I was just wondering if egg-laying animals feel pain when laying eggs? Comparable to giving live birth? Obviously, the question of whether or not animals feel pain is still, to some extent, under debate, because we can't ask an animal how it's feeling, but have there been any studies or reports that show whether birds (and other egg-laying animals) likely feel pain or not when egg-laying?

Also, I know there are other animals that lay eggs (snakes, frogs, platypuses...), but I decided to post the question here because A) Birds consistently lay eggs, whereas some reptiles and fish (and most mammals) give live birth, and B) I figured, since birds are a little more common as pets, and chickens in particular are used extensively in the egg industry. Of course, I'm interested to know whether laying eggs is likely painful or not for all egg-laying animals, or just some, or none. :)

Thank you for your consideration!

Great question!

For most animals other than primates (which includes humans) birth has evolved to be speedy and as stress-free (physiologically) as possible. For primates where the need to give birth to off-spring with very much larger heads/brains means that (a) the baby is much more juvenile (smaller) and the actual birth is longer and more painful to allow the pelvis to slowly accommodate (as the ligaments stretch) the very large head and then deliver it.

Having asked one of the experts at University of Bristol, their response is:

I think it's a really interesting question that we don't know the answer to - and would be very difficult to answer because behavioural signs of pain are so difficult to recognise in hens. I don't worry so much about the normal sized eggs but the super sized ones that are getting laid often have blood on the shell - and that makes me think that laying them is painful because it's probably associated with damage to the tissues.

But surely it must be painful for the kiwi?