The Toads of Delaware County
I've lived on my family's 25-acre farm in Delaware County, Ohio, for my whole life. I raise chickens and ducks on the farm. I've explored the property so much that I know it better than the palm of my hand. The property is mostly meadow, with a wooded fencerow, so I see lots of different birds throughout the seasons. During the summers I turn up stones and logs, looking for interesting discoveries. I mostly find sow bugs, ants, worms, centipedes, and various rodents. However, on occasion I see rabbits, snakes, toads, frogs, opossums, raccoons, foxes, and coyotes. One summer afternoon my dad was mowing (more like bushwhacking) when he found a gigantic toad, almost eight centimeters in length. I had lots of questions about this huge toad. That is how I got interested in knowing all about toads, their life cycle, and where and how they live.
The timing was perfect because I was in need of a science fair project topic for school. I happen to live down the road from a county preservation park that I visit on occasion. I came up with the idea of studying which habitat supports the largest toad populations in four of the six Delaware County preservation parks: Emily Traphagen, Blues Creek, Hogback, and Gallant preserves.
Before my investigation started, I conducted a sight survey that lead me to hypothesize that Emily Traphagen had the best toad habitat, followed by the Blues Creek, Hogback, and Gallant preserves. Emily Traphagen has a housing development next to it, and I thought that could positively affect the toad population. It also had the most forested area; about 65% of the park was forest. I thought Blues Creek would be second because almost half the park was woodland, and there were a lot of breeding spots. I thought Hogback would be third, because even though it was almost all woodland, I thought the wooded ridge and ravine in the preserve would negatively affect the toad population because their possible breeding areas would be down in the ravine. The elevation of the ridge would prevent water from accumulating during the breeding season. I thought Gallant Preserve would be the least populated by toads because it was mostly meadows, with about 40% woodland, and there were not many breeding spots.
Toads are different from other amphibians because they have coarse and grainy skin that never becomes slimy. Toads also do not have a pair of overdeveloped hind legs like those that power the leaping ability of their cousins the frogs. And unlike frogs, they have a distinct behavior of walking or creeping toward their prey.
The main species of my investigation was the Eastern American toad, Bufo americanus, and the occasional Fowler's toad, Bufo fowleri. Bufo americanus is common throughout Delaware County and Ohio. Bufo fowleri lives in cultivated fields and river valleys. Bufo americanus sometimes lives in river valleys but prefers heavily wooded areas (Wright, 1933). Adult toads eat earthworms, mealworms, crickets, pill bugs, ants, centipedes, beetles, slugs, but mostly just eat whatever moves and fits in their mouths (http://www.fcps.edu/islandcreekes). Adult toads can eat up to 10,000 insects in a year. They are preyed upon by raccoons, skunks, crows, garter snakes, and hognose snakes. (http://www.fcps.edu/islandcreekes)
To perform my investigation, I put my materials in my backpack and went to each park at dusk. Since toads are nocturnal, they were collected during the evening hours, between 7 and 10:30 p.m. I walked the trails and turned on my flashlight. When I found a toad, I would put it in the bucket. Then I took out a Plexiglas plate, a journal, and a pen to take data. I then carefully removed the toad from the bucket and placed it on the Plexiglas plate, measured its snout-to-vent (front-to-back) length in centimeters, and recorded its location and the habitat in which I had found it. Afterward, I released the toad where I had found it. I visited each park four times.
Later, during the fall, I took a Garmin GPS unit, my journal, and a pen to each park and walked the trails while looking at my journal to locate each toad's capture place. Then I took the location's GPS reading. At home I mapped the GPS coordinates using Google Earth, and I used the Delaware Appraisal Land Information System (DALIS) and ARC MAP to include the soil types at the points where all the toads were found.
During my experiment I encountered lots of unexpected and interesting things. During one of my four visits to the Emily Traphagen Preserve, I saw nothing but frogs. There were at least 12 frogs, if not 20! And at Hogback Preserve along the road I walked, I saw a toad almost every two steps.
