SI Vault
Bil Gilbert
December 13, 1982
He's a lovable creature and he's extremely rare, where once he flourished across North America. Now biologists are giving this animal a second chance to live happily ever after in Missouri
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December 13, 1982

The Utterly Delightful Otter

He's a lovable creature and he's extremely rare, where once he flourished across North America. Now biologists are giving this animal a second chance to live happily ever after in Missouri

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Erickson gave me a demonstration of this one hot summer day in a large 4WD pickup that had become mired in the rich gumbo of a dike extending into Swan Lake. While we awaited rescue by another state-owned truck, the principal entertainment was swatting mosquitoes and listening to otter bands on a receiver mounted on the bed of the pickup. None of the animals was visible from the spot, but according to the beeps, two males and a female were within a few hundred yards.

"In the three months since the first ones were released," said Erickson, "we have had only one free sighting—that is, without locating them first with the radio equipment—despite the fact that all the federal and state people on the refuge and hundreds of fishermen who use Swan Lake have been watching for them. Without telemetry that one sighting and a few signs would be all the information we would have about where they are, what they are doing or even if they were still living."

One otter, a female received in May, died during the radio implant operation. According to the attending vets, this was the smallest and weakest of the animals received. The remaining otters were held in cages to convalesce for several days, and then were released. Earlier, a female from the March batch had immediately left the water upon release and disappeared into a large adjacent soybean field. During the evening the area was struck by a ferocious thunderstorm accompanied by heavy hail. The next morning the internal transmitter began sending a mortality signal, and the female was found dead in the soybean field. "Our best guess is that she died from stress induced by the operation, the handling and release," said Erickson. "There is probably nobody who cares more about what happens to these animals than I do. Professionally my neck is on the line if it doesn't work. I also have some strong emotional feelings about the animals. I feel responsible for what happens to them. I hated losing those two otters that way, but I come back to the point that at least the first release is an experiment. The most important thing about it is learning some things about their basic behavior and how and where to release them. Despite those two deaths, I think this has been very successful so far because we know so much more about reintroducing otters than we or anybody else did three months ago."

In other efforts to reestablish otters, a few captive pairs have been released in scattered areas of several watersheds. In none of the previous attempts (notably in Arizona and Colorado) have all the animals been monitored by radio or direct observation. That makes their present status conjectural. Missouri biologists chose to put all their otters in one habitat basket. "Our reasoning," says Erickson, "was that we had a better chance of making continuing observations if they at least started from the same place. Also, we thought there would be better reproductive possibilities if we more or less saturated one area rather than spreading them over a large one. The obvious hope is that these animals will form the nucleus of a breeding population. If they reproduce and we get more animals than this area can carry, the assumption is that the young will disperse and naturally establish themselves in other territories."

At first there were doubts as to whether the otters would go along with this plan and settle down in a relatively small, stable community. In other circumstances they have been known to wander considerably, traveling, it has been reported, as much as 60 or 70 miles. However, thus far Missouri's new otters have behaved as if they find Swan Lake a desirable neighborhood. Some individuals were a bit restless immediately after their release. A male traveled 10 miles or so up a small tributary creek, but he, as well as others who made shorter trips, returned. As of late November, all but two were within three miles of their original release point, and most of their activities were confined to the federal sanctuary. Erickson suggests that this behavior demonstrates that Swan Lake provides an abundance of food for the otters and probably can support more.

In June there was a third death, the body of a male being found in a dense thicket. It had decomposed to the point that the cause of death couldn't be determined. However, malnutrition was obviously not a problem; that otter weighed 11 pounds when released and 16 at the time of its discovery.

Its foreleg bore an ugly puncture wound. A coyote or raccoon could have been responsible, but it is unlikely that a member of either species would have the opportunity or inclination to tackle a 16-pound otter. The best guess is that the attacker was another otter.

Our knowledge about the relationships of adult otters is sketchy. The telemetric data collected thus far show that they are at least intermittently social and, despite whatever fracas the dead one got into, reasonably amicable. Most of the animals have spent some time traveling, denning and resting together in pairs or trios. These associations don't seem to be permanent, with animals moving off to form new groupings or to live alone for a time. Also, no obvious sexual patterns have emerged: Male, female and mixed pairings have all been observed. Again, the availability of food and the generally excellent environment may be responsible, with the animals perhaps remaining casually together because there is no compelling territorial reason for them to separate.

So far as the most critical social arrangements, reproductive ones, are concerned, it's possible that some of these were made before the animals arrived in Missouri, because begetting pups is a two-stage phenomenon that can last a year. As with a number of mammals, female otters may retain vital sperm for many months after copulation before the actual fertilization of eggs. During this period there are no embryos and there is no way of determining if an animal will eventually become pregnant. Whether the population of the Swan Lake animals will increase will remain an open question at least until the whelping season next spring.

Meanwhile, the Grand River watch goes on. On a muddy day in the middle of the swamp, Erickson discovered a carp head, the remains of an otter's lunch.

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