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Abstract

Histological characteristics of testis tissues from 25 African elephants (Loxodonta africana) collected in Uganda, showed no consistent relationships among the following variables: Leydig cell size, cytoplasmic characteristics, and abundance; testicular testosterone content; and age. From these findings, plus field observations of sexual behavior, emerges the hypothesis that individual cyclicity in Leydig cell function was inherent in the elephant population studied. Testosterone content of testes from 32 elephants (including the 25 studied histologically) suggested that lone bulls were not of a senile nature since they contained relatively large quantities of testosterone and were relatively young (from about 12 to 25 years of age). Also, lone bulls were observed searching out estrous females. Among bulls collected from family units and herds, testosterone levels and behavior differed conspicuously. Behavior appeared to be directly related to testosterone content in several instances. Nonaggressive behavior among members of bull herds, plus the high proportion of such aggressive behavior among members of bull herds, plus the high proportion of such individuals with low testosterone content, suggest that some of these animals were in a depressed phase of sexual activity whereas others were undergoing pubertal development.