Wildlife Health Unit Monitors Wildlife Diseases

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Healthy and abundant wildlife populations are essential to hunting success and are often indicators of ecosystem health. Wildlife and environmental managers use information provided by the Department of Natural Resource’s Wildlife Health Unit in setting seasons, developing species management plans, monitoring environmental quality and drafting policy.

“It’s the job of the Health Team to monitor wildlife health statewide,” said Julie Langenberg, VMD and team leader, “We want to know what diseases are out there, disease prevalence and mortality rates and what may be on the horizon.”

Disease-related mortality and disease prevalence are factors wildlife biologists use in setting harvest limits. Much of the monitoring and research into diseases and wildlife health is funded by hunters, trappers and anglers by funds raised through license sales.

“In order to set safe harvest levels for game species we look at many factors,” says Langenberg. “It’s important to know overall population numbers, reproductive rates and hunter success rates and also how many members of the population you can expect to lose in a year from naturally occurring disease problems.”

The Wildlife Health Unit performs roughly 400 to 500 animal necropsies (laboratory investigations into the cause of death) each year. The 400 to 500 animals examined are a sample of thousands of animal deaths reported each year. A single event, such as a large scale die off of ducks from trematodes (an intestinal parasite) or botulism, can involve hundreds of ducks at one time and in one place.

“What we learn from the necropsy determines our course of action,” says Langenberg. “This spring people were reporting deaths around birdfeeders of redpolls, a kind of finch. Necropsy determined the deaths were due to salmonella poisoning which can easily be handled by thoroughly cleaning the birdfeeders.”

In addition to deaths directly linked to disease the unit gathers information on viral and parasitic problems that by themselves may not have a great effect on a population but when combined with other stresses such as habitat loss, pollution or severe weather, could have a significant impact.

Wildlife often are the sentinels pointing to underlying environmental problems according to wildlife experts. Sleuthing out the cause of wildlife die-offs can be easy…or extremely difficult.

For example, Langenberg’s team is working with water quality experts, environmental toxicologists, bird specialists and others investigating the cause of bald eagle deaths along the lower Wisconsin River.

“After several years of investigation and testing the cause of these deaths remains a mystery,” says Langenberg, “which suggests it may be a very complex interaction of several factors. When and if we learn what’s going on it could be a very important bit of knowledge concerning the lower Wisconsin River ecosystem.”

Wildlife disease surveillance can also serve to protect human health. For diseases such as West Nile Virus, which is spread among wildlife and humans by a mosquito bite, monitoring and recording deaths of crows and bluejays gives researchers a good picture of where the disease has spread. These birds are very susceptible to the disease and are a good early indicator that humans should take extra precautions to avoid mosquito bites.

“We are doing everything we can in the area of wildlife health with the funding we have,” says Tom Hauge, director of the DNR Bureau of Wildlife Management. “But like the rest of our wildlife, fisheries and law enforcement groups, we’ll likely have to make some hard decisions on what to cut if there is no fee increase. I expect we’ll still monitor for disease and continue to do necropsies but frequency and quantity may have to be adjusted. The net effect may be that it will take us longer to uncover and react to new disease threats, giving these problems time to cause more damage or gain a better foothold in our wildlife populations.”