188 Prof. R. Owen on the Natural Term of Life 



XXIII. — On the Natural Term of Life and of its chief Periods 

 in the Hippopotamus (Hippopotamus amphibius, Linn.). 

 By Prof. Owen, C.B., F.R.S., F.Z.S. 



It may be interesting to note, in relation to the longevity 

 of wild mammals (a constant in the determination of 

 which it is difficult to get facts), that the hippopotamus 

 the capture of which, shortly after birth, is noted in the 

 * Annals & Magazine of Natural History ' for June 1850 

 as having occurred in August 1849, died at the Zoological 

 Gardens in March 1878. The conditions under which this 

 animal lived to the age of twenty-eight years and eight or 

 nine months, were such as to support an inference that it died 

 of old age, and that the natural term of life of Hippopotamus 

 amphibius may be set down at thirty years or thereabouts. 



No special morbid appearance was discovered to suggest 

 that death from old age had been anticipated. The worn 

 state of the teeth was that of a vegetable feeder at the close 

 of natural life. It may be thought that some allowance should 

 be made for the artificial conditions under which this male 

 hippopotamus lived ; yet its health and vigour were such as 

 to enable him to procreate. 



The first offspring was a male, which was born February 22, 

 1871 ; it died on the 23rd of the same month*. 



The father had attained a size in 1854 indicative of the 

 procreative period ; but the exercise of the faculty was de- 

 layed both by the later acquisition of the female and the state 

 of their abode. 



Mr. Bartlett informs me : — " I believe the reason she did 

 not breed sooner was the fault of the construction of the water- 

 tank. I had the tank made to slope gradually at the side ; 

 and this form of tank enabled the animals to copulate, whereas 

 the sudden drop of 2 feet was unsuited to the purpose " f- 



The pregnant state of the female was suggested by " a 

 considerable change in her habits and appearance." The 

 coitus had been noted as on June 29, 1870, giving a period 

 of gestation of 7 months 22 days, =237 days. 



The periods of gestation of the Hippopotamus amphibius 

 determined at the Zoological Gardens of Amsterdam are 

 from 7 months and 21 days to 7 months 25 days. 



The second offspring of the same parents at the London 



* 'Proceedings of the Zoological Society,' March 1871, "Notes on 

 the Birth of a Hippopotamus in the Society's Gardens," by A. D. Bart- 

 lett, Superintendent. 



t Letter, July 17, 1879. 



