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Oliver Koemmerling via Wikimedia Commons // CC BY-SA 3.0
Oliver Koemmerling via Wikimedia Commons // CC BY-SA 3.0

Why Lady Mantises Eat Their Mates

Oliver Koemmerling via Wikimedia Commons // CC BY-SA 3.0
Oliver Koemmerling via Wikimedia Commons // CC BY-SA 3.0

If one out of every four of your sexually active friends got eaten, you’d probably start to consider a sex-free lifestyle. Unless, of course, you’re a male praying mantis, in which case you’d go for it anyway. The male bugs’ apparent eagerness to go to their mid-coital deaths has puzzled scientists for some time. One 2016 study may have an explanation: being eaten could actually increase a male’s chance of passing on his genes. The study was published in the Proceedings of the Royal Society B. 

Mantis sex is … intense. About 25 percent of encounters include sexual cannibalism, in which the female mantis literally bites her mate’s head off. But a little thing like that is not going to deter the missing male, who will go on humping like nothing has happened, even as the female continues to nibble him into nothingness. This can take hours.

True romance: a female mantis eating her mate's genitals. Image Credit: Oliver Koemmerling via Wikimedia Commons // CC BY-SA 3.0

He is, in essence, offering his body as a present. This sexual gift-giving is not uncommon in insects—the males in one cricket species even make gummy snacks for their mates—but most of these gifts are not also the gift-givers. From an evolutionary perspective, it makes a lot of sense: females can share the nutrient boost with their fertilized eggs, which gives the kids a better chance of surviving. Was that what was going on in mantises? To find out, researchers set up a little mantis love hotel. 

The first step was to provide a romantic meal. The scientists treated small crickets with radioactive amino acids, then fed those crickets to a group of male mantises. Then each male was paired with a female and allowed to mate. Half of the mantis pairs were separated before the female could get her chow on. The other half were left alone to play out their grisly romance. 

In eating her partner, a female also ate the contents of his stomach. So by tracking those radioactive cricket particles, the scientists were able to determine how females’ bodies were using their most recent meal.

As it turns out, even uneaten males were giving their partners a little something. On average, male mantises who survived passed on 25 percent of their radioactive amino acids via their ejaculate. But, as expected, a dead dad could do even more for his kids; gobbled-up males gave their mates a full 90 percent of their nutritious amino acids, and their mates passed the goodness on to their young. 

Being devoured also improved a male’s genetic success by increasing the number of eggs laid by his partner. Females in the coitus interruptus pairings—those who didn’t get to eat—laid about 37 eggs apiece. Those who finished their dinner dates, on the other hand, produced around 88. 

We’ve still got plenty to learn about these beautiful creatures and their slightly terrifying sex lives. But these findings do, at least, make sex-positive male mantises seem slightly less foolhardy. 

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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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