Breeding patterns of Arvicanthis neumanni in central Tanzania

Abstract

The breeding pattern of the grass rat, Arvicanthis neumanni, was investigated in central Tanzania in 2002 ⁄ 2003. Nine hundred and forty-seven animals were captured in three age groups: juveniles, sub adults and adults. These age groups were present in the population for an extended duration, but there was an increase in the number of sexually active individuals and juveniles 2–3 months after the onset of the rains (December 2002–May 2003). A peak in reproductive activity occurred between January and April. Litter size ranged between 5.58 ± 0.42 and 6.1 ± 0.26 in two study sites. There were no significant differences in the number of embryos implanted in the right and left horns of the uterus of pregnant females (t 22 = 0, P > 0.05 and t 36 = 1.68, P > 0.05, respec- tively). Sex ratio of A. neumanni was not skewed to either males or females. Breeding was seasonal and seemed to be associated with seasonal variations in primary productiv- ity, which relates to rainfall patterns.