Abstract
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.
Highlights
Large-bodied, apex predators have the potential to shape communities through cascading effects of consumptive and nonconsumptive interactions with lower trophic levels [1]
We use video data collected by Crittercam deployments to study the behavior and diel activity patterns of adult American alligators (Alligator mississippiensis, Daudin 1802) in two Atlantic estuaries in Florida
In four of the deployments video recording ended early due to system malfunctions, early detachment, or camera lenses becoming obstructed by vegetation or substrate; this includes one deployment where no viable data was recovered
Summary
Large-bodied, apex predators have the potential to shape communities through cascading effects of consumptive and nonconsumptive interactions with lower trophic levels [1]. Studies relied on limited data from direct observation [2] and/ or indirect estimates (e.g., allometry and metabolic scaling) to parameterize and inform ecological models (e.g., Ecosim, Ecopath) used to predict the potential impacts these species have on community and ecosystem processes [3], [4], [5]. While these techniques provide accurate estimates of minimum consumption rates necessary to sustain metabolic processes and allow for partial observations of animal behavior, they are limited in determining the frequency of feeding events, as well as the success of capture attempts, and do not allow for assessment of variation in these behaviors. We use video data collected by Crittercam deployments to study the behavior and diel activity patterns of adult American alligators (Alligator mississippiensis, Daudin 1802) in two Atlantic estuaries in Florida
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