What’s got two legs and a head for climbing? Rosy-faced lovebirds
Tartufo is the rosy-faced lovebird. He has more limbs than most people think. He can fly with his two wings. He uses his legs to grab branches and hop across the canopy. He relies on his head when he’s faced with a particularly steep tree.
Based on climbing experiments published this month in the journal Proceedings of the Royal Society Biological Sciences, rosy-faced lovebirds–a type of diminutive parrot–are members of a rare few vertebrates that walk with an odd number of limbs.
Plenty of animals have what the study’s senior author, Michael Granatosky, calls “effective limbs,” like a tail that acts as a tripod. Fewer animals actually use a spare leg to pull or push themselves along. Granatosky, who studies evolution of locomotion at the New York Institute of Technology, says that we are now talking about things that are much rarer in evolutionary history. Spider monkeys can climb through trees with their dexterous tails, while kangaroos use the tail as a spring to jump. “But” with these parrots, [we’ve found], an animal that uses its head as a propulsive leg
To determine how parrots use their heads to communicate with each other, the team created a “runway” that contained a pressure sensor that detects pulling and pushing motions. This allowed them to tell when a bird was pulling itself along or just hanging on to its mouth. All six of the rosy-faced lovebirds were able to do neck pull-ups to climb.
Granatosky had a pet cockatiel named Rex, according to Melody Young, the paper’s lead author and a graduate student from the New York Institute of Technology. “So he would look at his parrot climbing, and think ‘I want these forces .'”
But larger parrots like macaws are more difficult to study because they can bite hard enough for you to cut off your finger if they get grumpy. The team instead turned to sweet-tempered, rosy-faced lovebirds for a model. Young says that they are too friendly .”
” They would climb on you as much on the runway as they would on you,” Granatosky says. “Keeping them on the runway is the hardest part
But lovebirds aren’t defenseless. Their necks must be four times stronger than ours to climb with their heads. They also have to deliver bites with a force fourteenx their body weight. Granatosky says, “If they get feisty while we’re not wearing gloves, they can draw some blood
Parrots don’t always walk using three limbs. By tilting the runway, the researchers showed that they only began to use their mouths when going up a 45 degree slope, and relied more and more on their head as the runway got steeper.
For lovebirds, this makes the head an analogous to how people use their arms when rock climbing. Young is currently planning human experiments that will involve treadwalls, a section of rock climbing wall that moves in a similar way to a treadmill. This will help Young understand how novice and experienced rock climbers move up the wall. These experiments will be used as a starting point to study treatment options for people who need to build leg and shoulder strength and new ways to build climbing robots.
The bizarre use of a head to move the parrot’s head hints at something more mysterious about its brain. Granatosky says that animals’ brains create repeating patterns to guide their movements. “It’s why you don’t need to think about walking,” Granatosky said. Parrots “move like us,” unlike other birds that climb trees. Everything is left, right and alternating movements. Parrots are able to include a third, asymmetrical movement in that sequence which is “weird from a evolutionary perspective,” he said.
Since publishing the paper, Granatosky said that people have reached out to him with their own stories on tripedal movement or even head-assisted tree climb. Granatosky says that the most bizarre email was one about hunting dogs. “Dogs trained to put animals into trees, a small percent of them learn to use the head to climb the tree,” he says.