Like Humans Waltz And Polka, Lyrebirds Match Dance To Tune

lyrebird1Not every song has its own specific dance, but there are certain tunes — from the tango to the Twist — that demand distinct moves. Now scientists have caught birds doing something similar: Male superb lyrebirds (Menura novaehollandiae) coordinate movement to the type of song they’re singing. The study appears in Current Biology.

Male superb lyrebirds sing and dance to attract the ladies, and their repertoire can contain more than 90 tunes. They don’t have such a big variety when it comes to dance moves, but with their elaborate tail feathers, these visual displays can be pretty spectacular. To study the song-and-dance combo, a group of Australian scientists filmed a dozen of these birds in Sherbrooke Forest in Dandenong Ranges National Park in Australia, east of the city of Melbourne.

Despite having such a large number of songs to choose from, only four tunes were accompanied by dance (you can see a video of one here); the researchers named those songs A, B, C, and D (not the most inventive names, but this is a scientific paper we’re dealing with). Each of these four dances had it’s own set of moves, the researchers write:

Our analysis revealed that each of the four song types within the display was associated with one particular gesture. The gesture accompanying song A consisted of steps, often to the side, with wings motionless and a wide tail. In contrast, the male’s tail was narrowed while he sang song types B and C, and during the latter he nearly always jumped or bobbed, and flapped his wings. When males sang song type D, the tail was usually wide and the legs and wings still.

“Just as we ‘waltz’ to waltz music but ‘salsa’ to salsa music, so lyrebirds step sideways with their tail spread out like a veil to one song—which sounds like a 1980s video-arcade game—while they jump and flap their wings with their tail in a mohawk position while singing a quiet ‘plinkety-plinkety-plinkety,’” study coauthor Anastasia Dalziell of Australian National University said in a statement.

lyrebird2While the lyrebirds sometimes sang each of these songs without dancing, they never danced without an accompanying tune. And occasionally, just like we do when dancing, the birds would mess up. The researchers say that this shows that the song-and-dance routine is difficult for the birds

How these birds develop their musical theater skills isn’t known, but the males spend years practicing before they reach the age of maturity. These skills are incredibly important, because females choose their mates after watching several males put on these displays. What the females are looking for, though, is still a mystery. Dalziell said, “Sometimes after what seems to me to be a perfectly wonderful display by a male, I watch a female leave and check out his neighbor.”

Images credit: Alex Maisey/Current Biology

The Marsupial Lion Looked Awesome — Too Bad It’s Extinct


Here in the United States, we’re familiar with extinct megafauna like mastodons and mammoths, the saber-toothed tiger and the giant sloth. But the list of huge critters that went extinct long ago is sometimes surprising (there’s the saber-toothed salmon, for example), especially when we look outside North America.

In Australia, for example, there’s the marsupial lion (Thylacoleo carnifex), which lived about 1.6 million to 46,000 years ago. Despite its name and a size that was similar to that of a lion, it was not a cat — it’s more closely related to koalas and wombats — but it was the largest meat-eater ever to live on the continent.

That date for when the marsupial lion died out happens to match pretty closely to when humans first arrived on Australia, and that has led many scientists to wonder whether humans drove the species extinct. But a study released this week by the Proceedings of the National Academy of Sciences says no, that species and other megafauna of the region known as Sahul (which includes Australia and New Guinea) were the victims of climate change, not human hunters.

“It is now increasingly clear that the disappearance of the megafauna of Sahul took place over tens, if not hundreds, of millennia under the influence of inexorable, albeit erratic, climatic deterioration,” the study’s lead author, Stephen Wroe of the University of New South Wales, said in a statement.

It’s too bad that the marsupial lion was lost, because it appears that it would have been a pretty awesome animal: It had semi-opposable thumbs, for instance, which may have helped with holding prey. But I probably wouldn’t have wanted to meet one out in the wild.

Artwork by Peter Schouten, via EurekAlert

Cow Patties May Have Helped A Toxic Toad Invade Australia


The center of Australia, is a dry, hot, unforgiving landscape, but the edges of the continent are more diverse, with beautiful wooded mountains, lush rainforests and thriving cities. And farms. Lots of farms. About half of Australia is, in fact, covered in land used for grazing livestock (though I should note that some of that grazing does take place in rather harsh areas of the interior as well as nicer bits closer to the coasts). Like many lands around the world, Australia has been incredibly altered by humans.

Altering landscapes often facilitates the spread of non-native species, letting them become invasive pests. The phenomenon is best known among invasive plants, like purple loosestrife, but it seems to hold true for some animals as well, like the cane toad in Australia.

Cane toads, natives of South America, are a big problem in Australia. They first arrived in Queensland in 1935, deliberately brought to the country to help keep beetles in control to improve sugar yields. That plan didn’t pan out, and the toads quickly began to spread across the country. One more amphibian in the landscape might not seem like a huge problem, but cane toads secrete a toxic poison that kills most anything that eats them, even crocodiles. As cane toads have spread, they’ve devastated populations of many native Australian animals.

I first got interested in the cane toad when I blogged about a study in which scientists successfully taught cute critters called quolls to not eat the toads by feeding young quolls young toads (not yet poisonous) laced with a chemical that made the toads taste bad. And then last year, I got a chance to meet the mastermind behind the study, University of Sydney herpetologist Rick Shine, who I profiled in Science magazine. Shine became one of the leading cane toad researchers in Australia after the toads invaded his long-term research site outside Darwin.

