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Crews collar fawns to see why Utah's deer numbers drop

Published July 5, 2012 8:52 am

Experts are tracking does, their newborns and predators.
This is an archived article that was published on sltrib.com in 2012, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

Monroe Mountain, Piute County • Newborn mule deer are well prepared to avoid ending up as coyote food. Upon birth, they carry little, if any, scent and instinctively hide in brush and fallen timber, lying still for long stretches.

So, if predators have a hard time finding fawns, imagine how difficult it can be for humans.

Utah researchers, trying to determine the impact of coyote predation, recognized the challenges of tracking down the newborns and turned to technology for help in getting a four-year study off to a solid start.

In March, researchers and biologists captured 65 pregnant does on their wintering ground in Piute County. Radio collars were placed on their necks. Attention then was turned to the other end of the animal. Vaginal implant transmitters (VITs) were placed in the mothers-to-be before they were released.

"They moved onto [Monroe] mountain in mid- to late May, and our fist implant transmitters started being activated on June 1," says Brigham Young University graduate student and field research coordinator Eric Freeman.

The VITs send a signal from the time they are implanted. The does then expel the transmitters when they start delivering their babies. The signal changes its tone when the receiver drops below 95 degrees Fahrenheit, indicating birth has taken place.

Once a fawn is located — and there are almost always two with each doe — the researcher puts on surgical gloves to minimize the human smell.

The animal is weighed and measured, and a collar is placed on its neck. The collars are designed to expand twice as the fawn grows and then, eventually, fall off. The newborns are then placed back where they were discovered.

All this in an effort to learn why fawn numbers — and, by extension, mule deer populations — are declining.

The study — a partnership of the Utah Division of Wildlife Resources, BYU and Utah State University — is expected to cost $950,000, with DWR picking up the bulk of the tab. Most of that money comes from state auctions of big-game tags.

Sportsmen for Fish and Wildlife kicked in $100,000 and the Mule Deer Foundation added $75,000.

BYU is handling the fawn-collaring and monitoring portion of the project while USU works on the coyote collaring.

Since early June, Freeman and several colleagues have been roaming Monroe Mountain, waving antennas, tracking collared does and waiting for VITs to change their tone. Once it happens, they use the radio signal from the new mother and the location of the VIT to home in on the right area.

"It's like looking for an 8-pound loaf of bread with spots," says Freeman while scouring the brush for the fawn — or twin fawns — of a doe that picked a spot at 10,000 feet to give birth.

In this instance, even after seeing the doe and locating the expelled VIT, Freeman and two helpers fail to find a fawn. They climb on all-terrain vehicles for the 20-mile ride back to camp in the dark. Five hours later, they do it all over again.

The study's goal is to collar 240 fawns in four years. The team had tagged 65 through the end of June, surpassing the first-year goal of 60.

Freeman confirmed two fawn kills by predators (one mountain lion and one coyote). Brock McMillan, an associate professor at BYU, also witnessed a cougar taking down a doe while he was looking for fawns.

Mule deer populations across the West have been dropping for decades. The issue made headlines at the Utah Legislature this year with passage of two bills aimed at helping to stem the decline.

SB245 appropriated $500,000 to DWR to reduce coyote populations in areas where deer herds have suffered significant losses. Part of the Mule Deer Protection Act raised the bounty on coyotes from $20 for each animal to $50 and took effect July 1. SB87 added a $5 fee on big-game hunting permits for predator-control programs.

The Monroe Mountain study, however, was organized long before the Legislature acted.

"DWR and conservation groups felt like we needed better information of fawn mortality and what is causing chronically low fawn production," says Jim Karpowitz, DWR director and lead researcher in the last fawn mortality study conducted in Utah in 1984. "This is probably the biggest and best-funded study of its kind at any time in Utah. At the end of the day, we expect to have better information about fawn mortality and how predator control may impact fawn production."

Vance Mumford, a wildlife biologist from DWR's Cedar City office, says the recent low fawn-to-doe ratios on the Monroe hunting unit could be due to several factors, adding that this study should help pinpoint causes and possible remedies.

"Is the decline because of habitat loss, poor nutrition for the doe and young fawns or is it depredation? All three may play a role," Mumford says. "Mule deer can have high production rates. If everything lines up and there is a lack of predation and good habitat conditions, population can grow quite quickly. The potential is there, the question is what can we do to increase that survival — if anything?"

In 1999, the post-hunting season ratio on the Monroe Unit was 68 fawns to 100 does. The number plunged to 38 per 100 in 2010.

Anis Aoude, DWR's chief of big game, says any ratio above 60 signals a growing population. If the numbers drops below that level, it becomes a concern.

"It can be as low as about 50 and the population can still be OK," Aoude says, "but anything below 50 and it gets in the critical range."

For the study, the Monroe Mountain area was split. Half the fawns were collared on the north end and half on the south.

Twenty-five coyotes will be collared in each half. The halves are important because the study is being done in "an experimental cross-over design."

"We will have two years of coyote control on one half and, after two years, we will switch and control coyotes on the other half," Mumford says. "By using control on the coyotes, we kind of have a control for any mitigating factors."

USU researchers started collaring coyotes over the winter. Capturing the wild canines proved difficult, and the goal of collaring 25 coyotes on each end of the Monroe Mountain study area fell a little short before federal hunters began killing the predators on the north side. (The U.S. Department of Agriculture reduces the coyotes by shooting them from the air or trapping them on the ground. )

"We probably overestimated the number of adult resident coyotes on that mountain range," says USU assistant professor Julie Young, a co-principal investigator on the study and a biologist for the National Wildlife Research Center. "We knew nothing about the coyotes there."

Young says more than 50 coyotes have been killed this year. Interestingly, her team of researchers found at least one coyote — possibly two — had been killed by mountain lions. One of them was also partially eaten by the cougar.

Although lions are not part of this study, Young says her team will monitor the cats during the study using a strong collection of data on cougars from previous DWR research.

"Although we are studying coyotes and mule deer, there are a lot of other factors that could be important in how that relationship plays out," Young says. "It seems silly, given the radio collars already on the mountain lions and the information we already have on them, not to collect what information we can on them for this study."

Aoude is eager to see the results of the fawn study and then adapt management practices accordingly on Monroe Mountain and, possibly, across the state.

"It may tell us specific things we can do on that unit," he says. "If fawn survival is weather-dependent, we won't be able to do much. If it is predation, we can do more control. But we may see, like many other studies have shown, that malnutrition or diseases are a major killer of fawns early on. Predation usually comes in third."

brettp@sltrib.com —

Online • Photo gallery and video

O To view more photos and a video of the fawn tagging. > sltrib.com —

If you see a fawn all alone ... leave it alone

Mule deer does typically give birth to two fawns sometime in June. About that time each year, state wildlife officials get reports from the public about "orphaned fawns." The fawns are rarely orphaned, but are left alone by their mothers in an effort to protect them from predators. Elk also leave young calves alone for long periods. The best thing to do is leave fawns and calves alone and leave the area without disturbing them.






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