Date of Award
Thesis open access
Michele A. Johnson
Kevin D. Livingstone
Thomas J. Sanger
For oviparous ectotherms, embryonic environment can strongly impact post-hatching phenotype. Therefore, it is advantageous for females to choose nesting sites with conditions conducive to offspring development. In lizards that bury their eggs, the substrate temperature of the embryonic environment can have especially significant consequences for development. Abnormalities in craniofacial development and immobile limbs have been linked to high incubation temperatures outside the normal range of developmental temperatures. However, other factors, such as substrate moisture and depth, can impact offspring fitness as well.
To determine the extent to which temperature influences female nesting site choice in relation to substrate moisture and depth, we housed 35 wild-caught female brown anole lizards (Anolis sagrei) in small groups in the laboratory. In each cage, females had the choice of oviposition in one of two “nesting boxes” containing moist substrate: the Heated Box, which was placed over a heating pad controlled by a thermostat, and the Ambient Box, which was maintained in ambient conditions. In both boxes, we measured substrate moisture and depth for each nesting site and calculated the temperature at each location where an egg was laid.
I predicted that the lizards would avoid dangerously warm nesting sites near the base of the Heated Box and that the depth of nesting sites would thus be more variable in the Ambient Box. My findings indicate that females did not exhibit a preference between the Heated and Ambient Box, and on average, nesting sites in the Heated Box were warmer than those in the Ambient Box. The substrate moisture and depth of nesting sites did not differ between the Heated and Ambient Box; however, nesting site depths were more variable in the Heated Box in comparison to the Ambient Box. In both boxes, all oviposition sites were warmer than 26°C and with the exception of one 33.2°C nesting site, all nesting sites were cooler than 31.5°C, indicating that females avoided nesting site temperature conditions likely to result in low fitness offspring Temperature may be an important cue for female nesting sites in many taxa. Yet, the progression of climate change may increasingly pose challenges to oviparous ectotherm species in their current ranges.
Dennis, Abigail J., "Female Nesting Site Choice in Brown Anole (Anolis sagrei) Lizards: Implication for Embryonic and Post-Hatching Development" (2020). Biology Honors Theses. 34.