GALIS, F; VAN DER SLUIJS, I; NUSSBAUMER, M; VAN DOOREN, TJM; Leiden Univ.; Leiden Univ.; Nat. Hist. Mus. Bern; Leiden Univ.: Do large dogs die young?

Body size and longevity in animals are in general positively related in interspecies comparisons. Paradoxically, intraspecific comparisons in mammals have often led to the opposite conclusion, large individuals die younger than small ones. This discrepancy is not well understood. In dogs a negative relationship between body size and longevity has also been reported, but some data suggest that this may be due to differences in longevity between breeds rather than due to a direct relationship between body size and longevity. To investigate this further we have compared data on size and longevity from two databases. The first database (VMDB) contains data on approx. 45,000 dogs of 129 breeds and uses body weight as a size measure. The second database (Natural History Museum Bern) contains data on 859 dogs of 37 breeds and uses a skull measurement for size. For both datasets we indeed found a significant negative relationship between body size and longevity in males and females when data of all breeds were considered together. However, within breeds a significantly negative relationship between size and longevity was never found. The absence of a negative correlation within breeds indicates that the overall negative intraspecific correlation results from differences in longevity between breeds rather than from a direct relationship between body size and longevity. These differences between breeds are probably mainly genetic and result from strong artificial selection and inbreeding depressions. The results indicate that the selection programs have led to more heriditary problems in larger breeds than in smallerl breeds. Our data, thus, do not support the notion of a negative intraspecific relationship between size and longevity in dogs. Possible reasons for the heriditary problems in large breeds will be discussed.