Dear Readers, there are more species of bats on Earth than any other mammal group except for rodents, and yet we know very little about them. So for today’s update from New Scientist, I wanted to pick up on a few stories that shed light on their complex lives.
Vampire bats are not everyone’s choice as favourite small furry animal, but this article shows how little we know about their social structures. Imran Razik of Ohio State University was studying a colony of vampire bats which comprised 23 adult females and their young. Although vampire bats roost together, they normally raise their young individually, although bats form close ‘friendships’ with one another. The researchers noticed the burgeoning relationship between Lilith, a nursing female, and BD, a single bat with no offspring of her own.
When vampire bats form a friendship, they spend a lot of time grooming one another, and sharing food. It was noticed that BD spent a lot of time feeding Lilith, and that this increased as Lilith became ill, even though she was not sharing food reciprocally with BD. As Lilith became sicker, BD also spent more time looking after the baby, grooming it, carrying it and even feeding it.
When Lilith eventually died, BD adopted the baby fully. It is extremely rare for this to happen even amongst mammals that are more closely related to us, such as chimpanzees, so this is a very exciting observation. Why, though, do bats choose one individual over another to be their friend? As it’s hard enough to work this out even in humans, I think this could be a fascinating study.
Now, let’s have a look at the European free-tailed bat, a rather melancholy-looking creature if the photo is anything to go by. It’s long been known that birds can often reach extreme heights by finding thermals and riding them, but these are much less common at night. However, by attaching light-weight GPS monitors to lactating female bats, it was found that they could reach heights of up to 1600 metres. How do they do it? It appears that, although they fly in almost total darkness, they have an excellent knowledge of the landscape of their territory, and use the uplift from where south or west-facing slopes meet the prevailing winds of north-west Portugal, where the colony is located. They soar upwards, gently sail down and then find another slope of similar topography so that they can repeat the process. The team who studied the bats, led by Teague O’Mara from Southeastern Louisiana University, note that this gives a flight-plan that looks rather like a rollercoaster ride. One question would be ‘why go so high’? I would speculate that the bats’ insect prey may also fly high, probably to avoid predators, but this style of flight would be energetically very efficient for the bats. You can read the whole article here.
And now for another free-tailed bat. The Brazilian free-tailed bat was cited as the fastest vertebrate in the world at level flight during tests on the population from the Frio cave in south-western Texas. The bats clocked speeds of 100km an hour, with one bat having a maximum speed of 160km, faster than the spine-tailed swift at 112 km per hour. However, then the controversy started, over the way that the bats were measured, uncertainties about the wind speed, and whether the ‘level’ flight was actually level. Nonetheless, there is no doubt that these are extremely speedy bats – they travel more than 50km to their feeding grounds every night, and fly at heights of more than a kilometre. Perhaps they’re in an arms race with speedy prey?
You can read the whole article here.
Now you might think that with all these speedy, high-flying bats around, moths would stand no chance. In fact, some moths are able to hear the echolocation clicks given by bats and literally fold their wings and drop out of the air to avoid capture. What happens, though, if you have no ears?
Marc Holderied was studying earless moths, such as the Chinese Tussar Moth, at Bristol University. He found that when sound waves were projected at the wings of the moth, they bounced back much more quietly. Structures on the wings absorbed the sound at the specific frequencies that are emitted by the bats, in effect acting as a ‘stealth coating’. Holderied also studied another species of earless moth, Drury’s Owl Moth (Dactyloceros lucina) and found that it had the same structures on the wings. Moths who could hear didn’t have them.
Scientists are speculating whether similar structures could be designed to help with things like sound-proofing and noise-cancelling headphones. In our increasingly noisy world, that could surely be good thing.
You can read the whole article here.
Photo One by Uwe Schmidt, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
Photo Two by Emanuel Yellin – עמנואל ילין, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
Photo Three by Barry Mansell/Naturepl.com from https://www.newscientist.com/article/2112044-speedy-bat-flies-at-160kmh-smashing-bird-speed-record/
Photo Four By Ivo Antušek – https://www.biolib.cz/en/imagegalleryuser/id60700/?uid=295, Public Domain, https://commons.wikimedia.org/w/index.php?curid=13321460