September, 1945 



Brown & Yeager: Squirrels in Illinois 



473 



tained milk. This squirrel weighed 1.59 

 pounds, was 544 millimeters in total 

 length, and had about half completed the 

 molt. 



A female fox squirrel, too weak to 

 escape, was captured alive near Urbana, 

 Illinois, on April II, I94I. Diagnosis in 

 the Animal Pathology Laboratory of the 

 University of Illinois revealed a fractured 

 tibia and the presence of hepatic coccidio- 

 sis. On August 5, 1943, Dr. R. E. 

 Yeatter of the Illinois Natural History 

 Survey collected near Urbana a very weak 

 female fox squirrel ; diagnosis in the 

 University's Animal Pathology Labor- 

 atory "... revealed the presence of small, 

 circumscribed white foci in the liver and 

 spleen. In view of these lesions and the 

 history of the squirrel having been found 

 sick, we regard the possibility of tularemia 

 in this animal as being quite good . . . 

 cultures were not made." This female 

 had recently nursed young. 



The writers and others of the Illinois 

 Natural History Survey staff sometimes 

 found dead squirrels in wood duck nest 

 boxes. Usually these squirrels w^ere so 

 badly decomposed that cause of death 

 could not be determined. The number of 

 squirrels found dead was not great, and 

 the over-all evidence suggests that no ap- 

 preciable number of these animals die of 

 diseases or the effects of parasitism. 



PREDATION 



Predation losses in squirrel populations 

 are unimportant in Illinois. There are 

 numerous published reports of squirrels 

 being taken by hawks, owls, dogs and other 

 predators, but the writers found little 

 evidence that such losses reach serious pro- 

 portions in this state. Extreme agility and 

 a speed that attains a maximum of 12 miles 

 per hour in the fox squirrel (Cottam 

 1941), and probably an equal speed in the 

 gray squirrel, enable both species to elude 

 most predators effectively. 



In January, 1941, in the examination 

 of 680 wood duck boxes, one weak male 

 fox squirrel was found that showed con- 

 clusive evidence of having been attacked 

 by a raptoral bird. Talon punctures on 

 the dorsal surface reached to the body 

 cavity. Mange was present under the 

 forelegs and about the hocks. When re- 

 leased, the squirrel appeared dazed and 



climbed back to the box with difficulty. 

 Two months later another inspection re- 

 vealed that he had died in the box. No 

 sign of gunshot or other injury could be 

 found. 



A northern Illinois coon hunter reported 

 one instance of weasel predation on fox 

 squirrels. This attack was at night. The 

 hunter first heard a squirrel in a tree, then 

 a crash, followed by a struggle on the 

 ground. With the aid of a flashlight the 

 hunter saw the squirrel and weasel plainly. 

 The squirrel escaped, but it is not knov\n 

 how badly it may have been injured. 



The senior writer once flushed a feral 

 cat that w'as obviously trying to stalk a 

 barking fox squirrel. On snow' in north- 

 ern Illinois he observed a red fox stalk a 

 fox squirrel that was busily engaged in 

 eating an Osage orange fruit, but the fox 

 was frightened before reaching a springing 

 position. On another occasion the senior 

 author saw a red fox leap upon and cap- 

 ture a badly wounded fox squirrel, but 

 shouts caused the fox to drop its victim 

 and dash away. 



Fox and gray squirrels caught in steel 

 traps were occasionally attacked by hawks, 

 free-ranging dogs and other predators. 

 The red-shouldered hawk and red-tailed 

 hawk were the only raptors actually 

 flushed from trapped animals. A trapped 

 fox squirrel, caught late in the afternoon, 

 was killed during the night by a weasel. 

 Dogs are known to have eaten three fox 

 squirrels and one gray squirrel caught in 

 traps. It is recognized, of course, that 

 trapped squirrels attract the attention of 

 predators and offer easy prey, making them 

 unreliable criteria for measuring predation 

 losses. 



BREEDING 



The term breeding as usually employed 

 in this study includes pre-mating behavior, 

 mating and such physiological aspects of 

 breeding as oestrus, pregnancy, testes de- 

 velopment and changes in the Cowper's 

 glands. 



During the period of investigation, data 

 on breeding or young rearing were ob- 

 tained from a total of 4,790 squirrels, 

 which are listed in table 1 1 by species and 

 according to time and manner collected. 



The 1,075 squirrels shot or steel-trapped 

 by the waiters and used for detailed 



