Playing For Keeps
Scientists are taking a hard look at the playful river otter and uncovering a remarkably versatile survivor
- Michael Tennesen
- Jun 01, 1993
On an overcast day in northern California, along the redwood-forested coast of Trinidad Bay, Humboldt State University biologist Scott Shannon watches a group of adult male river otters from a weathered pier. The animals romp, wrangle and pounce on each other, seemingly oblivious to the needs that consume the time of most other wild animals: reproducing and finding food and shelter.
This cavorting, to just about anyone who has seen it, looks for all the world like sheer fun. Even scientists, society's trained skeptics, often can offer no other explanation for otter antics (though some argue that even if otters do play, it serves other purposes). Shannon, for one, says unequivocally of the phenomenon, "Otter play is social bonding and nothing else. Their play behavior bears no resemblance to their hunting behavior. Otters don't wrestle or pounce on fish."
But debating that point is not Shannon's purpose here. Like other otter scientists around the country, Shannon has been looking far beyond the question of the creatures' playfulness. With protective laws and vigorous reintroduction programs, river otters are making a comeback in this country-after nearly being wiped out in most places except sparsely settled areas like Alaska and Louisiana's bayou country. And the scientists who are studying the otters' recovery are finding them to be remarkably adaptable, tough and resilient, with a wide array of behaviors.
Take, for example, the Trinidad Bay river otters, which have occupied the region since the 1950s. The bay is a saltwater inlet of the Pacific Ocean-with no river at all. Says Shannon, "The otters here wouldn't know a river if they saw one. Otters are a lot more cosmopolitan than people think."
Otters may also be a lot more complicated, with behavioral family dynamics worthy of soap operas. Recently in the Trinidad group, Shannon observed one female otter, offspring of a matriarch he dubbed Old Mama, repeatedly attack a younger sibling. Old Mama responded by attacking one of the aggressor's pups. After the aggressor succeeded in driving away its sibling, Old Mama seemed to mourn, apparently losing interest in food and eventually disappearing.
Not all river otters, however, display such complex social behavior. In habitats that are less rich in food than California's Trinidad Bay-the shallow, rapid rivers of the Rockies, say, or the intermittent streams of Missouri-scientists are finding that otters devote little time to social interaction.
According to Wayne Melquist, a biologist with the Idaho Fish and Game Department and first to use radio telemetry to study otters, social behavior like play, at least among adult otters, kicks in "only when higher-order needs like food and shelter are met, whether in the wild or in captivity."
There was a time when this continent's landscape met those needs bountifully-and river otters, common everywhere, likely frolicked and enacted soap operas throughout the land. Then, between the middle of the nineteenth century and the early decades of the twentieth, the North American river otter all but succumbed to the destruction of 95 percent of the country's wetlands-and to trapping, bounty hunting and water pollution.
Until the 1930s, luxuriant dark-brown otter pelts were in demand for coats and hats (even though sunlight "singes" otter fur, making the hairs curl up and separate). Fur trappers were not the only threat. River otters are adroit and opportunistic predators of crayfish, crabs, mud puppies, frogs-and, in some locations, carp, trout, salmon and even waterfowl. So, from the Atlantic to the Pacific, bounty hunters slaughtered river otters in the name of protecting the food supply.
Well before the middle of this century, moreover, the otter began paying another price for its voracious appetite. In lean times, an indiscriminate palate may be a boon to survival, but like the bald eagle, the peregrine falcon and other successful predators at the apex of a food web, the otter has taken a hard hit from pesticides, toxic chemicals and heavy metals.
In the pristine environment of an earlier America, otters were so abundant that people thought little of doing away with them; there always seemed to be more around. The otter was essentially penalized for advantages that nature had conferred on it: long life (ten years or more) and few potential predators (bobcats or coyotes). The otter even dens in places that its few enemies have trouble finding, much less penetrating. Abandoned beaver lodges with underwater entrances are a favorite.
Now, thanks to a combination of laws regulating trapping and pollution, repopulation programs and restoration of some wetlands, the otter is making a minor but unmistakable comeback in no fewer than 16 of the states where it once tottered at the brink of extinction. Says David Hamilton, who heads an otter reintroduction program for the state of Missouri, "Otters are highly adaptable, and they have considerable survival traits. We used to think they were narrow in habitat; the truth, if anything, is that they're preeminent generalists. People call them semiaquatic, for instance, but even where there's little water they do just fine-as long as the water they've got is more or less pollution-free. The otter is one tough critter-not fragile in the least."
That toughness starts with reproduction. As little as ten days after giving birth, the female comes into heat again. As with other members of the family Mustelidae, to which otters belong (as do minks, weasels, ferrets, badgers, fishers, skunks and wolverines), the fertilized egg then "floats" in the mother's body for months, programmed not to implant itself in the womb, or even to divide again, until dead of winter.
