Notes on the Biology of the Jackrabbit in Iowa

White-tailed jackrabbits, Lepus townsendii campanius Hollister, are found throughout Iowa with the exception of a few southeastern counties. Over much of their range they are relatively rare. They appear in greatest abundance on the recently glaciated soils in northern and central counties, and on the Missouri loess soils of the west-central counties. Dry growing seasons seem conducive to hare abundance; populations decline during wet seasons. Jackrabbits provide considerable hunting sport during winter. Their pelts are utilized in felt manufacture and their flesh as a staple food for ranch mink. They are known to eat sprouting corn and soybeans, and occasionally damage shrubs and trees. High populations of 114 and 90 jacks per square mile are recorded here. High populations of near 30 jacks per square mile are more common. Average populations over the more favorable portions of their range seem to fall between 5 and 15 per square mile. Average winter weights of 7.5 and 7.9 pounds for males and females respectively are recorded. These contrast with spring weights of 6.8 and 8.3. Sex ratios are essentially even. Breeding activity begins late in February in most years but may be delayed by deep snow and cold temperatures m March. Two and possibly three or four litters per year are produced per female. Litters average 3.6 young rabbits each, and range from one to five. Corpora lutea average 5.75 per pregnancy and range from three to eight. A considerable loss of ova is suggested by the data