Ecological study of herpetofauna in the Arabuko-Sokoke and Gede coastal forests of Kenya

Abstract

The herpetofauna of the two coastal forests (Arabuko- Sokoke and Gede) of Kenya, were sampled using three methods namely: Quadrat, Time constraint and Opportunistic methods. During the study, 2,201 individuals were recorded comprising 49 species. The reptiles were represented by 14 families, 33 genera, 41 species and the amphibians by 4 families, 6 genera and 8 species. Snakes followed by lizards were the most diverse and abundant accounting for 24 and 16 species respectively. One species was testudine. Among the amphibian species, the Ranidae and Bufonidae were the most diverse with 4 species each followed by the Rhachopholidae and the Hicrohylidae with 1 species each. The forest differed in different vegetation types with a slight decrease in species richness from November to July. For each vegetation type, there was dominance of one or two lizard species, (e.g. Heliobolus spekii was found in Brachystegia woodland-only). There was diurnal variation in abundance activity of herpetofauna in various vegetation types, maximum activity falling between 9.00am and 12.00 noon, all vegetation types. Diversity was least in Cynometra vegetation type for both time constraint and- quadrat samples. Significant changes were registered in diversity ov~r time for both samples. Brachystegia woodland and Cynometra vegetation type& emerged as the most similar compared to the rest of and with for - x - the vegetation types. Population changes occurred over the sampling period with peaks in March-April in most of the vegetation types. Significant changes in species composition were recorded in Afzelia, Lowland rain forest and Gede forests. The highest species densities were observed in Brachystegia for H. spekii in January-February and the lowest for Habuya brevicollis in Afzelia and Gede in November-December. Seasonal variations occurreq and there was an increase in number of individuals during the dry season, especially the species which are specialists of a particular vegetation type (e.g. H. spekii). This could be due to improved visibility or more favourable conditions during the dry season than in the wet season.