Chimneys of the fiddler crab Uca rosea (Tweedie, 1937) reduce the risk of losing burrows to intruders

Abstract

In this study we determined the benefits of building chimneys in Uca rosea (Tweedie, 1937). We predicted that (1) burrows with chimneys (i.e., “chimneys”) would decrease intruder intrusion rates relative to burrows without chimneys (i.e., “burrows”), (2) intruders would take longer to locate and enter chimneys than burrows, (3) chimney owners would rebuild their chimneys the next day, and (4) females would build higher chimneys than males. We observed that intruders entered burrows more often than chimneys, and took longer time to locate and enter chimneys than burrows. More than 60% of the chimney owners rebuilt chimneys the following day. Crab carapace width was positively correlated with burrow diameter, and chimney diameter, height and width. Females built higher chimneys than males. This study shows that chimneys provide benefits to both sexes by reducing intruder intrusion rates, and by prolonging the intrusion time in burrows, especially in those built by females.