Two species of mice found in the mountains of Central America sing to mark their territory, according to a new study by UT researchers.

This finding came after postdoctoral student Bret Pasch researched two species of mice — the Alston singing mice and their cousins, the Chiriqui — and wrote his dissertation under associate biology professor Steven Phelps.

Pasch first became interested in the mice in 1999 while taking a tropical biology course in Costa Rica.

“I listened for the mice in the forest and caught a few,” Pasch said. “I have been returning on-and-off to study them ever since.”

Pasch worked with Phelps, who began to study the singing mice 10 years ago when he first came upon them in a field guide of mammals in Central America. 

“I was looking for a species that I could study that showed interesting variation in their social behavior… [so] I could use neurobiological and genetic methods with to understand the evolution of that behavior in detail,” Phelps said.

According to Pasch, the results of this study suggest a wider understanding of the geographical boundaries the mice inhabit.

“Our findings provide new insight into the role of vocal communication in shaping the geographic distributions of animals,” Pasch said. “Because closely related species often share similar ecological requirements — eating similar foods and living in similar places — as well as similar means of communication, the researchers suggest interspecific communication will be a common contributor to natural range boundaries.” 

The Alston and Chiriqui mice sound like small birds during their song, according to Phelps.

“Songs consist of a set of rapidly repeated notes, called trills,” Pasch said in a statement. “Notes are produced each time an animal opens and closes its tiny mouth, roughly 15 times per second.”

Pasch conducted a significant amount of independent field work before coming to a conclusion for his dissertation. Phelps said the combined field work is an impressive look at how animals behave in their natural environments.

The relationship Pasch found between the mice’s singing and the geographical boundaries are not the end of the Phelps’ lab studies on singing mice.

 “The next step for us is to understand whether the behaviors responses the mice show are learned or whether they’re evolution adaptations,” said Phelps. “And on top of that, I would like to know how the brain is processing those different signals.”