by Becky Crew
Secret Boys’ Club
CONCAVE-EARED TORRENT FROG
(Amolops tormotus)
MEET THE LITTLE FROG that gives a new meaning to telephone.
While most frogs have their eardrums on their body surface, the concave-eared torrent frog has ultrathin eardrums recessed inside its ears. This extremely rare species from the Huangshan Hot Springs west of Shanghai in China is one of only two frog species known to possess this kind of ear—the other being the wonderfully named hole-in-the-head frog from Borneo.
Being recessed, the ultrathin eardrum, which in the males is about one thirtieth the thickness of an average frog’s, is protected, and the shortened path between the eardrum and the ear allows it to detect very high-frequency sounds. While average frogs are restricted to hearing frequencies below 12 kilohertz, concave-eared torrent frogs can produce a chirp at a phenomenal 128 kilohertz. This ultrasonic frequency is more than six times higher than humans can hear.
Only a select few animals in the world are known to belong to the “ultrasonic club” and the researchers who discovered the ability suggest that it was developed in response to the extremely loud babbling of the streams and waterfalls around which they live. “Nature has a way of evolving mechanisms to facilitate communication in very adverse situations,” says the lead author of the study published in Nature in 2006, Albert Feng from the University of Illinois, who discovered the frogs’ ability. “One of the ways is to shift the frequencies beyond the spectrum of the background noise. Mammals such as bats, whales, and dolphins do this, and use ultrasound for their sonar system and communication. Frogs were never taken into consideration for being able to do this.”
In their study, Feng and colleagues discovered that during the reproductive season, the male concave-eared torrent frogs were adding ultrasonic calls to their regular calls, broadcasting their message over several frequencies at once. The researchers recorded the calls and played the audible and ultrasonic ranges to eight males in captivity. At the time, it was assumed that, like with most frog species, the female concave-eared torrent frogs were not physically capable of calling. The researchers found that six of the males responded to calls played back in both the audible and ultrasonic range, only one responded exclusively to the ultrasonic call, and only one responded exclusively to the audible call, suggesting that calls at the audible and ultrasonic frequencies could have different meanings.
At first it was thought that only the male concave-eared torrent frog males could emit, and respond to, ultrasonic calls, making territorial calls to one another and letting the females know they are around. In most species of frogs, the females don’t call, firstly because they don’t have the vocal equipment required, and secondly because the males do it so they don’t have to.
Because concave-eared torrent frogs are nocturnal and capable of jumping thirty times their body length they make difficult test subjects in the wild, which means it wasn’t until Feng and colleagues got the females in a laboratory setting that they realized how special these females are. In 2008, they discovered that the female concave-eared torrent frogs, like the males, can emit high-pitched birdlike chirps spanning the audible and ultrasonic frequencies. Publishing in Nature, the team reported that when the females were looking for males in captivity, they would emit an ultrasonic call, to which males would respond by leaping toward the call with 99 percent accuracy. “This is just unheard of in the frog kingdom,” says Feng.
Just how the female picks a male in the wild is as yet unclear. Is she calling a particular male, or is she signaling her whereabouts so multiple males can find her and compete? “We have a lot of work to do to figure out whether she directs the signal to one male or whether she lets a bunch of males come and compete, or whether there is any kind of dueling session during which she then decides: ‘Okay, you’re my guy. Hop on my back and I’ll take you to the creek!’” says Feng.
Things got even more complicated in 2011, when a study led by the coauthor of the 2006 and 2008 studies revealed that the female concave-eared torrent frogs might not actually be able to hear sounds emitted at the ultrasonic frequency. The females have thicker eardrums than the males, and no ear canals, which suggest that it’s possible they’re not as well equipped to hear at superhigh frequencies, despite being able to make ultrasonic calls.
Jun-Xian Shen from the Institute of Biophysics at the Chinese Academy of Sciences took females from the wild and first played them the males’ calls at the audible frequency and then the calls at the ultrasonic frequency in a dark room. Each time the audible calls were being played, the females responded by turning and jumping frequently toward the source, and sometimes they even called back. But when the ultrasonic calls were played the females neither moved toward the source, nor responded vocally.
