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From: TSS ()
Subject: UW study shows deer in CWD zone stick to home
Date: October 27, 2005 at 1:06 pm PST

University of Wisconsin-Madison

UW study shows deer in CWD zone stick to home
October 21, 2005

by Terry Devitt

White-tailed deer, it seems, are homebodies.

That is the upshot of an intensive study of the traveling behaviors of 173 radio-collared white-tailed deer in south central Wisconsin. The new results, which surprised researchers by revealing how little deer move about the landscape, are important because they may help researchers and wildlife managers better understand how chronic wasting disease (CWD) spreads.

"They are using small home ranges and not traveling long distances," says Nancy Mathews, a wildlife biologist at UW-Madison's Gaylord Nelson Institute for Environmental Studies. "The only dispersers are young males, and they only go five to seven miles before setting up a new home range."

A bundled-up whitetail tag team fits a radio collar and ear tag on a sedated deer for a study conducted by Nancy Mathews, associate professor in the Gaylord Nelson Institute for Environmental Studies. The face of the deer is covered to calm it. The team includes UW-Madison wildlife ecology students and veterinarians. Mathews is researching how deer use the landscape in the south central region of Wisconsin where chronic wasting disease has gained a toehold.

Photo: Wolfgang Hoffmann

Related story: Researchers ask hunters to refrain from shooting deer with radio collars

Mathews and Lesa Skuldt, her student in the UW-Madison department of wildlife ecology, presented findings from the Wisconsin Department of Natural Resources-funded study recently at the annual Wildlife Society conference held in Madison.

The results of the study are both encouraging and confounding, says Mathews. On the one hand, knowing more about how deer move about the landscape may help scientists home in on how CWD spreads among wild deer. On the other hand, the findings contradict the idea that deer are great travelers, moving long distances and possibly taking the disease with them.

"Based on the behavior of these deer, we cannot account for the distribution of CWD on the landscape," says Mathews who, with her students, conducted intensive, year-round telemetric studies of deer fitted with radio transmitters for the past two-and-one-half years.

"Adult does and their female fawns establish home ranges in the same location where they were born and stay there for their entire life," Mathews explains. "Once young bucks have dispersed, they too establish small home ranges and rarely leave them, even during the rut. Deer are not moving long distances, except for young bucks."

First identified in Wisconsin deer in 2001, CWD is a fatal brain disease found in deer and elk. It is transmitted through an agent called a prion, an abnormal protein that causes brain damage and, subsequently, the characteristic symptoms of the diseases: staggering, shaking, and excessive salivation, thirst and urination. There is no cure or treatment.

Nor do scientists know how the disease is transmitted from one animal to another. Understanding how deer use the landscape may help answer that question, says Mathews, by providing insight into the movement and behaviors of animals in an area where the disease has gained a toehold.

Scientists have generally assumed that deer transmit the infectious prions among themselves through direct contact. One alternate hypothesis is that areas where deer congregate - mineral licks, for example - may become hotspots for the disease. In those areas deer frequently lick the soil. They leave behind saliva that may also contain prions. Whether that behavior and the consumption of contaminated soil is at all associated with transmission is speculative, Mathews emphasizes, "but we can't rule out deer congregating around hot spots as another means of transmission."

In their new study, what the Wisconsin scientists found to their surprise was that deer in south central Wisconsin use very small home ranges, about one-half square mile in size. These ranges tended to be smaller in areas with a higher amount of forest edge. It may be, she says, that deer in the area have an abundance of high quality resources - food, water, mates - and do not need to travel long distances to find those resources on the south central Wisconsin landscape. The study also shows that the size of deer home ranges was not related to the number of deer harvested or deer density.

In general, according to the study's results, females and adult males stay close to home. Young bucks travel on average five to seven miles from their home range to establish new territories.

Young deer of both sexes, says Mathews, do tend to go on "exploratory" excursions lasting for less than a week, but they eventually return to their home range and family groups.

"They always come back and the females never leave, so it is unlikely they are contributing to large-scale transmission of CWD," says Mathews. "A big key for understanding transmission is young bucks. They are the only segment of the population that makes permanent movement out of their home ranges."

Mathews also found that even after one CWD positive doe was found in a social group of females, other females in the group continue to test negative. She says this suggests that CWD is not spreading rapidly among females within social groups.

The study was initiated in January of 2003 and results through June of 2005 constitute the data in Mathews and Skuldt's new report. Deer were fitted with radio collars and tracked intensively with each animal's range on the landscape being determined a minimum of 37 times a season or 148 times a year. Deer were located at all times of the day with the exception of midnight to 3 a.m.

File last updated: October 12, 2005

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© 2005 Board of Regents of the University of Wisconsin System

Where Do Whitetails Wander ?

by Bob Cooney

A "catch and release" program run by wildlife ecologist Nancy Mathews is showing us how deer move across the landscape. Mathews has dozens of deer traps set in the CWD "hot zone." A team of technicians tags and collars trapped deer, and a veterinarian sedates the deer and takes tissue samples.

By early December 2003, the team had trapped and released 64 deer, and 24 free-ranging deer were wearing radio collars. Mathews plans to collar more.

The team monitors and records locations of collared deer several times a week. Their data will bolster knowledge of deer behavior, and provide keys to controlling the spread of CWD.

The project has four goals:

Determine the dispersal rate of yearlings. Their movements are likely to spread CWD across the landscape.
Monitor buck movement. During the fall, rutting bucks may wander 10 miles a day seeking estrous females, making them likely candidates in spreading the disease.
Identify social groups of ad ult does, which may serve as reservoirs for CWD. Telemetry will help the researchers to understand interaction within and among the social groups.
Learn where and when deer spend time with cattle. There's no evidence that CWD can infect cattle, but livestock producers are understandably nervous.

Mathews has about 25 traps on private lands near Mazomanie and Arena. "Some of the landowners support the DNR's position and some don't, but they all back our research," Mathews says.

The landowners haven't always gotten good news about the deer on their land. A veterinarian performs a tonsil biopsy on each trapped deer. So far, two of the biopsies were positive for CWD; those deer were killed.

Mathews does comparison studies to assess differences in dispersal, home range and mortality. Results show how far deer disperse and how buck and doe dispersal differs. During the rut, a buck's range may expand to 10 square miles, which could include the home ranges of six to 12 doe groups. Since each doe group contains six to 20 animals, a well-traveled buck could encounter hundreds of females.

Data confirm that whitetail does form family units of adults and fawns, and that they're homebodies. Family groups establish home ranges — usually three to five square miles in the CWD zone — and don't leave them.

Deer in Mathews' study areas were hunted in summer, fall and winter of 2002, which changed their routine. They became less active at twilight and shunned fields during the day.

"We don't see the deer in the fields, but we've had good success at night with traps placed inside the woods," Mathews notes. "Using infrared cameras, we've verified that the deer are more active at night."

Deer haven't abandoned their home ranges. One infected doe led sharpshooters in a big circle for a day before eluding them. Two days later she was back in the center of her home range. Telemetry showed that she never left her home range while being followed.

A graduate student, field coordinator, and six technicians work full-time on this project. "Between morning trapping and night-time rocket-netting, crew members have been working 15- to 18-hour days," Mathews says. "They have to monitor a 100-square mile area, which is a lot of landscape to cover, and they've done it every day — in sub-zero temperatures, snow, rain and mud. The dedication of these young biologists has been essential to the success of the project to date."

This research is funded by Whitetails Unlimited, the National Cattlemen's Beef Association, and the Wisconsin DNR.

Graduate Students in Progress


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