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Tuan Cao via Wikimedia Commons
Tuan Cao via Wikimedia Commons

These Spiders Use Unlikely Bodyguards

Tuan Cao via Wikimedia Commons
Tuan Cao via Wikimedia Commons

Many ant species are territorial and aggressive. That maybe wouldn’t be so bad if ants were loners, but they tend to stick together in groups, sometimes tens of thousands strong. If you’re a bigger, tougher animal that eats ants, or one that stays safe by mimicking them, or makes your living as an ant parasite, those numbers are great. They make it that much easier to prey on them or blend in with a group. 

The jumping spider Phintella piatensis neither eats ants nor mimics them. It’s not a parasite, either, but it still loves hanging out with ants. In one field study, 90 percent of all Phintella spiders that biologists found were in the company of ants, including the Asian weaver ant Oecophylla smaragdina. This has had puzzled scientists because Oecophylla is known as a formidable predator with a taste for arachnids, and yet Phintella is drawn to them and doesn’t seem to come into harm’s way when it’s around them. In experiments, Phintella’s survival rate among the ants was much higher than those of other regular jumping spiders, and closer to spiders that eat or mimic the ants. 

What would drive Phintella into the company of an ant that it should be afraid of, scientists wondered, when there doesn’t seem to be any benefit? And why doesn’t the ant make a meal of it?

The answer to the first question is “something scarier than an ant.” For jumping spiders in the Philippines, that would be the spitting spiders of the genus Scytodes. While most spiders deliver venom from their teeth and spin silk into webs, these guys turn both into projectile weapons. They mix liquid silk and venom into a sticky fluid and “spit” it at prey, at once trapping it and poisoning it. The spider then approaches its prey and bites it, delivering another dose of venom that begins to liquefy its tissues. Phintella is a frequent victim of this hunting technique, and Scytodes spiders are known to build their webs directly over Phintella’s nests and attack the smaller spiders as they come and go from their homes. 

Scytodes stays far away from weaver ants, though, which got New Zealand biologists Ximena Nelson and Robert Jackson thinking that the jumping spiders hang out with the ants for protection. When they got the three arthropods together in the lab, they found that jumping spiders were more likely to build nests when they could see or smell ants than when other insects were around or there was no sign of ants. The spitting spiders, on the other hand, were much less likely to build their webs when they could see the ants. They were also more likely to die when the ants were around, while the jumping spiders largely avoided becoming ant food. 

To Nelson and Jackson, the differing nest-building responses and survival rates between the two spiders made it pretty clear that Phintella sticks close to the ants because they scare away or kill spitting spiders. And while ants would be happy to eat the jumping spiders, too, Phintella has a few tricks up its sleeves that turn enemy territory into a safe haven. 

First, jumping spider nests aren’t like typical spider webs. They’re more like silken cocoons, and provide some resistance to intruders. Phintella then beefs up the nest’s security even more with a tough, dense weave of silk that the ants have a hard time tearing through. It also adds hinged flaps to either end of the nest that act like doors. The spider can get in and out of the nest as it pleases and close the flap behind it to keep the ants out. 

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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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