Welcome to the University of Cambridge Department of Zoology
Mind, if we call you Kate, just to keep it clear.
Dammit, I've waited 45 years to get even with you pommies.
Aegean wall lizards have demonstrated the impressive ability to hide from avian predators by camouflaging themselves against rocks "that best match the colour of their backs". The Aegean Wall Lizard. Pic: Cambridge University On the look-out for a matching rock: the Aegean wall lizard That's according to Kate Marshall from …
Tip: All the Boffins have to do is contact any member of the British Royal Family who will divulge the secret of this ability in exchange for a 1 Kilo bag of Freeze Dry Grasshoppers and Crickets, or 'Pick n Mix' as her Majesty calls them.
Can i also express my long overdue thanks to the Boffins for their great sacrifice in obtaining the plans for the Second Death Star. Your heroism has saved countless lives in the galaxy.
This team released an earlier paper on the lizards where they discuss how the males tend to have more coloring to show off to females, and that gets them eaten more than females. Having fewer males doesn't really hurt the species and probably helps.
But I wonder if the males (that are showing off) stand on rocks that contrast against their backs, rather than blend in? It would presumably get them more females, but too much contrast will eliminate them all, not good. So there has to be a dynamic balance point, a 'fashion police tape' they don't cross. When birds are common, Disco becomes Grunge, and vice versa.
Also: do the lizards (and their predators) see colours the same way we do?
This is answered in the article, in the negative.
Actually, the question is ill-formed. Whether any two entities "see colo[u]rs the same way" is at best an epistemological question, but even then only if it's carefully qualified. In general, it's not well-defined. What does it mean to compare the quale of "seeing a color"? There are physiological responses in the retina, optic nerve, and brain, based on various factors (wavelengths and amplitudes of the light in question, cone receptors in the retina and their efficiency at the moment to those stimuli, etc), which vary among subjects due to health, genetic makeup, etc. There are processing effects, such as contrasting-color and color-sharpening effects. For humans and possibly some other subjects, there are psychological effects of many sorts.
The way I see color is almost certainly different in many respects from the way you see color; thus there is no meaningful "the way we see color" in any general sense.1
But in this particular case, for these purposes, we can comfortably say "no". The lizards and birds both have receptors for shorter wavelengths than any the human eye responds to, and the lizards' range appears to extend beyond what the birds perceive.
1There are all sorts of philosophical problems with color. It's quite an interesting area, really.
Raptors are generally not attracted to lizards, too small. They're left to smaller generalists such as crows and the like. Also the birds usually don't get to see the lizard squarely and from a very short distance, so sometimes the lizards do evade detection. If they didn't they would go extinct, yes?
"I could have come up with this conclusion from simply ten minutes of observation."
Nazz. That would be called 'jumping to a conclusion'
whereas the Boffins will have made scientific observations in some depth and making comparisons from observations of numbers of lizards as well as other species occupying a similar niche; That would be called a scientific observation.
Not necessarily any more accurate than your conclusion but they will have done some science.
As for visbility, given that raptors have different eye structure and light perception from us; what you see is not likely to be the same as they see while looking for a meal.
Your looking at photos expecting to see a lizard and that has been chosen to show it off a bit. You can easily miss lizards in the wild if you are just walking about.
Some raptors will predate lizards some of the species are quite small, the smallest being Falconets that are about budgie size. In Europe would not surprise me if something like a Merlin would think about it.
Perhaps a further visit to establish the roaming pattern of these lizards would provide proof that it's more Darwin and less clever.
If the blue lizards tend to roam over blue rocks then they will undoubtedly become more prevalent to their red cousins in the same area.
I've always found it irksome to hear how a species has managed to develop a certain characteristic to better survive, when in actual truth, the only choice they made was to have sex with something not dead.
On the contrary.. Lizards have a less advanced thermoregulation that doesn't allow them to keep their core temperatures well above ambient like us mammals do, but they are most definitely warmer than their surroundings when they're active. "Cold-blooded" is a bit of a misnomer, really.
There's a good chance the Boffins missed a bit by just looking at birds. Birds of prey, and opportunists, would most definitely not dismiss a snack of lizard. The pattern-matching is not perfect for visual detection ( as is clear from the pics), and if selection pressure would be purely visual there would have been a much stronger selection pressure to look more like the rocks.
Snakes, the other major predators of the lizards, don't go in for much acuity in the visual spectrum.. They tend to use infrared for their hunting. And when you're sunning on a rock that's more or less coloured like you, you tend to warm up the same, making you pretty much invisible from the infrared.
Dunno if they've looked at snakes as well, but you can't really explain a survival strategy until you've figured in all the other animals that use an animal as Lunch. It could well be the camouflage intended for snakes also works pretty well against birds. As long as they don't move....
> "As long as they don't move...."
I hike in the Southwest US desert a lot, and when it gets hot there is a type of smallish lizard that is cartoonishly fast on its feet. I think it evolved to outrun road runners. I also had a close encounter with a racing-type snake that was in the process of chasing down a very scared mouse out in the open.
Mind boggling how fast these reptiles can get when it's hot out.
I'd say movement definetly helps. Having actually spent some days going out and hunting snakes and lizards, the power of staying still for camoflage is very useful thats why a lot freeze if they think they are spotted. (Also some reptiles that hunt are definetly triggered by movement).
Sometimes the best way to find reptiles was either to stay very still and listen for rustling, or to poke about a bit using a stick in the undergrowth and see what moves.
