Sex and Age Composition and Breeding Biology of Cottontail Rabbit Populations in Venezuela

Abstract

Cottontail rabbits Sylvilagus floridanus continentis and S. f. valenciae were collected in the states of Falcon (Paraguana Peninsula) and Gu'arico (near Palenque), Venezuela, from November 1978 to December 1979. Sex ratios in neither area differed significantly from 50:50. Individuals in the 1to 8-month age classes were apparently under-represented in the shot sample. Breeding began at about 2.5 months of age and thereafter continued year-round. Mean litter size was 2.64 (107 litters) in 13 monthly collections from Paraguana, and 2.38 (13 litters) in two monthly collections from Palenque; pregnancy rates among adults averaged 89 and 81 percent, respectively. Monthly litter size in Paraguana, an arid region, was significantly correlated with total rainfall two months earlier. Total prenatal mortality was 17 percent at Paraguana and 20 percent at Palenque, with no evidence of loss of entire litters in utero. A preliminary life-table analysis estimated survival rate at only 0.6-0.7 monthly. Such low survival would reduce the mean number of young born per adult female from about 22 (potential natality) to five (realized natality) annually. The small litters and low survival of these tropical cottontails, compared to populations further north, tend to be compensated by their year-round breeding and earlier sexual maturity.