Tag Archives: animal behavior

The Mysterious Case of the Albino Red-Eyed Tree Frog

The other day I stumbled upon an intriguing picture of a red-eyed tree frog (Agalychnis callidryas) on Wikipedia:

The caption states that the frog is in “cryptic water conservation posture,” while the photo’s file name suggests it is in “camouflage mode.” What puzzled me is why a frog would turn ghostly pale on a green leaf. Not exactly inconspicuous.

So I asked Twitter:

@rowhoop, News Editor at New Scientist, said: “@ferrisjabr maybe the leaf looks like that in the UV part of spectrum, which birds (predators) are sensitive too. or maybe not.”

“@ferrisjabr Imitating bird droppings?” suggested writer, artist and editor @StanCarey

I liked these ideas so I decided to follow up with some herpetologists (scientists who study amphibians and reptiles).

Karen Warkentin, a biologist as Boston University who studies the ecology, evolution and development of frogs – including the red-eyed tree frog – responded as follows:

I don’t know that I’d trust what the image looks like all that much. The frog looks pretty washed out, maybe from flash? The frog is asleep (daytime). There’s lots of speculation but we really don’t know why these (or many) frogs change color. Red-eyed treefrogs can be darker or lighter green, but they can’t be dramatically different colors.

Ohhh…right. Flash. That does make sense.

A fellow herpetologist, James Hanken of Harvard University, independently agreed with Professor Warkentin:

I can offer two possible explanations of the strong contrast between the frog and its leafy background:

  1. The contrast is an artifact of the photographer’s camera setup.  The photographer used a close-up flash, and the bright light reflected right back at the camera lens and “washed out” the frog’s green color.  (The leaf remained dark green because it is oriented at an oblique angle to the camera lens and didn’t reflect the flash directly back at the camera.)
  2. If the strong contrast is real (which I doubt), then the frog may be better camouflaged against the leafy background when viewed in the ultraviolet or infrared spectrum, which some predators can see.
I have collected this species in the field (Costa Rica), and to me “camouflage mode” refers to the fact that the frog, by adjusting its body posture, is concealing its brightly colored flanks, thighs, toe webbing, and eyes.  By only showing its green color, these frogs truly are difficult to see when they’re sitting on a green leaf.

So it seems when red-eyed tree frogs camouflage themselves, they hunker down on a leaf and tuck away all the strikingly inked bits that make them so photogenic. They may even tune their body’s shade of green, but they probably do not turn albino on the spot. Perhaps staying so still during the hot day also helps them conserve water, as suggested in the original caption.

I guess this is yet another reason to be wary of what you read and see on Wikipedia (although I will defend its usefulness to the death! Seriously, some articles have the most amazing references and external sources: links to amazing primary sources).

I also noticed that the photographer behind this picture, one John J. Mosesso, has many nature photographs all over the web, especially in the National Biological Information Infrastructure’s Library of Images. John, are you out there? Any thoughts about this photo?

When Squid Fly: New Photographic Evidence

On August 2, I published an online article with Scientific American about flying squid. Not flying fish. Flying squid.

Marine biologist Silvia Maciá was boating on the north coast of Jamaica in the summer of 2001 when she noticed something soar out of the sea. At first she thought it was a member of the flying fish family—a group of marine fish that escape predators by breaking the water’s surface at great speed and gliding through the air on unusually large pectoral fins. But after tracing the creature’s graceful arc for a few seconds, Maciá realized this was no fish. It was a squid—and it was flying.

With her husband and fellow biologist Michael Robinson, Maciá identified the airborne cephalopod as a Caribbean reef squid (Sepioteuthis sepioidea)—a lithe, torpedo-shaped critter with long, undulating fins. They think the squid was startled by the noise of the boat’s outboard engine and estimated that the 20-centimeter-long mollusk reached a height of two meters above the water and flew a total distance of 10 meters—50 times its body length. What’s more, the squid extended its fins and flared its tentacles in a radial pattern while airborne, as though guiding its flight.

Macia eventually co-wrote a 2004 study in the Journal of Molluscan Studies that described several observations of flying squid, but the paper relied largely on anecdotal evidence. There were no photographs or videos.

Recently, however, on a cruise ship off the coast of Brazil, retired geologist and amateur photographer Bob Hulse captured what may be the best-ever photographic evidence of flying squid. Hulse sent the pictures to University of Hawaii oceanographer Richard Young, who passed them along to Ron O’Dor, senior scientist for the Census of Marine Life. O’Dor thinks he can analyze the photos to gain a better understanding of squid aerodynamics, which few people have been able to properly study due to lack of adequate documentation.

An abridged version of my online article will also appear in the October print issue of Scientific American, accompanied by one of Bob’s photographs. Unfortunately, due to spatial constraints, the printed magazine page cannot properly accommodate the glory of Bob’s photographs. He took his photos while aboard a cruise ship off the coast of Brazil, so he wasn’t exactly face-to-tentacle with the squid. An image cropped from such a distant image and pasted on a magazine page can only offer so much. What we need is one of those fancy setups straight out of an episode of CSI. You know, something like: ‘Computer: locate the squid; zoom in 3 billion and 4/5%! Now, identify the species. Thank you, computer. Now commence calamari conversion.”

Okay, enough of that. I have a better solution. Here are Bob’s pictures. When you click on them, the ocean should flood your browser. And then you can zoom in even further to locate the flying squid above the waves. Look for the triangular tips, the floppy fins, the fanned tentacles and the jets of water trailing the squid rockets.

Click and Zoom!

Photograph of flying squid off the coast of Brazil (Credit: Bob and Deb Hulse)

Photograph of flying squid off the coast of Brazil (Credit: Bob and Deb Hulse)

Photograph of flying squid off the coast of Brazil (Credit: Bob and Deb Hulse)