Wolf World Item # 234
Category: Ecology & Behavior
Vol. 58 (1994) 6 pp.
The recent colonization of the northwestern United States by an endangered wolf has raised concerns among hunters regarding competition for prey. The authors hoped that data on wolf prey selection might dispel misperceptions -- and decrease human-caused wolf mortalities that would impact wolf recovery.
World of Wolves
Prey Taken by Colonizing Wolves and Hunters in the Glacier National Park Area
Diane Boyd, Robert Ream, Daniel Fletscher & Michael Fairchild
Wolves were reduced in southeastern British Columbia and Alberta and were systematically exterminated within and near Glacier National Park, Montana, by the late 1930s....Recolonization of wolves began in 1982 with pack activity observed immediately north of Glacier National Park.
Wolf numbers have increased in Glacier National Park and surrounding lands since 1982, providing an opportunity to study wolf-prey relationships in an area containing a diverse ungulate and predatory community. Seven large predators, including humans, coyotes (Canis latrans), wolves, mountain lions (Felis concolor), wolverines (Gulo gulo), black bears (Ursus americanus) and grizzly bears (U. arctos) share the prey base. These predators may compete for prey, including white-tailed deer, mule deer (O[docoileus].hemionus), elk, moose (Alces alces), showshoe hare (Lepus americanus), American beaver (Castor canadensis) and various smaller mammals.
....Local hunters and residents have concerns about the affects [sic] of wolves on ungulates, and they may have a greater potential to affect wolf recovery than does the general public. Of 14 known adult wolf mortalities near Glacier National Park from 1982 to 1990, all were caused by humans. Misinformation regarding wolves and their impacts on prey adversely affects the ability of managers to carry out their mandate to increase populations of this endangered species. Therefore, it is important to provide managers and the public with accurate information on prey selection by wolves and humans....
....[F]ew researchers have studied predation by colonizing wolves in an ecosystem containing several ungulate and predator species. We predicted that this colonizing population of wolves would select more vulnerable ungulates (juvenile, old, post-rut males) than would established populations of wolves. Our objectives were to (1) compare characteristics of prey killed by wolves with those of prey killed by humans (hunter check-station data), (2) compare sex and age of wolf-killed ungulates with those of ungulates observed on transects, and (3) compare these data with those from other predation studies to characterize prey selection by colonizing wolves....
The study was conducted in southeastern British Columbia and northwestern Montana in the North Fork of the Flathead River Basin. The North Fork of the Flathead River separates Glacier National Park, where most wolf-killed prey were found, from adjacent lands, where hunters killed ungulates. In view of telemetry studies of elk and white-tailed deer, we believe that wolves and hunters were selecting from the same population of these prey....
From August 1984 through July 1991, we trapped, immobilized, eartagged, radiocollared, and released wolves. We located wolves from the ground or the air 4 times (or more)/week during winter (Nov-Apr). We determined pack sizes by direct observations during telemetry flights. We determined wolf travel routes by ground-based telemetry and subsequent skiing or snowshoeing along wolf trails 1-2 days after wolves moved out of the area. Most kills were found along these travel routes within 2 days of abandonment. We considered only prey known to have been killed by wolves in this analysis; scavenged carcasses were omitted. We examined carcasses for species, age, sex, skeletal abnormalities, parasites and degree of consumption....
We collected data on deer, elk, and moose killed by hunters in Montana at the North Fork hunter check station during the 1985-90 hunting seasons....
We captured and radiocollared 31 wolves from August 1984 through July 1991. The wolf pack consisted of 6, 12, 10, 10, 12, and 7 wolves in the early winters of 1984-85 to 1989-90, respectively. In summer 1990, the pack split into 3 packs containing 9, 7, and 2 wolves, dividing the former home range into thirds. We followed all three packs during winter 1990-91.
