Steven H. Fritts

Pack size and wolf pup survival: their relationship under varying ecological conditions

SummaryThe relationship between pack size and two parameters of reproductive success (litter size at 7–8 months and pup weights at 5–6 months) were determined for two wolf (Canis lupus) populations in northern Minnesota. Pup weights were not correlated with pack size for either population. Litter size, however, was correlated with pack size, but the direction of the relationship varied between the two study populations.In the superior National Forest, where prey were scarce and the wolf population was declining from high densities, litter size and pack size were inversely related. Pairs produced more surviving pups than did larger packs with one or more potential helpers. In the Beltrami Island State Forest, where prey were relatively abundant and the wolf population was increasing, pack size and litter size were positively correlated. The results suggest that ecological factors, such as prey availability, affected the ability or willingness of various pack members to provide food or other care for the pups.The lack of correlation between number of auxiliaries and number of pups in canid populations with low and declining prey densities may be explained on the basis of heterogeneous prey density resulting in drastic annual variation in litter production. No study to date has measured the actual benefit that pups derive from helping by auxiliaries, and the costs and benefits of it. The relationships discussed herein can be considered valid only after such research is completed.

The relationship of wolf recovery to habitat conservation and biodiversity in the northwestern United States

Abstract Gray wolves were systematically and fervently eliminated from the northwestern United States between the mid-1800s and early 1900s. Wolves disappeared from lower elevations first and generally persisted longer in more remote, mountainous areas. Preservation of large tracts of public land, primarily for commodity use, at the turn of the century, had the unforeseen effect of allowing conditions for wolf recovery to occur later. Improving attitudes toward the species and the recovery of ungulate prey populations from their turn of the century lows are the proximate factors making wolf recovery possible in areas with vast public lands. Planners for wolf recovery in the Northern Rockies identified three areas for wolf recovery, northwestern Montana, central Idaho, and the Greater Yellowstone area, because they consisted primarily of national parks, designated wilderness, and national forests. Those areas had previously been designated as public lands largely because they were too unproductive for agriculture; they consist in part of high elevation habitat that supports relatively few prey for wolves in winter. So far, recolonizing wolves have settled in lower elevation habitats where deer and elk are most abundant. Since private lands are most often in these lower elevations, they may be more important to the recovery and maintenance of viable wolf populations than was earlier envisioned. The negative symbolic nature of the wolf was a major factor in its eradication and continues to be a major factor in considerations of reintroduction and natural recolonization; the newer positive symbolic nature of the animal will ultimately facilitate its return and contribute indirectly toward long-term conservation of wild spaces and biodiversity in North America.