Animals that are used to living in the desert are great at surviving; they have many adaptations to conserve water and beat the heat. And these hot and arid areas aren't going to cool any time soon. In fact, climate change models predict that places like the Sonoran Desert in the southern USA and northern Mexico are going to get even hotter and drier. Will the animals that currently call this desert home be able to withstand a harsher environment? Danielle Blumstein and Matthew MacManes of the University of New Hampshire, USA, decided to find out what could happen if the cactus mouse (Peromyscus eremicus) isn't able to find water.

First, the team removed the water from the mice's cages for 3 days. Twice per day, the researchers measured the body temperature of the mice and also weighed each mouse at noon. Interestingly, the female mice had lower body temperatures while they were dehydrated but the male mice didn't lower their body temperature at all. Blumstein and MacManes believe that this may be to keep the male mice producing healthy sperm for when they are able to reproduce again. So, if the males weren't trying to keep cool by lowering their body temperature, how were they dealing with being hot and thirsty?

To answer this question, the duo needed to see how dehydrated the mice were every day. Testing their blood for electrolytes, Blumstein and MacManes found that the mice were indeed dehydrated, as the levels of some electrolytes increased. But the researchers also found something surprising; the mice weren't really losing that much water after the first day.

The water loss contributed to all of the mice losing weight – most of it on the first day – and they continued to lose a bit more each day afterwards. The team also noticed that the mice had stopped eating. Cactus mice can't get water solely from their food as some other rodents can and digesting their meals can actually make them more dehydrated. If they stop eating, they can absorb some of the water that is already in their intestines and save the water they would need to remove waste products after digestion. This strategy might work in the short-term, but these mice probably use a different strategy to conserve water in the long-term, when the tap runs dry.

D. M.
M. D.
When the tap runs dry: the physiological effects of acute experimental dehydration in Peromyscus eremicus
J. Exp. Biol