Habitat quality mediates personality through differences in social context

Abstract

Assessing the stability of animal personalities has become a major goal of behavioral ecologists. Most personality studies have utilized solitary individuals, but little is known on the extent that individuals retain their personality across ecologically relevant group settings. We conducted a field survey which determined that mud crabs, Panopeus herbstii, remain scattered as isolated individuals on degraded oyster reefs while high quality reefs can sustain high crab densities (>10 m). We examined the impact of these differences in social context on personality by quantifying the boldness of the same individual crabs when in isolation and in natural cohorts. Crabs were also exposed to either a treatment of predator cues or a control of no cue throughout the experiment to assess the strength of this behavioral reaction norm. Crabs were significantly bolder when in groups than as solitary individuals with predator cue treatments exhibiting severally reduced crab activity levels in comparison to corresponding treatments with no predator cues. Behavioral plasticity depended on the individual and was strongest in the presence of predator cues. While bold crabs largely maintained their personality in isolation and group settings, shy crabs would become substantially bolder when among conspecifics. These results imply that the shifts in crab boldness were a response to changes in perceived predation risk, and provide a mechanism for explaining variation in behavioral plasticity. Such findings suggest that habitat degradation may produce subpopulations with different behavioral patterns because of differing social interactions between individual animals.

Personality interacts with habitat quality to govern individual mortality and dispersal patterns

“…An observation seen previously in this system (Toscano et al., ), but which had not been tested across different quality habitats. Although crabs transplanted to different quality reefs may have altered their behavior and consequently their predation risk/dispersal propensity, previous personality studies in this system which span different environmental contexts (e.g., predation risk and conspecific density) found that relative behavioral differences between individuals remain similar when crabs shift their behavior to match environmental circumstances (Belgrad & Griffen, ; Griffen et al., ). In fact, the behavioral changes observed in transplanted crabs suggest that these differences in community interactions may be magnified by habitat degradation and dispersal as bold individuals that migrate to high‐quality reefs should become bolder, while crabs that find themselves on degraded, low‐quality reefs should either migrate or become shyer.…”

“…Previous work in this system has established that individual P. herbstii exhibit just such persistent personality differences. Specifically, differences in activity level and in refuge use between individuals on the same reef, reflecting personality, can last for months (Toscano et al., ) and are consistent across a range of different conditions, including predator presence/absence (Griffen et al., ), conspecific density changes (Belgrad & Griffen, ), and starvation levels (B. A. Belgrad 2015, unpublished data).…”

“…We conducted a caging experiment to test the effect of personality and habitat quality on individual mortality. Bolder individuals frequently forego refuge in the presence of predators (e.g., Belgrad & Griffen, ) so individuals exhibiting bold behaviors likely will experience higher mortality than shy individuals. However, differences in mortality may decrease with decreasing habitat quality as refuges become scarce in low‐quality habitat and shyer individuals become preyed upon.…”

Boldness related to size in the hermit crab Coenobita compressus at undisturbed, but not disturbed beach

“…(). We selected crabs as they were “wandering” the beach, rather than targeting aggregations, because this social context could alter crabs’ response (Belgrad & Griffen, ). For the same reason, they were tested away from other crabs (no crab was allowed within 2 meters of the focal individual).…”

“…Crabs were tested four times for startle time (the time taken for the crab to emerge from the shell after being tapped) following some of the methods provided in and Watanabe et al (2012). We selected crabs as they were "wandering" the beach, rather than targeting aggregations, because this social context could alter crabs' response (Belgrad & Griffen, 2017). For the same reason, they were tested away from other crabs (no crab was allowed within 2 meters of the focal individual).…”