Climate change presents African grazers with a difficult choice

Lions limit the opportunities for their prey, such as zebras and wildebeest, to adapt to a warming climate. As the temperature rises, grazers have to choose between avoiding the heat and avoiding predators such as lions. Joris Cromsigt of the Copernicus Institute for Sustainable Development discovered this phenomenon together with his international colleagues. They recently published their findings in Nature Ecology & Evolution.

Africa is home to the highest diversity of large mammals in the world, but it is also where the climate is warming the fastest. "As temperatures rise, the window of time in which herbivores and the animals that prey on them can avoid the heat is shrinking," says Michiel Veldhuis, researcher at the Institute of Environmental Sciences in Leiden and main author of the publication. Night time is cool enough for the animals to graze, but if they live alongside lions – which are also mainly active during the cooler night hours – then the animals are forced to look for food during the hotter times of the day. This discovery implies that climate change not only affects individual species, but also the relationships between species.

Visualising consequences of climate change

Veldhuis and his colleagues used camera traps spread around 32 protected areas in South Africa. Lions inhabit half of these areas. These data, collected between 2013 and 2017, show the daytime activity of various species of animals. The researchers then compared the daytime activity of grazers in areas with and without lions. This indicated that grazers in areas without lions looked for food during cooler periods than the same animals in areas with lions.

Changing relationships

Over a shorter time period, it is easier for mammals to adapt their behaviour to the changing climate than it is to adapt their bodies. Normally these animals would migrate to cooler areas, but in the process they are often blocked by man-made barriers, such as fences. "We still don’t fully understand the consequences of the shrinking time window," Cromsigt explains. For example, not all herbivores are hit equally: "Some species, such as the gemsbok, could bear the heat and avoid lions, but for other species like zebras, the higher temperature could have serious consequences."

Publication: Veldhuis, M.P., Hofmeester, T.R., Balme, G. et al. Predation risk constrains herbivores’ adaptive capacity to warming. Nat Ecol Evol (2020). https://doi.org/10.1038/s41559-020-1218-2