While numerous studies have been conducted on the effects of captivity on other classes of vertebrates, very few studies have investigated the effects of captivity and its related stresses on amphibians. Chronic stress results in elevated levels of corticosterone (CORT) released from the adrenocorticol cells, which in turn result in hyperglycemia, anorexia, and changes in behavior. This study investigated the effects of household stressors (irregular light patterns, noise, and handling) on the White’s tree frog, Litoria caerulea, a common exotic pet that is nocturnal in the wild. It was hypothesized that Litoria caerulea exposed to the aforementioned household stressors would exhibit elevated blood glucose levels, decreased appetite and thus decreased body mass, and other stress-induced behavior changes in comparison to frogs housed in a more natural, less disturbed environment (control). After 12 days of observation (and handling of the treatment group), the frogs were massed, blood samples were collected, and blood glucose and hematocrit levels were evaluated. Control and treatment frogs exhibited no significant difference in mass (p=0.785), hematocrit (p=0.375), or blood glucose levels (p=0.680). The frogs also did not show any significant difference in the frequency of behaviors exhibited between the control and treatment groups. However, over time the control group showed an increase in traveling throughout their enclosure (p=0.020) and a decrease in the frequency of bathing (p=0.049), which was not seen in the stressed frogs. Therefore, in this study, household captivity did not appear to have any significant physiologic effects on Litoria caerulea; however, activity level was decreased over time in stressed White’s tree frogs.
Hometown: Louisville, TN
Senior Thesis Title: “Response of White’s Treefrog (Litoria caerule) to Common Household Captivity Stressors”
Advisor: Dr. Drew Crain, associate professor of biology
Everyone has a special connection to his or her pet and shows affection to that special animal. Dogs receive treats for obeying commands, cats dine on tuna or Fancy Feasts on occasion, and fish get an extra shake of flakes out of the fish food can. In Erin French’s case, frogs get placed in scientific experiments to measure the effects of household stressors on their bodies.
While that may seem odd, French’s senior thesis focused on the levels of stress found in White’s Treefrogs while in human captivity, namely as pets.
“I’d owned White’s Treefrogs in the past, and because I plan on going into veterinary medicine, exotic animals primarily, I wanted to focus my thesis on an exotic animal typically kept as a pet,” French said.
Since White’s Treefrogs are nocturnal by nature, French wanted to test and examine the effects of elements such as noise, irregular light patterns, and other elements that are typical to normal human life. Her advisor, Dr. Drew Crain, associate professor of biology, has conducted similar stress studies in other animals, and he served as an experienced tutor to assist French in her analysis and research. Even though Crain had not conducted any studies on White’s Treefrogs, he was able to implement similar approaches to French’s study.
“We were able to apply some of the techniques that are used in field studies, both physiological parameters like measuring physiological blood parameters as well as behaviors,” Crain said. “She generated an ethogram where you monitor if they are behaving differently when they are stressed and when they are not.”
“It gave me a step up above other students who have never done undergraduate research before.”
– Erin French
As with any scientific experiment, problems will come up that force the experimenter to adapt his or her techniques. In French’s case, blood samples needed to be taken at the end of her experiment to analyze the frogs’ corticosterone (i.e. stress hormone) levels, but an adequate volume of blood could not be drawn to properly analyze it. Instead, French decided to look at blood glucose and hematocrit levels to formulate her results.
“Because the hormone causes an increase in blood glucose, it is an indirect measurement of that hormone,” Crain added. “We didn’t have enough blood to measure the hormone, but we did have enough to measure blood glucose and base results off of that.”
Through her adaptability, French was able to conclude that common household stressors had little effect on the physiology of White’s Treefrog. Aside from writing her senior thesis based on this study, she also presented her results to an audience of professors at the 2007 Appalachian College Association (ACA) Summit in Abingdon, Va.
Although it was difficult to stand in front of a room full of professors and describe her findings, French gained a practical skill that will prove useful in her field of work.
“Now I’m better prepared to present my studies to others in my field,” she said.
French’s study also gave her a useful tool in her veterinary school applications and interviews, as she had a concrete example of her work that was beyond the normal undergraduate applicant.
“The fact that every student here does a senior study gives them an edge over every other undergraduate at other institutions.”
– Dr. Drew Crain.
“It gave me a step up above other students who have never done undergraduate research before,” French said. “The interviewers were able to look over it and ask me questions about my work and see the kinds of studies I have done.”
“That is tremendous,” Crain said. “The fact that every student here does a senior study gives them an edge over every other undergraduate at other institutions. Vet school is extremely competitive to get into, even more so than medical school some would say. By Erin having an excellent senior study, she was able to take that into her interview and be one of the most interesting candidates. Instead of saying ‘I’ve taken this course or that course,’ Erin was able to show them a study that is typical in the veterinary field.”
French was accepted to her school of choice, University of Tennessee’s veterinary school, where she will attend later this fall. While her body of work at Maryville College granted her an interview, her senior study played a major role in her acceptance to veterinary school.