Ecosystems are shaped by complex interactions between species and their environment. However, humans are rapidly changing the environment through increased carbon dioxide (CO 2) emissions, creating global warming and elevated CO 2 levels that affect ecological communities through multiple processes. Understanding community responses to climate change requires examining the consequences of changing behavioral interactions between species, such as those affecting predator and prey. Understanding the underlying sensory process that govern these interactions and how they may be affected by climate change provides a predictive framework, but many studies examine behavioral outcomes only. This review summarizes the current knowledge of global warming and elevated CO 2 impacts on predator-prey interactions with respect to the relevant aspects of sensory ecology, and we discuss the potential consequences of these effects. Our specific questions concern how climate change affects the ability of predators and prey to collect information and how this affects predator-prey interactions. We develop a framework for understanding how warming and elevated CO 2 can alter behavioral interactions by examining how the processes (steps) of sensory cue (or signal) production, transmission and reception may change. This includes both direct effects on cue production and reception resulting from changes in organismal physiology, but also effects on cue transmission resulting from modulation of the physical environment via physical and biotic changes. We suggest that some modalities may be particularly prone to disruption, and that aquatic environments may suffer more serious disruptions as a result of elevated CO 2 and warming that collectively affect all steps of the signaling process. Temperature by itself may primarily operate on aspects of cue generation and transmission, implying that sensory-mediated disruptions in terrestrial environments may be less severe. However, significant biases in the literature in terms of modalities (chemosensation), taxa (fish), and stressors (elevated CO 2) examined currently prevents accurate generalizations. Significant issues such as multimodal compensation and altered transmission or other environmental effects remain largely unaddressed. Future studies should strive to fill these knowledge gaps in order to better understand and predict shifts in predator-prey interactions in a changing climate.

Prey organisms reduce predation risk by altering their behavior, morphology, or life history. Avoiding or deterring predators often incurs costs, such as reductions in growth or fecundity. Prey minimize costs by limiting predator avoidance or deterrence to situations that pose significant risk of injury or death, requiring them to gather information regarding the relative threat potential predators pose. Chemical cues are often used for risk evaluation, and we investigated morphological responses of oysters (Crassostrea virginica) to chemical cues from injured conspecifics, from heterospecifics, and from predatory blue crabs (Callinectes sapidus) reared on different diets. Previous studies found newly settled oysters reacted to crab predators by growing heavier, stronger shells, but that adult oysters did not. We exposed oysters at two size classes (newly settled oyster spat and juveniles~2.0 cm) to predation risk cue treatments including predator or injured prey exudates and to seawater controls. Since both of the size classes tested can be eaten by blue crabs, we hypothesized that both would react to crab exudates by producing heavier, stronger shells. Oyster spat grew heavier shells that required significantly more force to break, an effective measure against predatory crabs, when exposed to chemical exudates from blue crabs as compared to controls. When exposed to chemical cues from injured conspecifics or from injured clams (Mercenaria mercenaria), a sympatric bivalve, shell mass and force were intermediate between predator treatments and controls, indicating that oysters react to injured prey cues but not as strongly as to cues released by predators. Juvenile oysters of~2.0 cm did not significantly alter their shell morphology in any of the treatments. Thus, newly settled oysters can differentiate between predatory threats and adjust their responses accordingly, with the strongest responses being to exudates released by predators, but oysters of 2.0 cm and larger do not react morphologically to predatory threats.

Predators control prey abundance and behavior, both of which strongly influence community dynamics. However, the relative importance of these predator effects may shift with climate change stressors, suggesting understanding the potential effects on these different processes is critical to predicting effects of climate change on community function. We investigated the effects of global warming and ocean acidification on the transmission and detection of chemical cues from blue crab predators (Callinectes sapidus) by mud crab prey (Panopeus herbstii). We measured mud crab feeding rates in the presence of blue crab predator cues, using either predator cues stressed in acidified conditions or mud crabs stressed in warmed and acidified conditions. Mud crabs consumed less food in the presence of predator cues, but acidifying the cues or subjecting mud crabs receiving the cues to acidified environment did not affect this antipredator response. Mud crabs in warmed conditions consumed significantly less food regardless of predator cue, but this effect was reversed in ambient conditions. Therefore, climate change may produce shifts in community regulation as warming potentially compromises consumptive effects of predators by reducing motor function, whereas non-consumptive effects mediated by sensory transmission and detection remain unaffected by acidification. Overall, warming may have stronger effects than acidification on community dynamics in oyster reefs as global temperatures continue to rise.