Ravens Can Figure Out When Someone Is Spying on Them

Jana Mueller
Jana Mueller

Corvids, the family of birds that includes crows and ravens, are canny beasts. They've been known to exercise self-control, count, hold grudges, and more. Now, new research suggests they possess at least a rudimentary Theory of Mind—the ability to attribute mental states to others.

A study in Nature finds that ravens can tell when someone else can see them, guarding their food when a peephole to their cache is open. While previous research suggested that birds might have an awareness of other animals' mental states, the results have been inconclusive. The Nature study is evidence that corvids can do more than just track other birds' gaze; they may understand the concept of "seeing."

Vienna-based researchers set up two rooms separated by windows that could be closed with covers. These covers had peepholes in them that could also be opened or closed. First, the 10 ravens were each allowed to cache food, while other birds were in the next room and the windows were open or closed. Then, they were trained to look through the peepholes to find food in the other room, so that they knew that the holes could be used to see through the window covers. Afterwards, each of the ravens was again presented with food with one of the two peepholes open. The adjacent observation room didn't have any birds in it, but the researchers played the sounds of another raven recorded during one of the previous trials.

When the birds heard the sounds of another raven in the next room, and the peephole was open, the birds behaved as if they knew they were being watched—they hid their cache of food quickly and didn't add more food to it as often, as if they knew that it might be compromised. However, they behaved normally when the peephole was closed.

This suggests that ravens don't just track their competitors' gaze to know when they’re being watched, but can infer from past experience when they can be seen.

It 'Rained' Spiders in Brazil Last Week—and You Can Watch It If You Dare

iStock.com/aury1979
iStock.com/aury1979

If recent events are anything to go by, you should be less concerned about swallowing spiders in your sleep and more concerned about bird-eating spiders raining down on your head. As The Guardian reports, recent footage from the Brazilian countryside shows thousands of spiders seemingly suspended in mid-air. (Arachnophobes might want to give the video below a miss.)

In reality, they aren’t falling at all. The spiders, which likely belong to a South American species called Parawixia bistriata, are merely crawling on an ultra-fine and nearly invisible web that attaches to two objects, like trees or bushes, to form a canopy.

So why do they do it? To catch prey, naturally. They’re likely to snag a variety of insects and maybe even small birds in their communal web, which can stretch up to 13 feet wide. (And yes, they eat the birds, too.)

Brazilian biology professor Adalberto dos Santos tells The Guardian that P. bistriata are some of the rare “social” spiders that do this. They leave their webs up overnight, hide out in the nearby vegetation, and then return at dawn to feast.

While this natural phenomenon is certainly unsettling, it isn’t exactly rare. Residents of the southeast municipality of Espírito Santo do Dourado, where the video was shot, said these “spider rains” are common when the weather is hot and humid.

Here’s another video from Santo Antônio da Platina in southern Brazil in 2013.

Other species of spider have been known to jump into the wind and "surf" on strands of silk as a means of getting around. They do this to escape threats or get to food or mates in other locations, and cases of "spider flight" have been recorded all over the world. Some especially adventurous spiders have even been known to cross oceans by “ballooning” their way from one land mass to the next.

[h/t The Guardian]

FDA Recalls Several Dry Dog Foods That Could Cause Toxic Levels of Vitamin D

iStock.com/Chalabala
iStock.com/Chalabala

The FDA has recalled several brands of dry dog food that contain potentially toxic levels of vitamin D, The Atlanta Journal-Constitution reports. While vitamin D is essential for dogs, too much of the nutrient can result in kidney failure and other serious health problems.

The FDA has already received reports of vitamin D toxicity in dogs that consumed certain dry foods. Pet owners are advised to stop using the following products:

Old Glory Hearty Turkey and Cheese Flavor Dog Food (manufactured by Sunshine Mills, Inc.)

Evolve Chicken & Rice Puppy Dry Dog Food (Sunshine Mills, Inc.)

Sportsman's Pride Large Breed Puppy Dry Dog Food (Sunshine Mills, Inc.)

Triumph Chicken & Rice Recipe Dry Dog Food (Sunshine Mills, Inc.)

Nature's Promise Chicken & Brown Rice Dog Food (Ahold Delhaize)

Nature's Place Real Country Chicken and Brown Rice Dog Food (Ahold Delhaize)

Abound Chicken and Brown Rice Recipe Dog Food (sold at Kroger in Louisville, Kentucky, as well as King Soopers and City Market stores in Colorado, Utah, New Mexico, and Wyoming)

ELM Chicken and Chickpea Recipe (ELM Pet Foods, Inc.)

ELM K9 Naturals Chicken Recipe (ELM Pet Foods, Inc.)

ANF Lamb and Rice Dry Dog Food (ANF, Inc.)

Orlando Grain-Free Chicken & Chickpea Superfood Recipe (sold at Lidl stores)

Natural Life Pet Products Chicken & Potato Dry Dog Food

Nutrisca Chicken and Chickpea Dry Dog Food

For the full list of UPC and lot numbers involved in the recall, visit the FDA's website.

Symptoms of vitamin D poisoning usually develop 12 to 36 hours after pets consume a suspect food, according to PetMD. The FDA says those symptoms include vomiting, loss of appetite, increased thirst, increased urination, excessive drooling, and weight loss. "Customers with dogs who have consumed this product and are exhibiting these symptoms should contact their veterinarian as soon as possible," the FDA writes.

The agency says the situation is still developing, and it will update the list of recalled brands as more information becomes available. According to WKRN News, veterinary professionals recommend sticking to dog foods that have an AAFCO label (from the Association of American Feed Control Officials) on them.

[h/t The Atlanta Journal-Constitution]

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