Assisted dispersal of tropical dung beetles

Abstract

As habitat fragmentation and climate change degrade the suitability of natural habitats, many species are likely to become threatened with local or global extinction. In the future, conservation of species and management of degraded areas may need to employ radical solutions, such as assisted dispersal and colonisation. Here, we report the findings of a small scale, two-fold investigation into potential management actions for reintroducing functionally important species (dung beetles) in a fragmented system. We tested two a priori hypotheses: 1) dung supplementation will increase dung beetle population sizes in the short term; and 2) introducing dung beetles into a previously uninhabited area (assisted dispersal) will establish viable populations. Although we expected population sizes to increase following dung supplementation, there was no significant effect on beetle population sizes on eight small islands when compared to eight control islands. However, introducing 827 individuals of the common species Paragymnopleurus maurus to two previously uninhabited islands had mixed results. On one island, the newly founded population persisted beyond 51 days but rapidly declined on the other. Follow-up investigations suggested that invasive, predatory yellow crazy ants (Anoplolepis gracilipes) may have prevented population establishment on the island where this failed. Assisted dispersal, and colonisation, may provide mechanisms to combat some effects of fragmentation and climate change if isolation is the primary cause of the population decline, but success depends on extensive prior suitability assessment. Although suggestive, our results should be interpreted with caution because of experimental limitations. © National University of Singapore.