Scary good: The marsupial magic of the opossum

Ever shine a light into the night, only to be met with 50 sharp teeth, curled into a snarl just below two fiercely sparkling black eyes? Or maybe seen a curious-looking creature scuttling atop a backyard fence, a gaggle of blinking babies clinging to its tail and fur? Perhaps the same sort of creature has lain "dead" in your path or tricked you, some dark night, into thinking it's something as mundane as a run-of-the-mill raccoon.

If so, you - like most people - have an opossum story. Consider yourself blessed: The Virginia opossum is the only marsupial native to North America, a wondrous creature whose lineage traces back further than most of us can imagine.

Despite their evolutionary success and invaluable scavenger contributions, not enough of us truly respect the opossum, either as a helpful neighbor or even a perfect Halloween mascot. For Shanti Lindberg, a doctoral candidate in the UCLA Department of Ecology and Evolutionary Biology, it's time for a cultural reappraisal.

"Part of why people have fears or misunderstandings about them is because we're just so disconnected from nature," said Lindberg, who appeared on the UCLA College's "Cabinet of Curiosities" podcast to discuss her research into their pouches to better understand evolution. "I love them dearly, especially being able to work with them so closely."

A marsupial by any other name

Turns out there is an important housekeeping discussion to be had before discussing opossums. While the shortened "possum" may have caught on colloquially, that term actually refers to a different lineage of marsupials, says Lindberg - Australasia is home to the possums, while the opossums reside in the Americas.

Our familiar Virginia opossum, which Lindberg studies alongside the gray short-tailed opossum, is just one of more than 100 opossum species found throughout the Americas, some no bigger than a shrew and others the size of a well-fed house cat.

Lindberg's affection for these animals began during her undergraduate years in Oregon, when an opossum mother took up residence in her backyard crawl space. Over roughly three years, the two regularly crossed paths, and Lindberg watched her neighbor raise two litters of babies and peacefully mind her own business, contrary to misconceptions.

"They're really chill, and they don't want to start anything with you," Lindberg recalled. "They're just trying to forage and live their life."

Today, Lindberg is happily ensconced in the laboratory of Karen Sears, a UCLA professor of ecology and evolutionary biology renowned for work that includes groundbreaking bat research. The Sears lab uses opossums to investigate how mammals develop and evolve, with implications for understanding human health and biology.

Lindberg's research focuses on the evolution of the marsupial pouch, a structure that turns out to be far more varied than one might imagine. Rather than one standard design that many of us may associate with cozy cartoon kangaroos, marsupial pouches in different species can come in a creative array of options, including "doughnut hole" and "Mickey Mouse ears" variations.

Despite giving marsupials their name, not all species actually have pouches. Scientists once thought pouches were an ancestral feature that some marsupials lost over evolutionary time, but emerging research like Lindberg's explores the possibility that they evolved independently at different points in marsupial history.

Lindberg is investigating that question by comparing the Virginia opossum, which has a well-developed pouch, with the gray short-tailed opossum, which has none. By examining how the two species develop, she hopes to identify the biological processes responsible for these differences.

With relatives that thrived during and ultimately survived the age of dinosaurs, modern opossums are helping scientists like Lindberg better understand how developmental changes produce the diverse physical characteristics of all mammals, including humans.

And as unusual to us as the life cycle of marsupials may seem, there is much to learn and admire about their tenacity and adaptivity. Born after just two weeks in the womb, the opossums Lindberg studies are blind, deaf and fetal-like. Yet their forelimbs are sufficiently developed to help them crawl to one of their mother's teats and complete their growth outside the womb. For species with pouches, the teats are inside the structure, but for species without, babies use an enhanced oral shield that allows them to latch onto a teat.

Misunderstood, but mighty useful

Beyond offering scientists a window into mammalian evolution, opossums have plenty to contribute to the world, along with a mischievous knack for making suburban nightlife more lively.

"Imagine a world where we didn't have garbage workers," Lindberg said, describing the animals' role in consuming carrion and insects. "Virginia opossums are actually little ecosystem helpers."

They're also far less menacing than their reputation suggests. Although their 50 teeth, more than any other North American land mammal, make for a formidable display, they are not aggressive. Lovers rather than fighters, they are shy, avoid confrontation - and, perhaps most notably - rarely contract rabies, Lindberg notes, in part because of their relatively low body temperature.

Then there's their most theatrical defense mechanism: playing dead.

When threatened, Virginia opossums may hiss, bare those choppers and indeed "play possum," an involuntary response caused by extreme fear. As a last resort, their bodies stiffen and become completely motionless, sometimes with their tongues hanging out. Some even urinate or defecate to complete the appearance of a sick or dead animal, further discouraging potential predators. If left alone, they eventually recover and continue about their business.

"I can't even imagine discovering that for the first time as a human," Lindberg said. "Like, what the heck just happened? And now it gets up and walks away?"

Another misconception involves that distinctive, hairless tail, which may account for why raccoons with their fluffy striped tails seem to enjoy more widespread cultural popularity. (Although a quick social media search for "cute opossums" may instantaneously change hearts and minds!) Despite what cartoons might suggest, opossums don't hang upside down by their tails, which aren't designed to support their full weight. Instead, the tail functions more like an extra hand, helping them grasp leaves, sticks and other materials. Or, for a busy possum mom on the go carrying as many as 13 babies, the tail can sometimes provide one more place for youngsters to cling.

While it can be tempting to anthropomorphize nature and value species that seem more endearing to our limited human perspectives, Lindberg encourages everyone to recognize the value and beauty of every creature that shares this planet - and to appreciate how important it is to respect them all.

"Connect more with nature and your community. Step back and go see what's around us and why we should be protecting it and fighting for it," she said. "I'm getting kind of 'Lorax'-y, I guess, but my name is Shanti, and I speak for the critters."