Scientists Measure Secretary Birds’ Ridiculously Powerful Kicks

When Madeleine the secretary bird was hatched at the Hawk Conservancy Trust in England, caretakers thought that he was a she, and he wound up with a girl's name. Prim as that name is, Madeleine can still kick your butt—and now scientists know just how fast and furious his kicks are.

Secretary birds are unusual among birds of prey in that they spend most of their time on the ground and do their hunting on foot. They do their hunting with their feet, too. Their technique for dispatching the small mammals and reptiles they eat is violent, but elegant in its simplicity: They use their long legs, which make them look a bit like eagles on stilts, to kick and stamp their prey’s head until it’s dead—or at least stunned enough to swallow whole.

It’s impressive to watch, and when Steve Portugal was studying some of the Hawk Conservancy Trust’s vultures a few years ago, he sometimes got distracted by Madeleine, who puts on a daily show for visitors by stomping a rubber snake. One of the areas that Portugal’s research focuses on is, as he puts it, the “biomechanics of weird things.”

“I’m interested in the freaks of the animal kingdom, particularly animals that have slightly strange ways of getting about or getting their food,” he says on his webpage. Secretary birds fit that bill, and he decided to take a look at the ins and outs of Madeleine’s fancy footwork.

As they related in a recent study in the journal Current Biology, Portugal and his team hid force-measuring plates around Madeleine’s enclosure and baited him onto them with a rubber snake while filming everything with high-speed cameras. They found that the bird’s kicks come down with a force equal to five times his own 8.5-pound body weight. These blows are not only powerful, they’re also blink-and-you’ll-miss-it fast: Madeleine’s foot was only in contact with the snake for about 15 milliseconds.

Other raptors hit their prey with similar, and even higher, levels of force. Barn owls, for example, can land on rodents with a plummeting strike equal to 14 times their body weight. But that’s a whole owl plummeting out of the night sky—Madeleine and other secretary birds generate their impressive forces from a standstill with just one leg. The walloping might seem like overkill, but there’s a good reason for it. Many of the snakes that secretary birds feed on are venomous, and going after them with a kick that’s weak or slow enough to allow them to fight back could be disastrous for the birds.

Of course, not all their prey is so dangerous. In addition to hunting rubber snakes, Madeleine took an interest in Portugal’s research equipment. Early on in the experiments, the bird spotted the power cables for the force plates and started stomping on those instead of the bait.

Image credit: snowmanradio via Wikimedia Commons // CC BY 2.0 

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

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Watch a School of Humpback Whales 'Fish' Using Nets Made of Bubbles 

Just like humans, humpback whales catch many fish at once by using nets—but instead of being woven from fibers, their nets are made of bubbles.

Unique to humpbacks, the behavior known as bubble-net feeding was recently captured in a dramatic drone video that was created by GoPro and spotted by Smithsonian. The footage features a school of whales swimming off Maskelyne Island in British Columbia, Canada, in pursuit of food. The whales dive down, and a large circle of bubbles forms on the water's surface. Then, the marine mammals burst into the air, like circus animals jumping through a ring, and appear to swallow their meal.

The video offers a phenomenal aerial view of the feeding whales, but it only captures part of the underwater ritual. It begins with the group's leader, who locates schools of fish and krill and homes in on them. Then, it spirals to the water's surface while expelling air from its blowhole. This action creates the bubble ring, which works like a net to contain the prey.

Another whale emits a loud "trumpeting feeding call," which may stun and frighten the fish into forming tighter schools. Then, the rest of the whales herd the fish upwards and burst forth from the water, their mouths open wide to receive the fruits of their labor.

Watch the intricate—and beautiful—feeding process below:


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