At over three feet, you’d think the solo coral grouper would be threatening enough. Threatening sure, but a successful lone hunter? Well, not so much, according to National Geographic News Watch:

When hunting alone, groupers only catch their prey about 1 out of every 20 attempts.

So the grouper teams up with the even fiercer moray eel, or the very large Napolean wrasse, to go hunting. The fish are looking for smaller coral reef fishes that hide from their predators under rocks and coral. When the grouper detects the hiding prey, it signals its hunting friend and together they both flush the prey out of hiding.

The cooperation, however, ends there. Whoever gets the prey, eats it whole. There’s no sharing of the spoils. Still, for the grouper, it’s worth the shared hunting, says National Geographic News Watch:

When they have help, the ratio is significantly better—about one out of seven.

What’s most significant about this shared hunting are the signals the grouper makes to its partner during the hunt, say scientists. Researchers studying the fish observed dozens of events where groupers performed upside-down headstands with concurrent head shakes to indicate the presence and location of particular prey to cooperative partners. Their study, published last week in Nature Communications, call the groupers’ signals “referential gestures”. From the abstract:

In humans, referential gestures intentionally draw the attention of a partner to an object of mutual interest, and are considered a key element in language development. Outside humans, referential gestures have only been attributed to great apes and, most recently, ravens.

It’s likely that these gestures have been understudied in non-primate species, say Academy researchers, who point to hunting dogs and even bee dances as potential consideration for referential gestures.

The researchers of the study say that the mental processes underlying these gestures in fish, apes and ravens are unclear and may well vary among these taxa. Their findings point to the fish having developed cognitive skills according to their particular ecological needs.

Whatever the cause, these hunting tactics are pretty extraordinary. Videos of the behaviors can be found here. For more information on the study, visit the University of Cambridge website.

Image: jon hanson/Wikipedia

Publishing online in Naturwissenschaften last week, Israeli researchers have discovered that these corvids are not only clever, they’re also crafty.

The scientists studied a pair of brown-necked ravens (Corvus ruficollis) and found that they were very good at stealing food from Egyptian vultures (Neophron percnopterus).

The pair of ravens had their eyes on a high quality food source, large ostrich eggs.  Female ostriches lay their eggs in a communal nest—resulting in large concentrations of as many as 40 eggs. The dominant female and breeding male can only incubate 12-14 of these and discard the rest, creating a circle of unwanted eggs around the nest.

The ravens are after the discarded eggs, but the eggshells are so thick, they are inaccessible to these birds. According to a previous study by two of the same authors, the intelligent ravens are known to recognize their limitations.

That’s where the vultures come in. The vultures are smart birds, too, and like the ravens, are known to use tools. (In the avian world, scientists have found that tool-use equals bigger brains.) The vultures have found a way into ostrich eggs—rounded stones. They use the stones to crack the eggs and their sharp beaks do the rest.

So the ravens wait patiently, hiding from the vulture until the work has been done opening the egg and revealing its contents. At that moment, the ravens, working cooperatively, begin to harass the vulture until it flies away, leaving behind the delicious, accessible egg.

The vulture is not as bright as the ravens—and doesn’t learn from its mistakes. The ravens have targeted the same vultures more than once, with the same results.

The researchers seem to applaud the ravens’ kleptoparasitism. From the study:

It appears that the intellectual flexibility and response to ever-changing conditions has allowed this highly intelligent family to persist in extreme conditions—from the freezing tundra to the hot deserts…

Most apparent in the ravens is their innovative thinking and ability to predict the actions of the potential host or prey.

That’s Andrew Revkin, in his Dot Earth blog in the New York Times, writing about avian keratin disorder—a disorder of unknown origin affecting bird species in the Pacific Northwest and Alaska at ten times the usual rate over the past decade.

USGS biologists published two papers (they can be found here and here) last week about this disorder that causes beak deformities across almost 30 different species of birds. Stunning news! The studies and Revkin’s comparison really got our attention.

