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Tuan Cao via Wikimedia Commons

These Spiders Use Unlikely Bodyguards

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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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Animals
Watch as Hummingbirds Fly, Drink, and Flap Their Tiny Wings in Slow Motion
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Hummingbirds have more feathers per inch than nearly any other bird, but it’s hard to fully appreciate their luminescent colors when they beat their wings between 70 to 200 times per second.

For the enjoyment of birders everywhere, National Geographic photographer Anand Varma teamed up with bird biologists and used a high-speed, high-resolution camera to capture the tiny creatures in slow motion as they flew through wind tunnels, drank artificial nectar from a glass vessel, and shook water from their magnificent plumage.

[h/t The Kid Should See This]

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Big Questions
Why Do Dogs Howl at Sirens?
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A dog's behavior can often prove confusing to their human colleagues. We know they like to eat their own poop, but puzzle at their motivations. We're surprised when dogs give a ladybug the same greeting as a home intruder.

Topping the list of eccentric canine behavior: Why do dogs howl at sirens? Is there some genetic predisposition to responding to a high-pitched alarm from passing ambulances or police vehicles?

As it turns out, the reason dogs howl at sirens is because of their ancestry—namely, the wolf. When members of a pack are fractured and spread out, their companions will howl to provide a way of locating them. Think of it as nature’s GPS: By howling, dogs are able to communicate their respective locations to one another, even across long distances.

Since dogs really don’t know what a cop car is supposed to sound like, they’ll often interpret a siren as an animal’s howl. It’s also possible that dogs consider sirens to be a sign that something is abnormal in their environment, and that they want you, the pack leader, to be aware of it.

Contrary to belief, a dog is rarely howling because the noise hurts their delicate ears. If that were the case, some experts say, then they would display other behaviors, like running and hiding.

The more a dog hears and responds to a siren, the more they might be compelled to continue the behavior. That’s because dogs who howl and then notice the sound drifting away might begin to associate their vocalizing with the disappearance of the noise. In the future, they’ll probably recall that they “drove” the interloper away with their warbling and repeat the process.

While howling is usually harmless, sometimes it can be a sign that your pet is feeling separation anxiety from an owner or that they’re feeling unwell. If howling persists even without a screaming siren within earshot, you might consider taking them in for a check-up.

If you’ve wondered why dogs howl at sirens, now you know. It’s simply a way of signaling their location and not because it pains them. Owners, on the other hand, might feel differently.

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