RELATIVR VIABILITY IN MAMMALS AND lURDS. 453 



UNGULATA. 

 1. Perissodactyla. 



EhINOCEROTID^. fY^ Av.dur. Max. dur. 



liifliv. ni months, in montlis. 



Rhinoceros, whole genus 10 110 342 



R. bicornis (Two-horned African Rhino- 1 271 271 



ceros). 



>S. teioiis (Hairj-eared Rhinoceros) 3 132 342 



R. sondccicus (Javan ,, ) 1 130 130 



R. samatrensis (^wm.-Atv?[.n „ ) 4 7*5 17 



R, unicoryiis (Indian ,, ) 1 281 281 



Rhinoceroses, like Elephants, are large vegetable-feeding 

 mammals, with in proportion to their size a relatively low 

 potential longevity and viability. The maximum duration in 

 this record, nearly 29 years for a so-called " Hairy-eared " 

 example, has since been surpassed by an Indian Rhinoceros which 

 died after a duration of 40 years in our Gardens, and probably 

 therefore at an age of at least 42 years. The number of 

 examples in the record is not sufficient to make averages useful, 

 but these and information I have received elsewhere make it 

 clear that the viability is not good, and probably lower in the 

 case of the African species. 



J-AFllUU^. jj^^jy -jj months, in months. 



Tapirus americanus {Kva.eY\ca.n1.di.T^iv) . 13 43 188 



:?'. mc^iCTis (Malay Tapir) 2 4 5 



The record of over 15 years for an American Tapir no doubt is 

 under the potential longevity of these animals, but I can find no 

 reliable information from other sources. The very low figures for 

 the Malay Tapir refer only to two individuals, and there is no 

 sufficient reason to suppose that the Asiatic species is less viable 

 than the American. It must, however, be inferred that Tapirs 

 in regard to their size are short-lived creatures with low viability. 



EqUIDvE. ^°;.°'' .Av.dur. Max. dur. 



^ Inaiv. in months, in months. 



Equus, whole genus 21 116 346 



E . hemionus (K\a.ng) 1 220 220 



E. hemippus (Asiatic Wild Ass) 3 82 169 



(^=hemiomhs incUcus). 



E. onager {Onager) 2 198 219 



^. so??ia^iCits (Somali Wild Ass) 1 16 16 



^. ^cemojoMS (African Wild Ass) 3' 175 232 



E. quagga (Quaggei) 1 346 346 



^. ^iM-cAe^^i (Burchell's Zebra) 7 98 268 



E. grevyi (Grevy 's Zebra) 2 6 10 



^^ 5;e5?-a (Mountain Zebra) 1 46*5 62 



It is well-known that the usual duration of life in horses is from 

 15 to 30 years, and somewhere about 50 is probably the potential 

 Proc. ZooL. See— 1911, No. XXX. ' 30 



