By Peter Stewart

Invasive prickly pear cacti (Opuntia) are a serious problem in Laikipia County, Kenya. This invasive plant spreads rapidly across the landscape, turning diverse habitat into a green hell of pads and spines. As invasive plants like prickly pear spread, they can alter the behaviour of wild animals, triggering a cascade of consequences which impact on the ecosystem and the communities who inhabit it.

A stand of invasive prickly pear (Opuntia engelmannii) at a heavily-invaded site.

In a new project, our team from Durham University’s Conservation Ecology Group, in collaboration with Mpala Research Centre and Loisaba Conservancy, is working to understand how prickly pear affects the habitat use of wild mammals – a key aspect of their behaviour.

To achieve this goal, we are using motion-activated camera traps to record how many animals of each species are using sites invaded by prickly pear, and then comparing these numbers to nearby sites with little or no cactus. The camera traps also provide information about how different species interact with the cactus, whether eating its fruits or spiny pads, eating other plants which grow within the cactus stands, or using the cactus as cover to hide from predators.

An elephant feeds on the fruit of Opuntia engelmannii.

To process the huge number of photos collected by the camera traps, we need your help! We have set up a project on the online citizen science platform Zooniverse, where anyone can view the camera trap photos and classify the animals in them. You can click here to visit the project home page.

Before uploading images to Zooniverse, we pre-screen them with the machine learning tool Megadetector to filter out empty images – this means that most of the images on our Zooniverse page have animals in them!