This is just an annecdote.
Take it for what it is worth...
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In the '80s I incubated my first Mexican Milk snakes and my first batches of Grey-band Kings.
I incubated them in the same plastic containers as NA rat snakes with a damp medium varying from shredded newspaper to sphagnum, to vermiculite, with all eggs half buried.
Never a problem with the Rats.
Temps were in the mid 80s.
Both the annulatas and the alternas had the same problem: about 4 out of 5 babies were stillborn and fully developed. Over the course of 3 or 4 years, I tried more humidity, less humidity, lower temp (82F- was a little help)…, split the cltches up, etc.
I thought about the wild clutches I had found over the years of Pits, rats, one king, and several Ring-necked and realized they were usually piled into cavities, not buried in the medium, and thriving on the air humidity.
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I switched to keeping the eggs on top of the medium, not half buried, and had 100% hatches of both kings.
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Since then I switched to perlite, 50/50 perlite to water (by weight) and sit all eggs on the surface, not half buried, and temps averaging about 79F.… result: 100% hatch of every fertile egg, regardless of species.
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A friend on the Grey-band forum also suggested laying a damp paper towel on top of the cluth when the eggs indent to pip. This seems to soften the top of the eggs.
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I always wondered if it was thicker shells, shells that needed softening, or, since the eggs breath, the hatchlings at the end of incubation needing much more oxygen through the shell than freshly laid eggs, with different genera at different temps.
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Just food for thought.
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Regards, Bill McGighan

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