In new research, a team of scientists from the Ohio State University acquainted 49 frog-eating bats with a series of ringtones that attracted their attention, and trained them to associate flying toward just one of the tones with a reward: a baitfish snack. Between one and four years later, 8 of those bats were recaptured and exposed again to the food-related ringtone. All of them flew toward the sound, and 6 flew all the way to the speaker and grabbed the food reward, meaning they expected to find food.
“I was surprised! I went into this thinking that at least a year would be a reasonable time for them to remember, given all the other things they need to know and given that long-term memory does have real costs,” said Dr. May Dixon, a postdoctoral researcher at the Ohio State University.
“Four years strikes me as a long time to hold on to a sound that you might never hear again.”
In their study, Dr. Dixon and colleagues exposed wild-caught fringe-lipped bats (Trachops cirrhosus) to a highly attractive sound in the lab: the mating call of the male túngara frog (Engystomops pustulosus), one of this species of bats’ preferred prey.
Flying to that sound was rewarded with a piece of baitfish placed on mesh above the speaker.
Over time, the sound was mingled with and gradually replaced by a ringtone, but the reward was the same.
The researchers then introduced three other ringtones, none of which was connected to a food reward.
Bats were trained to discern the differences and eventually no longer flew toward the unrewarded sounds.
Each bat secured at least 40 snacks by flying to the trained ringtone over 11 to 27 days.
All bats were microchipped and returned to the wild.
Beginning a year later and for three additional years, the team captured bats and identified eight from the initial trial by their microchips.
In a follow-up test of their response to the original rewarded ringtone, all eight trained bats quickly flew to the sound and were able to tell the difference between that ringtone and a new, steady tone, though many of the bats did fly to an unrewarded sound from the initial training.
When 17 untrained bats were exposed to these sounds, they mostly twitched their ears in response to the sounds, but didn’t fly toward them.
“The study taught us a lot because there are relatively few studies of long-term memory in wild animals and we don’t have systematic understanding of long-term memories in nature yet,” Dr. Dixon said.
“If we can collect additional data on different species of bats, we could pick this apart and see what life histories select for long memories.”
Despite the human tendency to assume a long memory gives our species the intelligence advantage, nature shows us that memory flexibility — also called adaptive forgetting — may be important for survival.
“It’s not always true that being the smartest or having the longest memory is actually advantageous,” Dr. Dixon said.
“Research has shown that fruit flies selected for improved memories can’t compete as well against other fruit flies.”
“Just because it’s useful for humans to be so smart and have such good memories doesn’t necessarily mean it’s going to be the best thing for other animals.”
“That’s why we want to figure out when these skills are actually going to help animals and when they could be a liability.”
The findings were published in the journal Current Biology.
M. May Dixon et al. 2022. Long-term memory in frog-eating bats. Current Biology 32 (12): 557-558; doi: 10.1016/j.cub.2022.05.031
Source link: https://www.sci.news/biology/frog-eating-bats-long-term-memory-10917.html