I can help the 2Kates out with their bafflement about how the Lizards know about the colour of their back and how they have the ability to seek out matching rocks. They don't. 2Kates are confusing cause and effect and have fallen victim to that frequent cognitive bias called Hindsight Bias.
Those lizards who, by pure random chance, happen to sit on a piece of rock that resembles their backs are less likely to get spotted by predators, so to naive observers it would seem that they are "seeking" out matching rocks.
I think colour might be a subjective term, i.e we limit it to what we can see and call that coloured light. Mantis shrimp vision for example see's a massive spectrum of light compared to humans, there idea of colour might make ours look drab.
A dog can't see the full colour range of spectrum we see and so can't see green I think.
Weirdly experiments with cultures that use less words for colour or more, have trouble perceiving them, or better perceive them depending on their language. Things like shades of green or even green vs blue become indecipherable.
As simple as proving they can see their own backs.
I mean, they got eyes, right? They also have very flexible necks.
I'm not saying they have not done the maths. Just that it may be clutching at straws to not go for the obvious.
For example: https://www.newscientist.com/article/dn27574-octopus-has-automatic-camouflage-thanks-to-its-light-sensing-skin/
The only way to know if it is a learned method, is to check with some captive lizards. Though even then, animals can be quick learners and improvise on the fly.
PS, yes I know they tested and found out it "cannot see". Call me sceptical. :P
Many of the smaller teiids have got this problem solved. They don't have males at all, they all reproduce by parthenogenesis, alternating between years when one will play daddy and the next year the other will. Larger members of the teiids don't do this, which when the largest extreme b&w tegu can get to 5ft and 7-8kg is probably no bad thing.
Some monitor lizards in a female only environment will do this too including the Komodo.
As to seeing them, when a small lizard is still they're the very devil to see, and if it's seen you you don't have a hope of catching it. The larger ones like tegu, monitors and crocodilians really don't care much about being seen by humans, try to catch wild monitors or tegu and you're liable to lose fingers. Add autotomy to the mix, the ability to drop and regrow the tail, and it makes it harder. Apparently stage three of a wild tegu getting annoyed is a little tapdance, all I've experienced so far with my pet one is tail slaps, open mouth threat display and a feeding bite (think a dog with a pull toy, then imagine a lizard with as many teeth using your fingers/hand as the new toy, it's as unpleasant as it sounds).
Large wild monitors are interesting, friends have had a full size water monitor (about 6ft) make its way onto the balcony whilst they were stoned and help itself to leftover food on the table, they didn't argue.
Then again I have seen smaller wild ones do a runner, probably because they know they will end up in the cook pot, in fact I suspect I may have eaten one.
Your friends might have been quite lucky, a 6ft water monitor is more than capable of causing serious harm, up to and including crocodilian style death rolls while biting hands, fingers. Any cuts or blood and they can go into feeding mode, and then you'd better be a really fast runner or good at climbing trees. If your friends were in a hotel then the monitor might be more or less tame.. They are very intelligent and soon learn its easier to let the funny two legs give them food than try and eat one. My Tegu loves eggs, salmon, mice and of all things roast chicken from sainsburys.
That's one of the reasons they let it have the left overs, you don't mess around with a lizard that size foolishly, also wild ones mouths are dirty you are looking at a good few antibiotic injections, pretty sure it was a wild monitor it was at their house and its pretty junglish round there, also I would have expected the locals in village areas to have scared them away, or munched on them, there's lots of chickens usually left semi wild around a lot of houses in the countryside anything messing with them tends to have a short lifespan.
However if you go to some of the parks in Bangkok you can see them there wandering through the park and raiding bins during the day. They will walk right past you and ignore you, funnily enough there's no ducks on the park lake.
They're also venomous as are all the Varanids to a greater or lesser extent.. But even Komodo can get so tame one examples favourite game was to be led around by a three year old girl by her hand on it's tail and some have been said to let young kids ride them, although you wouldn't catch me having a child attempt it, either someone's going to get bit, or the lizard will disappear into the distance at 15-20mph with kiddie holding on for dear life. People really don't give reptiles credit for their intelligence and ability to bond with a person, a nervous Tegu will come back to their owner and curl up on their feet or lap, mine has done that. Mine has mapped my flat.. And knows the way back to his nice warm bedroom wherever I put him down.
I thought the Jury was still out on them being venomous but having a look I see maybe not. I can believe that about the Komodo's being tameable apparently crocodillians can be tamed as well. Large herps have some brain space for intelligence, and I can see them being good pets. Just never had room or lifestyle for anything larger than geckos though. :)
definitely seems to know what its background color is, because I've never found them in environments that weren't dark brown, or at least brownish leaves and wood trash. The funny part is they act like they are blind the way they react to stimuli, but then they have an odd defensive act that includes playing "opossum".- they do have eyes, however, and they know how to use them. I got a bite from one that simply made a home in my work boots, then waited until I got to work to bite me. It felt just like a mosquito bite despite the fact that I discovered the whole pack averaged individually larger than a silver dollar in diameter - when measuring their leg extent. There were at least three other individuals in my apartment when I went hunting for them. I found it was better to lay a trap with water in a bottle cap. They have to drink sometime!
That apartment had dark brown rug throughout. When I was a kid, we were constantly trying to rid the farm house of them, because we had dark brown wood flooring. In houses in similar surroundings, we never saw them in evidence when the floor was bright colored. Despite the fact that I have always had a clean house, and even my great aunt - we both had brown floors and would occasionally have to rid ourselves of the pesky critters!