Thermal and desiccation constraints drive territory preference in fiddler crabs

Territory quality is often critical for reproductive success, survival and ultimately fitness. Holding a good quality territory can make a male more attractive to females but can also have several other advantages. It can decrease the effects of environmental stressors, for example, by reducing the need for behavioural thermoregulation or decreasing the risk of predation. We found that, in the fiddler crab Austruca mjoebergi, male territories differed in the shaded mangrove and unshaded open areas of the habitat. The lower temperatures and wetter sediments of the mangrove areas resulted in lower desiccation rates allowing males to spend longer periods of time on the surface than they did in the sun-exposed open areas. Males lived at higher densities in the mangrove areas, and preferentially selected shaded territories when given a choice. Male fights to attain/retain territories in the mangrove areas were longer than those in the open areas. Because females do not preferentially mate with males with territories in shaded mangrove habitats, the advantages to males in maintaining these territories is likely a reduction in thermal and/or desiccation stress.