Fluctuating environments hinder the ability of female lizards to choose suitable nest sites for their embryos

Abstract

Nesting behavior is an important part of reproduction that affects maternal fitness. Females of most oviparous species choose microhabitats for nesting that have positive effects on embryo development. However, choosing suitable nest microhabitats could be challenging in environments that fluctuate unpredictably. In many reptiles, females avoid nesting in dry microhabitats because eggs rapidly desiccate. In nature, however, microhabitats with suitable hydric conditions at the time of oviposition may eventually become lethally dry during incubation. We designed an experiment to test whether female lizards (Anolis sagrei) avoid nesting in locations with unpredictable fluctuations in substrate moisture and choose sites with stable moist conditions. We provided captive lizards three nest conditions to choose among: 1) substrate that predictably alternated between suitable and lethal moisture conditions, 2) substrate that fluctuated unpredictably between suitable and lethal conditions, and 3) substrate with moisture levels that remained constant. For the constant choice, some females could choose moist substrate (which is suitable for embryos), and others could choose dry substrate (which rapidly desiccates eggs). Females always nested in substrates that were moist at the time of oviposition, regardless of the level of predictability. Additionally, while constantly dry substrate was avoided, females did not distinguish between predictable and unpredictable options, both of which resulted in 100% egg mortality. These results suggest that nest site choice is based on immediate environmental cues, rather than the level of predictability of future conditions of nest sites, which in turn can have negative consequences when environments fluctuate between suitable and unsuitable conditions.

Significance statement

Fluctuating environments pose challenges to females when seeking suitable locations for laying eggs. Female brown anole lizards choose moist nest conditions that facilitate embryo development. However, because moisture levels of nest substrate can unpredictably change, females that avoid nesting in microhabitats with unpredictable moisture fluctuations may have increased fitness. We tested the ability of females to select sites based on moisture predictability by providing them with options where substrate moisture remained stable, fluctuated predictably, and fluctuated unpredictably. Females did not discriminate among stable and fluctuating substrates. Rather, they always nested in moist substrates that were present at the time of oviposition, even if their nest site eventually fluctuated towards lethally dry conditions. Our results show that extreme fluctuations lead to poor choices of nest sites, which is problematic under global change where fluctuations in ambient conditions are expected to increase.