Scale-Dependent Habitat Selection and Size-Based Dominance in Adult Male American Alligators

Habitat selection is an active behavioral process that may vary across spatial and temporal scales. Animals choose an area of primary utilization (i.e., home range) then make decisions focused on resource needs within patches. Dominance may affect the spatial distribution of conspecifics and concomitant habitat selection. Size-dependent social dominance hierarchies have been documented in captive alligators, but evidence is lacking from wild populations. We studied habitat selection for adult male American alligators (Alligator mississippiensis; n = 17) on the Pearl River in central Mississippi, USA, to test whether habitat selection was scale-dependent and individual resource selectivity was a function of conspecific body size. We used K-select analysis to quantify selection at the home range scale and patches within the home range to determine selection congruency and important habitat variables. In addition, we used linear models to determine if body size was related to selection patterns and strengths. Our results indicated habitat selection of adult male alligators was a scale-dependent process. Alligators demonstrated greater overall selection for habitat variables at the patch level and less at the home range level, suggesting resources may not be limited when selecting a home range for animals in our study area. Further, diurnal habitat selection patterns may depend on thermoregulatory needs. There was no relationship between resource selection or home range size and body size, suggesting size-dependent dominance hierarchies may not have influenced alligator resource selection or space use in our sample. Though apparent habitat suitability and low alligator density did not manifest in an observed dominance hierarchy, we hypothesize that a change in either could increase intraspecific interactions, facilitating a dominance hierarchy. Due to the broad and diverse ecological roles of alligators, understanding the factors that influence their social dominance and space use can provide great insight into their functional role in the ecosystem.生境选择是一类主动的行为过程，其模式会随空间与时间尺度产生差异。动物会先选定核心利用区域（即家域（home range）），随后在斑块尺度内基于资源需求做出进一步的生境选择决策。社会支配地位可能会影响同种个体的空间分布格局，并伴随影响生境选择行为。 目前已有研究记录了圈养短吻鳄中存在体型依赖型社会支配等级，但野生种群中的相关证据仍较为匮乏。 本研究以美国密西西比州中部珍珠河沿岸的17尾成年雄性美国短吻鳄（Alligator mississippiensis；n=17）为研究对象，旨在验证两项科学问题：其一，生境选择是否存在尺度依赖性；其二，个体的资源选择偏好是否随同种个体体型大小而变化。本研究采用K选择分析（K-select analysis）量化家域尺度以及家域内斑块尺度的生境选择强度，以此明确生境选择的一致性及关键生境因子；此外，通过线性模型分析体型大小与生境选择模式及选择强度的相关性。 研究结果显示，成年雄性美国短吻鳄的生境选择具有显著的尺度依赖性。相较于家域尺度，短吻鳄在斑块尺度上对各类生境因子的整体选择强度更高，这表明本研究区域内的短吻鳄在选定家域时，所需资源并未受到限制。此外，日间生境选择模式可能受到体温调节需求的调控。 本研究未发现资源选择、家域面积与体型大小之间存在显著相关性，这说明在本次研究样本中，体型依赖型社会支配等级并未对短吻鳄的资源选择或空间利用行为产生影响。 尽管本研究未观察到明显的社会支配等级，这可能与研究区域生境适宜性较高、短吻鳄种群密度较低有关；据此我们提出假说：若上述任一条件发生改变，种群内种内相互作用将会增强，进而促进社会支配等级的形成。 鉴于短吻鳄在生态系统中承担着广泛且多样的生态功能，解析影响其社会支配地位与空间利用行为的关键因子，将有助于深入理解其在生态系统中的功能角色。