Marine subsidies change short-term foraging activity and habitat utilization of terrestrial lizards.

Heather V. Kenny,Amber N. Wright,Jonah Piovia‐Scott,Thomas W. Schoener,David A. Spiller,Louie H. Yang

doi:10.1002/ece3.3560

Abstract

Resource pulses are brief periods of unusually high resource abundance. While population and community responses to resource pulses have been relatively well studied, how individual consumers respond to resource pulses has received less attention. Local consumers are often the first to respond to a resource pulse, and the form and timing of individual responses may influence how the effects of the pulse are transmitted throughout the community. Previous studies in Bahamian food webs have shown that detritivores associated with pulses of seaweed wrack provide an alternative prey source for lizards. When seaweed is abundant, lizards (Anolis sagrei) shift to consuming more marine‐derived prey and increase in density, which has important consequences for other components of the food web. We hypothesized that the diet shift requires individuals to alter their habitat use and foraging activity and that such responses may happen very rapidly. In this study, we used recorded video observations to investigate the immediate responses of lizards to an experimental seaweed pulse. We added seaweed to five treatment plots for comparison with five control plots. Immediately after seaweed addition, lizards decreased average perch height and increased movement rate, but these effects persisted for only 2 days. To explore the short‐term nature of the response, we used our field data to parametrize heuristic Markov chain models of perch height as a function of foraging state. These models suggest a “Synchronized‐satiation Hypothesis,” whereby lizards respond synchronously and feed quickly to satiation in the presence of a subsidy (causing an initial decrease in average perch height) and then return to the relative safety of higher perches. We suggest that the immediate responses of individual consumers to resource pulse events can provide insight into the mechanisms by which these consumers ultimately influence community‐level processes.

Highlights

The ways in which consumers cope with spatial and temporal variation in resource availability have implications for ecological dynamics at the population, community, and ecosystem levels
Lizards in treatment plots used lower average perch heights immediately after the initiation of the subsidy, a change in habitat-use behavior that may allow these consumers to better capitalize on the pulsed food resource
Lizards showed increased movement rates immediately after the subsidy, which suggests that a change in time allocation to different behaviors accompanied the change in perch use

Summary

| INTRODUCTION

The ways in which consumers cope with spatial and temporal variation in resource availability have implications for ecological dynamics at the population, community, and ecosystem levels. Under this conceptual model, the timing and duration of the pulse determine which responses are most likely. We predicted that lizards would decrease their perch height and increase their attack rate as they shifted to more actively foraging for abundant prey in seaweed deposits on the ground. We used field data from this study to parameterize a heuristic model linking lizard activity and perch height in order to examine how pulsed resources could influence the habitat use of lizards by synchronizing foraging behavior and satiation responses

| MATERIALS AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST