Abstract
Animal activity patterns evolve as an optimal balance between energy use, energy acquisition, and predation risk, so understanding how animals partition activity relative to extrinsic environmental fluctuations is central to understanding their ecology, biology and physiology. Here we use accelerometry to examine the degree to which activity patterns of an estuarine teleost predator are driven by a series of rhythmic and arrhythmic environmental fluctuations. We implanted free-ranging bream Acanthopagrus australis with acoustic transmitters that measured bi-axial acceleration and pressure (depth), and simultaneously monitored a series of environmental variables (photosynthetically active radiation, tidal height, temperature, turbidity, and lunar phase) for a period of approximately four months. Linear modeling showed an interaction between fish activity, light level and tidal height; with activity rates also negatively correlated with fish depth. These patterns highlight the relatively-complex trade-offs that are required to persist in highly variable environments. This study demonstrates how novel acoustic sensor tags can reveal interactive links between environmental cycles and animal behavior.
Highlights
From a history of biochronological study, we can derive several overarching relationships which are relatively consistent among animals: 1) photoperiodic cycles are the most powerful entraining agent of circadian rhythms; 2) intra- and inter-specific interactions contribute to this behavioral rhythmicity [1]; and, 3) rhythms in behavior are often associated with exogenous processes over other scales [2]
Model results for the evaluation of autocorrelation are presented in Table 2; a first-order auto-regressive correlation structure provided the lowest Akaike’s Information Criterion (AIC) (1772.993), and was selected for further evaluation of the full model
While endogenous rhythms are most-often identified at the diel scale, there are several examples of aquatic animals exhibiting endogenous tidal rhythms, and these can persist in non-tidal environments [48,49]
Summary
From a history of biochronological study, we can derive several overarching relationships which are relatively consistent among animals: 1) photoperiodic cycles are the most powerful entraining agent of circadian rhythms; 2) intra- and inter-specific interactions contribute to this behavioral rhythmicity [1]; and, 3) rhythms in behavior are often associated with exogenous processes over other scales [2]. Inter-specific variation in rhythmicity and interactions with other organisms are tightly linked; playing a fundamental role in shaping the evolution of natural systems [3]. Adaptive foraging strategies and habitat use mediated by diel rhythms can facilitate sympatry by partitioning access to resources [6]. Minimizing predation risk whilst optimizing energetic gain is often achieved by organisms through behaviours linked to exogenous rhythms [7,8]. A common strategy for some fishes involves increased activity related to foraging at night, which facilitates both avoidance of visual predators and increased access to nocturnally active prey [9]. In understanding the links between external influences and behaviour, it is important to concurrently consider multiple entraining sources, and interacting factors that affect an organism’s choice or strategy (e.g. prey quality, predation risk and habitat)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
