When the Rains ComeA Naturalist's Year in the Sonoran Desert
by John Alcock
University of Arizona Press, 2009
This book follows the plants and animals of Arizona's Usery Mountains in the Sonoran Desert during the drought year of 2006 when the annual wait for rain went on far too long, detailing their responses to the dry spell and how they responded when the rains finally came down.
Authored by naturalist John Alcock, who has hiked the area for 30 years and is one of its most knowledgeable observers, the text follows the cycle of one year's seasons chronologically. Each month is worth a couple essays about the changes occuring during that time of year. These changes, he explains repeatedly, are related to and stimulated by the presence or absence of rain.
"Only very special plants and animals can survive and reproduce in a place that may receive as little as six inches of rain in a year," he points out, "a place where the temperature may rise above one hundred degrees each day for months on end."
When it finally drizzles one day in December, after many weeks of total dryness, Alcock hurries out to the desert and finds a colony of ants piled up several bodies deep around the entrance to their nests. Down on his hands and knees, he peers closely and sees that "many of the ants have small droplets of water adhering to their head, legs, or thorax, which supplies me with a hypothesis. Perhaps they have formed a rain-collecting brigade, using their bodies to intercept the droplets of drizzle before the water can reach the gravel."
Throughout the book, Alcock makes similar observations about the alarm calls of round-tailed ground squirrels, the mating competitions of male digger bees, the communal hunts of Harris's hawks, the adaptations of peccaries' reproductive cycle to the seasonal rains, the effects of urban sprawl, and more. Illustrated with the naturalist's photographs - many showing side-by-side versions of the same location ten or twenty years apart - the result is an impressive and highly readable document of the man's intimate knowledge of the place.
A professor emeritus at Arizona State University, Alcock also wrote the John Burroughs Medal winner In a Desert Garden as well as Sonoran Desert Spring and Sonoran Desert Summer, all revealing the surprising diversity of the desert's ecosystem.
