Temporal Variation in Abundance and Distribution of Butterflies in a Southern Nigerian National Park

Abstract

Aims: The aim of this study was to determine the butterfly diversity in Okomu National Park, Nigeria in order to make available information on butterfly species in this protected area. Background: Butterflies are a taxonomically important group for predicting the health of the environment. Objective: In order to establish butterfly abundance and distribution in Okomu National Park, a temporal variation study was conducted for a period of twenty-four months (July 2012 to June 2014). Methods: Eight transects (Disturbed habitat (DIS), Forest Edge/Plantation (FE/P), Moderately Open Forest (MOF), Forest Along Road/Moist Patches (FAR/MP), Riparian Habitat (RIP), Closed Canopy (CC), Shrub (SHR) and Grassland (GRA) were mapped out from the four ranges (Igwonwan, Arakhuan, Julius Creek and Babui) using visual level of disturbance and degree of canopy closure for transect walk, butterfly net and baited trap methods of butterfly sampling. Environmental variables (temperature, relative humidity, and rainfall) were concurrently sampled with butterflies. Results: A total of 143 species and 6,310 individuals of butterflies were obtained from the families; Nymphalidae, Papilionidae, Pieridae, Lycaenidae, and Hesperiidae. Nymphalid (3103: 49.2%) and Pieridae (2269: 36.0%) predominated and Hesperiidae was recorded lowest (8: 0.1%). Significant differences were observed in the abundance of butterflies in the transects (p< 0.05). Rainfall was positively correlated with butterfly abundance. Butterfly abundance was higher in rainy season compared to dry season except in RIP where a reverse trend was observed. Abundance was higher in FAR/MP (1633: 25.9%) and MOF (1251: 19.8%) compared to other transects, and was lowest in SHR (295: 4.7%). Conclusion: It can be concluded that butterflies in Okomu forest is abundant and stable, and as such continuous effort is required to conserve butterfly flora and fauna in this park.