Litter size, sex ratio, and age structure of gray wolves, Canis lupus, in relation to population fluctuations in northern Belarus

• Published in: Canadian Journal of Zoology
• Main Authors: Sidorovich, V.E., Stolyarov, V.P., Vorobei, N.N., Ivanova, N.V., Jędrzejewska, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2007
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Canis lupus; gray wolf
• Online Access: http://dx.doi.org/10.1139/z07-001; http://www.nrcresearchpress.com/doi/full-xml/10.1139/Z07-001; http://www.nrcresearchpress.com/doi/pdf/10.1139/Z07-001

Gray wolf ( Canis lupus L., 1758) population fluctuations in northern Belarus (Vitebsk region) between 1990 and 2003 were significantly affected by hunting pressure by humans. Mean litter size was inversely density dependent and varied from 4.8 to 7.7 pups (range 2–10). The increase in litter size with declining density of wolf population concerned only female pups, whereas the number of male pups in a litter was not related to population density. The sex ratio of pups varied significantly: the proportion of females reached 70% in a low-density wolf population and declined to 40%–50% in a high-density population. The age structure also varied. In years following heavy hunting pressure, 55% of individuals shot were juveniles <1 year old (with a strong predominance of females that constituted 69% of juveniles shot), and only 11% of wolves were older than 4 years. The mean age of all wolves shot was 1.5 years. In years following low hunting pressure, 34% of animals shot were juveniles and 20% exceeded 4 years. The mean age was 2.8 years. A female-biased sex ratio of wolf pups conforms to Hiraiwa-Hasegawa’s hypothesis of the advantaged daughter, proposed for species in which mothers are able to influence the reproductive success of their daughters through transmission of rank.