Reading passage
The coyote, known to older naturalists as the prairie wolf, is a medium-sized member of the dog family native to North America. Its scientific name, Canis latrans, means barking dog, a tribute to the yipping chorus that carries for kilometres across open country. Before European settlement the coyote's range was centred on the grasslands and deserts of the western half of the continent; today it is found from Alaska to Panama, one of the most dramatic range expansions ever recorded in a wild mammal.
Several forces drove that expansion. The most important was the destruction of the grey wolf, which was systematically exterminated across most of the United States by the middle of the twentieth century. Wolves kill coyotes and exclude them from their territories, so as wolf packs vanished, coyotes spread into the vacant ground. The clearing of forests for farms and suburbs also favoured them, because coyotes thrive in the patchwork of field, woodland and settlement that replaced the unbroken eastern forest.
Much of the coyote's success lies in its diet. Although it is a capable hunter of rabbits, mice and ground squirrels, it is fundamentally an opportunist. Seasonal studies have recorded coyotes eating grasshoppers, watermelons, juniper berries, fallen apples, fish, carrion and household refuse. In autumn, fruit and insects may make up the bulk of the diet in some regions; in winter, deer killed by cold or cars become crucial. This flexibility means that few environments, from desert scrub to city park, are unable to support them.
Nowhere is this adaptability more striking than in cities. Chicago is thought to host several thousand coyotes, which raise their pups in parks, cemeteries and railway corridors and hunt rodents along riversides and golf courses. Urban coyotes shift their activity into the night to avoid people, learn to cross roads safely, and can live longer than their rural relatives because nobody shoots or traps them. Researchers tracking radio-collared animals have recorded individuals commuting along expressways and sleeping within a few hundred metres of crowded pavements.
Socially, the coyote is more flexible still. In prey-rich areas it forms stable pairs that defend a territory year-round, sometimes joined by offspring from previous litters. Where food is scarce, it travels and hunts alone. Pairs mate for many years, and both parents feed the pups, which are born in a den after a gestation of about 63 days. Litter size, typically around six pups, tracks the food supply: in good years more pups are born and survive, while in lean years whole litters may be lost.
Communication holds this social system together. Coyotes howl to advertise occupancy of a territory and to locate one another, and a single pair can sound like a dozen animals because their cries bounce off terrain and shift in pitch. Scientists believe this auditory illusion, sometimes called the beau geste effect, discourages neighbours from testing boundaries. Body postures, scent marks and a vocabulary of barks, yips and growls regulate daily encounters at closer range.
As coyotes moved east they also changed genetically. DNA studies show that coyotes colonising the Great Lakes region interbred with remnant wolves and, occasionally, domestic dogs. The resulting eastern coyote is larger than its western ancestors and more willing to hunt deer, a hybrid vigour that may explain the speed of the eastward advance. Some biologists argue that this blending is not new: canids on the continent have exchanged genes for tens of thousands of years whenever their ranges met.
Such success guarantees conflict. Coyotes take sheep, poultry and occasionally pets, and control programmes in the United States remove tens of thousands of animals every year, yet populations rebound quickly because surviving females produce larger litters when numbers fall. Wildlife managers increasingly favour non-lethal methods, such as guard dogs, secure fencing and removing food sources, arguing that an animal this adaptable cannot be eradicated, only managed. The prairie wolf, it seems, has become a permanent neighbour.