Ecuadorian Cactus Absorbs Ultrasound, Enticing Bats to Flowers


Plants pollinated by nectar-drinking bats often have flowers that reflect ultrasonic waves, making it easier for the animals to locate flowers through echolocation. But one cactus does the opposite—it absorbs more ultrasound in the area surrounding its flowers, making them stand out against a “quieter” background, according to a preprint published on bioRxiv last month.

Espostoa frutescens is a type of column-shaped cactus found only in the Ecuadorian Andes mountains. It has small flowers on its side that open at night, attracting bats as they fly from flower to flower in search of nectar. One of its main pollinators is Geoffroy’s tailless bat (Anoura geoffroyi).

“Bats are really good pollinators,” Ralph Simon, a postdoc in Wouter Halfwerk’s lab at Vrije Universiteit Amsterdam and the lead author of the preprint, tells The Scientist. “They carry a lot of pollen in their fur, and they have a huge home range so they can transport pollen from plants that grow far apart. For plants with a patchy distribution pattern like this cactus, it’s especially beneficial to rely on bats for pollination,” he says.

For bats to find the flowers at night, they use echolocation, emitting ultrasonic calls too high for humans to hear that bounce off objects and allow the bats to form a mental map of their surroundings. Some plants have evolved techniques that take advantage of this sonar system and allow bats to better detect flowers, such as making their petals more concave, forming a more reflective surface that can bounce more echolocation back to the bat. But E. frutescens takes a different approach.

Each of E. frutescens’s flowers are surrounded by an area of wooly hairs called the cephalium. Simon and colleagues knew from past measurements that the hairs were sound-absorbent, and were interested in seeing whether this part of the cactus could be involved in helping bats find the flowers. They attached a microphone and speaker to a device resembling the shape and size of a bat head in order to mimic a bat, and played prerecorded echolocation calls to the cacti and measured how much sound was reflected back to the bat replica.

The team found that the hairy cephalium absorbed ultrasound, and that the greatest absorption occurred above 90 kHz, in the range of the frequency of Geoffroy’s tailless bat’s echolocation call. The sound that bounced back to the microphone from the cephalium area was about 14 decibels quieter than the sound that bounced off the non-hairy part of the cacti.

It’s a “totally different mechanism” than the reflection method other cacti use, says Simon. “Instead of making the flowers conspicuous, it dampens the background. The background absorbs the ultrasound, and the flowers show up in [the middle of] this absorbent fur.”

This mechanism makes sense from a communication standpoint, writes May Dixon, a graduate student studying bat behavior in Mike Ryan’s lab at the University of Texas at Austin who was not involved with the study, in an email to The Scientist. “If you are trying to send a message, you have to think not only about the message itself but also the context. For example, if you are calling someone, you should be loud enough for them to hear, sure, but you should also call from a quiet place,” she says.

“There is something wonderful about the ways that plants have found to communicate with animals through evolution,” Dixon notes. “A cactus has no sense of what it is to be a bat—it can’t see, smell, or echolocate—but here it is, sending a bat a message in a language that a bat can understand.”

The cephalium appears to have originally evolved to protect flowers from environmental stressors such as UV rays, drying out, getting too cold, or being eaten, but “during evolution, it co-opted another function, and it functions as a sound absorbing structure as well,” says Simon. The evolution of this mechanism benefits both cactus and bat. “From the bat point of view, with this mechanism, they save time. And for them, it’s important to save time, because they have to visit several hundred flowers each night to get enough energy,” he says.

The current study did not look at whether sites on the plants with the highest sound absorption in the bats’ echolocation range “indeed resulted in the highest detection and visitation rates by bats,” says Jan Komdeur, an evolutionary ecologist at University of Groningen in the Netherlands who did not participate in the research, in an email to The Scientist. In the future, researchers could investigate how often real-life bats approach hairy versus experimentally manipulated hairless flowers, he suggests.

