NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: https://mag.outdoornebraska.gov/i/377644
OCTOBER 2014 • NEBRASKAland 25 up a new home range 53 miles to the northeast near Central City, where the presence of otters had previously been documented just once. That male was caught in a beaver trap within that new home range in 2010, four years after its transmitter was implanted. That turned out be the only documented death of an otter in the study. Annual survival of otters is high when compared to many small mammals, ranging from 70 percent or greater in states with a legal trapping season to 80 percent or more in areas with no harvest, according to research. Wilson was pleased and yet still somewhat surprised that no otters died during his study, a first for a study sample of this size and duration. He was also pleased at the results of a companion study that collected otter scat and used DNA analysis to estimate the population density of river otters in the study area at about one every two-thirds of a mile, a number he categorized as "very high." Researchers floated the river searching the banks and sandbars for communal latrines, spots where otters leave the water to not only deposit scat but also leave scent markings, a form of communication, that are conspicuous in nature due to their size. Sites were visited twice, two weeks apart, and the DNA testing was used to determine the number of otters using each latrine and then estimate the number of otters living in the study area. The resulting data places the otter population in the study area among the highest ever recorded in the country. Wilson said, however, that few studies have used DNA samples to estimate population, so that could factor into the high density. So could the topography of the Platte compared to other rivers. "A lot of previous studies have taken place in rivers in the East, where you have one deep channel," Wilson said. "The Platte is really, in some places, six or seven rivers in one. It's more of a habitat complex than a river, and that's a qualifier that could account for the high density." Future Wilson isn't certain what Nebraska's otter population is, but believes a new study, paired with his research, will allow biologists to soon develop an estimate. Students in the Nebraska Cooperative Fish and Wildlife Research Unit at the University of Nebraska-Lincoln are now scouring the state's rivers for more evidence of otters, using scat surveys and trail cameras to document the presence of otters in a study that will continue through fall 2015. When biologists have a better idea how many miles of those rivers are occupied by otters, they will use known population densities formulated here and elsewhere to develop the estimate. Wilson isn't certain that the otter population is high enough in Nebraska to allow trapping, as Iowa, Missouri, Kansas and other states now do. But he does believe it may be time to consider removing river otters from the state's list of threatened and endangered species. "With high survival rates and continued expansion, it may be time to focus recovery efforts on other species in more critical need," he said. To make those changes is part of "a giant success story," Wilson said. "If you look at maps from 1970, much of the Midwest was basically devoid of otters. This is a rare type of success, that you can have an animal that's done so well after being completely gone for so long. "At least in my mind, it's a success when an animal comes off the threatened and endangered list. Then your resources are reallocated to the species of plants, animals and insects that really need it the most right now. Otters were there in the past, but now they're doing really well." Through these continued efforts, the river otter will once again be a staple along the waterways of Nebraska. ■ A river otter pauses after emerging from a beaver den on the Platte River on the Crane Trust property south of Alda. Three otters, including one that was carrying a surgically implanted radio transmitter, and two beavers emerged from the den. PHOTO BY ERIC FOWLER