On an unseasonably warm Saturday a few weeks ago, I drove down to a nature preserve 15 miles south of Boston called the Blue Hills Reservation. It’s a large forested area with plenty of trails, and I was planning to spend the afternoon hiking. But first, as I usually do when I visit the Blue Hills Reservation, I stopped off at the Trailside Museum on my way to the trailhead. The museum, managed by the Massachusetts Audubon Society, includes a small, outdoor, native-animal zoo. There are a variety of animals at the zoo, white-tailed deer, snowy owls, red-tailed hawks, turkey vultures, but I always check out the river otter display first. The otter enclosure is a large, concrete pit. One end of the enclosure is covered by a dirt floor with a towering rock pillar at its center. The rock formation is covered in ledges and crevices, which could presumably provide the resident river otter with some privacy if she so desired. But in all the times I’ve visited the zoo I’ve never actually seen the otter in this area. Instead she’s usually in the large pool down at the other end of the enclosure, showboating for a crowd of spectators.
When I looked over the edge of the enclosure, the otter seemed to be asleep on one of the logs floating on the surface of the pool, but she immediately opened her eyes and squinted up at me and a few families with little kids who had gathered around. She must have decided that her audience was now large enough to warrant getting out of bed, because she hopped into the water and began zooming back and forth across the pool, jumping up and over the floating logs or diving under them. And then she suddenly dove toward the edge of the enclosure, building up speed for her signature trick. When she reached the concrete wall, she pushed up and off the wall into a graceful backflip. The little kids peering over the top of the enclosure squealed in delight. The otter glided underwater, upside down across the pool before surfacing, turning around, and doing it all over again.
Otters have quite a reputation for playfulness. If you’ve seen otters in an aquarium or at a zoo, like me you’ve probably been delighted by their antics. Even in the wild, otters are known to engage in bouts of amicable wrestling, and they’re often seen sliding down snowbanks or muddy slopes on their bellies. A Youtube search for “otter” yields thousands of videos of wild and captive otters wrestling, sliding, and playing with their food. And of course there’s the recent viral video of Eddie, an arthritic sea otter at the Oregon Zoo playing basketball as part of a physical therapy regimen.
As I watched the Blue Hills otter backflip off the wall over and over, I began to wonder, is this something she was trained to do? Or maybe she’s just having fun? So when I got home after finally going on that hike, I emailed Norman Smith, the sanctuary director at the museum to find out. He referred me to Elizabeth Bastable, the museum’s volunteer coordinator, who explained that the river otter was not trained, and in fact backflipping “is something [otters] do on their own, even in the wild.”
The revelation that backflipping is a natural otter behavior made me wonder why, exactly, otters are so playful. Does their playfulness serve some greater purpose? Or is it really just pure fun? After all, wild otters have to earn a living. The law of natural selection mandates that they attend first and foremost to the business of finding food, reproducing, and otherwise surviving. So why waste so much time and energy on an activity as seemingly frivolous as backflipping, or wresting, or sliding?
A little digging through Google Scholar revealed that this question has been a subject of debate among scientists for some years. Articles with titles like “Sliding Behavior in Nearctic River Otters: Locomotion or Play?” and “Wrestling play in adult river otters” have tackled the issue. Most animals play when they’re young as a way to practice adult behaviors, but otters are some of the only animals that continue to engage in play as adults, making the behavior all the more puzzling.
In the end, scientists have been hard-pressed to find practical reasons for otters’ playfulness. The idea that otters slide across frozen ponds and down muddy river banks simply because it’s the fastest way to get from point A to point B, has been challenged by observations of otters repeatedly sliding down the same path. And otter play doesn’t seem to mimic practical, hunting behaviors either: biologist Scott Shannon notes, “otters don’t wrestle or pounce on fish.” The most reasonable explanation for play among otters may be that it reinforces social bonds and encourages group cohesion.
But not all otters are particularly social. Otters that live in hardscrabble environments where food is difficult to come by spend little time playing and instead focus most of their energy on solitary hunting. But in environments where food is bountiful, like a marsh or coastal inlet – or a zoo for that matter – otters can afford to devote more time to playing and forming social groups.
In general, otters are scrappy, well-adapted animals, which may help to explain why they’ve had the luxury of developing playful, social behaviors. They’re commonly called river otters, but they also thrive in a wide variety of non-riverine habitats, from salt marshes to ponds to swamps, and even areas with minimal water. They eat pretty much anything they can get their paws on, crayfish, frogs, crabs, small rodents, birds, and fish of all kinds. Otters have few natural predators, and at one time they could be found in wetlands across most of North America. But over the course of decades, unregulated hunting, increasingly polluted waterways, and widespread destruction of wetlands took their toll on North America’s otter population.
By the beginning of the last century, otters had disappeared from large swaths of their former range. But following 20th-century clean water and wetland protection legislation, otters have made a dramatic comeback. In a sign of the strength of this comeback, a river otter has taken up residence in San Francisco within the past few months. Nicknamed Sutro Sam after Sutro Baths, the ruins of an early 20th century, coastal swimming pool complex where he has made his home, the otter has become an instant Bay Area celebrity.
I didn’t come across any wild otters on my hike in the Blue Hills Reservation, but I very well could have. Wild otters have been spotted in the Neponset River, less than a mile from the otter enclosure at the Trailside Museum. Although they were once nearly extinct in the Bay State, otters can now be found across Massachusetts. A few years back a kayaker even snapped a photo of otters frolicking in the Charles River in suburban Boston. Perhaps they were socializing and reinforcing social bonds. Or maybe they were just having fun.