The abundance, species diversity and habitat usage of microbats in coastal mangroves of South-East Queensland

In cooperation with the University of Queensland

This project is being conducted by Julie Broken-Brow , an Honours Research student at the University of Queensland, School of Animal Studies. Long Grass Nature Refuge have given Julie a grant to assist with her research. Julie has also received a grant from the Australasian Bat Society

Background

    Microbats comprise approximately twenty-five percent of all terrestrial mammal species in Australia, yet they remain the least studied. The International Union for the Conservation of Nature has reported severe population declines across many microbat species worldwide. The primary threat to microbat populations is habitat modification. In Australia, one of the leading processes of habitat modification is land clearing and development.

    Mangrove communities in Australia are recognized as vital ecosystems; they act as coastal water filters, prevent erosion and provide essential habitat for benthic and wetland fauna.  It has become apparent in recent studies across Australia that mangroves may play a crucial role in microbat foraging, roosting and breeding. To date, there have been no studies which have looked at the ecological relationship between microbats and mangrove ecosystems. Many microbat ecologists believe that old growth mangrove forests support large microbat communities. The proposed research project may provide useful ecological knowledge for developing strategies for conserving microbats in coastal mangrove ecosystems.

Methodology

    The study will be conducted over three Avicennia marina (Grey mangrove) mangrove habitat types in South-East Queensland:

1. Old growth mangrove forest (characterized by high hollow density, open forest structure and large diameter at breast height)
2. Mature mangrove forest (characterized by low hollow density, open forest structure and moderate diameter at breast height)
3. Regrowth mangrove habitat (characterized by low hollow density, closed/shrublike structure and small diameter at breast height)

    In each habitat type the microbat population will be assessed using harp trapping and echolocation call detection. Trapping will be used to evaluate relative abundance and Anabat recording systems will be used to determine microbat activity. Trapping with four harp traps and Anabat call detection will be completed at each of the three replicate sites within the three mangrove habitat types (total of nine sites). This survey will be undertaken over a 5 month period from October to February.

    Habitat surveys will be carried out over the period of the field work. The habitat structure has been shown to be one of the main factors which affect microbats. These surveys will quantify vegetation qualities such as: tree density, average tree diameter at breast height, canopy cover and hollow abundance. These factors will be used to characterize the habitats at each of the sites.