Eggs and Hatchlings of Captive Dipsosaurus dorsalis

Abstract

A breeding colony of D. dorsalis has been established as part of a study of the temperature and moisture requirements of lizard eggs. The lizards are maintained in cages with a 24-hour photo-thermal period. Mating has been observed in the colony. A summary of clutch size, female snout-vent length and post-laying (3 to 12 hr) body weight are given in a table. Eggs were laid on the surface or in burrows readily observed through the plexiglass cage bottoms. Subsequent sifting of the sand never revealed eggs laid between these extremes. All eggs (N = 40) were found within 1 to 12 hours of laying. The eggs (N = 16) laid in burrows were smooth, translucent white and resilient. The red embryo disc could be observed through the shell. The clutches laid on the sand surface rapidly dehydrated resulting in a yellow, wrinkled and concave appearance. Eggs with sand packed around them from a poorly constructed (eggs partially covered by sand pushed into egg chamber) or collapsed burrow were also yellow and wrinkled but were flaccid instead of firm. Attempts made to rehydrate the eggs laid on the surface (N = 9) and in collapsed burrows (N = 15) were unsuccessful.more » No further attempts to hatch these eggs were made. When a clutch was found, the burrow was carefully excavated and the eggs were transferred without rotation of the minor axis to incubation chambers. An isopiestic technique was used to control the water potential within the incubation chamber. The eggs were incubated at 36.5 C (+-.4) and at water potentials of -0.25, -0.50, -0.75 and -1.00 bar (N = 4 at each water potential used). Of the 16 eggs incubated, one (-0.75 bar treatment) failed to hatch. Incubation time varied from 43 to 45 days (mean 43.4, S.D. 0.74) and does not appear to be correlated with the water potential used. Measurements were taken within 4 hours of hatching. The mean hatchling weight and snout-vent length were 4.62 gm (S.D. 0.52) and 4.74 cm (S.D. 0.12), respectively.« less