Elephants can lose two bathtubs full of water in a single day in hot weather | Science

By Christa Lesté-Lasserre25 November 2020, 11:30 am

When the weather is hot, elephants can lose up to 10 percent of all water in their bodies in a single day, according to a new study. That’s the equivalent of nearly two full bathtubs, the highest volume of daily water loss ever recorded in a land animal.

The findings won’t mean much to the zoo’s elephants, who generally “live pampered lives,” says Baptiste Mulot, a researcher on elephant behavior at ZooParc de Beauval, a French zoological park. But Mulot, who was not involved in the work, has deep concerns about elephants in the wild, especially when the world warms up. For a species that is already threatened with extinction, lack of access to water, he says, could lead to lower birth rates, reduced milk for baby elephants and deaths related to dehydration.

Elephants need hundreds of liters of water every day. But it’s not clear how climate change will alter their water needs.

So, in the new study, researchers led by Corinne Kendall looked at five elephants from the African savannah (Loxodonta africana) at the North Carolina Zoo, where she works as a conservation biologist. On six occasions over a 3-year period, the team gave the animals precise doses of deuterium, a harmless, heavy version of hydrogen that dilutes in the body’s water and can be traced in the animals’ fluids. The scientists regularly took blood samples for 10 days after the deuterium dosing to see how much was left each time, indicating how quickly the elephant was clearing body water.

The results were “surprising,” says Kendall. In cool temperatures (6 ° C to 14 ° C), males lost an average of 325 liters per day. But around 24 ° C, they lost an average of 427 liters, and sometimes up to 516 liters, the team reports this week in Royal Society Open Science.

It is up to 10% of their total body water, or up to 7.5% of their body mass. An elephant lost nearly 9 percent of its body mass in a single day, says study co-author Rebecca Rimbach, an ecophysiologist at Duke University. Since animals constantly replenish lost fluids through drinking, eating and metabolic processes, however, the net daily water loss of elephants would be lower. Overall, elephants need to drink at least every 2-3 days to avoid “potentially dangerous levels of dehydration,” he says.

“This is surprising when you consider that these are animals that have adapted to living in the African savannah,” says Kendall.

Horses in a hot environment can lose 40 liters in a day – around 6% of their body mass – and humans typically consume 3 to 5 liters – around 5% of our body mass, although this can almost double when active people, such as marathon runners or soldiers, are really sweating.

As global temperatures rise, wild elephants will need more water. However, it will become rarer as the pools of water dry up and water-rich plants become rarer. This could worsen the conflict between wild elephants and human populations for resources, says co-author Erin Ivory, an elephant behaviorist at the North Carolina Zoo. When elephants raid crops or destroy groundwater infrastructure, he says, violent clashes can be deadly for both species.

“But the problem is much bigger than that,” Mulot adds. An increasingly drier and warmer southern Africa will affect the water needs of a wide variety of animals, he says. “With the competition for resources in the face of global warming, we are in the process of eliminating all animal and plant species from the entire area.”