Frogs are famously hoppy (to the displeasure of this frog-phobic child) but new evidence has revealed the devastating impact hot and dry weather can have on the leaping potential of amphibians. Published in the journal Proceedings of the Royal Society B, new research has found that as some frogs and toads lose water they can’t jump as far, painting a worrying picture for their future on an ever-warming planet.
The research focused on three species; the coastal tailed frog (Ascaphus truei), the spadefoot toad (Spea intermontana), and the Pacific tree frog (Pseudacris regilla). The three amphibians are unique in their habitats, with A. truei favoring cold streams while S. intermontana is right at home in the desert and P. regilla is something of a wanderer. Live specimens from all three species were placed into tanks with controlled conditions so the researchers could dictate the amphibians' body temperature and degree of dehydration.
Across the board, all three leapers were initially able to maintain their mobility but there was a drastic drop off when they lost around 20 percent of their body weight from dehydration. At this point, all three species began hopping a shorter distance compared to when they were suitably wet. The critical point for being incapable of hopping altogether was at a 30 percent loss for the two frogs and 45 percent loss for the desert toad. The negative impact on jumping distance was even more pronounced when dehydrated frogs and toads were kept in warmer environments, with control conditions ranging from 15 to 30 degrees centigrade (59 to 86 Fahrenheit).
It’s thought the mechanism behind this environmentally-induced hopping handicap could be a disruption in the exchange of ions in the cells caused by the water loss, which could also have a knock-on effect on the transport of nutrients and removal of waste products in tissues. It could also be that as blood thickens from dehydration it puts a strain on the heart and makes the physical activity seem more exhausting.
While a hot, limp frog is a sad enough image on its own, these findings carry great weight in the face of planet Earth’s climate crisis. Not just for frogs and toads but also other “cold-blooded” animals who rely on stable environmental conditions to maintain a physical state conducive to bodily functions known as homeostasis. Other animals whose mobility may be similarly hampered by dehydrating conditions include insects and reptiles, who - while not hoppers - also need to be able to move efficiently when hunting or avoiding predation. Some animals are capable of altering their behaviors to wait-out the worst of unfavorable environmental conditions, but such behaviors are rarely conducive to a normal life and few can keep up with the rate of climate change.
“As soon as the temperatures went up a little bit, the tree frogs in particular would sort of hunker down in a way that reduces water loss, as if they were thinking, “This isn’t going to be good for me”,” said study author Dan Greenberg of Simon Fraser University, Canada, to New Scientist. “When we look at water loss and take it in concert with temperature, it really changes how we think about the way climate change is going to reorganise the ecological systems on Earth in the coming centuries.”