Relationships between reproduction and environment in the hippopotamus Hippopotamus amphibius in the Kruger National Park.

Abstract

Adult Hippopotamus amphibius cows react to adverse environmental conditions (reduced shelter in pools, overcrowding, food scarcity) by marked declines in conception rates (from 36.7%-5.6%). When environmental conditions are unfavourable calf survival is improved by extending the period of lactation and by calves suckling more than one cow. During favourable years some calves mature early (males 2 yr, females 5 yr) but generally sexual maturity is attained at 6 and 9-10 yr for males and females, respectively. The calving interval, when environmental conditions are favourable, is c.2 yr, and reproductive senescence and sterility are insignificant factors. The population sex ratio is 1:1. Hippos appear to be typical K-selected species.-from Authors