Seasonal variations in the breeding of the Nile rat (Arvicanthis niloticus)

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Abstract
The seasonal reproductive activities of the Nile rat A. niloticus were investigated over a period of 18 mo. Studies were carried on the effects, attributed to variations in the ambient temperatures and the availability of adequate nutritive material, on breeding activities. Breeding cycles in the male and female together with the effect of captivity on their reproductive activities were investigated. Although the Nile rat was a continuous breeder it still exhibited a seasonal reproductive pattern with peaks that coincided with the winter and rainy season at temperatures of 20.degree.-30.degree. C maximum and 10.degree.-15.degree. C minimum (relative humidity of 60-90%) and with the availability of food in the field. The male rat showed seasonal variation in the percentage of scrotal active testes and testicular weight and size. The average testicular weights, average combined length of the epididymis-vas deferens in the mature, recently mature, immature and sexually quiescent male rats were given. The 2 testes were equipotential. The female rat was a spontaneous ovulator. No vaginal plug was formed following copulation. The 2 ovaries were equipotential. Average weights and measurement in the female reproductive tract were given for females in different physiological states. The gestation period was 21-23 days. The litter size averaged 5.47/female and usually varied from 4-8. The rat could breed readily in captivity.