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Author Topic: Why Can't Certain Animals Right Themselves When Flipped On Their Backs ?  (Read 6548 times)

Offline neilep

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Beetles,Bugs, Crabs, Turtles.........all have great difficulty if they are flipped on their backs !

Why hasn't Nature fixed it for them so that this is easily remedied ?...Is it an evolutionary faux-pas ?...or not ?




 

Offline SquarishTriangle

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The first thought that comes to mind is that perhaps the occurrence of being upturned is not great enough to be a strong selective pressure for a particular species. But then supposedly, it would be fairly easy for a beetle to be flipped over during its everyday activities, and leave it in a vulnerable position. Would it perhaps be equally easy to flip it back up the other way?

I have a vague recollection of a documentary where a predator (probably a bird) would actually flip their prey over as a means of preventing a quick escape, and give itself a little extra time to enjoy its meal.

So let’s pretend I’m a six-legged creature with a big curved shell on my back, and I’ve just fallen off a pile of dung and landed on my back (totally realistic, I know). To get myself out of the situation, I might first try to wriggle my legs frantically about in the air and hope that it might turn me back over. After some time I might (hopefully) realise that wriggling a certain way starts to wobble me a little from side to side. If I then try to coordinate my movements in such a way that provides a little more wobble, I could just be on my way to finding my feet again.

Anyway, here’s a recent snippet from the AAAS website, at http://sciencenow.sciencemag.org/science-shots/index.dtl?page=102007:

Rollover.


A turtle on its back is an easy meal. Species with strong necks can right themselves with little trouble, but not all turtles have this ability. That's where shell shape comes in handy. According to a study published online 16 October in the Proceedings of the Royal Society B: Biological Sciences, turtles with high-domed shells can roll back onto their stomachs almost instantaneously. The secret? These shells have only one stable position, making it hard for turtles to balance on their backs. Turtles with weak necks and more stable shells would do best to flip on tilted terrain or near a rock they can use for leverage, lest they become bird bait. (Photo: Timea Szabo)
 

Offline neilep

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Thank you very much for this wonderful post in response to mine SquarishTrinagle. I also am grateful for the  snipppet and link you have provided.

I do think that the occurrence would happen enough times for evolution to have picked up on it and sorted it out by now......but.......who am I to know how things evolve......?   Though we understand the concept of evolution I imagine it's an incredibly complicated set of variables that lead to the paths it goes.

Do you think a crab or a turtle have the cognitive ability to recognize that a particular way of struggling is going to set them right ?...If so...then evolution would have allowed for an immediate instinctive technique that would fix the problem almost immediately...rather than have them finally see their way out hours later !...In My opinion anyway.

THANK YOU so much again for your great post.
 

Offline SquarishTriangle

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Though we understand the concept of evolution I imagine it's an incredibly complicated set of variables that lead to the paths it goes.

I tend to agree with you there for the most part. Although the 'survival of the fittest' concept works well in theory and is a good overview of the process of evolution, in reality there is often also room for 'duds' to pass the trials of life and reproduce successfully. For example, a particular animal may not, despite millions of years of evolution, actually be optimally designed for its lifestyle (ie. have the set of characteristics that would best equip it for its needs with minimal costs, energetic or otherwise.) However, be it 'luck' or whatever you want to call it, that animal may get by just as well. As long as it can somehow survive long enough to reproduce, it has a chance to see its genes into the next generation.

Trying to put it another way, there's no single answer to surviving and being successful as an individual. You just need a combination of traits that will get you through the variety of circumstances that life will throw at you.

I suspect the investment into a greater number of offspring by some of those animals you mentioned could just provide them with that greater margin for error they need to 'cheat' selection.

Ok, sidetrack...Some time ago I found a house sparrow that had somehow found itself lying on its back with its wings stretched out, and rocking a little from side to side. Other than that, there didn't seem to be anything obviously wrong with it. So then I decided to poke it (yes, poke...give me a break, I was 11 :P) from the side, just enough for it to get up and fly off!

I have no idea about the cognitive abilities or either crab nor turtle, and I couldn't even begin to speculate. :P

Final thought of the post (I hope). If, say, the beetle was to be redesigned with a dome shape for a back to make it easier for the beetle wobble itself upright, that would presumably hinder on its ability to fly. From that perspective, it would seem a reasonable trade-off to opt for a body shape for efficient flight (to get from place to place, escape predators etc.) at the risk of ending up in an awkward position, no?
« Last Edit: 12/01/2008 07:36:28 by SquarishTriangle »
 

Offline JimBob

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Neil, if you wouldn't drink so much you could get up after you fall down drunk.
 

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