5. Rabbit Management 
Vo 1 . 7 , No. 2 
Page 4 
W. R. Edwards, 0. A. Casteel 
9 
Reproduction by female cottontails during their first summer has been re¬ 
ported by several workers. Sowles (1957:240-241) cited three authors who re¬ 
ported juvenile breeding; he also reported that 11 of 31 S_. audubtm i i ar i zonae 
collected, which were either pregnant or lactating, were less than 9 months old. 
Lord (1958:273) concluded that in Illinois "juvenile breeding accounted for 
26.7% of the annual cottontail crop." Negus (1959:451-452) reported that 10 
of 30 juvenile females collected from the till plain region of Ohio, and 18 of 
36 from the unglaciated Allegheny Plateau, were reproductively active. 
During the spring and summer of 1983, an investigation of the breeding 
behavior of cottontails was conducted near Urbana, Illinois. In the course of 
this study, observations made in the field and subsequent histological exam¬ 
inations of ovaries revealed that two female cottontails born in early April of 
1963 produced litters in late July of that year and rebred after parturition of 
their first 1 i tters. 
Rabbit 81063A was pregnant and lactating heavily when collected for autopsy 
August 10, 1983- On the basis of size, the embryos were estimated to be 10-12 
days old, indicating that the female had bred and ovulated about July 31 , 1983- 
Examination of the ovaries revealed both corpora lutea and corpora albacantia. 
Judging from normal reproductive behavior, this female was probably bred immedi¬ 
ately following parturition; thus, the earlier breeding must have taken place 
on about July 3* Lens weights (Lord 1959) indicated that this doe had been 
born about April 5, 1983, and was therefore approximately 90 days old when 
bred in early July. 
Rabbit 81383A was pregnant and lactating heavily when Iivetrapped on July 
31, 1983; she had a spontaneous abortion on August 13 and was sacrificed for 
histological examination on that date. Examination of ovaries revealed corpora 
from at least two pregnancies. Relative size of embryos indicated that the 
latest pregnancy was initiated about July 23- Assuming a 28-day gestation and 
copulation immediately after parturition, this female had bred previously on 
June 25. On the basis of lens weights, this earlier breeding, presumably the 
first for 8 I 363 A, took place when she was approximately 85 days of age. 
Research is currently in progress which should provide additional informa¬ 
tion on sexual maturity and reproductive performance of cottontails during their 
first summer. 
Lord, R. D., Jr. 
1958. The importance of juvenile breeding to the annual cottontail crop. 
Trans. N. Am. Wildl. Conf. 23:269-275. 
1959- The lens as an indicator of age in cottontail rabbits. J. Wildl. 
Mgmt. 23(3):258-260. 
Negus, N. C. 
1959. Breeding of subadult cottontails in Ohio. J. Wildl. Mgmt. 23(4): 
451-452. 
Sowles, L. K. 
'957- Reproduction in the Audubon cottontail in Arizona. J. Mammal. 38(2) 
234-243. 
