Preliminary Experiments on Physical Tolerances of Eggs of Lizards and Snakes
1967
Fitch, Henry S. | Fitch, Alice V.
In lizards and snakes the egg is a vulnerable stage in the life cycle with limitations that must often restrict geographic range or local occurrence of a species. Eggs of the rat snake, racer, ring—necked snake, Great Plains skink and five—linked skink were exposed in mixed groups to various controlled conditions of temperature and humidity to determine some of the differences between species in their ranges of tolerance. In atmospheres of 60 to 90% relative humidity eggs of all kinds tested lost water rapidly over periods of days and were short—lived. Mold contributed to mortality. At higher humidities survival was prolonged. At 97.5% relative humidity eggs dehydrated slowly but sometimes survived for several weeks and produced normal hatchlings. The small, thin—shelled eggs of ring—necked snakes deteriorated much more rapidly than eggs of the other species tested, and those of the racer were most resistant. In incubation media of decaying wood, loamy humans, crushed limestone and sand, with water content of 2 to 68%, eggs of all kinds tested gained weight by absorption of moisture and most eventually hatched. Gains in weight were gradual and were not proportional to the moisture content of the medium. For all species tested the eggs were eury—thermal with limits of tolerance near 41@?C and lower limits near the freezing point, but there were minor differences between species, and for the ring—necked snake the range of tolerance was several degrees narrower that it was for the skinks. For the egg, temperature is much less limiting than moisture.
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