Diversity and Abundance Patterns of Amphibians in Rehabilitated Quarries of Bamburi Near Mombasa (Kenya)

Abstract

Amphibians are sensitive to changes in the environment and are, therefore, excellent indicators of success in restoring degraded habitats. As such, a clear understanding on how amphibian populations respond to changes in the environment is required. In order for conservationists to establish if the declining trends are changing, biodiversity recovery studies are essential especially in reclaimed habitats. This study focused on the recovery of amphibians, particularly on frogs, in reclaimed quarries of the Bamburi Cement Plant near Mombasa whereby the diversity, species abundances and composition at different stages of quarry re-establishment were assessed. The study area was divided into three zones based on the 13-year interval since the beginning of the rehabilitation process. Transect surveys and time-constrained search and size method were used for sampling 20 randomly selected sites. Sampling was done during the rainy and the dry seasons, with searches conducted between 900 and 1,600 hours during the day and between 1,800 to 2,100 hours at night. Recording of basic morphological data of collected specimens was done in the field to aid in grouping specimens before voucher materials were preserved in 10% formalin and stored in 70% alcohol. Further identifications and confirmations matching specimens to species were carried out using specialized classification keys from the National Museum of Kenya. Twelve species were encountered across the three zones, with Ptychadena anchietae and Phrynobatrachus acridoides, respectively, the most abundant. It was also noted that amphibian diversity across the quarries was independent of the age of ecological re- establishment (r = -0.5). This is indicated by the higher amphibian diversity in the south and north quarries (N = 1050 and 506 respectively) despite their relatively younger age since re- establishment compared to the central quarry (N = 438). Lower diversity in the central quarry, although the oldest, may be largely attributed to human disturbance. Additionally, exotic plantations across the study area are poor in species since they are monocultures and, thus, not heterogeneous enough to support higher anuran diversity. Since amphibians act as one of the best measure of environmental health, rehabilitation process in the quarries need to embrace mechanisms that support maximum biodiversity recovery such as replanting of more indigenous tree species as opposed to only exotic monocultures.