We asked our own bird expert, Dr. Jack Dumbacher (Curator and Department Chair of Ornithology and Mammalogy), about this epizootic (an epidemic among wildlife).

There are a couple dozen species that appear to be affected, but the two most impacted appear to be Black-capped Chickadee (Poecile atricapillus), and Northwestern Crow (Corvus caurinus). Other corvids (jays, ravens, etc.) also appear to be more affected.  Although there were some reports in the early 1990s, the number of affected birds appears to have peaked in the 2000-2001 season, and again in the 2006-2007 season.  It seems to be more prevalent in adults, suggesting that it is an acquired condition.  It appears to most profoundly affect the keratin layers of the bill, causing the bill to overgrow and often cross, but it can also affect other keratinized layers of skin, legs, feet, and claws.

The deformed beaks hinder the birds’ ability to eat, clean themselves, and care for their young.

Jack expressed surprise about the findings:

I had known of strange growths caused by knemidocoptes mites, and these can sometimes cause bills to overgrow, scales to enlarge or slough off, and other deformities.  I’ve even seen these in the field (in South African Cape Robins).  But this was specifically examined, and these birds appear not to have knemidocoptes mites.  I’d certainly not heard of this in multiple species in one place.

Some diseases—like avian pox or the disease caused by West Nile Virus—have affected multiple species, and have had significant impacts across bird species. In parrots, a circovirus causes a disease called Psittacine beak and feather disease, and can sometimes cause overgrown beaks and crossed beaks.

The cause remains unknown, and it may prove challenging to discover.  Many factors require consideration, including environmental contamination, bacterial, fungal, or parasitic infections, and dietary deficiencies.

Jack provided some insight and hope for response from the community.

It is hard to say.  The authors looked at the most likely causes—knemidocoptes mites, malnutrition, liver malfunction, other diseases, and nothing came up positive.  It is possible that this is caused by a new disease agent that is not yet known.  For example, when frogs first began declining, it was hard to pin down the cause, but now we have some evidence that a fungal pathogen—Chytrid fungus—may be part of the cause. There may be an unknown pathogen causing these deformities in birds.

One hopes that now that these excellent papers have been published, we will all keep an eye out for such issues.  The USGS has requested information on this phenomenon, and they have set up a website that discusses it and allows you to report an incidence.

Scientists and bird watchers alike can help researchers learn more. Jack, who has done virus research in avian populations around the world, hopes to lend a hand (and needle) to the project, too. Stay tuned.

Frans de Waal, PhD, one of the leading researchers in animal behavior and the author of The Age of Empathy: Nature’s Lessons for a Kinder Society, has said, “The possibility that empathy resides in parts of the brain so ancient that we share them with rats should give pause to anyone comparing politicians with those poor, underestimated creatures.”

Last week, two Austrian researchers found evidence of empathetic behavior in another creature, ravens.

Ravens are part of the corvid family, which includes crows and rooks, long believed to be very intelligent birds. (See our Science in Action video on crow tool-use here.)

Published in PLoS ONE, “This study investigates the post-conflict behavior of ravens, applying the predictive framework for the function of bystander affiliation for the first time in a non-ape species.”

The researchers observed ravens after a fight and found that the birds that weren’t involved in the fight (the bystanders) would console the victim of the aggression, especially if the bystander had a relationship with the victim.

Orlaith Fraser, PhD, one of the authors of the study, quoted in Wired, explains, “It’s not a good thing for your partner to be distressed.” Suggesting a possible evolutionary advantage of why corvids may express empathy for one another.

In addition, the scientists also found that after the conflict, the victim would cozy-up with the bystanders, in hopes of avoiding continued aggression.

“These results stress the importance of relationship quality in determining the occurrence and function of post-conflict interactions, and show that ravens may be sensitive to the emotions of others,” the study concludes.

Dr. Fraser adds, “It’s interesting to see these behaviors in animals other than chimpanzees. It seems to be more ingrained in evolutionary history.”

And perhaps, this study of ravens will “also play an important role in the empathy debate.”

Creative Commons image by Sigurður Atlason