SNAKES DIVERSITY AND DISTRIBUTION IN KAINJI LAKE NATIONAL PARK (KLNP), NIGERIA

Abstract

Snake is an important agent in ecosystem balance but people’s fear makes it difficult to conserve. Thus, its diversity is declining rapidly due to anthropogenic factors. Information on snake species in Kainji Lake National Park (KLNP) is scarce despite their socio-economic value as source of antivenin, food, leather products and pets. Therefore, snake diversity and distribution in KLNP Nigeria were investigated.

Ten transect strips of 2 km each were laid in five ranges (Oli, Ibbi, Kuble, Doro and Kali) randomly selected from seven ranges in KLNP. Visual Encounter Survey was conducted along each transect to determine snake diversity and relative abundance during the day (09.00 - 12.00 h) and at night (19.00 - 21.00 h). Visit was replicated twice in each month both in dry (December – April) and wet (June - October) seasons in two consecutive years (2013 - 2014). Dead snakes were collected, preserved in 20% formalin solution and their morphometric parameters measured. Respondents (226) from 12 villages randomly selected from 21 villages at the buffer zones of KLNP were interviewed using structured questionnaire. Relative Abundance and diversity of snakes were measured using Simpson’s (D) and Shannon-Weiner’s (H) diversity indices. Data were analysed using descriptive statistics and ANOVA at α0.05. Twenty-one species of snake belonging to 12 genera representing six families were identified. Eleven species (6 families) were observed at Oli, 14 species (6) at Ibbi, 13 species (4) at Kuble, 8 species (4) at Doro and 12 species (3 families) at Kali range. Bitis arientans (38.0%) had the highest abundance followed by Boaedon lineatus (15.5%), Dendroapis jamesoni (8.0%) and Naja nigricolis (7.0%) and the least encountered (1.0% each) were Bitis gabonica, Causus Litchtensteini, and Mehelya Crossi. Ibbi range had the highest diversity index (D = 0.781 and H’ = 1.667) and Kali range with the best evenness (0.957). Significant differences were observed in number of ventral scales (0.023), Inter-orbital length (0.025), snout- vent length (0.004) and head width (0.009) of different snake species. Pythonidae (8.5%, 48.5.0%),Viperidae (34.1%, 12.1%), columbridae (37.0%, 12.1%) and Elapidae (23.4%, 24.3% ) were encountered during the day and night respectively. During wet season, 16.8%, 47.9%, 0.0%, 35.3% of Culubridae, Elapidae, Pythonidae, and Viperidae were encountered respectively while 28.5%, 15.3%, 35.6%, 20.6% of Culubridae, Elapidae, Pythonidae, and Viperidae were encountered during the dry season respectively. Snakes are utilised for preparation of traditional medicine (55.0%), decoration (20.0%), leather products (11.0%), Pets and entertainment (10.0%) and food (4.0%). Majority of respondents (56.0%) observed a decrease in snake population in the last deacade. Half of snake bites occurred on the farm with Bitis arientans (50.0%) and Naja nigricolis (38.0%) responsible for most bites. The leg was the major point of bites (70.0%) and mostly in male respondents (85.9%). Twenty one species of snake were identified in Kainji Lake National Park. Bitis arientans and Boaedon lineatus were the dominant snake species. Ibbi range had the best snake species richness. Bitis arientans and Naja nigricolis were responsible for most bites in the study area.