Population dynamics of the Rodrigues fruit bat (Pteropus rodricensis): An analysis of long-term island wide bat count data

Abstract

The Rodrigues fruit bat (Pteropus rodricensis) is an insular Old-World fruit bat endemic to the Island of Rodrigues. The Mauritian Wildlife Foundation implemented a population monitoring program in 1974 and an estimate of less than 80 individuals was recorded in 1979. Following conservation efforts of reforestation of native flora, the population has experienced a steady increase, subject to decreases in numbers after severe cyclones. A standardized methodology was applied in 2016 creating a dataset suitable for population modelling and statistical analysis. The most recent population census (2022) revealed that the population has remained stable at around 20,000 individuals for the last 5 years. This study uses Generalised Linear Mixed Models (GLMMs) to analyse 17 years of population monitoring data in order to identify the climatic factors potentially driving the population trend. We identified that the strongest factors driving changes in the population numbers were linked to resource availability. Most notable were annual precipitation levels, which had a positive relationship with population size (β=1.745, P<0.001), and cyclones, specifically relating to cyclonic strength, which was negatively related with the population size (β=-0.205, P<0.0001). This study also critically analyses the population count methodology and offers recommendations and suggestions for future research to be conducted on the species.