Drought Strains Deer, Upland Bird Populations

2013-11-07T04:00:00Z Drought Strains Deer, Upland Bird PopulationsBy Mike Cothern - For the Times-News Twin Falls Times-News
November 07, 2013 4:00 am  • 

ROGERSON • During a hunting trip near Cedar Creek Reservoir last month, two sights caught my attention. While I wasn’t surprised at the impoundment’s low water level, seeing it reminded me how little precipitation fell across southern Idaho this year.

Shortly afterward, I came across a small herd of deer — does and fawns — hiding in the canyon below the dam. The two mothers did not appear to be in great condition. One of them, probably nursing twins, was thin enough that I could see the outline of her ribs.

Randy Smith, regional wildlife manager for the Idaho Department of Fish and Game, did not seem surprised at my observation. Several people in the northern part of the valley have told him that a lot of deer looked poor throughout the summer.

“This year’s dry conditions have made it tough on all sorts of critters,” he said.

How dry has it been? The U.S. Drought Monitor — a diverse partnership of weather, snow survey and climate professionals who produce an updated drought map each week — currently classifies the entire Magic Valley as under “severe drought.” The Twin Falls area, for example, normally receives almost 11 inches of precipitation per year; the water year ending Sept. 30 barely produced 7 inches.

Does and Fawns

“Wildlife abundance is driven by weather,” Smith said. While the last two mild winters produced limited mortality and kept the deer population up, the extended dry conditions have compromised the condition of not just lactating does. Smith reported that many harvested yearlings coming through the department’s check stations this fall also appeared to lack adequate body fat.

If dry conditions and poor forage hamper the ability of females to obtain adequate nutrition, their reproductive ability can be affected. Fewer twins will be born, Smith said, especially among younger does bred for the first time. The cascading effect of poor nutrition can in turn affect fawns that have a smaller supply of milk.

A doe’s poor milk production will greatly decrease a fawn’s chance of survival if it goes into the winter weighing less than 55 pounds. If that offspring weighs only 10 pounds more, the animal’s outlook is much better. Smith suspects that many fawns will weigh in around the more critical level and will be at risk this winter.

Ample moisture needed to temper the drought can kill animals weakened by that drought if the moisture comes in overwhelming amounts and with prolonged cold temperatures.

“While we are all hoping for some good precipitation this winter,” Smith said. “It would be great if it came down as snow in the mountains and rain in the lower country.”

Upland Birds

The drought also seems to have hurt upland game birds. While a warm, dry spring usually produces a good hatch, such was not the case this year, Smith said. “A lot of bird species did not do well.” He speculated that the two key components for chick survival — plant cover and insects — were insufficient due to the extreme dryness. An entomologist on the department’s staff reported that this was one of the poorest insect production years that he had ever seen, Smith said.

Pheasants, so closely tied to farming that they can actually benefit from a wet spring if it delays the first cutting of hay during their hatch, again fared poorly.

The only upland game bird that seemed to counter the trend of meager production in southern Idaho was the dusky grouse, formerly known as the blue grouse. This higher-elevation species did very well, Smith reported.

Fisheries

The drought’s effect on fish is less complicated than on big game and birds because that equation is driven mostly by the volume of available water. The Magic Valley’s finned resource, however, often subsists in a different type of environment than in the rest of the state.

“We are somewhat unique in that many of our fisheries enjoy the benefits of irrigation impoundments,” said Doug Megargle, the department’s regional fishery manager.

Megargle is happy to take advantage of the stored water that is strategically released to satisfy hundreds of thousands of acres of thirsty crops. Managing those fisheries, however, presents challenges when a drought year is thrown on top of those seasonally fluctuating water levels. Less water certainly equates to a reduction in habitat, but during critically low levels where survival isn’t likely, the department sometimes resorts to letting the public salvage a doomed fish population.

Another issue, Megargle noted, is that sometimes when reservoir levels are low, fish simply exit through the dams. When fish leave a system, are salvaged or simply perish and the department must rebuild a fishery, the recovery takes time.

“During a drought, managing the stocking of trout can become organized chaos at times,” Megargle said. “For example, Little Camas Reservoir this year was depleted early and the remaining fish salvaged, but a plan was in place to plant catchable trout back in that water body this fall.” Because of the severity of the drought and poor inflows, however, those fish could not be taken there.

“We try to find the most responsible use of catchable trout when they cannot be planted in their planned destination,” Megargle said. Economic factors to consider: the increased cost of holding fish longer than desired in hatcheries versus paying for their transportation to other locations.

While some reservoirs have recurring water issues similar to Little Camas, such as Thorn Creek and on occasion Oakley, others are immune to de-watering, Megargle said. These include Little Wood, Magic and especially Salmon Falls, which by the nature of their relatively high outlets can maintain safe minimum pools.

When might the current dry phase end? No clear consensus seems to exist among forecasters as to how much precipitation this winter might deliver; the Drought Monitor simply classifies the near-term outlook for the region as “drought persists or intensifies.”

Copyright 2015 Twin Falls Times-News. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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