While we joke that men are from Mars and women are from Venus, our gender differences can't compare to those of many other animals. For instance, the male garden spider spontaneously dies after mating with a female more than fifty times his size. And male blanket octopuses employ a copulatory arm longer than their own bodies to mate with females that outweigh them by four orders of magnitude. Why do these gender gulfs exist? Introducing readers to important discoveries in animal behavior and evolution, Odd Couples explores some of the most extraordinary sexual differences in the animal world. Daphne Fairbairn uncovers the unique and bizarre characteristics of these remarkable species and the special strategies they use to maximize reproductive success. Fairbairn also considers humans and explains that although we are keenly aware of our own sexual differences, they are unexceptional within the vast animal world. Looking at some of the most amazing creatures on the planet, Odd Couples sheds astonishing light on what it means to be male or female in the animal kingdom.