fish that was accidently caught when trying to catch a toad, found in the first week. The second week, two bones were found, one on the west side of the site and one on the east. One bone was identified as a deer bone by Rob Carmichael, which had teeth scratch marks. The other was a fully intact bird skull, which was unidentified. During the third week, a large Ardea herodias (Great Blue Heron) was spotted resting along the pond edge.
Throughout the weeks of surveying, twelve different species were identified, most found on multiple weeks. Rana catesbianus was found on five out of the six weeks with multiple types of surveys including meandering, turtle trap, and minnow traps. Rana clamitans (Green Frog) was only spotted twice with meandering and turtle traps. Anaxyrus americanus was found on two of the weeks by meandering. Thamnophis sirtalis was found on five out of the six weeks by meandering and pitfall traps.
Various different species of herpetofauna were discovered during the surveying at the Melody site. There were many different species due to the range of habitats that
provide support for the species. For the specific area of study, in the savanna and mesic prairie, many different species were found, one being an Anaxyrus americanus (American Toad) which was captured in one of the pitfall traps, the American Toad being a habitat generalist (Mierzwa and Beltz, 1994). This was a valid capture because American Toads are usually located in woodland, prairie areas that are near water (Dreslik et al. 2018). The toad could have potentially been returning to the water when it fell into the pitfall trap. Another species captured in one of the pitfall traps was the Chelydra serpentina (Common Snapping turtle). There were two snapping turtles, both of which were juveniles that could have been no more than a week old due to their size and the fact that they both still had an egg tooth. The snapping turtles may also have been on their way to the water beyond the mesic prairie coming from their lay/hatch site near a brush pile in the savanna habitat. This was a very interesting find that was not expected, but it makes sense in the case that snapping turtles lay their eggs around June; the development and hatch time would coordinate to the time which they were trapped (Dreslik et al. 2018). Another captured species was the Ambytstoma tigrinum (Tiger Salamander) in the pitfall trap. The weather was fairly warm when the Tiger Salamander was captured, but it was definitely not expected during this time of the year. It was interesting to see how large and chunky the Tiger Salamander was; its size suggests that it was eating significantly well and was very healthy. This provides evidence that there were resources in the environment of the Tiger Salamander, forests and prairie habitat, which allowed it to thrive (Dreslik et al. 2018). There are various resource points in a habitat which different species can use depending on their needs (Most, 2013). This means that the Tiger Salamander was able to find many of those resources in his habitat at the Melody site. This may also suggest that it is a favorable site for many other species who have similar patterns to the Tiger Salamander. There was also a Faxonius virilus (Northern Crayfish) captured in the drift fence, which is very good because it suggests that there will be nesting sites for snakes to hibernate in, built by the crayfish. Based on the patterns we saw from our trap captures, the Melody site seems to be a good environment for many different species that can work together with each other in their habitats to survive and thrive.
During the meandering surveys, various species were spotted. A couple of Lithobates pipiens (Northern Leopard Frogs) were observed, one near its usual habitat and one quite a distance away. Northern Leopard Frogs have precise habitat needs, just like the Tiger Salamander, so they usually stay near the area in which their resources are (Mierzwa and Beltz, 1994). One of the Northern Leopard Frogs was seen in a prairie that was far from the pond. Usually, Northern Leopard Frogs are found near streams, ponds, and wet prairies but if the environment is sufficient, sometimes they can be found in areas away from the water (Dreslik et al. 2018). This would be an indication that the Melody site has a healthy ecosystem and is sufficient in supporting many different species, as well as promoting a good survival rate and livelihood for those species. There were also multiple Thamnophis sirtalis (Common Garter Snakes) spotted during meandering. One was close by to the trap near a brush pile and the other one was found in the mowed lawn near the prairie of the site. The Common Garter Snake is usually found near forests, edge habitats, and near water, which means that the Melody site would be a perfect environment for them to thrive in (Dreslik et al. 2018). Also, since the savanna is mainly edge habitat, it would make sense for many snakes to be spotted there (Mierzwa and Beltz, 1994). With the amount of Common Garter Snakes observed and trapped even by the other groups it shows that the habitat in the Melody site is indeed beneficial for their survival. Another reason why so many Common Garter Snakes were spotted could be due to the time in which they are active, usually between March and November (Dreslik et al. 2018). It was getting near the end of the season but since the weather was so warm it could have prompted more of them to stay out and bask in the sun or continue their search for food. A couple of Lithobates catesbeianus (American Bullfrogs) were also observed. These observations were fairly predictable due to the natural environment of the American Bullfrog, which is in forests and prairies near permanent bodies of water (Dreslik et al. 2018). Movement within or between habitats can create a greater risk of predation (Most, 2013). The fact that there was so much movement seen by many different species could indicate that predation isn’t a major problem at the Melody site. Finally, tThere were also some interesting and unexpected findings during the meandering that were not related to herpetofauna. There were sightings of a Ardea herodias (Great Blue Heron) which shows that the Melody site provides resources to other types of animals, not just herpetofauna. In addition, there were animal bones found, one possibly from a deer and the other was a skull of a bird. This information could suggest that there are some predators, such as coyotes, in the Melody site that may have an impact on the populations of the herpetofauna, although predation is unlikely to be too prevalent based on the number of species captured and sighted.
Overall, there were many species sighted during meandering and being able to observe multiple of the same species could mean that they have adapted well to the environment at the Melody site. For the future, to improve this study, it could be beneficial to set up more drift fences in different areas along the site. There was a part of the savanna in the northern end of the site that had a lot of vegetation, which could potentially house many different species. These species could be captured there with another drift fence with additional pitfall traps and funnel traps. In addition, there could be another drift fence set up closer to the pond on the Melody site which could capture species that are moving in and out of the water. There were a lot of crayfish tunnels observed near the pond, so a drift fence with funnel traps could potentially catch other species of snakes other than the Common Garter Snake as snake often travel through these tunnels. There could also be another survey done in the spring and into the summer when all of the species are coming out of hibernation and laying their eggs. There could be a lot of hatchlings and juveniles at this time trying to move into the water from their hatch site. Moving forward with this study, some questions that came about were, why were some species so commonly seen and why were some species not at all sighted? If there were more time spent at the site and in a different season how different would our results be? Would the variety of species change and the number of species observed? These are all questions that could be explored if the site were studied for more time in the future.
We would like to thank the site provider, Robin Colburn, for allowing us to conduct this survey on her land, as well as Dr. Sean Menke, from Lake Forest College, and Professor Rob Carmichael, from the Wildlife Discovery Center, for helping us set up traps at the site and assisting in catching, trapping, and identifying species.
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