Where’s wallaby? – Counting the uncountable
Tuesday 3 June 2008
ZSL scientists have developed an innovative model that could revolutionise conservationists’ abilities to calculate animal population size without undertaking costly and often extremely difficult census work.
The scientists have found a way to adapt a series of formulae for the movement of gas molecules for use with information from camera traps, a method of obtaining images of animals in an area by using cameras that are triggered by movement. By doing this they are able to determine accurately the population density of a species.
Population density information is vital for successful conservation but is otherwise impossible to obtain without expensive and time-consuming surveys for species where individuals cannot be easily identified. Their research has been published in the Journal of Applied Ecology.
Dr Marcus Rowcliffe, ZSL Research Fellow and lead author of the paper, commented: ‘Most people assume that conservationists know exactly how many animals there are in any given area, but this is actually one of the greatest practical challenges we face, particularly when the animals cannot be individually identified. For example, counting animals in a jungle where there are lots of places to hide is costly and extremely difficult or even impossible.
‘Our new model makes it possible to calculate animal numbers by using the model developed for the movement of gas molecules and applying it to the process of contact rates between animals and cameras.’
The model was tested at one of the ZSL’s living collections, ZSL Whipsnade Zoo, where known populations of muntjac, wallabies and water deer were camera trapped and the results fed into the model. The estimated densities produced by the model matched the known population counts, demonstrating the efficacy of this approach.
Dr Rowcliffe added: ‘There are huge numbers of species that will benefit from this research. Pygmy hippos are a great example of a highly secretive species that we know almost nothing about, but which we will be able to calculate the population size of as a result of combining this research with camera trapping work that ZSL is currently undertaking in Liberia.
‘There are many other species which are seldom seen, so we struggle to gain knowledge of them, but which are nonetheless incredibly important parts of our world’s ecosystem.’