Treefrogs, African icons, penguins, baboons and lizards make the news

Shake, Rattle and Extol

© istockphoto.com/Mark Kostich

© istockphoto.com/Mark Kostich

There’s a whole lotta shakin’ goin’ on in the rainforests of Central America, where scientists have discovered male red-eyed tree frogs communicate during breeding season by rocking their plant perches.

In a move rivaling any of Jerry Lee Lewis’s antics at the piano, a male tree frog that feels another male is moving in on his territory will frenetically shake his booty, sending vibrations through the branch to the other frog. The receiving frog often returns the same signal, say researchers at the Smithsonian Tropical Research Institute in Panama, who observed the behavior in the wild and then simulated it in the lab using a robotic frog and a mechanical shaker.

Other studies have shown that insects send signals through plants and trees, but this is the first demonstration of plant-based vibration signaling in vertebrates. “In the case of red-eyed tree frogs,” says research leader Michael Caldwell of Boston University, these displays “convey information about the status and aggressive intent of the signaler. They also appear to carry information about the size of the signaler.”

The tree frogs also use audio and visual cues, but sending vibes adds a further option to the macho communication mix: Shake a branch, rattle your rival and extol your superiority.Even if you never have a chance to go there, it’s hard to imagine Africa's parks without their five most iconic mammals: lions, elephants, buffalo, leopards and rhinos. But these and other large mammals in many African nature reserves are headed for trouble, warn scientists from the Zoological Society of London and Cambridge University.

The scientists tracked numbers for 69 key species between 1970 and 2005 in protected areas throughout Africa and found an average population decline of almost 60 percent. Regions did vary—with an increase in southern Africa, a decline by more than half in East Africa and an 85 percent drop in West Africa. The plummeting numbers in West Africa stem from lack of resources, habitat destruction and a growing bushmeat trade, the researchers say.

“Although the results indicate that African national parks have generally failed to maintain their populations of large mammals, the situation outside the parks is almost undoubtedly worse,” says lead researcher Ian Craigie. “Many species like rhino are practically extinct outside national parks.”

There were some rays of light in the otherwise gloomy results: The rate of decline slowed in recent years, where there was better management. That, and the increase in mammal numbers in South Africa means you shouldn’t erase “African safari” from your bucket list just yet.

 

The Big Five Take a Dive 

Even if you never have a chance to go there, it’s hard to imagine Africa’s parks without their five most iconic mammals: lions, elephants, buffalo, leopards and rhinos. But these and other large mammals in many African nature reserves are headed for trouble, warn scientists from the Zoological Society of London and Cambridge University.

The scientists tracked numbers for 69 key species between 1970 and 2005 in protected areas throughout Africa and found an average population decline of almost 60 percent. Regions did vary—with an increase in southern Africa, a decline by more than half in East Africa and an 85 percent drop in West Africa. The plummeting numbers in West Africa stem from lack of resources, habitat destruction and a growing bushmeat trade, the researchers say.

“Although the results indicate that African national parks have generally failed to maintain their populations of large mammals, the situation outside the parks is almost undoubtedly worse,” says lead researcher Ian Craigie. “Many species like rhino are practically extinct outside national parks.”

There were some rays of light in the otherwise gloomy results: The rate of decline slowed in recent years, where there was better management. That, and the increase in mammal numbers in South Africa means you shouldn’t erase “African safari” from your bucket list just yet.

 

Survival of the Fattest?  

For a female Adelie penguin looking for a mate, it ain’t over ’til the fat guy sings. She wants a chubby hubby, and the male’s courtship song helps her find him.

The more a male Adelie penguin weighs, the better a parent he’ll make, and new research shows that this Antarctic bird discloses this weighty information in his courtship song (more a series of husky trills and squawks than anything remotely musical). The plumpest penguins maintained a steady frequency over the longest part of the call, an extended chattering in the middle. Only males with sufficient fat around their voice boxes can sustain the consistent pitch that conveys desirability.

“A fat male is a good choice for a female, because males do so much of the offspring care,” says one of the researchers, Dianne Brunton of Massey University in New Zealand.

After choosing a mate and laying eggs, the female Adelie penguin returns to sea—leaving  her big daddy to tend the nest until she returns to take the next shift. For the first two weeks the male does the bulk of the babysitting without breaking to eat. His stored fat reserves safely allow him to lose more than 20 percent of his body weight over the summer breeding season, the researchers say. Fortunately, his tuxedo is self-adjusting.

 

Gal Pal Power

Female baboons don’t just get by with a little help from their friends, they live longer, a recent study shows.

The study followed and evaluated the social interactions of 44 wild female baboons in Botswana’s Moremi Game Reserve. “Females who had the strongest, most stable and longest-lasting relationships with other baboons lived significantly longer than those whose social ties were more fragile and unpredictable,” says Joan Silk, the UCLA anthropologist who conducted the study with biologists Dorothy Cheney and Robert Seyfarth of the University of Pennsylvania. The baboons with solid relationships with fellow females also had more surviving offspring.

The gal pals worked hard at their relationships, spending hours grooming one another’s fur, socializing and confronting threats like predators and baboons from other troops. The researchers aren’t sure how having a tight social network adds years, but say it could have something to do with the stress relief grooming partners offer and the security best buddies provide.

“Our findings are strikingly similar to evidence from humans showing that social ties have important effects on our mental and physical health and our longevity,” says Silk.

Or, as a teen might text it: BFF R GD 4 U.

 

Lizards in the Lurch

The summer heat wave may be over, but for many lizards around the world the mercury is still rising. Unless we are able to slow global warming, 20 percent of all lizard species could be extinct by 2080, warns a group of international researchers.

“How quickly can Earth’s lizards adapt to the rising global temperatures? That’s the important question,” says Barry Sinervo, a biologist at the University of California-Santa Cruz who took part in a decades-long survey of lizard populations from 200 different sites in Mexico. He and his colleagues concluded that rising temperatures have already driven 12 percent of that country’s lizard population to extinction. They then compared their data with information from other sites across the globe, creating a model of extinction risks for other lizard species.

According to the model, many types of lizards have already hit the point of no return. About 6 percent of lizard species will be extinct by 2050, says Sinervo. And there’s no way to turn that around because the carbon dioxide released today will still be hanging around in the atmosphere decades from now.

But that’s no reason to throw in the towel. “If the governments of the world can implement a concerted change to limit our carbon dioxide emissions,” he says, “then we could bend the curve and hold levels of extinction to the 2050 scenarios.”  

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