In one of his more recent studies, published last November in PLOS ONE, Shine’s group looked at how cow patties might help cane toads survive the hot, dry Australian summer. Members of the group had noticed that toads could often be found on or near cow patties, and they wondered whether the amphibians were indeed more likely to hang out there.

The researchers walked transects set up on a farm located near their research site, recording the locations of both cane toads and cow patties during the dry season. Seventeen of the 26 toads they found were sitting on cow patties, and the remaining nine were fairly close to the piles of poo.

“Toads were found on cowpats more often than expected by chance, and toads that were not on cowpats were closer to them than would be expected by chance,” they write in their paper.

The cow patties, the researchers surmise, provide both a moist environment and food, in the form of dung beetles, which helps the cane toad survive the harsh Australian dry season.

Cane toads are already known to take advantage of water sources, like ponds, set up to supply livestock. Add in the continent’s 300 million cow patties deposited each day — that’s 28.5 million cattle each producing 12 cow patties per 24 hours — and livestock grazing has obviously provided the cane toads with a friendly environment that has helped them spread. Humans have tamed much of Australia to make it more liveable for themselves, but they also made it more liveable for cane toads.

Cane toad image courtesy of flickr user blundershot

To Count Bird Diversity In The Forest, Listen In The Morning

forestkingfisherIf you want to figure out how many different species of birds are in a forest, all you have to do is listen. But there are a few ways you can go about such a study: You and your colleagues can hang out in the forest for 12 hours a day, five days a week. Or you can set up microphones and record the forest sounds for analysis back in the lab, in which case you’ve got a few more options — let a computer listen and identify species, make your students listen to all of it, or listen to only some of the recordings.

But which way is best? The computer isn’t quite talented enough at this point, and though students are cheap, they’re not cheap enough to listen to all of the sound you’d collect. So the options are to count in person or listen to only some of the recordings. But which ones? And are they better than going into the forest yourself?

To figure that out, researchers from Queensland University of Technology in Australia set out to determine how many species of birds were in a eucalyptus forest in southeast Queensland. The study (in press) appears online in Ecological Applications.

They recorded five days of sounds from several sites in the forest and also had two experienced bird surveyors conduct on-site surveys of those areas at dawn, noon, and dusk for five days. Once the recordings were back in the lab, they were sampled in one-minute bites in five different ways (listening to recordings longer than 240 minutes is cost prohibitive and impractical for most researchers): randomly over the 24-hour period, randomly only in the three hours after dawn, randomly only in the three hours before dusk, randomly after dawn and before dusk, and every half hour over the full 24 hours.

Across all the sites in the forest, the researchers found 96 species using acoustic methods and 66 species with the traditional, in-person survey. And when they looked at their samplings of the acoustic data, they were able to find the most species in those three hours right after dawn, almost twice as many as can be found in the same time by the traditional method.

Sampling the recordings isn’t perfect — it doesn’t find all species, especially rare and cryptic ones — but the researchers say that using a computer to help identify the parts of a recording more likely to have a bird call would help avoid getting random samples of only wind. Thus, combining computer analysis with human listeners of these recorded forest sounds could help scientists get a better picture of biodiversity.

Relying solely on the computer to identify so many species isn’t an option for now, the researchers say, because the programs are plagued with false positives and negatives. However, one day they may get good enough that they can detect birds with high accuracy and cut out the need for humans to listen to hours of sound. (But there’s something about that that makes me a little sad.)

Image of a forest kingfisher courtesy of JJ Harrison, via wikimedia commons

How Cancer Evades The Devil’s Immune System


In the 16 years since Devil Facial Tumor Disease emerged among the devils of Tasmania, DFTD has devastated the island’s population of these carnivorous marsupials. The infection spreads easily among the violent animals — they bite each other, passing tumor cells from one devil to the next — and DFTD always ends in death.

A devil’s immune system should be able to put up some sort of fight against the cancer cells, but it doesn’t. And a group of scientists led by the University of Cambridge in England now say they know why; they report their findings today in the Proceedings of the National Academy of Sciences.

DFTD cells, they found, don’t express major histocompatability complex (MHC) molecules on their surface. These molecules alert the T cells of the immune system that a foreign cell is foreign. Without the molecules, the immune system doesn’t know it should fight back.

There are two types of MHC molecules — class I and class II. The DFTD cells likely don’t have class II molecules because the cells got their start as Schwann cells, a type of nervous system cell. In humans and rodents, Schwann cells are known to not express class II MHC molecules; it may be the same in devils.

The class I MHC molecules, though, were probably lost later, the researchers say, but not because of a mutation. Instead, these molecules are not expressed because of epigenetic changes that likely occurred years ago when a devil’s Schwann cells transformed into DFTD cells. It’s one of the changes that turned DFTD into such a horrible, dangerous disease.

But the discovery of how DFTD evades the immune system gave the researchers an idea on how they could prime a devil’s immune system to fight the disease: They suggest that modifying DFTD cells to express MHC molecules could work as a vaccine.

Time is running out, though. Already 84 percent of the devil population is gone. And a vaccine may not prove a savior. “Even if we had a perfect vaccine, we’d probably have to vaccinate every animal more than once,” Alexandre Kreiss, a research fellow at the Menzies Research Institute in Tasmania told the New York Times in January. “I don’t see us doing that for the whole population.”

Image courtesy of flickr user quollism