Missouri Department of Conservation

What Otters Eat in Ozark Streams

We have studied otter diets since we began stocking the animals and have found that their most important food is crayfish, which they eat almost exclusively from April until October. Crayfish populations in Ozark streams are among the highest recorded anywhere.

In winter, otters primarily eat fish. They mostly consume long-eared sunfish (35 percent), but also a significant amount of smallmouth bass (12 percent). Goggle-eye and suckers each account for about 10 percent.

Tracking Otters

Each year we collect otter carcasses from trappers and, among other tests, we determine their age from their teeth. Otters in Missouri are breeding at earlier ages and having more pups in each litter than previously documented. Many female otters are breeding as yearlings, giving birth to first litters near their second year of life. This cuts the generation time in half, and greatly increases the population growth rate.

Six years ago we enlisted two husband-and-wife trapper teams to live-trap otters and implant small radio transmitters in them. This allows us to determine where otters go, how long they live and how they die.

Of the more than 300 otter captures so far, we have documented 97 mortalities. Of these, 78 were trapped, six were shot, two died from bacterial infections, one was struck by a car and another was struck by a train. We couldn’t determine a cause of death for nine of the otters.

What this tracking study suggests is that when food is abundant, there is no other way than trapping to control otters. Without trapping, otter survival rates would contribute to rapid population growth and many more otter problems.