Biology subjects

McCormick, M. I.

Publications and source records attributed to McCormick, M. I..

2 recordsLinked to original sources

bioRxiv2025

Evidence of physiological assortment and movement dynamics among social groups of a coral reef fish

The trade-offs of group living are modulated by the phenotypes of individual members of a social group, particularly in dynamic and diverse habitats like coral reefs. Little is known about the patterns of physiological traits among fishes within social groups and the mechanisms that promote these patterns, which could elucidate the drivers of group composition and their downstream ecological and evolutionary impacts. Here, in the gregarious damselfish species Chromic viridis, we examined inter-group differences in whole-animal physiological traits and the tendency for fish to move either within sites (i.e., sections of continuous reef) or among habitats (i.e., reefs separated by sandy substratum) to a new social group. Using oxygen uptake as a proxy for aerobic metabolic rate, we found significant differences in maximum metabolic rate (MMR) and aerobic scope (AS) among schools from different habitats, with these traits higher in habitats with faster water flow rates. However, we found no differences in any metabolic traits (standard metabolic rate, SMR, MMR, AS) between groups from the same site. These trends could stem from a range of mechanisms, as mark-recapture studies of this species indicated a willingness to migrate to a new social group in over 30% of recollected fish. However, there were no effects of either body size or perceived habitat risk on the distance moved or movement type (i.e., over coral or sand). Our results indicate that, in social species, a combination of mechanisms may influence phenotypic differences among groups over different spatial scales.

physiology↗

bioRxiv2023

Kinematic performance declines as group size increases during escape responses in a schooling coral reef fish

Escaping predation is essential for species survival, but prey must effectively match their response to the perceived threat imposed by a predator. For social animals, one mechanism to reduce risk of predation is living in larger group sizes, which dilutes each individuals risk of capture. When a predator attacks, individuals from a range of taxa (e.g., fishes, sharks, amphibians) perform an escape response, to evade the attack. Here, using the schooling coral reef damselfish Chromis viridis, we assess if there is an optimal group size that maximizes both individual escape response performance as well as group cohesion and coordination following a simulated predator attack, comparing schools composed of four, eight, and sixteen fish. We found that fish in various group sizes exhibited no difference in their reaction timing to a simulated predator attack (i.e., escape latency), but larger groups exhibited slower kinematics (i.e., lower average turning rate and shorter distance covered during the escape response), potentially because larger groups perceived the predator attack as less risky due to safety in numbers. Both school cohesion and coordination (as measured through alignment and nearest neighbor distance, respectively) declined in the 100ms after the predators attack. While there was no impact of group size on alignment, larger group sizes exhibited closer nearest neighbor distances at all times. This study highlights that larger group sizes may allow individuals to save energy on costly behavioral responses to avoid predators, potentially through a greater threshold of the threat necessary to trigger a rapid escape response.

animal behavior and cognition↗