Data from: Thermal constraints on microhabitat selection and mating opportunities

Hot tropical environments constrain ectotherm mating opportunities when
mate selection occurs on the surface. Thus, microhabitats and refugia can
become a qualitative trait in mate selection. In fiddler crabs, the
enlarged claw of males can act as a heat sink, which becomes advantageous
when surface temperatures reach 50 °C during the day and crabs are
actively seeking to mate. Uca mjoebergi females prefer male burrows found
in the shade; therefore, we investigated the thermal constraints imposed
on males and females in shaded and unshaded habitats. Crab surface
activity decreased and body temperature increased as the day progressed,
with more crabs active in shaded than sunny microhabitats. Body
temperature was lower in male crabs found in burrows relative to crabs on
the surface. Male claw size explained 10% of body temperature. Our results
add further support to the hypothesis that thermal constraints imposed on
males can be overcome by the large claw acting as a heat sink and the
burrow acting as a refuge from heat. Classic sexually selected traits,
including ornaments and behaviours, can have a secondary purpose in
thermoregulation.