An alternative estimate of the rate of domestic dog population growth was derived from demographic data collected using household questionnaires. The death rate of dogs (d) was calculated using a Cox proportional hazards model of survival from longitudinal data (n ¼ 802). When pups (dogs under 3 months of age) were excluded from the model, neither age nor sex significantly affected survival. The percapita birth rate (b) was assumed to be the product of the sex ratio (q), the average litter size (l), and frequency (/) and pup survival (s) (b ¼ ql/s). These demographic parameters were estimated from crosssectional data (309 litters) and the rate of increase was calculated (r dogs ¼ b -d). Pup survival was estimated from a subset of puppies that remained in the household, because of the unknown fate of puppies that were given away or sold. We suspect that mortality of female puppies is greater than males. However, obtaining reliable data to accurately estimate pup survival is difficult, and the result of assuming equal mortality rates is an estimate of r dogs that is more conservative with respect to vaccination coverage (i.e., results in lower population-level immunity). This estimate of r dogs (0.088 dogs/y) was similar to other estimates from the region [41, 42] and close to those calculated directly from population sizes (r Serengeti ¼ 0.090 dogs/ y, r Ngorongoro ¼ 0.102 dogs/y) ( Table 3) . A comparison of the stable age distribution (calculated from cross-sectional data assuming a roughly constant rate of population growth) was consistent with age distributions predicted from the estimated demographic parameters.