Bat Rocks Out in Speaker-Like Roost

A bat with a rock-star name builds a speaker out of leaves to amplify and modify its calls.

A clever bat has discovered that certain leaves function like a speaker system, since the leaves help to transmit, amplify and modify sound, according to a new study.

The bat species name appropriately sounds a bit like a rock group: Spix's disk-winged bat. Spix's discovery is described in the latest issue of the Proceedings of the Royal Society B.

Humans usually get all of the credit for using objects to amplify and modify sound. Now it's known that this bat does too, with the amplifier serving double duty as a roost.

"Our study provides the first evidence of the potential role that a roost can play in facilitating acoustic communication in bats," co-authors Gloriana Chaverri and Erin Gillam wrote.

The researchers found that the bats -- native to parts of South America -- seek out particular leaves from plant species such as Heliconia and Calathea. One or more bats go inside large, single leaves that naturally curl into a megaphone-type shape.

As the bats literally hang out, they call to each other, with the leaves affecting those communications. Chaverri, a professor at the University of Costa Rica, explained how the leaf "tech" works.

"Leaves appear to amplify incoming calls as sound waves get increasingly compressed when they enter the leaves," she told Discovery News. "Outgoing calls are amplified possibly due to sound directionality: Instead of sound being dispersed over a large, area, they are aimed in a specific direction and so retain most of the energy of the original sound."

The calls could be translated to something like: "Where are you?" and "I'm over here on the left." The question is referred to as an "inquiry call" and the answer is known as a "response call."

"Inquiry calls allow bats to stay nearby while they are flying," Chaverri explained. "Inquiry calls are also used to inquire about roost location. When bats enter a leaf roost, if they hear an inquiry call, they start vocalizing response calls. Therefore, response calls announce roost location."

The leaves also distort the calls, but it remains unclear if that helps or hampers the bats. The speaker-like boost is definitely a benefit, though, according to the researchers.

They believe other bats might exploit natural resources for sound amplification, such as bats that roost in bamboo stems and those that go into tree cavities and rock crevices.

"These structures might act as resonators, which are known to amplify sounds in other animals," Chaverri said. "Some examples include burrowing frogs and mole crickets."

She added that many other organisms live inside the tubular leaves chosen by the bats. These include frogs, scorpions and various types of insects.

Mirjam Knoernschild of the University of Ulm's Institute of Experimental Biology told Discovery News that she agrees with the new study's conclusions.

Knoernschild said that the authors' "work on sound amplification by tubular leaves is a new and valuable contribution to the field of animal communication."

For now, it's a mystery as to how the bats discovered the communication benefits of particular leaves. Was it trial and error, just a fortuitous coincidence, or the brilliance of one or more smart bats?

Chaverri and Gillam indicate that they might try to solve this mystery in a future research project.

The cocoa frog is one of six new frog species that were recently found in a rainforest-dominated mountainous region of southeastern Suriname. “At a time when so many frog species are declining and undergoing extinctions worldwide, it is particularly uplifting to discover so many new frogs in a single area,” Trond Larsen, a tropical ecologist and director of the Rapid Assessment Program at Conservation International, told Discovery News. He and his team found about 60 new species in the South American country.

The tiny Lilliputian beetle measures just 2.3 mm long and could be the smallest dung beetle in the entire Guiana Shield and among the smallest in the world. “Dung beetles act as a cleanup crew in the forest,” Larsen said. “By burying dung, they not only control parasites and disease, including those that affect people, but also disperse seeds and recycle nutrients that enable forest regeneration.”

Leeanne Alonso, director of Global Biodiversity Exploration for Global Wildlife Conservation, went on the expedition with Larsen. She thinks this beetle might be small and red to look like a seed stuck in poo, thereby fooling predators. “Dung beetles in forest areas are a good indicator of mammal diversity,” she added. Without mammals providing their food source, there would be few such insects.

The collection of new animals includes 11 species of fish that are probably new to science. “Small, brightly-colored tetras similar to this one are popular in the aquarium trade, and sustainable exports of wild species could provide financial support to local communities and incentives to conserve the species’ natural habitat,” Larsen said.

Alonso added that, as new species go, fish are relatively rare. “It’s amazing that so many were found in this region, which I believe has the world’s best and most beautiful and pristine forests in the world.” She loved it so much that she took her family there on a vacation after the research work ended.

Bats are another “good indicator of habitat quality,” Alonso said. She explained that, in this case, the bat thrives on fruit, so the region must support plenty of healthy fruit-producing trees.

Genuine coral snakes are highly venomous, but this false coral snake’s name is itself somewhat misleading, as the researchers found out the hard way. Alonso said that a helicopter pilot transporting the scientists was bitten by one. “His arm really swelled up,” she said, explaining that all such snakes have sharp teeth and venom, just not as poisonous as the “real” coral snake this species resembles.

This extraordinary new insect displays waxy fronds at the end of its body that was built for jumping among plants. “Maybe the fronds are meant to resemble anthers of a flower, helping with camouflage?” Alonso said, admitting that nature sometimes works in still-mysterious ways. She continued, “So little is known about insects from this region, so this was a real find.”

Top-level predatory big cats, such as this margay, are yet another sign of healthy habitat. More of them generally means there are more prey animals to feast upon. “Margays love to sleep and hide in caves at the site,” Alonso added.

Six new katydids, including this one, were discovered. Larsen described it as a “gangly species with oversized, spiny hind legs.” The newly discovered katydids "are indicative of the pristine, healthy forests of the Upper Palumeu Watershed," Larsen said, "and the forests in turn help to ensure continued flows of clean, plentiful water used by people throughout the rest of the country.”

“Despite their generally diminutive size, water beetles can be useful indicators of water quality, and also help to filter and keep water clean,” Larsen said. “Many of the 26 new water beetle species discovered on this survey are probably restricted to isolated habitats, especially in the mountains of southeastern Suriname, and may occur nowhere else.”

Eleven new fish species were found in the region, dubbed a "tropical Eden" by the researchers. Larsen said, “This new sucker-mouthed armored catfish was rare, and only encountered in the narrow, upper reaches of the Palumeu River.

“This delicate slender opossum is really cute,” Alonso said. “It’s hard to find small mammals like this, which are indicative of primary forest.”

Coprophanaeus lancifer

is the largest of all South American dung beetles, Larsen shares. Despite its name, this species feeds more frequently on dead animals than on dung. A highly unusual case in the Animal Kingdom, both males and females of this species possess a long horn on their head, which they use during intense battles with other individuals of the same sex. The vast difference in adult body size seen here is primarily determined by how much food was available to the developing larva. This species is capable of rapidly burying large animal carcasses, providing an important ecological service that sustains rain forest health.

“Given the beautiful coloration, high visibility and popularity of frogs in the poison dart frog family (Dendrobatidae), most species in this group are relatively well known,” Larsen said. “Therefore, the discovery of this species potentially new to science is particularly exciting. The toxic secretions of poison dart frogs hold great potential to yield new medicines that could greatly benefit the world -- yet with frogs declining globally, their protection in the wild is essential.”

The researchers could have just scratched the new species surface in southeastern Suriname, given that other animals, fish, insects and more unknown to science could be found there. The region’s human population is currently small -- only about 500,000 -- but it’s growing and there is a threat of future habitat-destroying activities, such as mining and logging. Alonso hopes that the wilderness can be protected, with money-generating activities such as ecotourism allowing both humans and amimals to thrive there.