From bears and bobcats to coyotes and hyraxes, wildlife invasions in towns and cities worldwide have drawn increasing attention in recent years. For those not used to seeing wild animals lurking in their neighborhoods, the invasion may seem sudden and unexpected. But wildlife has in fact been creeping ever closer to humans—or, more accurately, human communities have been pushing further and further into wildlife habitat. And with few natural areas left to which they can retreat, growing numbers of wild animals are taking their chances in our towns and cities.
Cities and outlying residential areas have much to offer wildlife, including an abundance of food, which can be found in gardens, in poorly secured trash containers, and on the ground around bird feeders. Some wild animals invade our neighborhoods because they offer safety from predators, which can improve survival and the chance of reproductive success. (The movement of prey into residential areas, however, may be followed by the movement of predators.) Other wild animals come because they have nowhere else to go, having been squeezed out of their native habitats by land development or natural disaster.
Natural disaster is a fairly infrequent cause of wildlife invasions, relative to other factors inviting wildlife into our backyards, but this past June and July residents of Los Alamos, New Mexico, had an unforgettable brush with the effects of disaster on the movement of wild animals. Indeed, the Las Conchas Fire, the largest wildfire in the state's history, burned tens of thousands of acres of forest, causing black bears and other animals to take refuge in the city. Residents returning home from a mandatory evacuation were greeted by advisories from the New Mexico Department of Game and Fish on how to ensure their safety and that of the city's new, and hopefully temporary, inhabitants.
In many instances, hunger and the opportunity for an easy meal brings wild animals into our backyards. In February 2011, on the outskirts of Verkhoyansk, a small town of about 1,300 people in the far reaches of northeastern Russia, some 400 wolves attacked local livestock, killing more than 30 horses in just four days. A drop in populations of rabbits, the wolves' usual prey, was thought to have precipitated the massive attack, with livestock, and horses in particular, representing the most plentiful and easiest target in the desolate, frozen landscape. The town's solution to the problem was to assemble teams of hunters to kill the wolves.
Wildlife invasions have become routine in some places. For example, in the desert southwest of the United States, coyotes, bobcats, scorpions, rattlesnakes, and javelinas are regular visitors. This is especially true in Tucson, Arizona, where sprawl and the construction of growing numbers of houses and apartment complexes has brought large numbers of humans into contact with wildlife. While in many instances the animals come and go without incident, the occasional small pet is killed and scorpion stings are common.Rock hyraxes (Procavia capensis), small hoofed rodentlike mammals native to Africa and the Middle East, have taken up residence and wreaked havoc on peoples' gardens in villages in the region of Galilee in northern Israel. A study published in 2011 in the journal Wildlife Research revealed that the recent population expansion of rock hyraxes is due in large part to the abundance of human-made boulder piles left surrounding new residential areas following construction. Boulder piles are ideal den sites for rock hyraxes, and the proximity of such ideal habitat to residential areas inevitably invites conflict between human inhabitants and the garden-devouring hyraxes.
Many peoples' initial reaction to suburban and city wildlife is characterized by fear or irritation, often followed by a desire to extirpate the interlopers. In some cases, such as when wild animals are startled or become used to being fed, they can create real problems, immediate and long term, for residents. In addition, some wild animals carry diseases that can be transmitted to humans and hence may pose risks to public health.
But seeing wild animals so near to our homes offers a rare opportunity to cautiously observe and better understand the creatures we've displaced or inadvertently attracted. This is perhaps the first time in human history that so many people live close to wildlife. And the more human sprawl chips away at the world's remaining natural environments, the more we can expect to be sharing our yards with unexpected visitors from the wild.
Kara Rogers is the senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is also a member of the National Association of Science Writers and a contributor to the Britannica Blog, where she runs a series called Science Up Front. She holds a Ph.D. in Pharmacology/Toxicology, but enjoys reading and writing about all things science. You can follow her on Twitter at @karaerogers.
This post also appears on the Britannica Blog.