Poultry Talk Ontario (pto.ca)

Is there a particular reason why some egg membranes are thick/tough? Like when you crack an egg and it doesn't tear the membrane? Is it because of humidity or lack thereof; healthy diet?
Someone asked me this question, so I thought I'd ask here. I didn't find much on the Web.

Not deeply scientific. but I expect a healthy hen producing a healthy egg, and so much fresher than from the store.

Turkey eggs have a heck of a thick membrane likely for prtection in the wild because turkey Mums basically play football with the eggs!