Ever since I started breeding snakes, I was always told by those much wiser than I that if my eggs rolled over, the snakes inside would surely die. The reason for this disaster sounded practical enough. It was either the young embryos would be crushed beneath the weight of the fluid in the egg, or eventually the young would somehow suffocate beneath this mass. Being the cautious young breeder that I was, I always followed this advice, carefully placing X’s on the top of each egg and making sure that each egg stayed in it’s original position. As the years went by and I occasionally turned over an egg here and there by accident, I noticed that this either may not be entirely true, or I had some pretty resilient snakes because they never seemed to show any negative effects.
Recently, I acquired a gravid Black Ratsnake (Elaphe obsoleta obsoleta) on a white bag run, and decided to put this train of thought to the test. I kept her for a week and she laid six good looking eggs. I let her rest a few days, fed her, and released her back into the wild.
The eggs were laid in a nest box of moist towels on July 15th. I carefully removed all six eggs and placed a small “X” on the top of each so I would know which side was laid face up and numbered each one. I then placed them in a ventilated plastic shoe box with a moist towel underneath and over them and let them sit for one week. On July 23, I turned eggs numbers one and two 180 degrees so the ‘X’ was now face down.
Eggs three and four I turned 90 degrees, so the ‘X’ was on the side. Eggs five and six I left alone as a control. I let them sit this way for approximately two weeks. On August 1st, I turned eggs three and four another ninety degrees so the “X” was now face down like eggs one and two. On August 14th, I turned eggs one and two another 180 degrees, so now the ‘X’ was facing upright again after spending a month upside down. On September 26th, after 73 days incubating at room temperature (76F - 80F), all six eggs hatched and all young have been feeding on frozen thawed pinks after their first shed.
They all appear outwardly healthy and have good appetites. If the results of this experiment prove true for all snakes, then in conclusion, it would seem that egg rolling by itself has no bearing on neonate mortality.
Article compliments of the author and The Greater Cincinnati Herpetological Society
The effects of turning snake eggs during incubation has been studied in a few species of reptiles and the effects are largely dependant on the species (Deeming). Studies on turning Cornsnake, Pantherophis guttatus and Ball Python, Python regius eggs during incubation found they were unaffected by turning (Marcelleni & Davies 1982). As were the eggs of Leopard Geckos, Euplepharis macularius & Garden Fence lizards, Calotes versicolor. Eggs from the turtle Chelydra sepentina which were inverted on day 40, went on to pip upside down. Another interesting ditty, was the fact that turning the eggs of the Turtle, Chelydra scripta actually shortened the incubation period by 4 days. In contrast the eggs of the Lizard species Dipsosauraus dorsalis are quite suspectable to turning as are a lot of Crocodillian & Chelonian sp, especially in the first half of incubation, but not so in the initial 12 hours after they have been laid. - Sue Knight
Marcellini D.L. & Davies S.W. 1982. The effects of handling on reptile egg hatching. Herpetological Review, 13, 43-44
Deeming D.C. Reasons for the dichotomy in egg turning in birds and reptiles. Chapter 19. Egg Incubation. Denis C. Deeming & Mark W.J Ferguson. Cambridge University press.