Effects of Habitat Fragmentation on Non-volant Small Mammal Communities on Borneo (Sabah, Malaysia)
About
PhD candidate: Jennifer Brunke
Supervisors: Apl. Prof. Dr. Ute Radespiel, Dr. Benoit Goossens
Institution: University of Veterinary Medicine Hannover
Collaborators: Sabah Wildlife Department, Michael W. Bruford, Cardiff University
Date: 2011
Summary:
The increasing fragmentation of tropical rain forests due to anthropogenic landscape changes poses increasing problems for their biodiversity. Changes in natural habitats affect individuals of different species in various ways. In contrast to large mammals, the knowledge about how small mammals can cope with habitat fragmentation is in its infancy. However, small mammals are not less important for maintaining ecological balance within habitats and are not necessarily less vulnerable to anthropogenic changes.
More than 60 non-volant small mammal species are known to occur in Borneo. More than half of these species are endemic to Borneo. Taxonomically, communities of Bornean non-volant small mammals contain various species of Eulipotyphla (i.e. Erinaceidae and Soricidae), Scandentia (i.e. Ptilocercidae and Tupaiidae), and Rodentia (i.e. Sciuridae and Muridae) that differ largely in lifestyles and ecology. As a result of large-scale logging activities and habitat conversion, 20% of Bornean small mammals are already listed as endangered, vulnerable, or near threatened by the IUCN. To develop effective conservation measures and determine the susceptibility of small mammal species, it is essential to understand the consequences of anthropogenic disturbances on population numbers and viability.
©Rudi Delvaux
Summary:
The increasing fragmentation of tropical rain forests due to anthropogenic landscape changes poses increasing problems for their biodiversity. Changes in natural habitats affect individuals of different species in various ways. In contrast to large mammals, the knowledge about how small mammals can cope with habitat fragmentation is in its infancy. However, small mammals are not less important for the maintenance of ecological balance within habitats and are not necessarily less vulnerable to anthropogenic changes.
More than 60 non-volant small mammal species are known to occur in Borneo. More than half of these species are endemic to Borneo. Taxonomically, communities of Bornean non-volant small mammals contain various species of Eulipotyphla (i.e. Erinaceidae and Soricidae), Scandentia (i.e. Ptilocercidae and Tupaiidae), and Rodentia (i.e. Sciuridae and Muridae) that differ largely in lifestyles and ecology. As a result of large-scale logging activities and habitat conversion, 20% of Bornean small mammals are already listed as endangered, vulnerable, or near threatened by the IUCN. To develop effective conservation measures and determine the susceptibility of small mammal species, it is essential to understand the consequences of anthropogenic disturbances on population numbers and viability.
Objectives:
This project assessed the susceptibility of non-volant small mammal species to increasing habitat fragmentation and accompanying changes in habitat conditions in the remaining lowland rainforest along the Kinabatangan River. Numerous woodlands have been cleared or converted to anthropogenic landscapes along the river. Nowadays, oil palm plantations dominate the landscape and forests are restricted to isolated patches. These forest fragments provided an ideal setting for assessing fragmentation effects on the native biota since they vary in size, degree of habitat disturbance and connectivity.
With this project, we wanted to learn about the factors determining their vulnerability towards habitat fragmentation and habitat disturbance. To achieve this, we monitored small mammals in a larger number of forest patches along the Kinabatangan River and assessed the influence of various environmental factors (e.g. patch size, degree of isolation, barriers of various quality and size, habitat structure, edge effects) and species-specific traits (e.g. habitat specialisation, activity pattern, degree of terrestriality, reproductive rate) on their population viability.
Methods:
To assess the potential correlations between fragment quality and the diversity and abundance of small non-volant mammals within these patches, structural habitat variations across forests were identified, and the diversity and abundance of small mammal species were described for each study site. The species richness and number of small non-volant mammal communities were directly related to the various habitat characteristics, and existing habitat preferences and specialisation were recorded. Using state-of-the-art genetic modelling approaches, we estimated the impact of habitat fragmentation and disturbance on the diversity and gene flow of small mammal populations. Genetic structures across fragments and the effects of potential barriers (small/large rivers, oil palm plantation) were also be tested and contrasted to isolation by distance effects. Different predictions on the impact of habitat fragmentation on genetic diversity, gene flow and structure were investigated by means of mitochondrial and nuclear markers.
Outcomes:
The actual endangerment of Bornean small mammals was evaluated by acquiring knowledge about species, species-specific susceptibilities and viabilities toward habitat disturbance. Furthermore, this project provided valuable results that will be of prime importance for the management of existing and newly established conservation areas. The results were reported and contributed to the ongoing comprehensive management plan for the Lower Kinabatangan Wildlife Sanctuary, which tackles the problem of forest fragmentation and forest degradation.