To test whether or not the females were simply ignoring the calls, the team measured their auditory brain responses as they listened to the males’ calls. When lower frequency calls at the auditory frequency were played, a peak of activity in the females’ midbrains could be seen, indicating that they were picking up the sounds. But nothing over 16 kilohertz provoked any kind of brain activity, which shows that, as the structure of their ears suggests, the females simply cannot hear at very high frequencies.
So why is this? The researchers suggested that unlike the males, who need to be out looking for females and making themselves known above the sounds of the waterfalls around them, the females spend a lot of their time in rocky cracks, trees, or muddy caves, where the sounds around them are muffled. Perhaps the females simply don’t need to hear sounds at such a high frequency. According to Shen, who published the findings in Nature Communications, this is the first demonstrated amphibian, bird, or mammal species in which the males have the capacity to hear at the ultrasonic frequency but the females likely do not.
Seriously, female concave-eared torrent frogs, get a load of these jerks. They have their own language now? Why can’t they just e-mail each other about … whatever it is boys talk about? Do they really need an entire secret language so they can make comments about the concave-eared torrent frog equivalent of boobs at any possible opportunity?
I guess it would be pretty handy at the bar. They can literally decide who they’re going to go home with right in front of your faces, like, “Okay you can take the hotter one and I’ll take the less hot one, but I get to use your basketball season tickets for the whole of January.” “Deal, but you’re buying drinks.” “Deal.” And you’ll be like, “What are you guys talking about?” and they’ll be like, “Stocks?”
And then one of them will say something to the other one—you can tell, female concave-eared torrent frogs, because their mouths are moving—and they’ll both start snickering to each other really obnoxiously and you’ll be like, “What are you guys LOLing about?” and they’ll be like, “Stocks?”
But whatever, female concave-eared torrent frogs, let them have their own secret language, you be the bigger man in the scenario. They can talk about whatever the concave-eared torrent frog equivalent of boobs is in front of your faces and they can LOL about how your best friend clearly wants to do all of them (I’m right there rolling my eyes with you, female concave-eared torrent frogs), but you’ll always be the only ones who actually have the concave-eared torrent frog equivalent of boobs, and there’s nothing the least bit funny about LOLing about something you just LOL’d your way out of seeing.
A Love Affair with Beer Gone Wrong
AUSTRALIAN JEWEL BEETLE
(Julodimorpha bakewelli)
SOMETIMES IT IS POSSIBLE to love beer just a little too much. The Australian jewel beetle is a glossy, golden-brown beetle around 1.6 inches long, found all over Australia in arid and semi-arid areas. It belongs to the Buprestidae family of jewel beetles, so-called because of the iridescent coloring running through the 15,000-odd species, including shimmering greens, purples, blues, and bright yellows.
In late 2011, the Harvard University–based Annals of Improbable Re
search blog awarded its annual Ig Nobel Prizes, the aim of which is to “honour achievements that first make people laugh, and then make them think.” Last year’s biology category was won by two entomologists, Darryl Gwynne from the University of Toronto at Mississauga in Canada and David Rentz from the Australian national science agency, the CSIRO, for their research into the strange sexual habits of the Australian jewel beetle more than twenty years ago.
In September 1981, Gwynne and Rentz stumbled on something remarkable in the Dongara area of Western Australia, 218 miles north-northwest of Perth. “It was pure serendipity and a happy coincidence because I study these differences in behavior. We did not set out to study the beetles. David Rentz and I … happened to stumble across the beetles one sunny morning on our field trip,” says Gwynne.
