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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
What Makes a Cat's Tail Puff Up When It's Scared?
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Cats wear their emotions on their tails, not their sleeves. They tap their fluffy rear appendages during relaxing naps, thrash them while tense, and hold them stiff and aloft when they’re feeling aggressive, among other behaviors. And in some scary situations (like, say, being surprised by a cucumber), a cat’s tail will actually expand, puffing up to nearly twice its volume as its owner hisses, arches its back, and flattens its ears. What does a super-sized tail signify, and how does it occur naturally without help from hairspray?

Cats with puffed tails are “basically trying to make themselves look as big as possible, and that’s because they detect a threat in the environment," Dr. Mikel Delgado, a certified cat behavior consultant who studied animal behavior and human-pet relationships as a PhD student at the University of California, Berkeley, tells Mental Floss. The “threat” in question can be as major as an approaching dog or as minor as an unexpected noise. Even if a cat isn't technically in any real danger, it's still biologically wired to spring to the offensive at a moment’s notice, as it's "not quite at the top of the food chain,” Delgado says. And a big tail is reflexive feline body language for “I’m big and scary, and you wouldn't want to mess with me,” she adds.

A cat’s tail puffs when muscles in its skin (where the hair base is) contract in response to hormone signals from the stress/fight or flight system, or sympathetic nervous system. Occasionally, the hairs on a cat’s back will also puff up along with the tail. That said, not all cats swell up when a startling situation strikes. “I’ve seen some cats that seem unflappable, and they never get poofed up,” Delgado says. “My cats get puffed up pretty easily.”

In addition to cats, other animals also experience piloerection, as this phenomenon is technically called. For example, “some birds puff up when they're encountering an enemy or a threat,” Delgado says. “I think it is a universal response among animals to try to get themselves out of a [potentially dangerous] situation. Really, the idea is that you don't have to fight because if you fight, you might lose an ear or you might get an injury that could be fatal. For most animals, they’re trying to figure out how to scare another animal off without actually going fisticuffs.” In other words, hiss softly, but carry a big tail.

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Animals
10 Notable Gestation Periods in the Animal Kingdom
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The gestation periods of the animal kingdom are varied and fascinating. Some clock in at just a few weeks, making any human green with envy, while others can last more than a year. Here are 10 notable gestation times for animals around the globe. The lesson? Be thankful that you’re not a pregnant elephant.

1. ELEPHANTS: 640-660 DAYS

Elephants are pregnant for a long time. Like really, really long. At an average of 95 weeks, the gestation period is more than double the length of a human pregnancy, so it shouldn't come as a shock that female elephants don't often have more than four offspring during their lifetimes. Who has the time?

2. HIPPOS: 8 MONTHS

A photo of a mother hippo and her baby in Uganda

Yes, it takes less time to make a hippopotamus than it takes to make a human.

3. GIRAFFE: 14-15 MONTHS

Baby giraffes can weigh more than 150 pounds and can be around 6 feet tall. Another fascinating tidbit: giraffes give birth standing up, so it's pretty normal for a baby to fall 6 feet to the ground.

4. KILLER WHALE: 17 MONTHS

There’s a reason for the long wait: after that 17 months, Baby Shamu emerges weighing anywhere from 265 to 353 pounds and measuring about 8.5 feet long. Yikes.

5. OPOSSUM: 12-13 DAYS

A baby opossum wrapped up in a blanket

Blink and you'll miss it: This is the shortest gestation period of any mammal in North America. But since the lifespan of an opossum is only two to four years, it makes sense.

6. GERBILS: 25 DAYS

Hey, they get off pretty easy.

7. GORILLAS: 8.5 MONTHS

It's not a huge surprise that their gestational periods are pretty similar to ours, right?

8. BLACK BEAR: 220 DAYS

A pair of black bear cubs

Also less than a human. Interestingly, cubs might only be 6 to 8 inches in length at birth and are completely hairless. 

9. PORCUPINE: 112 DAYS

This is the longest gestation period of any rodent. Thankfully for the mother, porcupine babies (a.k.a. porcupettes) are actually born with soft quills, and it's not until after birth that they harden up.

10. WALRUS: 15 MONTHS

Baby walruses? Kind of adorable. They certainly take their sweet time coming out, though.

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