San Diego Reader

Shawn Powell and I are driving south on Jackson Drive, carrying three opossums in Powell's Hyundai Santa Fe. Our mission is to liberate them. We could stop and dump them out on the sidewalk, but that would be injudicious. They'd be apt to wander into the road and become roadkill. A volunteer for Project Wildlife, the local animal-rescue group, the 34-year-old Powell expends an extraordinary amount of time and energy nursing young and injured opossums to where they're fit to survive in the wild, so she likes to give them the kindest possible launch. She has a spot in mind for the two juveniles contained in one of the plastic kennels on her back seat: a park abutting Lake Murray. It's dusk when we reach it, and Powell scans the grassy expanse to see who else might be using the area. "This doesn't look too bad," she says. "Usually I come here when it's a little darker, but I think this is okay."

In the distance Powell and I make out the figures of a dog accompanied by its owner. Dogs are everywhere, Powell points out with a shrug. "When I first started doing this, I thought the farther away from people and dogs, the better, but I've changed that view 180 degrees over the years. Now I think [the opossums] do better around people because there's more garbage. There's more food. There's water sources." She also likes "anyplace along the river anywhere in San Diego, because you've got that immediate water source. I also really like canyons. If there's landscaping where I can see it's being cared for and watered, I'm okay with releasing them."Powell told me she thought the two opossums inside the kennel were around seven or eight months old. The little male had been rescued from a swimming pool. He'd almost doubled in size in the ten days he'd been in Powell's care. His female companion had been picked up from a house near El Cajon Boulevard and 50th Street. "She just had a lot of fleas on her," Powell said. Otherwise, her only problem was her small size, but a steady diet of opossum formula and cat kibble had fixed that.

Now Powell grasped the carrier and strode to the edge of a thicket where the land sloped downward. Within a few steps, we found ourselves at the base of a huge eucalyptus tree, amidst a cluster of palms. Powell sprinkled a Baggie containing cat food into the litter of fallen leaves underfoot, confessing that she had no idea whether the opossums would linger to eat it. "It just makes me feel better," she said. Then she opened the carrier. The lighter-colored female streaked down the slope, but the little male stayed close, sniffing the air.

The jangling collar of the dog, along with the voice of its owner talking, grew louder. Powell and I and the male opossum froze, hoping to remain unnoticed. But with a confidence that seemed almost psychic, the dog, a German shepherd, made a beeline for our hiding spot. As soon as its owner realized her pet was about to confront us, she called it away. But her curiosity had been aroused, and when Powell and I returned to the car, the duo circled back to where we'd just released the two opossums.

"I'm gonna go talk to her," Powell said, leaping out of the driver's seat. When she returned, she reported that she'd told the woman she was a Project Wildlife volunteer who had just released some young rabbits. "A lot of people don't like possums. So I tell people bunnies, and they're, like, 'Oh, cute little bunnies!' " The ploy seemed to work on the German shepherd's owner, who returned to her car with the dog and drove off.

Powell said that one of the hardest parts of doing the animal-rescue work was not knowing what happens to the animals after they're released. "Everyone always asks me, 'Well, how do they do?' But we don't know." Project Wildlife doesn't have the resources to put radio collars on the animals to track what happens to them, but Powell said she wished some local biology students would decide to study opossums and share the information.

Some already have. Back in the early 1970s, a San Diego State professor named Don Hunsaker was one of the world's leading experts on opossums, and his laboratory on the SDSU campus was a hotbed of marsupial-related activities. Hunsaker edited and contributed two chapters to The Biology of Marsupials, a 1977 book that still ranks as one of the most thorough scientific discussions of New World marsupials ever published. He later retired from teaching to become a fellow at the Hubbs-SeaWorld Research Institute and today spends most of his time studying the effects of human activities on the endangered California gnatcatcher and least Bell's vireo. But he sounded delighted when I told him I wanted to learn more about why he'd worked with opossums and what he had learned about them.

In Texas, where Hunsaker grew up, "It was Possum City," but it was reptiles and lizards that initially fascinated him, and he resolved to become a herpetologist. While studying zoology at the University of Texas, he was the first to discover that the "push-ups" performed by certain lizards are a form of body language that tells other lizards what species they are, what sex they are, and if they're feeling aggressive or amorous. He got his doctorate in 1960, then moved west to join the faculty at San Diego State University, where he turned his attention to geckos. While researching the local lizard and snake populations, he founded the San Diego Herpetological Society and became its first president. "I get all involved in whatever I'm doing, but after a while, I answer the questions I'm interested in, and I move on."

By the late 1960s, Hunsaker felt he'd demonstrated that reptiles -- driven primarily by instincts rather than what they've learned -- were "a real good model" for studying animal behavior. He was ready to study creatures that were less instinctual yet still primitive. He spent time at the San Diego Zoo pondering various possibilities, and the kangaroo and wallaby colonies caught his eye, in part because the marsupials' reproductive systems are considered to be more primitive than those of placental mammals, and their social systems also aren't very advanced. (Although they congregate in groups, membership within those groups appears to be fluid.)

The only problem was that studying wild kangaroos and wallabies would have required more long-distance commuting than Hunsaker found appealing. So he started to reflect upon the marsupials closer at hand. Geological evidence indicates that the first marsupials developed in North America about 100 to 120 million years ago. For the most part, mammals out-competed them here, but one species that appeared around 50,000 years ago, Didelphis virginiana, was a tenacious little survivor. (Its correct common name is the Virginia opossum; the word "possum" is slang, if commonplace.) Hunsaker says topological and climatic barriers confined the Virginia opossum to the Southeast for most of its history. It took a human being to transport at least a couple of them across the Rockies and the great Southwestern deserts around 1890. Once here, the opossums thrived. "A basic rule of thumb is that all species expand to the limits of their environment, and the possum's a good example of that," Hunsaker says. "Today they're one of the most common mammals in the state."

Hunsaker thinks whoever imported them into California was dreaming about dinner fare -- he can't imagine anyone wanting an opossum for a pet. "They're mean. They bite," he says. In the years when he was studying the animals, he was nipped so many times he became allergic to opossum saliva. "And they've got extremely strong jaws." Backing up that chomping power are more teeth than found in the mouths of any other American land mammal (50, as opposed to 42 for coyotes, foxes, and bears), and "they can snap real quick at you." But he could imagine working with them as research subjects.

These reflections coincided with an opportunity to work in South America, home to more than 70 species of opossums (as opposed to North America, where the Virginia opossum is now the sole remaining marsupial). As part of a U.S. State Department technology-transfer project, he was assigned to the Colombian Department of the Interior, and over a two-year period he observed a number of the South American marsupials in the wild. Some of them looked like otters or squirrels, bright-eyed and inquisitive. "That's where I got the idea that these marsupials were much more sophisticated than anybody had ever thought."

Hunsaker wound up buying land in Colombia and using it as a research station. After his stint with the State Department project ended, he continued traveling with graduate students from SDSU to do more research in South America, encouraging other American scientists to follow suit. He set up a New World marsupial laboratory on the San Diego State campus, and for a number of years, he and his students conducted experiments involving both the Virginia opossum and its South American cousins. "We did a lot of behavioral work," he recalls. "But the field work was easiest to do on the [North American] opossum, because they're local."

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