We found 243 wolf-killed prey, 211 from snowtracking and 32 from aerial observations. Of the 229 ungulates killed, 138 were white-tailed deer (60%), 68 elk (30%), 15 moose (7%), and 8 mule deer (3%). Other prey included 2 beavers, 1 porcupine, 2 mountain lions (a kitten and an adult), 3 ruffed grouse, 2 ravens, 1 coyote, 1 striped skunk, 1 golden eagle, and 1 meadow vole. Sample sizes for wolf-killed prey other than white-tailed deer and elk were too small for further analysis.
Hunters brought 706 animals through the check station during the 1985-90 hunting seasons: 438 white-tailed deer (62%), 138 elk (20%), 120 mule deer (17%), and 10 moose (1%). Hunters killed fewer fawns (6%) than expected, whereas wolves killed more fawns (40%) and adults 6 (or more) years old and fewer yearlings and 2-3 year olds than expected (Table 1). Among adult deer these patterns resulted in median ages of 3.5 and 5.5 years for hunter- and wolf-killed white-tailed deer, respectively....
When sexes were analyzed separately, the age distribution of male white-tailed deer killed by wolves was different from those killed by hunters, whereas the age distribution of females in the 2 samples was similar....
The age distribution of male elk killed by wolves was similar to the distribution of male [elk] killed by hunters. Age distributions of females killed by wolves and hunters also were similar. When sexes were combined, and unknown-sex prey were added, the distributions were different. This was due to our inability to determine sex of most wolf-killed elk calves. Wolves killed a higher proportion (43%) and hunters a lower proportion (13%) of calves than expected (Table 1). No other differences were significant, although wolves tended to kill more older elk than did hunters....
Sex ratio of wolf-killed white-tailed deer differed from that of hunter-killed deer. Sex ratio of wolf-killed deer differed from the population for 1990-91. The sex ratio of wolf-killed elk did not differ from that of hunter-killed elk, but the sex ratio of wolf-killed elk differed from that of the population....
Forty percent of wolf-killed deer, 6% of hunter-killed deer, and 22% of observed white-tailed deer were juveniles. Wolves selected fawns at a higher rate relative to their occurrence in the population....Our data, like those of Fritts and Mech (1981), suggest that low-density, colonizing wolves kill a higher proportion of fawns than do established wolf populatons.
Similarly, 43% of wolf-killed elk, 13% of hunter-killed elk, and 16% of observed elk were juveniles. As did Carbyn (1974), we found that elk calves were vulnerable to predation by wolves. This may be especially true where wolf density is low relative to prey density....These data suggest that colonizing wolves select elk calves at a higher rate than do wolves in established populations.
The age structure of female white-tailed deer and elk (other than fawns and calves) killed by hunters was probably comparable with population age structures of female deer. Assuming hunters and wolves are selecting from the same populations, this suggests that wolves select more older, adult female white-tailed deer and elk than do hunters....
Wolves killed a higher proportion of male white-tailed deer and elk than occurred in the populations. Because most hunting pressure is limited to male white-tailed deer and elk, males may be wounded more frequently and become easier prey for wolves. Orphaned pups in the Ninemile Drainage near Missoula, Montana killed several male white-tailed deer wounded by hunters. Male white-tailed deer and elk also enter winter in relatively poor condition after expending much energy during the autumn rut, predisposing them to starvation and predation throughout winter....
Wolves in the Glacier National Park area selected age and sex categories of white-tailed deer and elk differently than did hunters. Although hunters selected for nonjuvenile prey, the juvenile ungulates strongly selected by wolves (and not desired by hunters) are not available as adults for future hunter harvest. This may cause conflict in the future and needs further study. Wolves are only one of many predator species in this region. Little research has been conducted on the other large, wild carnivores (grizzly bear, black bear, mountain lion, coyote, and wolverine) in Glacier National Park that share the ungulate prey base with the wolves. Other predator studies should be established and coordinated to provide linked data for optimal management of predators and their prey.
Table 1: Ages of wolf- and hunter-killed white-tailed deer and elk in the Glacier National Park area during winter 1985-91.