Numerous attempts have been made in the mass media and in the sciences to describe the gender differences between human males and females. While we joke that men are from Mars and women are from Venus, human gender differences don’t come close to those of our other relatives in the Animal Kingdom. Odd Couples: Extraordinary Differences between the Sexes in the Animal Kingdom, introduces readers to important and interesting new discoveries in animal behavior and evolution. I discovered this myself a few years ago while visiting the Natural History Museum of Los Angeles. Housed within the Spider Pavilion was a yellow “orb-weaving” female garden spider (Argiope aurantia). Lying motionless next to this large spider was a much smaller spider. I later learned that the smaller male spider was preparing to mate with the much larger female; a very dangerous task indeed, since the male garden spider spontaneously dies after mating with a female more than 50 times his size! I understand much more about these arachnids now that I’ve read this engaging new book by Daphne Fairbairn, a professor of biology at the University of California, Riverside. She knows the yellow garden spider well, along with the seven other examples from the Animal Kingdom she highlights in the book.

Odd Couples: Extraordinary Differences between the Sexes in the Animal Kingdom begins with an intimate foray through the roots of extreme sexual differences and reproductive behaviors of several species. Fairbairn starts with examples from male northern elephant seals, which I learned can weigh in at almost 3 tons, about 4 times the weight of females. This major difference, as with so many biological oddities described in the book, appears to emanate in the selective advantage that size affords male seals in the race to sire offspring. A successful “harem master” has the build of a professional sumo wrestler, for it is his job to eject an opponent male that challenges his authority and attempts to mate with a female in his harem.

There are a number of other sexual oddities in the Animal Kingdom that Fairbairn describes. For instance, “great” bustards – which, by the way, get their name not because of the impressiveness of their amazingly gorgeous plumage but, rather, the huge size of the adult males (historical records credit males with weights of up to 24 kg, or 53 lb), which qualifies them as the heaviest flying birds. Not so for females, however. Female great bustards are much smaller than males. This vast discrepancy in size “makes great bustards the unchallenged bird champions in terms of sexual size dimorphism. Other examples of extraordinary differences between the sexes in animals highlighted in the book include the female cichlids, which guard their eggs and larvae – even from the hungry appetites of their own partners. The key to this particular sexual dimorphism lies in the reproductive behavior of males and females. One of the oddest animals I encountered in the book is the male blanket octopus, which employs a copulatory arm longer than its own body to mate with a female that outweighs it by 4 orders of magnitude! Fairbairn further goes on to reveal to the reader why dwarf male giant seadevils parasitically fuse to their giant female partners for life. The book concludes with remarks on our experiences as humans, which tend to bias our perception (or misperception) of what is “typical” of animals in general.

This very engaging and well-organized book tackles some of the fundamental questions in animal evolution and behavior by addressing questions such as “What does it mean to be a male or female in the animal kingdom and why do these gender gulfs exist?” In doing so, evolutionary biologist Daphne Fairbairn reveals the unique and strange characteristics – in size, reproductive behavior, ecology, and life history – that exist in the animals described in this book and the special techniques and strategies they use to maximize reproductive success.

ELIZABETH COWLES teaches freshman-level biology, biochemistry, and entomology at Eastern Connecticut State University. She has taught at the undergraduate and graduate college levels for over 20 years. Her interests include insect toxicology, protein characterization, and astrobiology. Cowles holds degrees in biology and biochemistry from Cornell University and Michigan State University. Her address is Department of Biology, ECSU, 83 Windham St., Willimantic, CT 06226; e-mail: cowlese@easternct.edu.