Small Rodent Populations in Selectively Felled and Mature Tracts of Kibale Forest, Uganda

Abstract

Live trapping of small rodents was conducted in two adjacent tracts of tropical evergreen forests, selectively felled (K14) and relatively undisturbed mature forest (K30). Small rodents representing 14 species were examined. With the exception of Hybomys univittatus Peters in K14, two species, Praomys (Hylomyscus) stella Waterhouse and Praomys jacksoni de Winton, were the most abundant species in both types of forest during 1977-1978. Most rodent species were represented in both K14 and K30, but those normally associated with forest edges and Savanna habitats such as Lophuromys flavopunctatus Thomas were more abundant in selectively felled than in mature forest. Rodent density ranged from 0.7 to 26 rodents/ha in K14 and from 0.7 to 21.3 rodents/ ha in K30. Both rodent species richness and diversity were higher for plots located in selectively felled than in uncut mature forest. Furthermore, rodent species diversity was positively highly correlated with the estimated percent ground vegetation cover (which was also significantly higher in K14 than K30), whereas rodent species richness was inversely correlated with tree species richness. Seasonal fluctuations in rodent populations were similar in both types of forest but were of greater magnitude in the selectively felled forest than in the mature one. MOST STUDIES ON THE ECOLOGY of small African rodents have concentrated on communities in savanna, secondary bush, or formerly cultivated land. Delany (1972) and Fleming (1975) have summarized most of these studies. Those few studies on forest-inhabiting rodents were mostly of short duration (e.g., Delany 1964; Dieterlen 1966, 1967). Recently information on long-term studies of small forest rodents has become available (e.g., Delaney 1971, Cole 1975,Jeffrey 1977, Happold 1978, Emmons 1980). Some of these studies indicate that a simplification of the tropical forest ecosystem leads to changes in small rodent communities, allowing both population increases by formerly rare species and invasion of forest by species normally associated with forest edges and savanna (e.g., Jeffrey 1977). It has also been suggested that, since most of these small rodents are also seed and seedling predators (Synnott 1975; Genest-Villard 1980; Kasenene and Isabirye-Basuta, in press), their increase in numbers in the wake of forest degradation could affect tree regeneration and possibly the future floristic composition of the forest. This paper reports the results of two studies that investigated long-term trends in the numbers and species composition of small rodents in a relatively undisturbed mature forest and in an adjacent selectively felled forest. We were particularly interested in the effects of selective logging on rodent species richness and diversity.