File:Bulletin (1944) (19808283023).jpg

Title: Bulletin
Identifier: bulletin2319441945illi (find matches)
Year: 1918 (1910s)
Authors: Illinois. Natural History Survey Division
Subjects: Natural history; Natural history
Publisher: Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
September, 1945 Brown & Yeager: Squirrels in Illinois 483 the more abdominal position of the testes, the scrotum was less pendent. Oestrus.—The earliest evidence of first-season or winter oestrus observed in fox squirrel females was December 11 in Alexander Count\^ (southern zone), tables 15, 16 and 17. The latest oestrus records for the first season in the southern and central zones were Januarj' 27 ; the two observations were a year apart. In gray squirrels the earliest evidence of winter oestrus was December 16, and the latest was February 11, both observations in the southern zone. The external indication of oestrus, commonly called "heat," is a swollen, pro- truding condition of the vulva. During oestrus the uterus is enlarged and con- gested with blood, by w'hich the vulva is commonly discolored. This condition is easily observed in external examination. Following copulation the congested con- dition of the uterus clears. The uterus becomes spongy and thick-walled, and fetal nodes, 3 millimeters in length, appear about 10 davs after successful coitus. Pregnancy.—An attempt was made early in the survey to distinguish oestrus and early pregnancy by the use of vaginal smears, but this proved impractical under conditions prevailing in the field. The oestrual period thus was probably not dis- tinguished as precisely as is desirable, and perhaps an unknown number of very early pregnancies were listed under the heading of oestrus. Pregnancy could be determined with some certainty by noting the relaxed and perforated state of the vulva and development of the mammae. Somewhat advanced stages of pregnancy (15 millimeter fetuses) could be detected by palpating the lower abdomen. The earliest and latest first-season pregnancy records for fox squirrels were January 1 (one animal with 3 fetuses averaging 6 millimeters in length) and March 22 (one animal with 3 fetuses averaging 19 millimeters in length), table 16. The first-season peak of fox squirrel pregnancy, based on 43 adult females, 23 of them pregnant, table 15, came during the first half of February. In gray squir-
Text Appearing After Image:
Fig. 11.—Glans penis and urethra of adult male squirrel, with Cowper's glands attached in an uncoiled and in a nearly natural position in each case. Left, fox squirrel; right, gray squirrel. Coles County, late January, 1944,

Note About Images