North Dakota Game and Fish manages some furbearer populations with necropsies

Bismarck, North Dakota – In this week’s episode of North Dakota Outdoors, Mike Anderson describes how necropsies are used to control some furbearer populations.

Furbearer biologists in North Dakota use necropsies to manage river otters, fishers, mountain lions, and bobcats.

“Necropsies are simply an autopsy on an animal. For furbearer management, we’re doing necropsies to collect some very basic demographic and population information from these animals so we can survey them,” said Steph Tucker, furbearer biologist with the ND Game and Fish.

Tucker stated that after the pelt has been removed, hunters and trappers must turn over the animal’s carcass to the Game and Wildlife Department. When controlling these species, conventional techniques like the ground or aerial surveys are impractical.

“So, things like mountain lions, you know, they’re really low densities on the landscape. They have huge home ranges. They’re nocturnal. They’re very secretive, even when they’re moving about during the day. So, we have to come up with other ways to survey the populations and monitor those population trends,” said Tucker.

Because of this, population models are essential for managing these furbearers.

“Population model is just a statistical estimate of the population abundance or trend. In this case, mostly trends. So, we’re trying to determine is the population increasing or decreasing,” said Tucker.

When conducting necropsies, researchers gather two crucial pieces of data.

“We want to know how old the animal is when it died so that we can estimate survival based on that age information. And the second thing is we want to find out if it is a female, was she reproductively active in the last year? And if so, how big was that litter that she might have had?” said Tucker.

Additionally, biologists weigh and measure these species, look into what the animals have been eating, and, if necessary, carry out disease surveillance.

The growth rings on the roots of these furbearer species’ teeth provide biologists with an accurate age estimate.