Why do males and females frequently differ in body size and ...(in as sit-and-wait predators on their we...)

On the other hand, in many large mammals such as deer and sheep, females and young tend to be found in areas that have high quality food or other resources, she said. Males are able to find groups of females in these predictable places and defend them against other males. Large males, often with big weapons such as horns or antlers, are most successful in these male-male contests.

Fairbairn explained that in most birds males are bigger than females because their large size helps males display themselves in a more striking manner to attract females.

The book is intended for specialists in the field as well as readers with a general interest in why males and females can be, and often are, very different.

The books common theme is that gender roles adopted by males and females in different species strongly influence the evolution of sex-specific sizes, forms and structures, Fairbairn said.

Fairbairn, who joined UCRs Department of Biology in 2001, has authored or coauthored more than 75 scientific articles and has previously edited Evolutionary Ecology: Concepts and Case Studies (Oxford University Press, 2001) with two other biologists.

Her next book, which she plans to write for a general audience, will focus on the many ways of being male or female in the animal kingdom.

Wolf U. Blanckenhorn of the Universitt Zrich-Erchel, Switzerland, and Tams Szkely of the University of Bath, United Kingdom, are the other editors of "Sex, Size & Gender Roles: Evolutionary Studies of Sexual Size Dimorphism."