“Not only because of the high temperatures, but also because of the presence of people.”

The Earth's temperature is rising, and mountain caribou are taking notice, too. To avoid the heat, caribou increasingly live at night. Herbivores appear to accept the risk of attacks by nocturnal predators.

Alpine ibex, also known by its Latin name Capra Ibex, must live mainly during the day. And this is not without reason. Ibex are warm-blooded and therefore highly dependent on the external temperature. Because it is warmer during the day than at night, the caribou do not have to waste valuable energy keeping warm.

As global temperatures rise, alpine ibex must adapt. During the day it can become so hot that it is no longer able to dissipate heat properly. As a solution, the fawn changes its lifestyle to a more nocturnal one. This is not without risks: predators such as the wolf hunt mainly at night.

The evidence for lifestyle changes is based on more than three million observations in the Swiss and Italian Alps over thirteen years. The scientists, from the University of Sassari in Italy, among others, looked at the behavior of ibex in two separate areas, in the months from May to November. The two Alpine regions were almost identical in terms of climate and vegetation, with one important difference: only at the Italian study site was the wolf active at the time.

Using collars equipped with GPS trackers, scientists were able to monitor herders' activity levels from 2006 to 2019. Local weather stations provided hour-by-hour air temperature data. After statistical analysis of all the data, it was found that the peak temperature during the day in particular had an impact on the rhythm of life of the caribou. The warmer the day, the greater the activity the following night.

tourism

Contrary to expectations, the caribou in the area also went out at night with the wolf. This is astonishing, the scientists wrote in the scientific journal Proceedings of the Royal Society. According to them, the results show that alpine ibex accept the risk of being attacked.

“It's an interesting study,” says ecologist Inger de Jong of Vrije Universiteit Amsterdam, who was not involved in the study. “But don’t forget the human impact.”

De Jong conducted similar research in Tanzania, where she saw mammals moving away from an area where humans were present. “There is also a lot of tourism at the Italian research site. So it is possible that the alpine caribou there may have to shift their activities to the night, not only because of the higher temperatures, but also because of the presence of people.”

Nocturnal vomiting is not the best solution. Because the caribou evolved to live during the day, they cannot see well at night. This may make it more difficult to find food or maneuver through rocky landscapes. The brightness of the moon can be a useful tool: animals appeared to be more active during clearer nights.