Curious by Nature

by Candace Savage

• ISBN13: 9781926706467
• ISBN10: 1926706463
• Format: Nonspecific Binding
• Copyright: 2012-01-06
• Publisher: Open Road Integrated Media, Inc.

Summary

"Curious by Nature: One Woman's Exploration of the Natural World" showcases Candace Savage's exploration of the varied ways we relate to wildlife from our retelling of fairytales about the big, bad wolf to our struggles to find a balance between harvesting trees and allowing grizzly bears the space to roam. Along the way, she asks intriguing questions to which she sets out to find answers, such as what brings out the mothering instinct in mammals, what are the forces behind the spectacular displays of the northern lights, and just how do crows calculate the optimum height from which to drop their whelks? Savage has spent the last 25 years exploring our complex relationships with the natural world: our prejudices, our growing body of scientific knowledge, our awe. She is particularly interested in bridging the gap between mythology and science, between longing and fact. Creating a livable future for ourselves and for other species, she believes, calls for both knowledge and love, and a deep sense of the value of wildness. This book is a record of Savage's ongoing quest to engage readers in a conversation that enriches our lives and the lives of the animals whose stories she tells.

Excerpts

Clever Corvids: A Mind for Food

Brainy animals, like people and crows, tend to take a carnal delight in food—flower and fruit, fish and fowl, animal and vegetable. They are often "generalists," able to identify and exploit a wide array of nutritional resources. Whereas a specialized animal may be able to get by with low mental wattage (just enough to permit it to recognize a few preferred foods), a generalist has to run a regular inventory on dozens of edible items, an occupation that calls for curiosity, perception, memory, and, often, inventiveness. For such an animal, a well-stocked brain may be an essential means to a well-stuffed belly.

Most species of corvids have wide-ranging tastes in food. Almost all are omnivores (like ourselves) and typically seek food both in trees and on the ground—seeds, nuts, berries, caterpillars, grasshoppers, frogs, field mice, birds’ eggs, nestlings, garbage, carrion, and other delicacies. The birds appear to be born with an innate ability to recognize and acquire some of these items. Eurasian jays go through a stereotyped (and presumably inborn) routine when they catch wasps, which involves capturing the insect and then biting repeatedly near the stinger to disable it. Jays do not have to learn the hard way to avoid this hazard. But they are nonetheless highly capable of learning about other dangers in their food supply. For example, when a captive jay was fed two species of grasshopper, one poisonous and one safe, the bird hungrily gobbled up both of them. But once was enough. Even though the insects were ingested together, the jay somehow identified the culprits and thereafter refused to eat them any more, although it continued to welcome the more palatable kind.

It seems likely that the foraging behavior of many corvids is largely shaped by experience. Their education may well begin in the nest, as they become familiar with the items their parents bring to them, and continue during the weeks when they hang around home as fledglings. Young jays, for example, are not born knowing about the relationship between small acorns and mighty oaks. When they first see oak seedlings, the birds take no interest in them. But once they notice adults obtaining nuts from beneath the plants, the youngsters begin to pull at all sorts of vegetation. In time, either through trial-and-error learning or closer observation of their parents, they learn to restrict their efforts to oaks and, even more specifically, to the first-year plants that are mostly likely to yield edible cotyledons.

Even as adults, corvids are constantly on the lookout for clues about what’s on today’s menu. To obtain up-to-the-minute information, they keep a sharp eye on other members of their flock or family group. Has one of them found a feast that could be shared? Has someone found a smaller prize that could be stolen or duplicated? Crowd around and take a look. Don’t stand back; it pays to be curious. If one of your companions flies strong and hard away from the nighttime roost, follow it eagerly in the hope that it is heading for food. When a flustered songbird rages and swoops at you, take it as a sign that it has eggs or chicks nearby and calmly search the bushes. Watch the ducks come and go from the marsh until you know where to look for their nests. For an experienced corvid, the airwaves are crackling with information.

Search Images
No one knows how, or if, birds think about what they learn. But biologists suspect that they store their knowledge in the form of "search images." In one laboratory experiment, a group of blue jays was trained to peck a key and obtain a food reward whenever they saw a picture of a certain species of moth. At first, the moths were shown against plain cards so that their color and form could be clearly observed. But later they were pictured in their natural cryptic environment. Even though the insects now blended almost perfectly into the background, the trained jays still picked them out with little difficulty. By contrast, they seldom responded to similar images of a different type of moth, presumably because they had not formed a search image for this species and could not detect it under camouflage conditions.

The classic demonstration of search images was made in 1970 by a researcher with the fitting name of Harvey Croze. On a sandy beach where carrion crows gathered mussels, Croze laid out a row of empty shells, each with a piece of meat beside it. Within a few hours, the crows had found and eaten all these tidbits. The next day, Croze set out another row of shells, only this time he hid the food underneath them. When the crows returned, all they could see were empty shells on the sand, a sight that would not ordinarily spark their curiosity. Yet the birds found, overturned, and fed from all but two of them. From a single experience, they had learned that empty mussel shells could be a siggn of food and had apparently formed a searchh image for them.

Once learned, never forgotten. Even when Croze began setting out shells without meat in them, the crows continued to investigate them now and then. If he baited one at random, the crow that hit the jackpot would suddenly turn its attention to checking empty shells, in a single-minded attempt to strike it lucky again.

The last phase of Croze’s experiment, in which the birds were winners and losers by turns, begins to approach the complexity of real-life foraging. It’s a game of chance, and the stakes are literally life and death. If you consistently score, you will obtain enough energy to survive and reproduce. But if you lose too often, you burn up more calories in the search for food than you take in from what you ingest. Even crows and ravens, birds that are reputed to "eat anything," have to be selective in their food choices. To do this, they must constantly scan their home range for possible nourishment, like the crows that kept a watchful eye on Croze’s mussel shells. Then they must determine which of their options is currently the best bet. (Thus, a crow that found a baited shell immediately put its money on searching for more of them.) And finally, as the source of food on which they are foraging becomes depleted, they must decide when it’s time to head for greener pastures. How much energy does it pay to expend on checking mussel shells? At what point would you be better off to search for fruit in the cherry orchard or hunt for insects in the bushes? Somehow, corvids make these choices and make them well.