The role of individual behavior type in mediating indirect interactions

Abstract

Abstract. Trait-mediated indirect interactions (TMII) play an important role in structuring natural communities, and numerous studies have experimentally demonstrated their presence in a variety of systems. However, these studies have largely examined the presence or absence of traits that are responsible for these interactions, without considering natural variation between individuals in the extent to which these traits are manifested. We used a well-documented TMII to investigate the importance of individual behavior type for determining the strength of the TMII. The toadfish Opsanus tau has an indirect positive influence on bivalve survival because the mud crab Panopeus herbstii, a consumer of bivalves, reduces foraging effort in the presence of toadfish. We quantified variation in the strength of persistent individual mud crab responses to toadfish and resulting variation in the strength of TMII. We demonstrate that the strength of this TMII is strongly influenced by mud crab size and behavior type, strengthening with the intensity of response of individual mud crabs to toadfish predator cues. Further, we demonstrate that the spatial distribution within intertidal oyster reefs of crabs with different behavior types is not random; mud crabs inhabiting subtidal areas, where predator cues are more persistent, are significantly less responsive to toadfish cues than mud crabs from intertidal areas. This spatial behavioral structure should lead to spatial variation in the strength of TMII. Given the widespread importance of TMII and the broad occurrence of individual personality or behavior types across numerous taxa, these results should be generally applicable. The distribution of behavior types within a population may therefore be a useful metric for improving our ability to predict the strength of TMII.

Predator–prey interactions mediated by prey personality and predator hunting mode

“…Numerous studies have documented mud crabs seeking refuge within oysters in response to toadfish ( [19,20,44,54]; our behavioural data). Although the predator avoidance behaviour is not as strong as with blue crabs, our rspb.royalsocietypublishing.org Proc.…”

“…Although mud crab refuge use and mortality were measured during two separate experiments, our previous research has determined that relative refuge use between individuals should remain consistent across these experiments ( [20,44], B. A. Belgrad 2015, unpublished data).…”

“…34% of diet consists of other crabs; [41]), toadfish are ambush predators which feed predominantly on mud crabs (77% of diet in South Carolina; [42]). In turn, mud crabs strongly reduce their activity levels and increase their time in refuge in response to different predators [43], and exhibit a bold-shy continuum of personality types [20,44]. Thus, ecological theory predicts that mud crabs should have an elevated predator avoidance response and higher predation risk in the presence of toadfish than blue crabs [34,35].…”

“…These behavioural changes also have an enormous impact on the natural community. Shifts in the distribution of prey to avoid predators can alter competitive interactions between different prey species [18], whereas reduced foraging by prey in response to predation risk can reverberate across trophic levels [19,20].…”

Indirect effects of invasive species affecting the population structure of an ecosystem engineer

“…However, a few studies showed that strength of TMIIs within populations varies according to individual behavior (Griffen et al 2012) and body size (Rudolf 2006, 2008, 2012, Preisser and Orrock 2012, Krenek and Rudolf 2014. Body size often represents the state of ontogenetic development of individuals (de Roos and Persson 2013) and is affected by changes in resource and habitat use.…”