Diane K. Boyd

Characteristics of dispersal in a colonizing wolf population in the central Rocky Mountains

Gray wolves (Canis lupus) were eradicated from Montana in the 1930s and the adjacent Canadian Rockies by the 1950s, but recolonized these areas in the 1980s. We studied wolf recovery in and near Glacier National Park (GNP), Montana, from 1979 to 1997. During this period, 31 of 58 tagged wolves dispersed. Most wolves (57%) did not make exploratory forays 3 months before permanent separation from their natal pack. Wolves usually left their natal home range quickly (median = 4 days; mode = 1 day) after separating from the pack. Mean dispersal distance was not different (P > 0.05) between males (113 km) and females (78 km), excluding an unusually long dispersal of 840 km by a yearling female. Wolves tended to disperse in a northerly direction to areas of higher wolf density. January-February and May-June were peak months for dispersal. Mean dispersal age (M = 28.7 months; F = 38.4 months) was not correlated with maximum pack size. Twenty percent of dispersers were ≥57 months old at dispersal. Sex ratios of dispersers and captured wolves (both 71% F) differed from parity (P = 0.002). Annual survival rate (x ± SE) for dispersers and biders (philopatric wolves) did not differ (dispersers = 0.76 ± 0.10; biders = 0.77 ± 0.14). Wolves killed by humans died closer to roads (x = 0.13 km) than wolves that died from other causes (x = 0.85 km). Eighty percent (n = 30) of wolf mortalities were caused by humans, with proportionately more dispersers (90%) than biders (60%) dying from human causes. Dispersers produced more litters than biders. Effects of mountainous terrain and management on wolf recovery are discussed.

Population dynamics of a recolonizing wolf population

Breeding populations of wolves (Canis lupus) were absent from the western United States for about 50 years following their extirpation by humans in the 1930s. Here we describe the recolonization by wolves of northwestem Montana and southeastern British Columbia, from the initial production of a litter by a pair of wolves in 1982 through the mid-1990s when 3-4 packs produced litters. Sex ratio of captured wolves favored females (38/54 = 70%; X 2 = 8.96, 1 df, P < 0.005). Litter size in early summer (x = 5.3, SE = 0.4, n = 26) and in December (x = 4.5, SE = 0.5, n = 26) were relatively high compared to similar counts in established populations elsewhere. Pack size in May was unrelated to litter size in June (r s = -0.13, 23 df, P = 0.25) or the following December (r s = -0.12, 23 df, P = 0.28). Annual adult survival rate (0.80) was relatively high in this semi-protected population and was higher among residents (0.84) than among wolves that dispersed (0.66) from the study area (Z = 2.24, P = 0.025). Although dispersal was common among radiocollared wolves (19/43 = 44%), population growth within the study area averaged 20% per year from 1982 to 1995. Low human-caused mortality rates and maintenance of connectivity for wolves between this small population in the United States and larger populations in Canada will enhance the probability of persistence and expansion of this population.

Survival of Colonizing Wolves in the Northern Rocky Mountains of the United States, 1982-2004

Abstract After roughly a 60-year absence, wolves (Canis lupus) immigrated (1979) and were reintroduced (1995–1996) into the northern Rocky Mountains (NRM), USA, where wolves are protected under the Endangered Species Act. The wolf recovery goal is to restore an equitably distributed metapopulation of ≥30 breeding pairs and 300 wolves in Montana, Idaho, and Wyoming, while minimizing damage to livestock; ultimately, the objective is to establish state-managed conservation programs for wolf populations in NRM. Previously, wolves were eradicated from the NRM because of excessive human killing. We used Andersen–Gill hazard models to assess biological, habitat, and anthropogenic factors contributing to current wolf mortality risk and whether federal protection was adequate to provide acceptably low hazards. We radiocollared 711 wolves in Idaho, Montana, and Wyoming (e.g., NRM region of the United States) from 1982 to 2004 and recorded 363 mortalities. Overall, annual survival rate of wolves in the recovery areas was 0.750 (95% CI  =  0.728–0.772), which is generally considered adequate for wolf population sustainability and thereby allowed the NRM wolf population to increase. Contrary to our prediction, wolf mortality risk was higher in the northwest Montana (NWMT) recovery area, likely due to less abundant public land being secure wolf habitat compared to other recovery areas. In contrast, lower hazards in the Greater Yellowstone Area (GYA) and central Idaho (CID) likely were due to larger core areas that offered stronger wolf protection. We also found that wolves collared for damage management purposes (targeted sample) had substantially lower survival than those collared for monitoring purposes (representative sample) because most mortality was due to human factors (e.g., illegal take, control). This difference in survival underscores the importance of human-caused mortality in this recovering NRM population. Other factors contributing to increased mortality risk were pup and yearling age class, or dispersing status, which was related to younger age cohorts. When we included habitat variables in our analysis, we found that wolves having abundant agricultural and private land as well as livestock in their territory had higher mortality risk. Wolf survival was higher in areas with increased wolf density, implying that secure core habitat, particularly in GYA and CID, is important for wolf protection. We failed to detect changes in wolf hazards according to either gender or season. Maintaining wolves in NWMT will require greater attention to human harvest, conflict resolution, and illegal mortality than in either CID or GYA; however, if human access increases in the future in either of the latter 2 areas hazards to wolves also may increase. Indeed, because overall suitable habitat is more fragmented and the NRM has higher human access than many places where wolves roam freely and are subject to harvest (e.g., Canada and AK), monitoring of wolf vital rates, along with concomitant conservation and management strategies directed at wolves, their habitat, and humans, will be important for ensuring long-term viability of wolves in the region.

