She applied the “Page 99 Test” to her new book, Walking Sideways: The Remarkable World of Crabs, and reported the following:
Page 99 discusses territorial behavior of fiddler crabs. Fiddlers live in the intertidal zone and are active during low tide, when people can easily observe them without snorkels or scuba gear. Fiddlers are unusual, since they are not active when underwater, but out in the air. Fiddlers are small (1-2 inches across) and named for the enlarged claw of the males, which they wave to attract females. They dig burrows with multiple uses: to hide from predators, use during high tide, recover from a molt when soft shelled and especially vulnerable, and (for some) mate. While most are tropical, some species live in temperate zones and hibernate during the winter. Since burrows are of major importance, they defend them from other crabs. When a wandering crab approaches a burrow “owner” the owner may chase it away or make contact and push it away. Fights may ensue, in which one crab is picked up and flipped over by the other. I describe a study of a species which also defended burrows of their neighbors, but only when the neighbor was smaller and the intruder was of intermediate size. This provides an advantage to the defender since it is easier to have the smaller original neighbor than to re-negotiate territory boundaries with a new larger neighbor. In another species, males protected female neighbors from male but not from female intruders. Since females sometimes mate with their neighbors, this “chivalrous” behavior could result in mating opportunities.Learn more about Walking Sideways at the Cornell University Press website.
Crabs have other fascinating behaviors - varied feeding behaviors and defenses from predators, walking (sideways and forwards), swimming, communications (visual, chemical, or sound) that are described. Other chapters cover other aspects of crab biology including their habitats (deep sea, freshwater, dry land, even trees), anatomy and physiology, reproduction and life cycle, ecology (including the important change from small floating larva to bottom-dwelling adult, extensive migrations (land crabs must migrate many miles to release their larvae in the ocean) and interactions with other organisms. Various crabs live with seaweeds, sea anemones, sea urchins, or jellyfish – which generally provide protection to the crab. Of greatest importance to a hermit crab is finding the right size snail shell to live in – this can produce aggression or cooperation. The chapter “Crab Problems and Problem Crabs” covers various diseases and parasites that crabs can have (including a bizarre parasite that causes “parasitic castration”), as well as crabs that are themselves parasites or arrive in new locations and make trouble – “invasive species.” There are also chapters dealing with interactions of crabs and humans – one about crab fisheries, another about eating crabs, and the last chapter about crabs as pets, in astrology and mythology, and in popular culture.