Evolutionary Biology: closed eyes at birth

[dash_zero]

I think i may have heard it somewhere that the only (or majority?) animals that are born with their eyes closed (e.g. kittens, mice) are those that come in litters, and also, that this is thought to have come about due to the favourbility for mothers who have a large number of young at once, and the offspring m not having visual stimulii which may result in them crawling off etc. Can anyone verify whether this is an accepted theory?

[B00]

I've just thought of a reason why their eyes maybe be closed at birth (not that i'm saying you're wrong mind!). If it is only litters of a species which have their eyes closed- could it have anything to do with the fact they move around in the womb and eyes could be scratched/damaged?

Or am I talking utter twaddle as usual?

[Clanad]

Not twaddle, Boo, just inexplicable since Hares are born fully furred and with their eyes open while rabbits are naked and blind at birth, though both are born in fairly large numbers in each's litter...

[B00]

Oh :-(

Here's me thinking I was onto something there Clanad

[trevHCS]

You're very close with the idea that it's related to litters, but it's not related to scratching, or at least that's not a major issue as most mammals are born with soft claws (if applicable) I guess to prevent damage to their neighbours and the mother.

Eyes only open at a certain stage of brain development, and how fast your brain develops depends heavily on how long you've had to grow before being kicked out.

Taking a dog as the first example. Puppies tend to come in large numbers so pregnancy can't last too long due to space issues, but it's going to be very well protected by the mother and the pack so it can be born underdeveloped.

Now if you take a wilderbeast - there's to my knowledge usually only one (maybe two) born, therefore there's room to grow. Also it needs to be up and running pretty darn quick otherwise it's breakfast for a lion, so needs a fully developed brain & sight.

OK, people might seem to break this rule, but in reality although our eyes are open, the vision is pretty hopeless for the first month or so. It's just that we were in there long enough to develop our brains to allow sight. This can be shown if you look at premature babies as they often have their eyes tightly shut.

So in essence it's down to what evolution thought was the best policy given the circumstances.

Why hares have their eyes open - erm, yes. :-) I don't know a huge amount about the biology of the hare, but since it's fully fured I'm guessing they might need or some relative of theirs has needed to be up and running quicker than average.

[wildwood]

It is more a matter of the nature of the 'nest' that young mammals are born in. A rabbit makes a lined cosy nest under ground well away from predators so the young can be born at an early stage and develop gradially.
An young hare (leveret) is born is a mere scrape in a meadow so needs to be mobile from an very early age or it won't stand a chance, so the young are retained in the womb for as long a time as practical.

The marsupials go to the extreme and have young in a very premature stage, the neonates not even having vestigal eyes, evenso, they crawl from the vagina into the pouch - at least with the macropus - a phenomenal distance for such as small thing which is still basically an embryo.

[artytype]

I watched that programme Animals in the Womb over Christmas. One of the animals features was a labrador , we were told by the presenter that the pup that we were watching had it's eyes closed to protect them from the urine that it and it's siblings pass whilst in the womb.Makes sense to me.