Lacey's Lab:

Some behavioral ecologists are keen on birds. Others fancy fish. And Eileen Lacey? She's got a fondness for subterranean rodents.

"Why rodents? I don't know," says Lacey, an IB professor and the first-ever female curator at the university's Museum of Vertebrate Zoology. "I always had pet rodents as a kid." But wherever her childhood fascination with backyard squirrels came from, it has definitely been a driving force in her career. She "lucked into studying African naked mole rats" as an undergraduate at Cornell, then headed to the Yukon to study arctic squirrels in graduate school--and now is working to characterize the social structure and behavioral ecology of several South American rodent species.

Most subterranean rodents live in their burrows solo and go about life more or less alone. But a few species around the world share burrows, divide labor and sometimes co-parent. Why the group-living strategy is used by some species and not others is still a mystery, and one that Lacey has spent the last 15 years trying to solve by comparing two species of tuco-tucos in southern Argentina.

Berkeley zoology Professor Oliver Payne Pearson described the two tuco-tuco species--named after their tuck-tuck vocalizations--in the mid-1980s. He noted their different behavior: despite the fact that they both live in the Limay River valley, Ctenomys haigi is solitary, while the aptly-named Ctenomys sociabilis lives in groups.

"Despite Pearson's work, almost nothing was known about these species," Lacey says, so in 1993, she packed up her camping equipment and went south to tease out the ecological and evolutionary reasons why the species have adopted two different strategies for survival. She's returned every year since.

"That's really why I do any of this," says Lacey of living and working in the field. She doesn't mind sleeping on the ground for months, or getting her water out of a creek and her electricity from a car battery. "What I'm happiest doing is going and studying unstudied creatures. I love being the first person out there seeing and describing a system."

The two tuco-tuco species live a stone's throw away from one another on opposite sides of the Limay river. Both inhabit arid steppe grasslands, not unlike eastern Montana, pocked with patches of wet meadow. But they use the habitat differently: while the solitary tuco-tucos tend to tunnel in drier soil, the group-living species only make their homes at the borders of the wet patches.

"We still don't know why that is," says Lacey, but the relatively large distances between wet patches makes it more difficult for members of the group-living species to successfully disperse--which may explain why they tend to inhabit the same network of tunnels for generations.

Now, to understand more about the roots of rodent social behavior--Does it arise because of ecological characteristics, or due to a species' evolutionary history? Has it evolved just once, or many times?--Lacey is looking for patterns in rodent species across other landscapes and genera.

"Last May, we decided to chase down another of Pearson's reports," Lacey says. This one was also about a social tuco-tuco species that had been overlooked by scientists since Pearson published in 1959. C. Peruanus, the Peruvian tuco-tuco, lives on the high, dry Andean plateau called the altiplano. A second species, the highland tuco-tuco, lives nearby but is solitary.

Just like in Argentina, the determining variable seems to be habitat--the social critters live in the moist valley bottoms, while the solitary ones live in higher, drier areas. And that makes Lacey suspect that social living is a strategy that's evolved more than once in response to a common set of ecological pressures--or in other words, an example of convergent evolution.

Now that she's got a handle on behavior of tuco-tucos, Lacey is turning to new collaborations with neuroscientists Daniela Kaufer, also an IB professor, and Darlene Francis, in the psychology department, to understand how differing social systems affect animal physiology.

"Are these differences in social environment clearly associated with differences in fitness, survival, glucocortocoid levels? What are the effects of social and solitary systems on individuals' neurogenesis and neuroanatomy? All the grunt field work to describe the social system has set the stage for asking these new questions," Lacey explains.

Lacey, her collaborators and some of their graduate students are studying the effect of social structure on mothers' stress levels, which can be measured by monitoring levels of a class of hormones called glucocorticoids. They're also studying whether social systems have an impact on an individual's number of receptors for neuropeptides like oxytocin and vasopressin, which are critical for social recognition and the establishment of relationships between mammals.

"We're trying to make connections from large-scale ecology and the structure of social systems down to the level of genes. In some ways, that's what we all dream about-- understanding that complete picture," says Lacey.

Meanwhile, she's established herself as an expert on C. sociabilis, the colonial tuco-tuco, whose small geographic range has received formal protection from the Argentinian government. In Argentina, she gives talks about the animals and her research, cosponsors local graduate students and shares data and observations with national park authorities.

She also offers advice when tuco-tuco well-being is at stake: when a bridge was to be built across the Limay River, she helped develop a tuco-proof design ("like a miniature cattle guard") to keep the two distinct species from coming into contact and interbreeding.

At home in Berkeley, Lacey juggles research with curatorial responsibilities and teaching behavioral ecology and mammalogy. "Teaching is important to me," she says--and it shows. In 2007, she received the university's most prestigious teaching honor, the Distinguished Teaching Award. "Berkeley students are amazing," she says. "I always learn from them while they are learning from me."

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