The biology of small rodents in Mayanja Forest, Uganda

1148 small rodents representing 16 species were caught in Mayanja Forest, Uganda from regular trappings between September, 1967 and August, 1968 inclusive. These were restricted to five compartments which had been subjected to extensive felling in 1962–65 leaving at the time of the survey a dense herbage and scrub. Rain fell in all months of the year with the wettest periods from September to November and February to May. The most frequently caught species on the ground (Praomys morio and Lophuromys flavopunctatus) showed small differences in their responses to three baits (peanut butter, banana/wheat flour, powdered rat diet), the only exception being Lophuromys which wasnot attracted to the rat diet. Off the ground, where peanut butter was the bait, there was little or no decline in the catch rate over the first three nights trapping in one situation for Hylomyscus stella, Grammomys dolichurus and Thamnomys rutilans and only. at most, a small drop after six nights. The catch of Praomys fell quite steeply after the first night and thereafter more slowly to the sixth. Trappings revealed differences between species occurring on and off the ground. Lophuromys flavopunctatus and L. sikapusi, Hybomys univittatus, Malacomys longipes, Aethomys kaiseri, Lemniscomys striatus, Mus minutoides and M. triton were almost entirely obtained on the ground; H. stella, T. rutilans. G. dolichurus and Graphiurus murinus off the ground and P. morio and Oenomys hypoxanthus spent an appreciable amount of time in both situations. P. morio, L. flavopunctatus and H. stella were apparently the most numerous species. Of the remaining 13 species the maximum number caught for any one was 41 and for each of seven of these species less than ten were caught. Detailed information is provided on the species of plants, heights and nature of habitat from which animals were trapped above ground. No large scale fluctuations in the numbers of rodents were recorded throughout the year. Observations on their ecology are generally consistent with those from elsewhere in Africa. The recent man-induced modifications of the habitat enriched the fauna without eliminating any of the more typical forest species that might be expected. The condition of reproductive tracts, body weights and extent of molar tooth wear have supplied information on the time of reproduction and population structure of the species obtained. The reproductive data include litter size. abundance of placentation scars, testes weights and occurrence of lactation. In Lophuromys flavopunctatus there are apparently two main breeding seasons coinciding with the rains whilst in Praomys breeding appears to be more protracted. The limited data on the remaining species indicates breeding to take place at various times of the year with indications of coincidence in some species with the wet seasons. L.flavopunctatus, H. stella and P. morio bred in captivity. In development, pigmentation of the skin was followed by appearance of dorsal hair, then belly hair and finally opening of the eyes. The last phase is attained in six days in Lophuromys, 16 in Praomys and 21 in Hylomyscus. Females probably start breeding at approximately 38 days in Hylomyscus and just over two months in Praomys. Gestation periods based on time from fertilization at postpartum oestrous average 29.5 days in Hylomyscus, 30.5 days in Lophuromys and 36 days in Praomys. Mean litter sizes (from field collected females in brackets) were Hylomyscus 3.57 (3.21), Laphuromys 2.20 (2.17) and Praomys 3.29 (3.33). The moult to adult pelage is taking place at 31 days in Laphuromyus, 45–48 days in Hylomyscus and 61 days in Praomys. Further moults take place place in later life. These three species were mainly active at night with Hylomyscus displaying greater total activity than the other two species. Little time was generally spent feeding and drinking.