Wildlife Conservation Grants for Graduate Student Research
Linking Chemicals & Animal Behavior

Ethan Clotfelter

Ethan Clotfelter, a behavioral ecologist and professor at Amherst College in Massachusetts. Photos by Frank Ward

Are contaminants in our environment lowering our quality of life? This is a question that Ethan Clotfelter, a behavioral ecologist and professor at Amherst College in Massachusetts, may be helping to answer. In 1994, the Zoological Society of Milwaukee gave Clotfelter a grant for conservation research, which helped him launch his career. “That field experience helped lay the foundation for my Ph.D., and that has helped lay the foundation for the rest of my work.”

Studies have shown that many chemicals, such as pesticides, can have negative effects on animals. These chemicals particularly interfere with the endocrine system. The endocrine system regulates body activities through glands such as the pituitary, thyroid, ovaries, and testes. Clotfelter’s work centers on the effects these contaminants have on behavior, as well as interactions between animal physiology and animal behavior. “Most of my research focuses on the selective pressures that shape animal social interactions, particularly reproductive, parental and aggressive behavior,” he says.

Betta splendens

Betta splendens

One of Clotfelter’s projects involves studying the effects of chemicals called phytoestrogens on fish. He studies fathead minnows (Pimephales promelas) and Siamese fighting fish (Betta splendens), also known as bettas (small photo). Phytoestrogens are naturally occurring compounds found in many plants. Phytoestrogens have hormone-like capabilities that in some ways can have effects similar to pollutants such as industrial waste, pesticides, insecticides and hormones found in municipal waste. “Significant phytoestrogen levels have been reported downstream from some pulp and paper mills, but little is known about their effect on fish populations,” he explains. Observing fish behavior is a good tool for studying endocrine-disrupting chemicals. Many fish species exhibit changes from exposure. Already Clotfelter has shown that phytoestrogen results in hyperactivity in fathead minnows, and he hopes to get similarly interesting results from Siamese fighting fish.

By studying how environmental contaminants alter the behavior of these species, scientists may discover ways to protect other animals and humans. Most of us know that chemical waste such as lead and mercury has an adverse effect on humans, but the consequences of many other chemicals on the human body are still unknown. The human endocrine system acts in a similar manner as that of “lower” vertebrates like the ones Clotfelter studies.

Clotfelter is also involved in a joint study with colleagues at Indiana University of how hormone levels influence the behavior of dark-eyed juncos (Junco hyemalis), a sparrow-sized songbird. He and other researchers put testosterone implants in both male and female juncos, and observed the behavioral and physiological changes that resulted from this hormone exposure. Previous studies showed that testosterone implants in male juncos decreased their parental behavior while increasing their energy allocated to courtship, mating, and territory defense. Clotfelter focused on females and found that testosterone implants delay their reproduction. “It also results in higher levels of testosterone in the eggs, which may have a cross-generational effect,” he says. “There is also evidence that it makes females more aggressive and potentially less attractive to males.”

Although these studies could be useful for humans, Clotfelter will stick with studying animals. “First and foremost, I am interested in the animals and animal populations.”

Teresa Dickert