The pair observed male Australian jewel beetles flying 3–7 feet above the ground at the Dongara site, scouting for the large, flightless females, when two of them landed and started trying to mate with a 0.8-pint beer bottle, widely known as a “stubbie.” “We have recently observed this to be quite a common occurrence in the Dongara area of Western Australia,” they reported in the Journal of the Australian Entomological Society in 1983. This behavior was first observed by Australian zoologist Athol M. Douglas from the Western Australian Museum, who published photographs of a male Australian jewel beetle mating with a stubbie, as well as another being attacked by a handful of ants during the act, in 1980.
Surveying the area, the entomologists found two more males mating with their own stubbies, and just one stubbie without a beetle was located. They conducted a brief experiment at the site, which involved placing four stubbies on the ground in an open area to see if they would attract the beetles. Within half an hour, two of the bottles had attracted males, and beyond that time frame, four more were observed to mount the arranged stubbies.
The behavior was put down to the beer bottles’ basic visual similarities to the large Australian jewel beetle. The shiny brown color of the glass resembles that of the beetles’ coloring, plus the dimpled glass at the base of the bottle and the tiny bumps on the beetles’ elytra, or hardened forewings, both reflect light in the same way. The contents of the bottle held no attraction for the males; in fact, stubbies with beer left in them were left entirely alone, and when bottles of different shades were left out for the male beetles by the entomologists, they were also ignored. “It looks like it is visual cues,” says Gwynne. “We washed out bottles to rule out ethanol and the color and patterning of the bottles resembles the brown wing covers of the beetles.”
Just how these males could make such an unfortunate mistake in identifying females of their own species is less clear, but Gwynne suggests it has to do with the difference between how the males and females of the Australian jewel beetle species choose their mates. “Males typically compete, take risks, and occasionally make mating errors. Females are typically choosy and get mated in a nonrisky way,” he says, and adds:
The lion’s share [of investment in offspring] typically comes from the female because—even in species with no parental care—the female invests so much in the egg, compared to the male investment in the tiny sperm. As a consequence, producing offspring for males is cheap so they are always playing the mating game.
As ridiculous as this all sounds, this behavior can have serious effects on the male Australian jewel beetles. Gwynne and Rentz described how once on the bottles, the males would not stop trying to copulate with them until they were physically displaced. In the wild, this means they could unwittingly starve or exhaust themselves to death—according to Gwynne, they observed some males falling off the bottles with heat exhaustion—and render themselves completely vulnerable to predators such as ants. Ants are known to attack and eat the lovelorn males alive, as Douglas had observed twelve months earlier. “In one of the observations, a male, at the side of the bottle, was being attacked by a number of ants (Iridomyrmex discors), which were biting at the soft portions of his everted genitalia. A dead male, covered with ants was located about an inch away from this same bottle,” Gwynne and Rentz reported in their 1983 paper. “Improperly disposed of beer bottles not only present a physical and ‘visual’ hazard in the environment,” they concluded, “but also could potentially cause great interference with the mating system of a beetle species.”
Okay, sure, Australian jewel beetle males, those stubbies look “similar” to your females. Because they’re both long and brown. Or you’re all just superdrunk and covering for each other. Which is fine, you’re allowed to all go to the pub together and talk about sports and beer till 4 A.M. You’re even allowed to get so loaded that you try to fuck a stubbie every once in a while. It’s cool, we’ve all been there. But when it gets to the point where you’re actually getting killed over it, Australian jewel beetle males, it’s probably a good time to ease up on the beers. Just a bit.
Or you can just keep going as you are and get eaten alive by other insects and when your children ask why you didn’t come home last night, your wife—yes, your wife, Australian jewel beetle males, you do actually have one—will have to tell them you fucked yourself to death and now they can never have new shoes. And the kids will be like, “Well at least he died getting it on,” and your wife will be like, “Nope, he was fucking a stubbie.” And the last thing your children will ever say about you, Australian jewel beetle males, is “Holy shit, Dad was a total pervert.”
Won’t Rat You Out for Chocolate
RAT
(Rattus)
“I’m here to save you! You’re free!”
“Are you insane? This is a change room, get the hell out of here!”
