Owner Advantage in the fiddler crab, Uca mjoebergi. Are owners more motivated than floaters in response to high quality territories?

Resource owners generally win contests against intruders, a phenomenon referred to as the 'Owner Advantage' (OA). Uca mjoebergi is a typical fiddler crab that is highly sociable, territorial and lives in mixed sex colonies on intertidal mudflats. Burrows are used in territory defence, for mating, and as refuge from predators and environmental stresses. Fights are common between owners and floating males who battle for ownership of the territory and burrow. \n\nExperiments were conducted from 28th Sept - 30 Dec 2006 at the lower reaches of Ludmilla Creek within East Point Reserve, 5km North of Darwin, NT. Previous experiments have revealed that owners win more contests than floaters because they are more motivated. This experiment was designed to test if owners are more motivated than floaters in response to high quality territories.\n\nThe results revealed that owners won more contests in 'high quality' territories than in 'natural' territories but this difference was not significant. Although owners win more contests in 'High quality' territories, the lack of significance may indicate only a small asymmetry between owners and floaters. It is possible that owners and floaters have similar abilities to perceive the food availability and be similar in motivational level.

资源持有者通常会在与入侵者的争斗中获胜，这一现象被称为“所有者优势（Owner Advantage，OA）”。莫氏招潮蟹（Uca mjoebergi）是典型的招潮蟹（fiddler crab）类群，具备高度群居性与领地意识，栖息于潮间带泥滩的两性混合种群中。洞穴可用于领地防御、交配，以及作为躲避捕食者与环境胁迫的庇护所。领地所有者与游荡雄蟹之间的争斗十分常见，二者会为争夺领地与洞穴的所有权展开搏斗。

本实验于2006年9月28日至12月30日期间，在北领地（NT）达尔文市以北5公里处的东点保护区（East Point Reserve）内拉德米勒溪（Ludmilla Creek）下游河段开展。此前的研究表明，领地所有者比游荡雄蟹赢得更多争斗，原因在于前者的争斗动机更强。本实验旨在验证：当面对高质量领地时，领地所有者是否仍比游荡雄蟹具有更强的争斗动机。

实验结果显示，领地所有者在“高质量”领地中赢得的争斗次数多于“自然”领地中的情况，但该差异未达到统计学显著性。尽管领地所有者在“高质量”领地中获胜次数更多，但显著性缺失或许仅表明，领地所有者与游荡雄蟹之间的实力不对称程度较低。二者或许具备相似的食物可获得性感知能力，且争斗动机水平相当。