Animal-Borne Imaging Reveals Novel Insights into the Foraging Behaviors and Diel Activity of a Large-Bodied Apex Predator, the American Alligator (Alligator mississippiensis)

Large-bodied, top- and apex predators (e.g., crocodilians, sharks, wolves, killer whales) can exert strong top-down effects within ecological communities through their interactions with prey. Due to inherent difficulties while studying the behavior of these often dangerous predatory species, relatively little is known regarding their feeding behaviors and activity patterns, information that is essential to understanding their role in regulating food web dynamics and ecological processes. Here we use animal-borne imaging systems (Crittercam) to study the foraging behavior and activity patterns of a cryptic, large-bodied predator, the American alligator (Alligator mississippiensis) in two estuaries of coastal Florida, USA. Using retrieved video data we examine the variation in foraging behaviors and activity patterns due to abiotic factors. We found the frequency of prey-attacks (mean = 0.49 prey attacks/hour) as well as the probability of prey-capture success (mean = 0.52 per attack) were significantly affected by time of day. Alligators attempted to capture prey most frequently during the night. Probability of prey-capture success per attack was highest during morning hours and sequentially lower during day, night, and sunset, respectively. Position in the water column also significantly affected prey-capture success, as individuals’ experienced two-fold greater success when attacking prey while submerged. These estimates are the first for wild adult American alligators and one of the few examples for any crocodilian species worldwide. More broadly, these results reveal that our understandings of crocodilian foraging behaviors are biased due to previous studies containing limited observations of cryptic and nocturnal foraging interactions. Our results can be used to inform greater understanding regarding the top-down effects of American alligators in estuarine food webs. Additionally, our results highlight the importance and power of using animal-borne imaging when studying the behavior of elusive large-bodied, apex predators, as it provides critical insights into their trophic and behavioral interactions.体型庞大的顶级与 apex 捕食者（apex predator，例如鳄形目动物、鲨鱼、狼、虎鲸）可通过与猎物的相互作用，在生态群落中产生强烈的下行控制效应。由于此类往往具有危险性的捕食物种的行为研究存在固有难度，学界对其取食行为与活动模式的了解相对匮乏——而此类信息对于理解它们在调控食物网动态与生态过程中所扮演的角色至关重要。本研究借助动物搭载成像系统（Crittercam），于美国佛罗里达州沿海的两处河口生境中，对一种隐蔽性强的大型捕食者——美国短吻鳄（Alligator mississippiensis）的取食行为与活动模式展开研究。本研究利用回收的视频数据，分析了非生物因子对其取食行为与活动模式的影响差异。研究结果显示，猎物攻击频次（均值为0.49次/小时）以及单次攻击的猎物捕获成功率（均值为0.52）均显著受日间时段影响。短吻鳄发起猎物捕获尝试的频次在夜间达到峰值。单次攻击的猎物捕获成功率在晨间最高，日间、夜间与日落时段依次降低。水体垂直位置同样对猎物捕获成功率存在显著影响：短吻鳄在水下发起攻击时，其捕获成功率可达水面攻击时的两倍。此类估算值为全球范围内首份针对野生成年美国短吻鳄的相关数据，同时也是全球少数针对鳄形目物种的此类研究案例之一。从更广泛的视角来看，本研究结果表明，由于过往研究对隐蔽性夜间取食互动的观测较为有限，学界对鳄形目动物取食行为的认知存在偏倚。本研究结果可为学界进一步理解美国短吻鳄在河口食物网中的下行调控效应提供参考依据。此外，本研究结果凸显了借助动物搭载成像系统研究隐蔽性大型顶级捕食者行为的重要性与有效性——该技术可为这类物种的营养级与行为互作研究提供关键洞见。