Pulsed seaweed subsidies change short-term foraging and habitat use behaviors in the lizard Anolis sagrei

Background/Question/Methods

Resource pulses are infrequent, high magnitude and ephemeral increases in resource availability, and pulsed subsidies are resource pulses that cross habitat boundaries. Recently, there has been increasing interest in understanding how resource pulses and pulsed subsidies affect community dynamics. While many studies have investigated population-level responses to pulsed subsidies, fewer studies have looked at how shifts in consumer behavior drive these responses.This paper seeks to investigate the short-term behavioral responses of the brown anole (Anolis sagrei) to experimental seaweed subsidies, focusing on changes in their habitat use and foraging behavior. This study was conducted in five pairs of 5m by 10m shoreline plots on islands in the Bahamas. One plot in each pair was randomly selected for seaweed addition while the other served as an unsubsidized control. Subsidized plots received seaweed subsidies consistent with the amount deposited during natural seaweed deposition events. Eighty-seven lizards were observed and video recorded for up to 20 minutes. For each observation, we measured mean perch height, number of moves, number of bites, and horizontal distance from seaweed (in seaweed addition plots). We used linear mixed models to compare behaviors between control and treatment plots as a function of time since seaweed addition.

Results/Conclusions

Following seaweed addition, average perch height decreased and number of moves increased in seaweed addition plots with respect to control plots. Lizards also used lower perch sites when they were closer to the seaweed deposits. The changes in both perch height and movement rate were greatest immediately after seaweed deposition and became less pronounced within 48 h. Previous studies have shown that seaweed deposition increases the consumption of marine prey items by A. sagrei, with subsequent increases in population density and individual growth rate. The results of this current study provide evidence supporting the role of short-term behavioral responses as one possible mechanism underlying these patterns. Additionally, the short-term focus of this study reveals that initial behavioral responses to seaweed addition are rapid and ephemeral, and therefore may only be discernible with high temporal resolution. The data also suggest that adult lizards had more pronounced behavioral responses to seaweed addition than juveniles, but sample sizes were not large enough to confirm this trend. This study documents rapid and pronounced behavioral shifts by consumers in response to pulsed resource subsidies. Future research will investigate how these behavioral shifts are translated into population and community level responses.