The Distribution of Senescence 



39, Tomilin, 1936; Baboon, Papio papio, 27— Duetz, 1938; 



P. anubis 30 -\ Krohn, in press; Gibbon, Hylobates lar, 32 -\ 



Duetz, 1938; domestic cat, 31— Mellen, 1939, 1940; 27, Com- 

 fort, 1955: Chapman's zebra, 40 — Weber, 1942: Echidna, nearly 

 40 years — Duetz, 1942). A large group, including almost all 

 ruminants, many medium-sized herbivores and carnivores, 

 large bats and the larger rodents (beaver, capybara, the domes- 

 tic rabbit) have recorded maximum ages between 12 and 20 

 years (Golden agouti, 15 — Duetz, 1938). The maximum ages 

 of very many rodents and small carnivores are not accurately 

 established, since few specimens have been kept, but it is likely 

 that a very large group among these forms has a potential life- 

 span approaching ten years. The small Chiroptera certainly 

 have a much longer life than most mammals of comparable size 

 — ringed horseshoe bats have been recovered after at least 

 7 years (Bourliere, 1947). This agrees with their slow rate of 

 reproduction. 



The shortest-lived mammalian group ( < 5 years) includes 

 rats, mice, voles, and other small rodents, and the small 

 insectivores. (Rat — 4 years 8 months in a white rat probably 

 already 1 year old — Donaldson, 1924; laboratory mouse, 3 

 years 3 months — Kobozieff, 1931; Micromys minutus, nearly 

 4 years — Pitt, 1945; golden hamster (Cricetus auratus), usually 

 2-3 years maximum — Bruce and Hindle, 1934; Deansley, 1938; 

 one specimen in London Zoo, 3 years 11 months — Flower MS; 

 guinea pig, 7 years 7 months — Rogers, 1950; Blarina, 18 months 

 — Pearson, 1945 ;Sorexfumeus, 13-14 months — Hamilton, 1940.) 

 The real life-span of whales has never been established, but it 

 is almost certainly not more than 30-50 years at the most, and 

 probably less. The age of maturity of whales has been placed as 

 low as 2 years (John, 1937). Ruud et al. (1950) found that blue 

 whales reach sexual maturity in about 5 years — no individual 

 in their very large sample was apparently older than 12 years, 

 judged by the baleen pattern. The life-span of dolphins in the 

 wild appears to be of the same order (15 years — Sleptzov, 1940; 

 30+, one specimen — Parker, 1933). 



Detailed records of many other mammalian species are given 

 by Flower. 



Recent data on the longevity of seals were reviewed by Laws 



47 



