University of South Carolina

South Carolina’s globe-trotting mice

By Steven Powell,, 803-777-1923

Some former inhabitants of South Carolina made the news again this month. A Harvard scientist’s research paper was highlighted by the New York Times, the BBC and elsewhere, and the subject was, once again, some of the photogenic rodents that are housed in a unique installation at the University of South Carolina.

At the center of attention is the deer mouse, which is the most populous mammal in North America. Deer mice and related species are part of the Peromyscus genus, which are only distantly related to the common house mouse. Shy and retiring, these nocturnal mice tend to avoid human contact and structures, so despite their abundance they’re rarely seen by people.

“There are almost certainly some living in your backyard, but you’ll probably never see them,” said Gabor Szalai, the associate director of USC’s Peromyscus Genetic Stock Center. “I’m sure I would be able to find them there, though, because I know what attracts them – they love peanut butter.”

Since 1985, USC’s center has served as the world’s sole laboratory source of Peromyscus mice. “The uniqueness of these animals is that they represent a wild-type species,” Szalai said. “Although they are housed in our facility, we breed them as they would breed in the wild.”

Despite living for generations in captivity, the mice retain behavior from the wild, such as the way they construct burrows in the ground. Retired USC researcher Wallace Dawson, the founding director of the Peromyscus Genetic Stock Center, published a seminal paper in 1988 in Behavior Genetics about the inheritability of this behavior.

The recent work by Harvard University’s Hopi Hoekstra built on this research. Hoekstra’s team used deer mice (P. maniculatus) and oldfield mice (P. polionotus) – two species that are closely related enough to interbreed – from the USC center to isolate the genetic underpinnings of their burrowing behavior. Their report was just published in Nature and is being widely circulated in the media.

These two species, despite being so closely related, are quite different in another respect: deer mice are polygamous, and oldfield mice are monogamous. “Monogamy in animals is very unusual,” Szalai said. “They form the pair bond very young, and you can see the behavior somewhat in how the families act.”

Families of the two species of mice, a mother and father with their litter in a single cage, had different reactions to having the lid removed when observed for this story. Deer mice separated from their sleeping group and, as individuals, curiously explored for new ways out. The oldfield mice, in contrast, stayed together as a group, despite looking inquisitively toward the new stimuli as well. Superficially, the oldfield mice’s behavior showed differences that might be expected from closely bonded animals.

Given that the two species can be interbred, the monogamy-polygamy difference represents a real opportunity for further genetic study. “We’re working on getting that research to move forward,” Szalai said.

Providing the tools for research is a fundamental focus of the stock center. Since Dawson established it in 1985, more than 27,000 mice have been part of research studies throughout the world, resulting in dozens of publications. “We send mice everywhere, but the recipient has to adhere to the same quality of care that we have here,” Szalai said.

But preservation is an important aspect of the center’s mission as well. In 2004, as Hurricane Ivan threatened the Florida panhandle, some refugees from there were sent to South Carolina.

“The genus Peromyscus contains the most populous mammal in North America, the deer mouse,” Szalai said. “But also within the genus you have the most endangered species of North America, which is a beach mouse of Florida. They estimated that the whole species had about 100 individuals.”

In the face of the oncoming storm, a number of these Perdido Key beach mice were captured, sent to the stock center and propagated. Their descendants now live in several aquaria and zoos in the state of Florida.

“It’s a very nice success story,” Szalai said.

Posted: 01/22/13 @ 4:50 PM | Updated: 02/13/13 @ 4:37 PM | Permalink