Testing for wolf-coyote hybridization in the Rocky Mountains using mitochondrial DNA

Hybridization between gray wolves (Canis lupus) and coyotes (Canis latrans) has been documented in the Great Lakes region of the United States and Canada but has not been extensively studied in the Rocky Mountain region. We used mitochondrial DNA (mtDNA) to evaluate potential gray wolf-coyote hybridization in wolf populations in the western United States, Alberta, and British Columbia, including wolves reintroduced into Yellowstone National Park (YNP) and central Idaho. A restriction site and a length difference in the control region (D-loop) of mtDNA was used to differentiate wolf and coyote haplotypes. All 90 wolves tested had wolf haplotypes. We concluded that the wolf populations in the Rocky Mountain region have not hybridized with coyotes as they have in the Great Lakes region. This method could be used to test other wolf populations for wolf-coyote hybridization and monitor the translocated YNP and Idaho populations in the future.

Prey Taken by Colonizing Wolves and Hunters in the Glacier National Park Area

The recent colonization of the northwestern United States by an endangered wolf (Canis lupus) population has raised concerns among hunters regarding competition for prey. Data on wolf prey selection may dispel misperceptions and thereby decrease human-caused wolf mortalities that would affect wolf recovery. We assessed the extent to which the early stage of colonization affected wolf prey selection by comparing our results with those from established wolf populations. We examined 243 prey killed by colonizing wolves in the Glacier National Park area of Montana and adjacent British Columbia during winters 1985-91 and compared characteristics of these with those of ungulates killed by hunters

Serologic Investigations of Canine Parvovirus and Canine Distemper in Relation to Wolf (Canis lupus) Pup Mortalities

Twenty-one serum samples from 18 wolves (Canis lupus) were collected from 1985 to 1990 from northwestern Montana (USA) and southeastern British Columbia, Canada, and evaluated for antibodies to canine parvovirus (CPV), canine distemper (CD), infectious canine hepatitis, and Lyme disease; we found prevalences of 13 (65%) of 19, five (29%) of 17, seven (36%) of 19, and 0 of 20 wolves for these diseases, respectively. Pups died or disappeared in three of the eight packs studied. In these three packs, adult pack members had CPV titers ≥ 1,600 or CD titers ≥ 1,250. In packs that successfully raised pups, CPV and CD titers were low. We propose that CPV or CD may have caused some pup mortalities.

FACTORS CORRELATED WITH FORAGING BEHAVIOR OF WOLVES IN AND NEAR GLACIER NATIONAL PARK, MONTANA

Abstract We examined prey selection, search distance (measured as km traveled/kill), and spatial use of recolonizing wolves (Canis lupus) in a multi-prey system in northwestern Montana, USA, and southeastern British Columbia, Canada, from 1986 to 1996. Our objective was to explore factors affecting these parameters to better understand wolf–prey relationships of recolonizing wolves. Within white-tailed deer (Odocoileus virginianus) winter ranges, wolves selectively killed elk (Cervus elaphus) over deer. Number of wolves (r = 0.67, P = 0.03), year (r = 0.68, P = 0.02), and possibly human hunter-days/elk harvested (r = 0.55, P = 0.08) were positively correlated with variation in proportion of deer killed by wolves annually. Outside of severe winters, white-tailed deer, elk, and moose (Alces alces) appeared to be equally vulnerable to wolf predation. Search distance of wolves varied by up to 12 times annually. Snow depth (r = 0.73, P = 0.03) and proportion of total kills by wolves that were deer (r = 0.66, P = 0.06) were negatively correlated with the annual variation in the total search distance of wolves. Search distance per wolf was correlated negatively with year (r = 0.66, P = 0.06) and exponentially with hunter-days/elk harvested (r = 0.70, P = 0.04). Space use by wolves may have been in response to local changes in deer abundance. Wolves appeared to select the most profitable prey species. Severe winters and wolf selection for deer, coinciding with a decrease in elk numbers, increased wolf hunting efficiency by reducing search distance. Further research is needed to determine whether reduced search distance equates to increased kill rates by wolves in this system. Based on the time, expense, and difficulty of gathering data on wolf search distance in this sytem, however, we recommend against assessing impacts of wolves on prey via measuring kill rate. Rather, we suggest monitoring impacts of recolonizing wolves by directly assessing cause-specific mortality and recruitment rates of prey species.