Some important qualitative observations I made included determining the different habitats at each park. Hogback had a spacious garden with a small creek, a woodland ravine and ridge, and a slow-moving, almost stagnant stream in the ravine. Emily Traphagen had lots of breeding areas (places with a lot of standing water), an abundance of insects (which means plenty of toad food), dense undergrowth, and several small ponds with cattails. Gallant Preserve had many ditches and culverts. There were also some lights at a shelter that I thought might attract toads. Blues Creek was mostly wooded forests and meadows and had more breeding sites than any of the other parks. There were many insects there, too.
During my four visits to each park, I found 10 toads at Emily Traphagen, all in a woodland habitat. At Hogback I found 21 toads: 10 in woodlands, one in a garden, five in an open woodland habitat, three in a woodland ravine, and two on a woodland ridge. At Blues Creek I found 18 toads: 14 in a woodland habitat, two in a semi-open woodland habitat, and two in a garden. At Gallant I collected 17 toads: 10 in a woodland habitat, four in a garden, and three at a woodland edge. (see the pie graphs).
At Emily Traphagen and Hogback, 100% of the toads I collected were juvenile. At Gallant Preserve, about 94% of all the toads I collected were juvenile and almost 6% were adult. At Blues Creek, 80% of the toads I collected were juvenile, and 20% were young adults. I determined this by measuring their size. Toads that were four centimeters or less were juveniles. The average body length I measured at Emily Traphagen was 2.63 centimeters. At Hogback it was 1.93 cm, at Gallant Preserve it was 2.58 cm, and at Blues Creek it was 2.66 cm.
The average number of toads per kilometer at Emily Traphagen was 1.1 toads, at Hogback it was 5.03 toads, at Gallant it was 2.5 toads, and at Blues Creek it was 2.7 toads.
My data only somewhat supported my hypothesis that Emily Traphagen would be the best toad habitat, followed by Blues Creek, Hogback, and Gallant. The data showed that Hogback had the most toads, Blues Creek the second most, Gallant third most, and Emily Traphagen fourth. The part I got right was in putting Blues Creek in second place.
The results of my study showed that toads like dense woodlands more than any other habitat. Also, habitat diversity may have a positive effect on toad populations, as Hogback had the most diverse range of habitats and the highest number of toads of all the parks. Emily Traphagen had the smallest number of toads, perhaps because it is isolated by subdivisions (housing developments), and people spray insecticides to get rid of mosquitoes. These insecticides also kill other insects that are the toads' food source. Even though Emily Traphagen had the least number of toads, it had the same soil types as Blues Creek. Blues Creek has almost twice as many toads as Emily Traphagen but had the same percentage of toads for each soil type.
Variables such as food sources were probably more important than others, such as soil type. If I did the same survey in the spring, I may have found more toads in poorly drained soils (soils with high concentrations of clay), because that is where the toads' breeding areas are found. As toads get older, they move to well-drained soils (soils comprised of sand clay and silt), which are typically found in a forest. As autumn approaches, they move to looser, loamier soil, where they can burrow for protection from the elements during hibernation (www.scps.edu/islandcreekes). I also learned that because of a toad's life cycle, no matter how many toads are collected, juveniles will be more numerous than any other age, because only about 30 or 40 of the millions of eggs in each pond actually grow up to be adults.
Some uncontrolled variables that could have influenced my data are: water availability, soil types, human influences, food sources, predator populations, and weather conditions. The presence or absence of moonlight may have affected how many toads I was able to see during my evening collection.
Some practical uses of my discoveries might be that scientists could study how human populations affect the population of certain species of wildlife nearby, especially since the park that had the fewest toads was the park closest to human habitation.
Some new research questions that come to mind are: How do toads gather at breeding ponds? Also, since there has been a lot of controversy over whether toads are diurnal or nocturnal, I would like to study the question, are toads really nocturnal? I would also like to find out which gender of toads eats the most.
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More About This Resource...
Supplement a study of biology with an activity drawn from this winning student essay.
- Do students know how toads are different from frogs? What habitat do they think toads prefer?
- Send students to this online article, or print copies of the essay for them to read.
- Working alone or in small groups, have students research a different toad species (preferably one native to their region) and report on its habitat preferences.
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