Jorge Schondube, an ecologist at the Universidad Nacional Autónoma de México who was not involved with the study, agrees that research on real-life bats is needed. “The pattern’s very clear, but now [researchers] need to show how the mechanism is actually changing the behavior of the bats,” he says.

Still, he’s impressed by the findings so far. “Nature is very creative. And by being creative, it allows the origin of completely new and unimaginable things. It’s really surprising that something like this can happen, and the paper shows it really, really beautifully. . . . What we’re seeing here is something that has not been seen before in terms of sound.”–enticing-bats-to-flowers-66981?utm_campaign=TS_DAILY%20NEWSLETTER_2020&utm_source=hs_email&utm_medium=email&utm_content=82166272&_hsenc=p2ANqtz-9in3Tqjl731fVW0JE_k3Ht2NOEvCOnql7E5ADhmEp4j43Rrs5Q6gxTipSPvHXAs-8C6MvOvVFdBpktnFeyya1pvZPF2A&_hsmi=82166272

Robert Provine, neuroscientist with pioneering work in laughter, yawning, hiccupping, and tears, dies.


Neuroscientist Robert Provine, known for his groundbreaking research on common but mysterious human behavior such as laughter and yawning, died October 17 of complications from non-Hodgkin’s lymphoma, according to The Washington Post. He was 76.

Provine studied human social behaviors through innovative methods. In one 1993 study, his team observed people laughing outside of the lab setting, such as in shopping malls or while walking down the street. He found that, contrary to scientific belief of the time, most instances of laughter were based not in response to overt humor, but instead in an effort to strengthen social bonds, acknowledge a superior’s authority, or, when used negatively, to exclude someone from a group.

“Laughter is part of this universal human vocabulary. Everyone speaks this language. Just as birds of a given species all sing their species’ typical song, laughter is part of our own human song,” Provine once told NPR, according to the Post.

Born on May 11, 1943 in Tulsa, Oklahoma, Provine showed an aptitude for science at a young age when he built telescopes in high school. He received his bachelor’s degree in psychology from Oklahoma State University in 1965 and PhD in psychology from Washington University in St. Louis in 1971. He was a member of the American Association for the Advancement of Science, the Association for Psychological Science, and the Psychonomic Society, and wrote two popular science books: Laughter: A Scientific Investigation in 2000 and Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond in 2012.

“Provine’s research on topics such as yawning, laughter, tickling, and emotional tears provided fascinating insights into the fundamental building blocks of human social behavior,” according to a memorial on the University of Maryland, Baltimore County’s (UMBC) website. Provine taught at UMBC for four decades before becoming a professor emeritus in 2013.

“His approach was just amazing. It was different than what pretty much anyone was doing,” Robert Spencer, one of Provine’s former PhD students and currently the chief of neuropsychology at the VA Ann Arbor Healthcare System, tells The Scientist. “He was opening up a whole new set of methods, things that he would refer to as ‘sidewalk neuroscience,’ which was essentially ethology as applied to humans. And he answered questions you just can’t answer in synthetic lab situations,” he says.

Spencer remembers Provine as having a quirky personality, a distinctive Oklahoma accent, and a lab that “looked like a museum,” adding that it was “just full of equipment that he had built himself” in order to conduct experiments. In addition, he had many interests outside of the lab, such as saxophone playing, race car driving, and martial arts.

He is survived by his wife of 23 years, his son and daughter from his first marriage, and three grandchildren.–researcher-of-universal-human-behavior–dies-66622?utm_campaign=TS_DAILY%20NEWSLETTER_2019&utm_source=hs_email&utm_medium=email&utm_content=78428564&_hsenc=p2ANqtz-9rEINL9K9sYAcnp9kSxgo46D44ioSo_zR3e3MkXqwoeczqjTYDR5a4v3X7Cc4X3sqANvMx6eWvkiUiGKo7lYg5Cj8Sjw&_hsmi=78428564