by By Bernd Heinrich
HarperCollins, 2009
Research suggests that female wood frogs exercise no choice in their mate; rather, the male frog “chooses” them. “Why then,” Bernd Heinrich asks in his new book, “do male wood frogs call out?” In Summer World: A Season of Bounty, Heinrich, biology professor emeritus at the University of Vermont and author of 13 other nature books, answers this and other intriguing questions.
The wood frog question was prompted in part by something he witnessed on a rainy April night in 1995: hundreds of wood frogs hopping across a patch of highway in New Hampshire, while Heinrich was on his way to Maine. Over the next few springs, Heinrich studied wood frogs, noting how scores of males would arrive at a vernal pool on a particular night and jam, physically and vocally, along the banks. A female would arrive and one of the males would latch on to her. The pair then swam to a spot where her eggs could be released and fertilized.
After researching and observing the wood frogs, Heinrich surmised that male wood frogs call out because more voices make for a louder message that travels farther out into the woods. Maybe it’s like the boys at the fraternity house turning up the music to let the sorority girls know where the action is, Heinrich says.
Throughout Summer World, Heinrich takes readers with him as he attempts to solve puzzles like this, often with experiments. Are birds capable of learning to hunt for caterpillars by using caterpillarcaused leaf damage as a tracking clue? Why doesn’t the maple sugar borer multiply until the food supply is exhausted?
Heinrich tempers academic prose with anecdotes. During his study of bald-faced hornets, he flees to his truck as they attack “like Sidewinder missiles.” Heinrich occasionally reaches for the broad brush to deliver a nature lesson, as when he describes how humans and other creatures have evolved over millions of years. But mostly he just sticks to science up close.
Unlike Henry David Thoreau’s ruminations on ant warfare, Heinrich doesn’t offer up allegorical insight when he witnesses ant battles. He counts the ants, follows them 250 feet along their narrow trail, witnesses black queens being mugged by a gang of reds, and watches as black ants submissively allow red ants to carry them off to a red colony. Thoreau, the social critic, suggested humans are like mindless ants with their shared desire for armies and combat. Heinrich, the scientist, wonders what the heck is going on. He excavates a red ant nest to learn all he can.
After several summers of ant study, Heinrich acknowledges that his findings are not original. “… But no discoveries can be made without exploring, and thanks to my ignorance, I had been lured to try. I had fun. I learned much about ants, and they had helped make several summers special.”
Summer World is Heinrich’s instructive reminder that paying close attention has its own rewards.