The biology of Rattus rattoides with particular reference to the role of olfaction in reproduction : a laboratory study

Rattus rattoides is a pest widely spreading over south-eastern China. In Fujian Province it destroys one fifth of the crops (rice, wheat, sweat potato, peanut, sugar cane, banana and other vegetables) in the field every year. A good range of pesticides have been applied to minimize the pest's damage, yet its biology is hardly studied. This preliminary study is to investigate some aspects of reproductive biology and the roles of olfactory cues in the reproduction of this rodent. All the experiments were carried out in Fujian, P. R. China during June 1990 to June 1991. The results of the investigations suggest that this species has the potential to be tamed as an experimental laboratory species and olfactory cues from an adult male or female play important roles in the growth and sexual development of young of the two sexes. 1. The average and the maximum body weights were examined. The growth rate of male and female rats before and after weaning were observed. No obvious difference has been found in body size and weight between sexes in adults of this species. The reproductive ability of the females in laboratory was found similar in different months with two low breeding rates in February and August. 2. The sexual maturation of the males developed in three stages: (a), the elevation of testosterone titre in blood; (b ), the growth of the body and testes reached a plateau and mature sperm had been transported into the convoluted ducts; (c), the cessation of the growth of epididymes and the success of reproduction. 3. The timing of the onset of puberty (vaginal opening) of females was found to be variable when measured in different seasons, but the body weights at the time of attaining puberty were similar. The onset of puberty of the females was accelerated by cohabiting with adult males or by the olfactory cues from adult males, and was delayed in the presence of olfactory cues from adult females. 4. Mean lengths of oestrous cycles of the adult females in different seasons were not significantly different from each other. Olfactory cues from adult males or housing under group conditions did not alter the lengths of the females' oestrous cycles. 5. Group-living significantly retarded the growth and sexual development of young males. Olfactory cues from adult males greatly promoted the growth and development of testes in young conspecifics