Odd Couples: Extraordinary Differences Between the Sexes in the Animal Kingdom

Balancing descriptive natural history with probing evolutionary biology, Fairbairn (Sex, Size & Gender Roles, coeditor), professor of biology at the University of California Riverside, examines eight striking cases of extreme size differences between males and females of the same species. Her goal is to explore “why sexual differences are such a pervasive and significant part of the fabric of animal variation,” and her case studies run the gamut from enormous elephant seals to birds, fish, spiders, octopi, and tiny barnacles. With male southern elephant seals growing to eight times the size of females, these animals present the largest discrepancy in size among mammals. But their differences are proportionally miniscule compared to those of deep-ocean seadevil fish: females can weigh over 500,000 times more than their male counterparts. Fairbairn also discusses sometimes bizarre relationships between sexes, as when females choose from a selection of displaying males, males become little more than testes attached to females, and males die immediately upon inseminating a female in a single act of sexual congress. The conclusion she draws from this amazing diversity is as profound as it is simple: “there is no ‘normal’ or ‘typical’ pattern of sexual differentiation across the animal kingdom.” 34 illus., 7 tables, & glossary. (May)