RATS TEND TO GET quite a bad rap because of their disease-harboring abilities, but in some aspects, we’re really not that different from rats. Nature is rife with animals that display prosocial behavior, which essentially means looking out for your peers. Even insects such as bees and ants display this kind of behavior, but unlike humans and other primates, they don’t “share” in the distress or pain of someone else: They don’t display empathy. Until very recently, it was not known if nonprimate mammals were similarly motivated by empathy, but it turns out that not only do rats look out for their fellow rat, they will give up chocolate, of all things, to do it.
A small team of scientists led by psychology postgraduate student Inbal Ben-Ami Bartal from the University of Chicago stumbled on just how empathetic rats are when testing the effects of stress on food sharing amongst them. “Like many scientific discoveries, this one was accidental, or rather serendipitous,” says Bartal, adding:
I was testing the restrainer that we were planning to use inside one of the home cages. When I trapped the rat, I noticed the free rats started circling the restrainer frantically, and seemed distressed, to my untrained eye. I repeated the experiment with a different cage the next day, and realized that I might be seeing something overarching. Then we thought about allowing the free rat to release the trapped rat.
Bartal and her colleagues designed and set up experiments in which two rats that normally share a cage were moved into a test arena. One rat was held captive in a small restrainer device that could only be nudged open from the outside, while the other rat was left free to run around the arena, able to see and hear the distress of its trapped cagemate. The researchers observed that the free rat acted far more agitated when it was in the presence of a trapped rat compared with being in the arena with an empty restrainer, exhibiting what’s known as “emotional contagion,” a phenomenon that occurs in animals with the capacity for empathy—they can share in the fear, distress, or pain experienced by their peers.
The rats didn’t just “feel” the distress of their trapped cagemates, they also actively set about improving their situation by figuring out how to open the restrainer door and free them, taking multiple tries before eventually becoming quite proficient at it. To make sure the rats were acting purely in the interests of their cagemate, the researchers tested their behavior in another setup,
whereby opening the restrainer door, the free rat would release the trapped rat into another compartment. This meant the reward of social interaction had been discounted—and sure enough, the free rat continued to release its cagemate. The experiment had shown that the rat had no other reason to free its cagemate other than to put an end to its distress. “We were not surprised by the rats’ behavior, since multiple studies have demonstrated emotional contagion in rodents. But we were surprised at how robust this behavior was, and how persistently free rats would continue to circle the restrainer—they would continue this behavior for hours,” says Bartal.
To test just how robust the rats’ need to stop the suffering of their cagemates was, the researchers gave the free rats a choice—release your companion from the restrainer, or focus your attention on securing a delicious treat for yourself instead. They placed free rats in an arena with a trapped cagemate as well as another restrainer filled with a pile of chocolate chips to see which restrainer the rat would concentrate on. They found that the free rat was equally likely to open the restrainer to free its cagemate before focusing on the chocolate restrainer, which meant that putting an end to the distress of a fellow rat was equally as rewarding as hoeing into a pile of chocolate chips. In cases where the free rat released its cagemate before working on the chocolate restrainer, 52 percent of the time it would share the chocolate with its cagemate, the researchers reported in Science.
But not all rats displayed such “honorable” behavior. About 25 percent of the rats tested failed to free their trapped cagemate. Bartal says while it’s unclear exactly why this occurred, it could be due to the different personalities in the rats: Some were too stressed out, others couldn’t figure out how to open the restrainer, and others were just plain mean. “Some are ‘scaredy rats’ who are too overwhelmed with personal distress to be able to successfully assist the trapped cagemate (opening the door is hard and the rats need to move around a lot and keep trying in order to figure it out). Some rats are unable to figure out the door opening, and there is the occasional bully who appears to be uninterested in opening the door and even attacked the trapped rat once he gets out. Now we want to see what distinguishes those populations out, biologically,” says Bartal. Another idea she plans to test is what happens when the free rat and trapped rat are strangers, or even competitors. Does empathy in rats have its limits?
