Biochemical Soul Musings on Nature, Science, Evolution, Biology, and Education


Adaptation of the Week – Bird/Crocodile Symbiosis?

Earlier this week, thanks to the wonderful science & nature Twitter community, I followed a link from someone now forgotten to an article entitled "7 Symbiotic Wonders of the Aerial World."

Therein, in symbiotic relationship number one, sat a photograph that I found utterly astonishing:

WP00955. Nile Crocodile (Crocodylus niloticus) with Egyptian Plover or Crocodile Bird (Pluvianus aegyptius) - digital reconstruction of popular myth attributed to Herodotus, 5th Century BC.

"Plovers and Crocodiles"

According to the WebEcoist website which published this list of "symbiotic wonders."

"It looks like something out of a storybook - and in fact it can be traced back to accounts told thousands of years ago - a crocodile opens its mouth, invites a bird in before … what?  ::Chomp:: it swallows the sap alive? Amazingly, the crocodile remains still while the plover picks meat from its mouth. This cleans the crocodile’s teeth and prevents infection while providing a somewhat scary meal for the hungry bird."

The image stewed in my head for a couple of days, and I mentally bookmarked it as an excellent adaptation to cover in my Adaptation of the Week series. The story began to write itself as I drove to and from work.

It's quite easy to see how such a relationship, once begun, would be reinforced over successive generations, with the daring plovers becoming well-fed and the tolerant crocodiles' pearly whites gleaming like Smilin' Bob's.

Egyptian Plover (Pluvianus aegyptius)

Egyptian Plover (Pluvianus aegyptius)

But how would such a symbiotic relationship begin, I wondered?

Regardless of the incremental steps that naturally must have occurred, at some point a single dumb, brave, or incredibly hungry bird had to have been the pioneer to first brave the feast-laden crocodilian death-trap. Imagine being the first bird to firmly plant talons on that massive reptilian tongue. No doubt others had come to this place before - but none had survived unscathed.

And what of the first crocodile. Was he just so stuffed that he couldn't bear the thought of shoving one more feathered morsel down his gullet ("it's only wafer thin"). Or perhaps he was the Einstein of the ancient crocodiles, somehow sensing the advantage of letting the little plover do its thing.

In reality, I thought, the relationship probably came in many fits and starts, with the birds initially pecking around the crocs, grabbing whatever leftover bits they could. The crocs tolerated them, much as cattle do with egrets. Perhaps a fair number of plovers did end up as croc snacks. But over time, the crocs most friendly to the plovers gained a slight advantage, with the "friendly alleles" slowly increasing in frequency throughout the population. The birds, of course, now had to compete with one another, becoming bolder and more adventurous.

Nile Crocodile (Crocodylus niloticus) with Human Hand (Lucas skywalkerus)

Nile Crocodile (Crocodylus niloticus) with Human Hand (Lucas skywalkerus)

In the end, this beautiful relationship was forged and stabilized, to the benefit of both parties (though I imagined that crocodiles who break the contract probably continuously cropped up).

I had my article, plainly written right there in my brain. But of course, as with any good article dealing with, anything, I first had to do a little bit of research. What species of bird is it? How common is the relationship?

I make my way back to the original "7 Symbiotic Wonders" article and click on the above image to get the image credits.

The photography website (Warren Photographic) immediately opens to the same image with the following caption:

"WP00955. Nile Crocodile (Crocodylus niloticus) with Egyptian Plover or Crocodile Bird (Pluvianus aegyptius) - digital reconstruction of popular myth attributed to Herodotus, 5th Century BC." [emphasis mine]


That's not a real image, but a photoshopped one?  I immediately googled the bird (Pluvianus aegyptius), which pulled up this Wikipedia article:

"It is also sometimes referred to as the Crocodile Bird because it is famous for an unconfirmed symbiotic relationship with crocodiles. According to a story dating to Herodotus, the crocodiles lie on the shore with their mouths open, and the plovers fly into the crocodiles' mouths so as to feed on bits of decaying meat that are lodged between the crocodiles' teeth. The crocodiles do not eat the plovers, as the plovers are providing the crocodiles with greatly-needed dentistry. Two prominent ornithologists have supported this story anecdotally,[who?] but the behaviour has never been authenticated (Richford and Mead 2003)." [emphasis mine]

You mean to tell me that after all of this thought, the whole thing is only an ancient myth?!

Apparently the author over at WebEcoist didn't do his research for the article (sorry Ecoist). I mean, c'mon! The original image they used as the lede explicitly states that it's only a myth.

So much for my Adaptation of the Week...

What a croc!!

In the end, I decided to do some research and find a REAL symbiotic relationship:

And in return?

And in return?

(I photoshopped this)

Update: I found a great post on SkepticWiki that discusses this exact supposed phenomenon, and it even talks about how some creationists  use the "crocodile bird" (erroneously) as an example of a behavior that could not have evolved naturally. Right...

Previous Adaptations of the Week:

  1. Timber Rattlesnake Camoflage
  2. The Aye-Aye’s Freaky Finger (I’ve Been Cursed by an Aye-Aye!)
  3. Flatfish Eyes & Recapitulation Theory

Behavioral Mimicry in the Golden Garden Spider

I witnessed a pretty awesome display today by my friendly neighborhood Golden Garden Spider (Argiope aurantia), that I had never before seen. In fact, I had no idea that spiders would make such defensive displays.

As I approached her web, I noticed the web start to vibrate back and forth in quite an exaggerated fashion. So I ran and grabbed my camera. When I got back out she had stopped, but she started back up immediately as I got close.

Note - my hand is actually about 6 inches from the web. Also, my hand produced no wind (you can see this clearly toward the end of the video - the last ten seconds are by far the best).

Considering the bright yellow and black markings, my nearest guess is that she was mimicking the movement of a carpenter bee or some other poisonous hymenopteran (we have lots of carpenter bees). It seems clear that it was her way of saying "get the fuck away from me! I'm dangerous". Of course, it may be that it's not mimicry at all, but to me it looks very similar to the movement of the carpenter bees against that very same wood as they bob forward and backward.

For another cool picture of an Argiope, see my previous post (which also has some cool black widows from my house).