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Field & Street

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Mammals have been in the news lately. A wandering coyote appeared in a park on the northwest side, and a colony of beavers has built a dam that's flooding a heron rookery on Baker's Lake in Barrington.

As usual, animals make the news only when they're a problem. The coyote was captured and transported to the Palos Forest Preserves in the southwestern corner of Cook County. The fate of the offending beavers is less certain. These industrious rodents make the U.S. Army Corps of Engineers look like amateurs when it comes to dam building. Knock down one of their structures, and they may replace it in a day.

The discovery of a coyote wandering into Chicago was interesting but not surprising. These adaptable canines have been increasing in numbers throughout northeastern Illinois in recent years, and we know from the experience of other cities--LA especially--that they can survive in the middle of very dense human populations.

Coyotes are really remarkable animals. They are among the species that have benefited from the arrival of European humanity in North America. They were creatures of the prairie prior to settlement, but now they have spread east all the way to Maine.

Their increase is especially remarkable because it came in the face of almost maniacal persecution by humans. There is still a bounty on coyotes in some states, and huge eradication programs involving guns, traps, poisons, and aerial bombardment have been mounted against them.

Their ability to withstand this onslaught, to thrive in spite of it, really should be expected. Take an adaptable animal with a high reproductive potential, put it in an environment with ample food and shelter, and it will stand up to the most fearful persecution. We are no more likely to be able to kill off coyotes than we are to rid our cities of rats and mice.

We may have even improved the coyotes' chances by creating a strong selection pressure toward behavioral flexibility, wariness, and intelligence. Our hatred may have produced a super coyote.

The history of the coyote in Illinois is very nicely told in a new book recently published by the University of Illinois Press. Mammals of Illinois, by Dr. Donald F. Hoffmeister ($34.95), is an encyclopedic compilation of everything in the world that is known about the furry creatures of the Prairie State. Dr. Hoffmeister is an emeritus professor of ecology, ethology, and evolution at the University of Illinois and the former director of the university's Museum of Natural History. He has been studying the mammals of our state for upwards of 40 years, and he is obviously the man to write the definitive treatment of our mammals.

Of the coyote Dr. Hoffmeister writes, "The increase in the number of coyotes in Illinois in the last 40 years is phenomenal in my estimation. In 1950, if one shot or trapped a coyote, it was sufficiently newsworthy for one's picture or story to appear in the local paper. In 1950, I know of eight accounts.... Between 1950 and 1969, at the cooperative wildlife research laboratory at Southern Illinois University, only nine coyotes were brought in and identified.

"In the mid-1970's, about 3,000 coyotes were taken annually for their pelts, by the early 1980's, more than 10,000 were reported taken annually and the resident population was supposed to be between 20,000 and 30,000."

Coyotes were present in Illinois at the time of settlement. They were usually called "prairie wolves" to separate them from timber wolves. A bounty was put on them very early in the state's history, and from Dr. Hoffmeister's account, we can conclude that it was successful for a time but that the coyote eventually won out.

Beavers have had a rather similar history in Illinois. They were trapped widely beginning at the end of the 17th century to supply raw materials for men's hats, and they had nearly vanished from the state by 1850. Efforts to reintroduce them began as early as 1929, and they can now be found along rivers, drainage ditches, and other permanent waterways throughout the state.

Some Illinois beavers build dome-shaped lodges for living quarters, but most live in burrows dug into river and stream banks. Great horned owls take a few young beavers, but with timber wolves and pumas gone from the state, adults are safe from predation. Beavers have a tremendous effect on their surroundings. Their dams turn streams into ponds, and their eating habits can deforest substantial areas. Hoffmeister reports on some captive animals that felled one tree per day per beaver, each tree between one and three inches in diameter.

Hoffmeister's book illuminates the past as well as the present. He provides brief accounts of Pleistocene creatures such as the giant ground sloth and the American mastodon, animals known from fossil specimens to have lived here in the time of the glaciers. And he provides the sad history of timber wolves, black bears, pumas, elk, and bison, animals that were here to greet the early settlers but that have long since vanished.

Illinois' location enriches our mammalian fauna. We have cottontails living throughout the state and we also have swamp rabbits, a southern species, living in the bottomlands of far southern Illinois. And in northwestern Illinois we have the white-tailed jackrabbit, an animal of the shortgrass prairie that has colonized the relatively sparse vegetation of our sand prairies.

We have gray squirrels, animals of the deep forest, as well as fox squirrels, animals whose original home was in the oaks of our prairie groves. Along the Kankakee River, we have small numbers of red squirrels, animals more usually seen in the pine forests of the North Woods.

Here in Chicago, gray squirrels are the common species, but we have some fox squirrels in our larger parks. Hoffmeister tells of a survey made of 22 towns in Champaign County. Gray squirrels were the only squirrel species present in two towns: Champaign and Urbana, which are biologically one even if they are administratively two. Fox squirrels were the only species in 16 towns, an unsurprising result when you consider that Champaign County was a prairie studded with oak groves before settlement.

The distribution of some Illinois mammals is even more strikingly affected by our natural history. The plains pocket gopher, for example, is found south of the Illinois and Kankakee rivers, but not north of them. Hoffmeister concludes that these animals were isolated there when the Mississippi River changed its course in the late Pleistocene, and that the gophers have never been able to cross the rivers to expand to the north.

Our two species of ground squirrels--the thirteen-lined and the Franklin's--are found only north of the Shelbyville glacial moraine. North of the moraine, soils tend to be deep and soft. South of the moraine, a hardpan underlies shallow soils, making digging difficult for these burrowing animals.

Mammals of Illinois looks at each of our extant species one by one reporting range, diagnostic characteristics, color, chromosomes, and dental formula along with habitat, habits, food, reproduction, and other life-history details. Color and black-and-white photos show each of the animals discussed, and there are numerous drawings showing such things as typical burrows of the fossorial species.

One of the most striking things you find in reading these species accounts is the shortage of basic life-history information available about many of these animals. I am used to studying birds, creatures who live very public existences. There is much we don't know about our birds, of course, but we can generally say what their nests look like and where they build them. We know when they breed and how many eggs they are likely to lay. We usually have some information--even if only in the form of a few anecdotes--about their courtship behavior and the size of their breeding territories.

But all sorts of facts as basic as these are just not known for many of our mammals. The problems in discovering them are very great. When you are dealing with small, elusive, nocturnal animals who spend their lives hiding in the grass--or even underground--you can't study life histories just by pulling up a chair and quietly watching. Hoffmeister's book underscores the fact that you don't need to go to the Amazon to learn new things about biology. There are still all sorts of discoveries waiting to be made within an hour's drive of your house.

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