The river otter doesn't den in water at all, but above or outside it. In this the animal differs from the sea otter, an endangered mammal more than twice as large that spends its entire life in the ocean, from the coast of California north to the coast of Alaska.
In spring, after the river otter's pups are born (usually two or three), the mother puts time and effort into teaching and protecting them-sometimes to the point of keeping the youngsters away from other otters.
The young are quick learners; if they stumble into trouble at all, they likely don't do it a second time. Only the very youngest otters are vulnerable to the rare predator that attacks them; pound for pound, they're among the strongest animals on Earth. Says Missouri's Hamilton, "They have incredible strength, agility and swiftness."
That sort of wrestling does not mean playfulness, either. One visitor-a retired Missouri wildlife division chief-once rested his hand on the edge of a cage when Hamilton was working with some caged otters. Recalls Hamilton, "The animal came from one end of the cage to another and had the tip of his finger off in the blink of an eye." If an otter flees instead of fighting, it is fast; by alternating loping steps and 10-to-20-foot belly slides, it can move at speeds as high as 18 miles an hour.
The river otter hunts for food just about anywhere there is water, in swamps, marshes, lakes, seacoasts and puddles. Along rivers or streams, the adults' home ranges do not always overlap. In those cases, resources are apportioned noncompetitively, and otters save energy that might otherwise be lost to territorial disputes.
In a more fecund habitat, on the other hand, like a marsh or a bay, home ranges (which can cover as much as 10 miles in each direction) seem to always overlap. Not only that, the animals may join in loose-knit groups of three or four or more. One researcher has seen marshland groups as big as 17. These groups, says Shannon, often split into highly territorial matriarchal families and wandering, nonterritorial groups of males.
It is in these situations, according to Shannon and others, that the otter's talents for society-perhaps weakest in riverine habitats and absent altogether in the animal's mustelid relatives-start to appear. In addition to playing and bickering, group members sometimes forage alongside one another in productive wetlands. Though some researchers have found that group foraging is often less successful than hunting alone, the otters' apparent confidence in the abundance of available prey and the possible pleasures of togetherness frequently seem to override any interest the animals may have in maximum effectiveness.
Speculates Missouri's Hamilton, "Perhaps, between their efficiency as hunters and the fact they know there's plenty of food to go around, they've simply got time on their hands." Much of the new understanding of otters comes from the Missouri program. There, the state Department of Conservation has established what is arguably the nation's most successful otter restoration effort: the population has grown from fewer than 50 individuals in 1980 to an estimated 3,000 to 4,000 today.
Such programs depend, of course, on appropriate habitat, and wetlands restoration throughout the nation, though limited, has also been a boon to otters. In California, for example, as in states farther east, historically farmers levied and drained land for farming and pasture-including, in the nineteenth century, much of the Suisun Marsh. That 54,000 acres of brackish tidal wetlands at the junction of the San Joaquin and Sacramento rivers is home to the state's largest concentration of otters.
Fortunately for the otters, according to California Fish and Game biologist Gordon Gould, by the twentieth century farmers in the Suisun Delta began selling back their pastures to sportsmen for conversion to "duck clubs"- pieces of land (some 250 today) that for the sake of hunting have either been permanently reflooded or are flooded seasonally, before the migrations of waterfowl. Together with a state wildlife refuge, the Suisun Marsh now makes up one of the nation's largest contiguous wetlands.
The surprise here to the uninformed is that an animal named for rushing freshwater would flourish in this region of salty standing water. But that's hardly news to biologists studying the animals. Says Shannon, "River otters don't live in the water, they just hunt in it. Fresh or salty, otters don't care what kind of water they hunt in, as long as the food they need is there."
That food supply, plentiful and uncontaminated, is one of the keys to the river otter's future in North America. So too, certainly, is the creature's image as a playful charmer. Points out Bill Grenfell, a wildlife consultant to the California Department of Fish and Game, "On a cuddle-factor scale of one to ten, otters are easily a ten, or maybe a ten-plus."
But if you want to see them in the wild, you may simply have to settle for evidence that they have been around. At least, that's what the Missouri biologists do when they want to count the growing numbers of the elusive creatures living within their state.
The scientists wait for a clear winter day with fresh snow cover, then look from the air not for otters, but for tracks, which are increasingly numerous. Says Hamilton, "They have a habit of taking a few leaps and then sliding on their bellies, and from the air it looks like Morse code along the streams."
What does the code say? That river otters may be back to stay.
California writer Michael Tennesen visited otter biologists to report this story.