Among insects, at least, it is thought that the coloration is expressed more highly in gregarious species. That is, if you are a lone, brightly-colored individual, you will tend to stand out as a tasty snack for local predators. But, if there are several brightly-colored specimens, you are no longer considered “conspicuous”, since you’ve got neighbors who look just like you do, so no individual stands out any more than the others. This is known as “density-dependent aposematism”, and populations have been shown to change coloration based on local population densities: low density results in more “cryptic” (that is, less conspicuous) coloration, and higher densities allow for a shift to more noticeable coloration.
In the case of other aposematic species, it could be that, as I mentioned previously, the bright colors go hand-in-hand with their poisonous nature. In the case of frogs, the poison is likely to be a contact poison: the predator picks the frog up, quickly realizes his mistake, and drops the would-be meal. I would not be surprised to learn, then, that such toxins can influence pigmentation (I say I would not be surprised to learn because offhand, I don’t know that such is, in fact, the case); the toxins directly influence the color change, so as the toxins become stronger, brighter coloration follows.
As a matter of fact, some time ago we had a student at our research station here in Panama bring in a snake that he was convinced was a harmless coral-snake mimic because of the mnemonic.
He ended up in the hospital (but fortunately survived). Actually, it’s the only case we’ve ever had of someone being bitten by a coral snake at the station.
Not to change the subject…but why are tropical fish, corals, shells, etc. so brightly colored? At a depth of >30 feet, you cannot perceived red and orange…yet tropical corals growing at depths >200 feet are red and orange. The coloration doesn’t make sense to me…why invest in bright coloration if your potential mates are unable to perceive them?
Poor guy. Pretty bad luck - from the looks of it you’ve got 8 (!) species of coral snakes in Panama ( with a rare ninth verging into Darien from Colombia ) and maybe half look like they fit mnemonic and half don’t. My understanding is that coral snake bites are pretty rare, period. They’re usually cryptic in habit ( as cryptic as anything that brightly colored ever gets, anyway ) and pretty mellow.
By the way if you don’t personally have a copy ( though no doubt copies are floating around in your lab ), The Venomous Reptiles of Latin America by Campbell and Lamar is a must-have. Keys to every country with photos of most species and many photos of common mimics as well. Lovely book.
Yes, and they have small mouths, and have a hard time opening their jaws wide enough to bite even a finger. It’s actually usually pretty hard to get them to bite you.
It’s on my bookshelf at home. I agree with your assessment.
Well, the stonefish is amongst the most venomous fish, and the venom has a fair chance o being injected into anything swallowing it. Which just goes to show how blurry the line is betwen venomous and poisonous.
The parrot/puffer fish oin the other hand are poisonous.
The equally venomous lion fish ( http://www.marksmarine.net/encylo/lion/lion_fish.htm ) is closely related to the stonefish and can be very brightly coloured. Which I guess shows that the evolution of protective colouration is depandant on umerous factors.
In these cases the two species have adopted diferent stategies. The stonefish is an ambush hunter, and uses its camouflage to ambush prey more than for hiding from predators. The lionfish uses stealth hunting techniques, and as with the stonefish its posion makes it relatively safe from predators.
Last Friday my family went on a hike in the jungles of central Trinidad to see Howler and Capuchin monkeys and other interesting flora and fauna. While I was looking up into the trees, my son said, “Mom, you’re standing on a snake.” I sure was. It was a **fer de lance[/], one of the deadliest snakes in the world. And it was camouflaged beautifully on the jungle floor.
I picked it up on a stick so we could get a better look at it and take pictures, etc. That was before I read that the fer de lance is very aggressive and kills more people than any other reptile in the Americas. Yet again, Jill beats the odds.
Just would like to add, that predators don’t instinctivelly know tha those brightly colored creatures are poisonous. They usually have to get a taste of one or two and get horribly sick before they make the connection. So needless to say, a couple have to ‘take one for the team’ so that the predator will no longer eat the others.
