Keeping Yukon’s river otters in the swim

Until recently, Yukon's river otters have managed to glide beneath the research radar. Lontra canadensis, a member of the weasel family, is not common in the territory and its distribution here is patchy.

Until recently, Yukon’s river otters have managed to glide beneath the research radar. Lontra canadensis, a member of the weasel family, is not common in the territory and its distribution here is patchy. However, the numbers aren’t so low that our otters are under any immediate threat, and biologist Don Reid would like to keep it that way.

Reid, who works for the Wildlife Conservation Society in Whitehorse, has spent the past three years trying to understand the habitat needs of southern Yukon’s river otters. “As a conservation biologist, my particular interest was how best to conserve the animal as new development proceeds,” says Reid, who as a graduate student first studied otters in northeastern Alberta.

“In the Yukon River drainage, otters have been rather an overlooked animal because many people considered them to be really quite uncommon and not ecologically very important,” he says. “That’s probably true for a considerable portion of the territory, but where there are lots of smaller-sized lakes and associated streams with beavers, there is a considerable number of otters.”

If Yukon’s river otter population is healthy, why worry?

For one major thing, some North American otter populations and their close relatives, the European otter, have suffered elsewhere, Reid says. In some U.S. states – like Kansas, Missouri and Nebraska – the animals were virtually extirpated, probably as a result of over-trapping, habitat loss and shoreline disruption. State wildlife managers have had to ask other jurisdictions, such as Ontario, for replacement otters in attempts to restore local populations.

Reid also mentions Europe as a cautionary example of what could happen here. “In Europe there’s a different species, but an ecologically very similar species: the European river otter,” he says. “Most countries in Europe have had to declare the species threatened or endangered. They’ve had to get involved in very serious attempts to restore shoreline habitats.”

Reid and contractor colleagues Rene Rivard, Kim Melton, Maria Leung and Milena Georgeault have been paying particular attention to otter land-use choices in the Yukon. They have been focusing on above-ground movement and latrines, says Reid.

Otters tend to use site-specific habitats repetitively. If scientists can map them and find a way of understanding why otters choose these sites, they can develop an effective conservation tool for planning lakeshore development, trails and campsites, forestry work, and similar human development.

“We as an organization chose specifically to work with wetlands and valley-bottom habitats in the Yukon because we see these places as the ones most likely to be at risk from growing human populations – humans wanting to do their thing on the land,” says Reid. “It’s site-specific conservation planning for these particular habitats.”

In winter otters have a difficult time with ice cover, he adds. They have to get out of the water to breathe and into the water to forage for fish. In winter otters mostly travel along routes connecting places with open water. “It’s interesting here in the Yukon how much open water there is in winter. All of their above-ground movements are quite directional between water places.” This means that some trails, though, will divert from open shoreline through bush and forest, says Reid. These more hidden trails make otters less vulnerable to predators like wolves.

The relationship between beavers and otters is not symbiotic. In fact, otters are likely happier to see beavers than beavers are to see them, for several reasons. Beaver ponds make good otter habitat, says Reid. “In winter the ice at the crest of the dams is usually quite weak and easy for otters to penetrate. The otters find an added benefit in the beaver lodges and bank burrows themselves.”

“I actually think that otters fairly often usurp active beaver lodges and force the beavers into using adjacent bank burrows,” he adds. However, there are more abandoned beaver lodges in many Yukon landscapes than inhabited ones, so a forced eviction isn’t always necessary. “It’s not always an antagonistic fight for space, but it sometimes comes down to that.” One of the interesting, as yet unanswered, questions about the interaction of the two species is whether a drastic drop in a local beaver population can cause serious problems for otters, says Reid.

Some open-water areas essential for otters in winter are created by upwelling of warmer water in lakes, such as the outflow from Marsh Lake at Lewes Marsh.

“Also, because of our mountainous terrain there are a lot of water tables high up on the slopes,” says Reid. These continually drain water into the soil or bedrock and seep down to lakeshores. These seeps can appear as open-water streams through much of the winter, Reid adds. The open-water sites are “biodiversity hotspots” in winter, providing important feeding and resting areas for many creatures other than otters, including muskrats, mink, swans, waterfowl and dippers.

Another feature of the river otters’ on-land habitat is their latrines, which also serve as communication and social centres. “They are places where otters go to defecate, but that is often combined with scent marking,” the biologist says.

In these latrines otters pile up dirt and moss, in effect creating their own little “transmission towers.” Defecating on the tops of these piles increases the airflow and wafts the scents further.

The messages can contain a myriad of information. These are not necessarily territorial statements, says Reid. He suspects the scat markers have more to do with announcing who is in the neighbourhood than with warning other otters away. “I think a lot of the time these animals are happy to be in social groups; they are not antagonistic or solitary.”

Markers may also announce which fish or insect larvae are on the local menu at any given time.

A female otter advertises when she is coming into estrus.

The boreal winter can be tough on otters, as it is with many other animals. However, family groups of mother and two young are quite common. Another sign that they are doing reasonably well overall is that otters appear to have the time to enjoy play. They will expend energy on tumbling around with one another. Reid hasn’t seen them actually sliding down snow banks in the Yukon, but he has found the well-used slides themselves when following tracks in the snow. In these cases the otters have left their direction of travel to repeatedly climb a slope and slide down before heading on their way again.

River otters are also known to live in the ocean, and can be seen in the Lynn Canal near Skagway. They have a completely different lifestyle and ecology when they are in the ocean, but being the same species they can, in fact, mate with the inland otters, says Reid. That doesn’t hold for sea otters (Enhydra lutris), who are also members of the weasel family but aren’t closely related. And sea otters almost never come on land.

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at http://www.yukoncollege.yk.ca/research/publications/your_yukon

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