A proposed mechanism for enhanced water-conservation in egg clutches of the Mexican Kingsnake, Lampropeltis mexicana (Serpentes: Colubridae)

Abstract

Laying eggs on a wet substrate minimizes water stress for flexible-shelled reptile eggs because they absorb water through the permeable shell. This water gain contributes to reduced water-loss in aggregated eggs. This water-conserving feature is demonstrated in eggs of Lampropeltis mexicana in a water-balance experiment investigating both naturally laid clutches and eggs in arranged clusters. Water-loss rates of eggs decrease as more eggs are added to the aggregation, with a threshold at approximately 15 eggs. There is no further reduction in water-loss rate for eggs in an aggregation of 20, which exceeds the typical maximum for natural clutch size in this species. Blowing dry air over the egg clutch causes this water-conserving feature to disappear, but it re-appears when the air is still (air current turned off). This is the first time that an increase in water-vapor pressure in an aggregation of eggs has been demonstrated experimentally; the results suggest that laying aggregations of eggs may benefit development through moisture conservation.