The Effects of Breeder Loss on Wolves

Abstract

Managers of recovering wolf (Canis lupus) populations require knowledge regarding the potential impacts caused by the loss of territorial, breeding wolves when devising plans that aim to balance population goals with human concerns. Although ecologists have studied wolves extensively, we lack an understanding of this phenomenon as published records are sparse. Therefore, we pooled data (n = 134 cases) on 148 territorial breeding wolves (75 M and 73 F) from our research and published accounts to assess the impacts of breeder loss on wolf pup survival, reproduction, and territorial social groups. In 58 of 71 cases (84%), ≥1 pup survived, and the number or sex of remaining breeders (including multiple breeders) did not influence pup survival. Pups survived more frequently in groups of ≥6 wolves (90%) compared with smaller groups (68%). Auxiliary nonbreeders benefited pup survival, with pups surviving in 92% of cases where auxiliaries were present and 64% where they were absent. Logistic regression analysis indicated that the number of adult‐sized wolves remaining after breeder loss, along with pup age, had the greatest influence on pup survival. Territorial wolves reproduced the following season in 47% of cases, and a greater proportion reproduced where one breeder had to be replaced (56%) versus cases where both breeders had to be replaced (9%). Group size was greater for wolves that reproduced the following season compared with those that did not reproduce. Large recolonizing (>75 wolves) and saturated wolf populations had similar times to breeder replacement and next reproduction, which was about half that for small recolonizing (≤75 wolves) populations. We found inverse relationships between recolonizing population size and time to breeder replacement (r= —0.37) and time to next reproduction (r= —0.36). Time to breeder replacement correlated strongly with time to next reproduction (r=0.97). Wolf social groups dissolved and abandoned their territories subsequent to breeder loss in 38% of cases. Where groups dissolved, wolves reestablished territories in 53% of cases, and neighboring wolves usurped territories in an additional 21% of cases. Fewer groups dissolved where breeders remained (26%) versus cases where breeders were absent (85%). Group size after breeder loss was smaller where groups dissolved versus cases where groups did not dissolve. To minimize negative impacts, we recommend that managers of recolonizing wolf populations limit lethal control to solitary individuals or territorial pairs where possible, because selective removal of pack members can be difficult. When reproductive packs are to be managed, we recommend that managers only remove wolves from reproductive packs when pups are ≥6 months old and packs contain ≥6 members (including ≥3 ad‐sized wolves). Ideally, such packs should be close to neighboring packs and occur within larger (≥75 wolves) recolonizing populations.

Managing dingoes on Fraser Island: culling, conflict, and an alternative

“…As a result of lethal control, wild canids typically have younger age structures, larger litter size, smaller pack size, higher emigration and higher non-cull mortality (Brainerd et al 2008;Wallach et al 2015). Following lethal control, profound changes to social dynamics have also been observed in other top predator groups (wolves : Haber 1996;Brainerd et al 2008;bears: Wielgus et al 2001;large cats: Cooley et al 2009) and these changes influence predator-prey dynamics (Wallach et al 2015).…”

“…Following lethal control, profound changes to social dynamics have also been observed in other top predator groups (wolves : Haber 1996;Brainerd et al 2008;bears: Wielgus et al 2001;large cats: Cooley et al 2009) and these changes influence predator-prey dynamics (Wallach et al 2015). Social integrity, therefore, is a key consideration when evaluating the ecological influence of top predators, such as dingoes (Wallach et al 2015).…”

Viability of a small, geographically-isolated population of beluga whale, Delphinapterus leucas: effects of hunting, predation, and mortality events in Cook Inlet, Alaska

“…Heavy hunting pressure on wolves decreased the average size of social groups and led to lower natural survival for a variety of reasons (Haber, 1996). Specifi cally, a review of multiple studies showed that removal of breeding wolves, Canis lupus, led to decreased wolf packs or to the dissolution of packs, and that pup survival was higher in larger packs and was correlated with the presence of auxiliary nonbreeders (Brainerd et al, 2008). Heavy hunting pressure on cougar populations, Puma concolor, was correlated with increased immigration, reduced kitten survival, and reduced female population growth (Cooley et al, 2009).…”

Reproduction and Mortality of the High Arctic Wolf, <em>Canis lupus arctos</em>, in Northeast Greenland, 1978-1998

“…Larger packs kill more ungulate prey than smaller packs but have less food available per pack member than smaller packs (Fritts and Mech 1981;Messier and Crête 1985;Ballard et al 1987;Messier 1987;Thurber and Peterson 1993;Dale et al 1995). Pack members ("auxiliaries") help feed the pups in larger packs thereby increasing pup survival (Brainerd et al 2008). Pack size and litter size in an increasing Wolf population with abundant prey in Minnesota were positively correlated, and litter size in a declining population at low prey density was inversely related to pack size (Harrington et al 1983).…”