Daniels, T. J., & Bekoff, M. (1989). Population and social biology of free-ranging dogs, Canis familiaris. Journal of Mammalogy, 754-762.
Population size and density, age structure, survivorship patterns, sex ratios, and social organization of urban, rural, and feral dog (Canis familiaris) populations were examined in Cd. Juarez, Mexico (urban site) and on the Navajo reservation (rural and wild sites) between June 1983 and December 1984. Urban and rural dogs were less social than expected whereas feral dogs characteristically lived in packs. Seasonal variation in the structure of feral dog packs was influenced by reproduction, both directly (pups born into the pack) and indirectly (pregnant females may temporarily emigrate form the pack to give birth).