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Multimillion-dollar study shines light on deer

Published: Wednesday, Feb. 20, 2013 11:24 a.m. CST

(Continued from Page 1)

(MCT) — Hunters continued to be the leading cause of buck mortality in Wisconsin — and by a wide margin.

Fawn survival was higher in 2012, likely due to an early spring. The leading source of fawn mortality continues to be predators.

And the buck recovery rate was in line with estimates used through the years by state deer managers.

These are among the leading findings of the second full year of Wisconsin deer research.

A 2012 summary of the state’s deer research was released recently by the Department of Natural Resources.

The results don’t vary a great deal from the first year. The most notable difference was markedly higher survival of fawns (47 percent in 2012 vs. 27percent in 2011) through 7 months of age in the northern study area.

“The relatively mild winter and early green-up is likely a big factor there,” said Karl Martin, chief of the DNR’s wildlife research section. “It points out the value of doing multiyear studies, so you get as much data over as long a time period as possible.”

Similar to the first year, 73percent to 92percent of the buck mortality was due to hunters.

And also in line with the first year, fawns survived at higher rates in the eastern study area (63percent through seven months) than in the north (47percent).

The studies were initiated by the DNR in late 2010 at the request of hunters.

The work is formally divided into two projects: a buck mortality study and a fawn recruitment and predation study.

The buck study is intended to improve the accuracy and precision of the Sex-Age-Kill deer population model. The fawn study is designed to improve understanding of recruitment rates and causes of mortality.

To gain insight into regional differences in Wisconsin’s deer, the studies are taking place in two areas: A 3,557-square-mile area in Sawyer, Price and Rusk counties (representative of the northern forest) and a 2,318-square-mile area in Shawano, Waupaca and Outagamie counties (mixed agricultural habitat).

The northern study area is 34percent public land, 80percent forested, has wolves, bears, coyotes and bobcats as the primary predators and a road density of about 1.6 miles per square mile.

The eastern study area is 3percent public, 35percent forested, has coyotes and bobcats as the primary predators and about twice the road density as the northern study area.

The hunting pressure is higher, too, in the eastern study area, with between 21 and 36 hunters per square mile of deer range on opening day of the gun deer season. In the north, it’s between eight and 15 hunters per square mile.

Blood and other samples taken from deer in the study also provide insight into the health of the herd.

At a cost of more than $2 million, the work represents Wisconsin’s largest investment in deer research. The projects are funded through the Federal Aid in Wildlife Restoration Act, an excise tax on hunting and shooting equipment.

The project is entering its third year of field work. Data for the first year were first collected in late 2010 through late 2011. The most recent report summarizes data from January 2012 through January 2013.

To study the deer, researchers and volunteers capture and place radio collars on the animals.

The signals are then monitored to track the animals’ movements. If a mortality signal is received, the researchers attempt to find the animal and determine the cause of death.

Among the findings over the last year:

Adult male deer are most targeted by hunters. In the north, adult buck survival was 31percent; in the east, it was 27percent. Between 73 and 91percent of the mortality of adult bucks was due to hunters, mostly during the gun deer season in November.

In the north, hunters killed eight adult bucks (five during the archery season and three during gun season), wolves killed two and coyotes took one.

In the east, hunters killed 11 adult bucks (eight firearm, one archery, one wounding). One adult buck was also killed by a vehicle. Predators did not kill an adult buck in the east.

Yearling male deer survival was 52percent in the north and 58percent in the east. Hunters caused from 82 to 92percent of the mortality. In the north, hunters killed 11 yearling bucks (nine with firearms and two with archery equipment); predators killed no yearling bucks last year in this study area.

In the east, hunters killed 14 yearling bucks, two were killed in vehicle collisions and one was killed by a coyote.

Among adult female deer, 73percent survived the year in the north and 86percent survived in the east.

Most fawns were born in late May in both study areas. Most fawn mortalities occurred within a few weeks of birth.

Predators were the leading cause of fawn mortalities (55percent) in both study areas. Unknown predators (the researchers were unable to identify the predator) caused the most fawn mortality in the north, followed by bears. In the east, coyotes were the top predator on fawns (five), but road kills took nearly as many (four).

So with two years of data, how are the studies shaping up?

“The buck recovery rates from 2012 are in line with what we’ve historically used for the two areas,” said Robert Rolley, DNR wildlife population ecologist. “We’ll be interested to see more years of data before we make any conclusions.”

One challenge the researchers have is sample size. They hope to get more animals “on the air” this year.

The results of this winter’s trapping efforts have been good, according to Jared Duquette, DNR deer researcher.

As of Jan. 26, crews in the northern study area captured 12 adult bucks, 14 button bucks and 33 does.

In the eastern study area crews had caught eight adult bucks, nine button bucks and 12 does.

The efforts included the capture of 20 deer in the northern study area on Jan. 3, a single-day record. The researchers hope to radio-collar 40 bucks in the north.

The fawn study will continue through the end of 2013. The buck study is scheduled to run through 2015.

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