Camera trapping is a highly useful tool for estimating animal abundance for wildlife management and conservation. Following our previous blog post we continue to explore camera trapping methods.
An increasing number of researchers and conservationists use camera traps triggered by a passive infrared (PIR) sensor to study wild animal populations. However, there is a common problem that the PIR sensor does not detect all animals that move past the camera. Moreover, the sensitivity of the PIR sensor is dependent on the size and the surface temperature of the animal, which means that larger animals are detected more easily than smaller ones. Also, plants blocking the ‘view’ of the sensor can cause differences in detection probability between different habitats and sites.
As camera traps are often used to compare different species of animals in one habitat or habitat use of a single species in different habitats, these differences in detectability can result in erroneous conclusions. Therefore, photographic capture rates obtained with camera traps need to be corrected for differences in detectability. This can be done by measuring the distance at which each animal is first photographed for each individual picture, however this task is often too time consuming for researchers and conservationists.
In our article, we present a simple method that allows for the estimation of the effective detection distance for animals of different sizes in different habitats.
We placed a line of markers in front of each camera trap and then used these markers to get a rough estimate of the distance at which animals passed the camera and were detected.
The distance intervals obtained with the markers can be used to estimate the effective detection distance for different species and different habitat types using conventional distance-sampling techniques. Simulations showed that the estimates are accurate so long as sufficient markers are used.
We applied this method to eight areas in two different habitat types, and found that the effective detection distance was four times higher for the largest mammals in these areas than for the smallest.
This means that uncorrected capture rates heavily overestimate the abundance of large mammals compared to small mammals, demonstrating the necessity of this method to obtain more accurate estimates.
This low-budget method increases the set-up time of camera traps only slightly, but allows researchers and conservationists to correct camera capture rates for detection bias, so that better comparisons across different animal species and habitats can be made.
Select a blog
Our people are our greatest asset and we realise our vision for a world where wildlife thrives through their ideas, skills and passion. An inspired, informed and empowered community of people work, study and volunteer together at ZSL.
At ZSL, a key area of our work is the employment of Nature-based Solutions – an approach which both adapt to and mitigates the impacts of climate change. These Solutions, which include habitat protection and restoration, are low-cost yet high-impact, and provide multiple benefits to people and wildlife. We ensure that biodiversity recovery is at the heart of nature-based solutions.
A blog for lovers of ZSL London Zoo, bringing you extraordinary animal facts and exclusive access to the world's oldest scientific zoo.
Do you love wildlife? Discover more about our amazing animals at the UK's biggest zoo!
We're working around the world to conserve animals and their habitats, find out more about our latest achievements.
From the field to the lab, catch up with the scientists on the cutting edge of conservation biology at ZSL’s Institute of Zoology.
A day in Discovery and Learning at ZSL is never dull! The team tell us all about the exciting sessions for school children, as well as work further afield.
Every month, one of the pieces held in ZSL’s Library and at ZSL Whipsnade Zoo will feature here as Artefact of the Month.
Read testimonials from our Members and extracts from ZSL's award winning members' magazine, Wild About.
The Chagos archipelago is a rare haven for marine biodiversity. Hear from the team about our projects to protect the environments in the British Indian Ocean Territory (BIOT).
ZSL works across Asia, from the famous national parks of Nepal to marine protected areas in the Philippines. Read the latest updates on our conservation.
An Open Access journal for research at the interface of remote sensing, ecology and conservation.