They are some of nature’s best adapters, able to thrive anywhere from the open undeveloped landscapes of the west, to the paved streets of suburbia and even city parks. Deer are in fact so ubiquitous across the U.S. that they are often thought of as little more than pigeons on hooves. But despite their seeming hardiness, deer populations in many states are actually in decline.
The downward population trend has hunters and those who depend on the revenue generated from hunting deeply concerned, as well as biologists who warn that thousands of dead deer are a red flag about the health of the entire ecosystem.
According to the Denver Post, the nation’s largest herd of mule deer, located in northwestern Colorado, has decreased by more than two-thirds since 2005 — from 105,900 to 32,000. The number of hunting licenses issued has tried to follow suit, from 130,106 in 2007 to about 80,000 for this year, slashing deeply into conservation budgets.
“Mule deer are an indicator species. If mule deer herds are in poor health, it probably means the land itself is in poor condition and that a lot of other species are at risk,” National Wildlife Federation public lands policy director Kate Zimmerman told the Denver Post.
Across Colorado, the deer population is down by about 36 percent, and similar declines have been documented in several other western states.
In Wyoming, mule deer populations have declined by 168,000 or 31 percent since 2000 according to recent numbers released by the Western Association of Fish and Wildlife Agencies (WAFWA). The report also highlighted significant declines in North Dakota, Utah, and New Mexico.
One culprit behind dropping deer numbers may be the explosion in oil and gas development seen across the West in the last decade. A maze of well pads, pipelines, and service roads now crisscrosses the landscape mule deer were once easily able to navigate.
For example, mule deer populations in the Pinedale Anticline, a gas field in Wyoming’ s Sublette County, have decreased by 60 percent since gas development took off in the area in 2001.
In addition to the habitat disruption and fragmentation caused by oil and gas development, wildlife experts also believe that several climate-related factors may be driving down deer numbers. Drought may be one of the biggest deer killers in the West. Sharp reductions in snowpack is causing streams to run dry earlier in the summer, and when the water is gone, key forage dries up as well. Studies of mule deer have found that if a doe is underfed during her pregnancy, she will lose 90 percent of her fawns. A doe that has enough to eat only loses 5 percent of her fawns.
As wildfires have become more frequent and intense in the West, changing management practices to suppress fires may also have contributed to the decline of deer populations. When brush is cleared as it often is to limit the risk of wildfires, deer lose both key shelter to hide from predators and important food sources.
This August, Colorado wildlife officials are gathering for a summit to discuss how to best boost deer numbers.