Where the wild things are: Using remotely sensed forest productivity to assess arboreal marsupial species richness and abundance

Aim: Highly productive areas have long been hypothesized to support a greater abundance and diversity of animals than less productive areas. However, evidence for this is equivocal and, until recently, has been difficult to test at a landscape level. For the first time, we use imaging spectroscopy to investigate the relationship between plant productivity and arboreal mammal species richness and abundance at a landscape scale. Location: A eucalypt forest in New South Wales, Australia. Methods: Using a common index of plant productivity - normalized difference vegetation index (NDVI) - as a proxy for available energy, we test the ability of species-energy theory and optimal foraging theory to explain variations in arboreal marsupial species richness and abundance. We obtained NDVI data from an airborne imaging spectrophotometer. Results: Species richness increased in relation to NDVI among 53 eucalypt forest sites, based on five arboreal marsupial species. The presence and abundance of a eucalypt folivore specialist, Petauroides volans, increased in relation to NDVI. The relative abundance of all arboreal marsupials collectively also increased in relation to NDVI among sites, even with P. volans data excluded. In support of optimal foraging theory, the observed locations of P. volans had a higher NDVI value than the average for sampling transects. In addition, the average NDVI of eucalypt forest remnants was positively related to the overall abundance of P. volans. An important caveat is that NDVI did not explain all the variation in arboreal marsupial populations. Main conclusions: Assuming that NDVI is an appropriate proxy for available energy in a eucalypt forest, our results are consistent with predictions from species-energy and optimal foraging theories. Remotely sensed measures of productivity and forage quality, used in conjunction with other important landscape characteristics, provide a potentially powerful tool to evaluate habitat and biodiversity hotspots at scales relevant to wildlife management and conservation.