Examining 27 Years of Black Bear Mortality Data in Colorado

Drought & Over-Hunting Led to High Black Bear Mortality & Low Recruitment Mortality Rates Have Leveled in the past Two Years

The Colorado Division of Wildlife’s (DOW) data for the period 1979 to 2006 show that black bear (Ursus americanus) mortality came largely from sport hunters (86%), with livestock growers coming in at a distant second place (7%). Mortality from poaching, roadkill, or human conflicts rated third at 6% [Figure 1].

As Figure 1 shows, the years 1999 to 2002 saw a significant jump in black bear mortality in Colorado. That spike resulted from droughts and, in one year, a late springtime frost. Bad weather depleted bears’ foodstuffs, which caused desperately hungry bruins to migrate towards urban interfaces. Starving bears foraged in trash cans, gardens, bird feeders, and dumpsters. “Nuisance” bear kills jumped in 2001, 2002, and 2004.

Black Bear Mortality Graphic

Notably, human-bear conflicts (including roadkills) involve more females than males, according to the DOW. But removing females from the population has long-term consequences. Tom Beck, a now-retired DOW biologist, conducted a decade-long study of bears on the Uncompahgre. His study found that females gave birth every other year to an average of 2 cubs, and that the females did not breed until they were almost 5 years old. Thus, we know that mortality, particularly on breeding females, can greatly influence bear populations, including recruitment.

In 1992, Colorado citizens passed an initiative that prohibited the hunting of black bears during the time when females are raising young cubs (it eliminated the springtime-bear-hunting season). It also eliminated the use of bait and hounds for hunting. As Figure 1 shows, prior to the initiative, sport hunters killed an average of 498 bears per year (1979 to 1992), and after the initiative, sport hunters killed an average of 572 bears per year (1993 to 2006).

For the first time in 2005, DOW set limits on the number of bears that could be hunted. The DOW was concerned that it had allowed over-exploitation on Colorado’s black bear population. As a result of the new hunting quota system (coupled with four contiguous years of high mortality (1999 to 2002)), the total mortality of black bears in Colorado has dropped dramatically in the past four years—from a high of 1,269 bears in 2002 to a new low of 602 in 2006.

A recent study conducted in New Mexico has informed bear-hunting quotas in that state. The biologists learned when bears entered and left their dens—and the timing was regional. Bears entered their dens 11 days earlier in the northern part of the state than in the south because of food availability differentials. Males and females entered and left the dens at different times.

Moreover, New Mexico now takes annual mast surveys (that is, they look at food availability of various bear crops such as acorns) to predict how the population will respond. This information has facilitated better management practices in that state.

While we applaud the DOW’s recent efforts to lower black bear hunting quotas, and its bear study in the Aspen-Carbondale area, we urge the Division to annually gather masting surveys, determine den entrance and exit dates, and assess methodologies to better protect breeding females.

by Wendy Keefover-Ring


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