Do female collared lizards change field use of maximal sprint speed capacity when gravid?

Locomotor ability is well-documented to decrease in gravid female lizards. However, no studies have examined what proportion of maximal sprint speed capacity gravid females use in nature or how a reduction in maximal capacity translates to changes in sprint speeds used in nature. Gravid females may compensate for reduced locomotor ability by increasing the proportion of their maximal capacity used in nature, or by changing their antipredator behaviour. I measured maximal sprint speed in the laboratory for female collared lizards (Crotaphytus collaris) while gravid and nongravid and then compared those to speeds used in the field while foraging and escaping predators, and also while gravid and nongravid. Females had significantly lower maximal sprint speed capacity while gravid, and they ran slower while foraging and escaping predators. However, gravid females did not increase the proportion of maximal capacity used in those contexts compared to when not gravid. Gravid females compensated for reduced locomotor capacity by staying closer to refugia but not by remaining more cryptic. These results suggest that the costs of reduced locomotor capacity may not be associated with direct costs while foraging or escaping predators, but instead with potential indirect effects associated with the change in antipredator behaviour.