GROWTH AND LONGEVITY 77 



30 years, but the animals having the longest lives are 

 vertebrates, and these have also been most successful 

 in invading the most variable habitats on land and in 

 fresh water. The arthropods and vertebrates are the 

 dominants on land, where the rarity of the atmosphere 

 makes it possible to move swiftly and the constant pres- 

 ence of an abundance of oxygen permits a rapid rate 

 of living. The arthropods have never as individuals at- 

 tained constant body temperature, though a few species 

 of ants and bees as colonies maintain a rather high tem- 

 perature. If the arthropods possessed long life and the 

 ability to maintain constant temperature, they would per- 

 haps excel the vertebrates. 



Fishes have been known to live for more than a hun- 

 dred years (Giinther, 1880). The giant Japanese sala- 

 mander has lived 52 years; Amphiuma, 27; Siren, 25; 

 Hyla, 20; Eana, 16; and Bufo, 13 (Fowler, 1925). Many 

 reptiles live to great ages. Ditmars (1902) estimated 

 the ages of certain giant tortoises at 350 and 400 years. 

 Other types of tortoises have been known to live for 

 from 60 to 143 years (Babcock, 1928). Many birds and 

 mammals live to great ages. Among vertebrates gen- 

 erally, larger species of animals live longer than smaller 

 types of comparable structure. Animals which grow 

 quickly to a rather definite size are usually comparatively 

 short-lived. Mammals which live long lives commonly 

 breed less frequently than smaller, short-lived types. 



Ecologically, longevity is related to the balance of 

 life in any locality or habitat. It is correlated with food 

 supply, favorable seasons for feeding and growth, avail- 

 able space in which to live, time required to reach matur- 

 ity, and other factors. By acquiring ability to live long, 

 vertebrates are able to have the lives of parent and 

 offspring overlap and thus heritages, such as particular ^ 



