The lure of the camera trap
Images of wildlife in National Geographic magazines and documentaries starring David Attenborough have dazzled audiences for decades—their cameras revealing places and animals that many people may otherwise never see. More recently, scientists have been developing smart new ways of using cameras to deepen our knowledge of ecosystems and their animals.
Heat-in-motion sensing camera traps are giving us an unprecedented level of information about animals in the wild – which in turn will help wildlife managers make sounder, more effective conservation decisions.
The latest devices are typically shoebox-sized or smaller. They shoot digital still or video images, and are triggered when an infra-red sensor detects heat in motion – in other words, a warm- or cold-blooded animal that contrasts against the background temperature when it moves across the field of vision. The temperature-differential triggers the camera’s shutter.
In theory, you just need to tie one to a tree and collect the digital output. However, getting meaningful results from camera trapping is not that simple, says ecologist Paul Meek from the NSW Department of Primary Industries (NSWDPI).
For a start, there are different survey designs, different placements and different settings (eg time-sequence, lens position and angle, use of bait) that can be used, not to mention the plethora of ways in which wildlife researchers store, manage and analyse their image data.
As with any consumer product, there are differences between models – such as the degree of accuracy in detecting targets, and differences in image quality, flash type, weather-proofing, robustness and shutter speeds. Some trap cameras have a long trigger latency of more than 1 second, a serious limitation when targeting fast animals. Paul Meek says wildlife ecologists would like to see trigger times of 200–500 milliseconds.
After he realised the need for the global community of ‘camera trappers’ to share their knowledge about this rapidly evolving technology, Paul managed to secure funding for the First International Camera Trapping Colloquium in Wildlife Management and Research, held at Taronga Zoo in 2012.
With NSWDPI colleague, Peter Fleming, Paul brought the symposium presentations together into a book that details experiences with wildlife camera trapping in remote areas of Australia, South America, Bhutan, the United States and Africa.
Importantly, the book discusses how camera trapping can improve wildlife monitoring – from detecting the presence of shy, small or nocturnal animals or of threatened species; to estimating local population densities and size; to monitoring animals in tropical forests across the globe.
In the remote Himalayan kingdom of Bhutan – a Buddhist country where respect for all life forms underpins wildlife management policy – camera trapping is the preferred method of studying creatures like shrews or rodents. Small animals like these sometimes die when caught in traditional pitfall traps. In Bhutan though, the death of a shrew at the hands of a researcher is no more acceptable than the death of a tiger.
Not that tigers have escaped the camera trap. On 11 April 2000, Bhutanese researchers captured the first photograph of a tiger in Bhutan at 3,000 m altitude – 2,000 m higher than the earlier accepted ‘limit’ for tigers. (A later claim, in 2010, by another research team that they had captured the first image of tigers at high altitude in Bhutan has been disputed.)
Elsewhere, researchers are using camera traps to study:
- the impact of feral camels on water availability and native animals in the Australian outback
- how possums and gliders use glide poles, rope bridges and other man-made structures to cross busy roads and highways
- the spread of devil facial tumour disease among Tasmanian devils by tracking its incidence among animals from different areas
- the rediscovery of an ‘extinct’ species, the saola (Pseudoryx nghetinhensis), in Vietnam.
Both camera and data-management technologies are evolving rapidly. Researchers can now extract data directly from photos, reducing the time spent on labour-intensive data entry. They have also developed ways of using pattern-recognition technology to automatically identify individual animals.
New internet and mobile phone apps are improving the way users can share data. In fact, cheap digital camera and mobile phone technology mean any ‘citizen scientist’ with a device can take part in wildlife surveys.
Camera traps are also powerful tools for educating local communities about wildlife. Images of animals in distress, playing, or tenderly nurturing young have helped rally support for conservation programs across a range of cultures, without the need for language.
“Camera traps are not a panacea for the challenges of wildlife surveys,” notes Paul. “Like other tools, such as radio-telemetry tags or live traps, they have advantages and constraints.”
“On the other hand, they are helping bridge many gaps between researchers, wildlife managers and the broader community. I think the future of camera trapping is truly exciting.”
You can order a copy of the book Camera Trapping: Wildlife Management and Research online through CSIRO Publishing