FIRST WOLF DEN IN WESTERN U.S. IN RECENT HISTORY

Gray wolves (Canis lupus), once common throughout the conterminous United States, were exterminated everywhere except northeastern Minnesota by the 1930s (Mech 1970). The last wolf taken in Montana by a government trapper was in 1936 (Ream and Mattson 1982). In the northern Rocky Mountains, wolves have been observed and killed occasionally during the past 50 years, but no reproduction or dens have been documented (Brittan 1953; Day 1981; Ream and Mattson 1982; Singer 1979; Weaver 1978). This note describes a wolf den in Glacier National Park (GNP), Montana in 1986 and reports 5 additional dens in GNP and adjacent British Columbia (BC) in 1982, 1985, and 1987. The study area was in the North Fork Flathead River drainage and adjacent Wigwam River drainage immediately to the west and covered approximately 5000 km2. The North Fork originates in BC and flows 50 km southeast where it crosses into the U.S. and forms the west boundary of GNP for 70 km. Wolf surveys in Montana from 1972 to 1979 yielded no evidence of wolf reproduction, and an adult female wolf radio-collared 7 km northwest of GNP in 1979 did not den in 1979 or 1980 (Ream and Mattson 1982). The closest known breeding population to Montana prior to 1982 was approximately 100 km north of GNP in Alberta (Ream and Harris 1986). In 1982, a litter of 7 pups was discovered at a rendezvous site 10 km northeast of GNP (B. McLellan, pers. comm.). On 18 May 1985, McLellan captured a lactating female wolf (W8550) in a grizzly bear (Ursus arctos) leg hold snare, radio-collared and released her, and she returned to her den 12 km north-northwest of GNP within 24 hours. Seven black pups were observed near this den on 8 July 1985. W8550, another gray adult, 3 black adults and the 7 black pups (Magic Pack), moved south into GNP in November 1985, where it remained for most of the time thereafter. The size of the pack was reduced to 8 when 4 members of the pack disappeared in March, 1986. W8550 initiated denning activity 20 km south-southeast of the Canadian border in GNP on 15 April 1986, and remained at the den until 20 May when she began to move short distances. On 31 July she was observed from a fixed-wing aircraft at this den, with 5 pups and 7 other adults. The pack remained at the den and rendezvous site until 29 July when they moved 15 km north to another rendezvous site in GNP. On 6 August the authors hiked in to examine the den. The 1986 den consisted of 5 den openings dug into a flat-topped, heavily forested knoll that rose 3 m above an adjacent 2 ha meadow. Scats and trampled vegetation, and earlier aerial observations, indicated that the meadow was used as a rendezvous site after the pups left the den. The den openings were located within an area of 400 m2 extending 40 m along the edge of the knoll. Den openings were well hidden in Engelmann spruce (Picea engelmanni), Douglas-fir (Pseudotsuga menziesii), and lodgepole pine (Pinus contort) forest, with Engelmann spruce dominating at the immediate den openings. When visited in August, most of the meadow was dry, although wet meadow vegetation dominated the lower portions and the intermittent creek that meandered through the meadow. Three openings were dug down into the flat top surface of the knoll and 2 were dug into the steep, north-facing side. By wriggling in as far as possible and reaching with a 3 m wood stick, we could not reach the end of 1 north-facing den hole, probably the natal den. The other 4 holes were 1, 2, 2, and 3 m in depth. The entrance holes averaged 30 cm in width and 50 cm in height. Another den hole had been dug to a depth of 1 m, 400 m northwest of the den area described above. It probably was dug in the early spring and and not used much as there were only 2 old (>2 months) scats found near the entrance. It was in lodgepole pine, 5 m northwest of a 40 ha meadow and was more conspicuous than the other den holes. W8550 was apparently displaced as the alpha female of the Magic Pack in late January 1987 and was seen alone for several months thereafter north of the border. Later, 4 other members from the Magic Pack joined her and she denned in BC during late May. Remaining members of the Magic Pack denned in GNP in late April but we never found what we were sure was the natal den. Radiocollared male W8401, alone for 2 years, found a mate and denned in late April,40 km west-northwest of GNP in BC, 7 km north of Montana.

Successful rearing of young by wild wolves without mates

Two lone-female wolves ( Canis lupus ) and a lone-male wolf each successfully raised litters of young in northwestern Montana and southeastern British Columbia. This unusual reproductive behavior occurred in a low-density population of wolves colonizing an area containing a relatively dense population of ungulates.