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Spring moisture boosts mule deer numbers

1/20/2006

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TWIN FALLS, Idaho — Just as a rising tide lifts all boats, a mild winter boosts all deer populations, a trend that hunters should notice across the Rockies this fall.

There is no better evidence of the impacts of favorable climate and habitat conditions than in south-central Idaho, where mule deer are rebounding after seven years of profound drought.

In the state's Magic Valley Region, which extends from the Smoky Mountains and Boise River headwaters south through the Snake River Plain to the Utah line, hunters should see fair numbers of older bucks, but high numbers of young deer, say wildlife managers.

The resurgence in deer numbers is largely a function of habitat conditions.

"We're having excellent fawn recruitment in many parts of the region this year," said Randy Smith, Idaho Fish and Game's Magic Valley regional wildlife manager (208-324-4350) in Jerome, Idaho.

"The most dramatic increase this year has been in hunting units 55 and 56, south and east of Burley."

Smith cites a combination of ample spring rains in both 2004 and this year, plus a mild winter this past year, for the bump in mule deer populations. He said the rebound was overdue after several years of declining fawn production and poor recruitment of young deer into the breeding population.

"Mule deer numbers in the Magic Valley Region continue to increase or remain stable," said Smith.

"Early spring and late summer rains in 2004 improved habitat, which is boding well for mule deer."

And for mule deer hunters, Idaho's archery season opened Aug. 30 in most hunting units and closes Sept. 30. The general rifle season is generally Oct. 10­31.

The Magic Valley Region has a variety of seasons for rifle deer hunting, ranging from the permit-only hunts in units 44, 45, 52, 54, 55 and 57 to general any-weapon seasons in units 43, 46, 48, 49, 52A, 53 and 56 and late-season trophy opportunities in units 45, 47 and 49.

Aerial surveys

While game managers don't intensively survey the entire region, they conduct aerial inventories twice a year on segments of mule deer winter range.

The first count following the hunting season helps biologists determine the number of bucks and fawns relative to the number of does in the population.

The second survey in early spring allows biologists to count deer in trend areas and evaluate winter survival, said Smith.

"The comparison of fawn ratios pre- and post-winter enables biologists to estimate winter fawn survival," he said.

"The proportion of the deer population comprised of fawns at the end of winter allows biologists to infer whether a population is declining or increasing and provides the best indicator of reproductive performance of the herd during the past year."

To get a good variety of habitat conditions, hunting season types and herd dynamics, Magic Valley Region biologists inventory units 45, 54, 55 and 56. Here is what they've noted over the last three years in each unit:

Unit 45

One of Idaho's best trophy mule deer units, Unit 45 is located in winter range that concentrates deer from a wide area of the Smoky and Galena mountains. The unit extends from Mountain Home east to Camas and Mormon reservoirs, Highway 20 south to the Snake River and Interstate 84.

Wintertime population surveys give a good indication of its appeal to deer.

In 2004, biologists counted 5,410 mule deer, one of the highest populations of any hunting unit in Idaho.

In 2004 the number was even higher at 7,144 deer, and this past winter biologists counted 6,267 mule deer.

Even more remarkable than the total population is the percentage of bucks. Last winter, biologists counted 37 bucks per 100 does.

The number of fawns surveyed in the pre-winter count was 61 fawns per 100 adults, and in the postseason count was 50 fawns per 100 adult deer.

"Deer observed in the Bennett Hills (Unit 45) trend area declined by 12 percent from the 2004 levels, but were 16 percent higher than in 2003," said Smith.

"Comparison of the pre- and post-winter fawn-to-adult deer ratios suggests excellent winter fawn survival of around 75 percent and a recruitment rate of 33 percent."

If you were lucky enough to draw one of the 75 early-season (Oct. 5­31) tags or one of the coveted 50 late-season (Nov. 10­24) mule deer tags for this area, you'll have your pick of some remarkable mule deer.

Unit 54

This unit includes a wide swath of sagebrush and cheat grass habitat from Twin Falls south to the Utah line and Goose Creek west to Highway 93. It was one of the hardest-hit units by the drought in recent years.

Unit 54 is also managed by special permits, this year 450 permits are available for the October rifle season and another 20 for late-season trophy hunters.

In 2003, biologists counted 1,133 mule deer in Unit 54, but the next year the population bumped to 1,832 deer and this past winter the number was 1,817 deer.

In the post-hunting season count they observed 29 bucks per 100 does. The number of fawns counted in the prewinter count was 53 fawns per 100 adults and in the postseason count was 42 fawns per 100 adult deer.

"The trend area count in Unit 54 was similar to last year and 60 percent higher than in 2003," Smith said.

"A comparison of pre- and post-winter fawn-to-adult deer ratios suggests that fawn survival was higher than 75 percent. Of the four survey areas, Unit 54 had the lowest ratio of fawns entering the winter, and even with excellent fawn survival, the lowest recruitment rate of 30 percent."

Unit 55

Another permit unit, District 55 borders Unit 54 to the east and extends from the Snake River south to Utah and east to I-84's southern jag.

The population has soared from a low of 607 deer in 2003 to 1,941 mule deer this past winter. Fawns average 68 per 100 adults.

The district has one of the few early-season buck seasons. Twenty-five permits are issued for a season that extends from mid-August through late September. Another 350 permits are available for the October deer season.

Unit 56

The only general-tag season in the inventory, Unit 56 is the southeasternmost of the Magic Valley units. It extends from I-86 to the north to Rock and Deep creeks on the east to I-84 on the south and west sides.

In the latter half of the general season in Unit 56, hunters are restricted to 2-point bucks only.

Total population rose from 556 in 2003 to 994 in 2004 to 1,284 deer in 2005, said Smith. The postseason ratio of 13 bucks to 100 does was lower than other trend areas but near the statewide average. About 62 fawns per 100 adults were counted in 2005.

"The deer populations in Units 55 and 56 have shown dramatic growth since 2003," Smith said.

"Observed postwinter fawn ratios suggest recruitment rates of 40 percent in Unit 55 and 37 percent in Unit 56; indicative of population increases. The buck-to-doe ratio in Unit 56, following the general any-buck hunting in 2004, was 13 bucks per hundred does compared to an average of 15 bucks per 100 does from 1998­2002."

For more on hunting the Rocky Mountain region, check out Andrew McKean's new book, "The Ultimate Guide to Hunting the West."


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