His boyhood love of frogs intact, faculty mentor Tyrone Hayes exposes students to a biologist’s life in the field

By Nancy Chapman, Public Affairs

Associate Professor Tyrone Hayes with Bufo alvarius, otherwise known as a Colorado river toad. Peg Skorpinski photo

27 February 2002 | Tyrone Hayes, associate professor of integrative biology, conducts research on the metamorphosis of frogs. But you’ll find few frogs in his Valley Life Sciences laboratory. What does populate his lab are several student research assistants and his two young children, Tyler, 9, and Kassina, 6. They are as accustomed to accompanying their father to labs, classrooms and field research outings as they are to eating dinner together.

Hayes the family man had a good role model in his own parents. “My parents didn’t direct my interests,” he says, “but they encouraged them.”

Brought up in the swampy lowlands of South Carolina before the invasion of industrial parks and strip malls, he can’t remember a time when he wasn’t fascinated with animals. Frogs, soft-shelled turtles, salamanders, herons, muskrats, bullfrogs, armadillos, and the occasional alligator inhabited the drainage ditches and flood plains around his home.

Throughout his childhood Hayes systematically observed the swamp fauna. He kept many animals for short periods — lizards, tadpoles that he watched as they metamorphosed into frogs, fish. Using field guides for identification, he tried to catalog all the animals he found in nearby Congaree Swamp, now a national park. In the third grade he kept a bird record.

“When I was working on a senior project in high school, my father helped me dig a pond in the backyard. We poured concrete into the hole, and I added turtles that I was studying,” he says.

Partly on the strength of his personal statement on armadillos, he was accepted to Harvard, where he majored in organismic and evolutionary biology. Then he came to Berkeley for his Ph.D. After a stint as a postdoc at the National Institutes of Health, he returned to campus, where he has been teaching and conducting research for six years.

Field studies
Today, Hayes’ research centers on sex differentiation in reptiles and amphibians. He conducts fieldwork in the U.S. and Uganda, Kenya, and Tanzania — the countries that border Lake Victoria — as well as southern Africa. Using a species of bullfrog from southern Africa, he studies male and female growth patterns to determine how anomalies in the usual patterns are encouraged genetically and in the environment, and how they are related to frog behavior in the wild.

Amphibians are particularly good research subjects because of their vulnerability to the environment, Hayes says. Many other animals gestate in a protective environment such as the womb or an egg. Amphibians, in contrast, produce eggs that are completely exposed.

“Every critical stage of development, from fertilization on, is exposed,” Hayes says. “Thus they are very sensitive to whatever environment they are in.”

Outstanding mentor
An outstanding teacher recently honored with a College of Letters and Science Award for Distin-guished Research Mentoring of Undergraduates, Hayes helps his students acquire laboratory, grant writing, publication and presentation skills. And he makes it a point to include support for student researchers in his grant applications to the National Geographic Society, which has funded all his trips since 1992.

“It’s really hard to get funding for that first trip, because you aren’t yet experienced,” Hayes says. “I always try to give students experience in the field.”

Before each of his research trips to eastern Africa, Hayes sends an advance team to do reconnaissance — for information on local people who will assist the expedition, signs of political unrest or military activity, official permits to observe wildlife or bring home specimens.

“Official stamps are critical to take into villages, especially when we’re bringing animals out,” Hayes said. “We usually bring back 10 live frogs — five males and five females — from each species, and also specimens that we have preserved for DNA samples.”

On a typical research expedition to Africa, his team has no “camp” — no tents or kitchen to call home.

“We move too often, and it’s too wet,” he says. Instead, the Berkeley team eats canned provisions or food purchased in the villages. “Sometimes you can buy goats on the street that were killed and roasted just that morning. Sometimes a town has no food, so we move on.”

Environmental health
Hayes is interested in ways that pesticides may interfere with the thyroid hormone that regulates development in frogs. This line of inquiry is of great significance to human society, as pesticides are ubiquitous and the hormonal mechanisms that control metamorphosis are important.

His team uses variations in the normal pattern of color changes in frogs as indicators of abnormal agents in their African environment. “Females of several species of frog change color at puberty in response to estrogen,” says Hayes. “We have exploited this natural process by using animals to test whether certain chemicals exhibit estrogenic properties.

“In other words, if a chemical prematurely induces a color change in a juvenile, we can identify it as an estrogen mimic. Because estrogen is involved in puberty in other animals and can induce breast cancer, then such chemicals in the environment may represent generalized threats to environmental health and public health.”