December 2, 2014

Peer Review: Chima Amadi ’15 Finds Hamsters Are More Aggressive in the Winter

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By SHIRA POLAN

Chima Amadi ’15 spent this past summer studying aggressive behavior in the most unlikely of animals: Siberian dwarf hamsters.

Amadi, an animal science major in the College of Agriculture and Life Sciences, said a life-long interest in animals led him to initially pursue the pre-veterinary track at Cornell. However, he soon switched to pre-med in his junior year, fearing that he would not be able to save enough animals due to the prohibitive costs for owners.

“If I can’t save lives, it’s not a good career for me,” he said. “Who is going to pay 20 grand to get an MRI for a small animal when you can simply buy a new one for very little money?”

Despite no longer being pre-vet, Amadi joined a research team established by the joint efforts of Iowa University and Indiana University to investigate animal aggression.

Amandi said that the project was not quite what he had expected when he applied for the internship.

“Honestly, I hadn’t read the information too closely, and I thought that the research was on Siberian tigers. Once I got the internship, I discovered it was actually on Siberian hamsters,” Amadi said.

The research, taking place at the Center of Integrated Study of Animal Behavior at Indiana University, investigated changes in hamster vocalizations depending on season, sex and social conflict.

“We hypothesized that the hamsters would be more vocal in the summer than in the winter,” Amadi said. “They can vocalize to express aggression, and we wanted to find out if day length could affect aggressiveness, and if that differs between sexes.”

To do this, Amadi and his fellow researchers kept Siberian dwarf hamsters in enclosures and observed the interactions that took place when an “intruder” hamster was placed in the “resident” hamster’s enclosure. This occurred over a period of seven weeks, where the light exposure was altered to mimic seasonal changes in the wild.

While measuring the frequency of the hamsters’ vocalizations, the researchers categorized the sounds into broadband or ultrasonic frequencies.

“Before the first attack, the hamster would emit a broadband call, which had an affect on the interaction — the intruder would back off,” Amadi said. “We also found that females were actually more aggressive than males, and would emit more broadband calls during interactions.”

The researchers also found differences in aggression and vocalization during the short day photoperiod, which mimicked winter sun exposure.

“Short day hamsters were more aggressive than long day hamsters,” Amadi said. “This makes a lot of sense, since in the winter, both males and females need to compete for the same, limited resources.”

Amadi said that while there were no direct implications for humans in these findings, the research shows that Siberian dwarf hamsters can be used as an effective model for investigating the intertwined effects of factors such as season and gender on communication in mammals.

“Studying animal behavior can [also] tell us a lot about the environment,” he said. “If we know that behavior changes with changes in season, we can have a marker for issues such as global climate change.”

Currently, Amadi has moved onto research at Cornell, where he is studying the origin of ovarian cancer with Prof. Alexander Nikitin, pathology, at the College of Veterinary Medicine.

While he no longer works in the field of animal behavior, Amadi did visit the CISAB Exotic Feline Rescue Center after completing his internship, where he was finally able to observe tigers.

“I stood five feet from the tigers, and I actually noticed them perform similar behaviors to the hamsters. They weren’t all that different,” he said.

Amadi said he intends to take a gap year after graduation, and then attend medical school to earn an MBA and M.D. in oncology in order to study ovarian cancer.

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