ABSTRACT

Long-term research is vital for understanding long-lived, dynamic systems like forests, yet for bats such research is notable for its absence. Recent advances in technology over the last 10–20 years means that long-term studies of bats are viable and can be cost-effective. I outline three case-studies of long-term research on forest bats using different techniques. These involve annual monitoring of populations at cave roosts, periodic monitoring of forest bat activity with ultrasonic detectors and advanced mark-recapture modelling of annual banding data to describe population dynamics. Annual counts over a 17 year period of a large maternity population of Eastern Horseshoe Bats Rhinolophus megaphyllus in a sandstone cave revealed a relatively stable population in the absence of major perturbations. There were only minor variations with climatic fluctuations, suggesting the cave and associated feeding grounds in a high rainfall gully could function as a climate refuge for the species. The second case study used acoustic detectors over a 14 year period to describe changes in bat use of forest regenerating (harvesting/fire) from the 1970s when specific environmental protection was not practised in New South Wales (NSW) forests. Forest regeneration was a dynamic process, especially in relation to changing vegetation density. Dense regrowth regenerating from harvesting rapidly dominated and persisted over a considerable period of time and provided unsuitable habitat for most bat species. Our third case study used mark-recapture of banded bats to estimate population dynamics in an experimental forest with environmental protection similar to that practised today in NSW forests (protection of riparian zones; habitat trees, rainforest). Analysis of 14 years of annual banding data demonstrated little effect (either no effect, or minor positive and negative effects) of harvesting history on survival and no effect on abundance or body condition. Environmental protection measures (and tracks) appeared to mitigate the impacts of dense regrowth and bats likely used these features at a local landscape scale. Long-term banding data also revealed negligible effects of weather extremes on survival and we suggest our high elevation study site represented a climate refuge that buffered bats from the effects of weather extremes. No single technique provides all the answers to bat ecology, rather each captures a different piece of the puzzle and, most importantly, each can be applied over long periods of time.

This content is only available as a PDF.