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Nonlethal injury is a pervasive stress on individual animals that can affect large portions of a population at any given time. Yet most studies examine snapshots of injury at a single place and time, making the implicit assumption that the impacts of nonlethal injury are constant. We sampled Asian shore crabs Hemigrapsus sanguineus throughout their invasive North American range and from the spring through fall of 2020. We then documented the prevalence of limb loss over this space and time. We further examined the impacts of limb loss and limb regeneration on food consumption, growth, reproduction, and energy storage. We show that injury differed substantially across sites and was most common towards the southern part of their invaded range on the East Coast of North America. Injury also varied idiosyncratically across sites and through time. It also had strong impacts on individuals via reduced growth and reproduction, despite increased food consumption in injured crabs. Given the high prevalence of nonlethal injury in this species, these negative impacts of injury on individual animals likely scale up to influence population level processes (e.g., population growth), and may be one factor acting against the widespread success of this invader.

Invasive species alter invaded ecosystems via direct impacts such as consumption. In turn, an invasive species’ ability to thrive in new habitats depends on its ability to exploit available resources, which may change over time and space. Diet quality and quantity are indicators of a consumer’s consumptive effects and can be strongly influenced by season and latitude. We examined the effects of season and latitude on the diet quality and quantity of the invasive Asian shore crab Hemigrapsus sanguineus throughout a non-winter sampling year at 5 different sites spanning 8° of latitude across its invaded United States range. We found that diet quality, averaged through time, largely follows an expected latitudinal cline, being higher in the center of its range and lower toward the southern and northern edges. We also found that while some sites show similar patterns of diet quality variation with season, no pattern is consistent across all latitudes. Finally, we found that crabs at sites with low diet quality during summer reproductive months did not compensate by increasing total consumption. Because the Asian shore crab is an important consumer in its invaded ecosystems, understanding how its diet quality and quantity vary with season and latitude can help us better understand how this species influences trophic interactions and community structure, how it has been able to establish across a wide ecological and environmental range, and where future range expansion is most likely to occur.

Antipredator behaviours can be lost relatively quickly in populations that are relieved of predation, as is known for several species inhabiting islands. Flight initiation distance (FID) is often studied in the context of island tameness; however, little is known about the factors that influence and maintain FID variation in predation-free populations. Here, we studied FID in foals of an isolated predator-free population of feral horses (Equus caballus L., 1758) on Sable Island, Canada, to determine if FID could be used for research on consistent individual differences in risk aversion and island tameness. In addition to testing for temporal, spatial, and sex effects on FID, we compared repeatability estimates at two temporal scales (within and among days). Similar FID for measurements obtained on the same day and for males and females indicated an absence of short-term desensitization and sex effects. In contrast, FID decreased for measurements made on subsequent days and from east to west, which could reflect habituation to human presence and (or) other temporal and spatial processes. Repeatability was high (0.42 ± 0.06), but tended to decrease with increasing time intervals. This study highlights the potential of FID for individual-based research on the ecology and evolutionary dynamics of risk aversion in predation-free populations.Key words: boldness, Equus caballus, fear, horse, personality, risk aversion, temperament.Résumé : Les comportements anti-prédateurs peuvent disparaître assez rapidement dans les populations ne faisant plus l'objet de prédation, comme cela est le cas pour plusieurs espèces habitant des îles. La distance de fuite (DF) est souvent étudiée dans le contexte de la docilité insulaire; cependant, les connaissances sur les facteurs qui influencent et maintiennent les variations de la DF dans les populations sans prédateurs sont toutefois limitées. Nous avons étudié la DF chez des poulains d'une population de chevaux feraux (Equus caballus L., 1758) isolée et sans prédateurs à l'île de Sable (Canada) pour déterminer si la DF peut être utilisée pour étudier les différences individuelles sur le plan de l'aversion au risque et de la docilité insulaire. En plus de vérifier la présence d'effets temporels, spatiaux et du sexe sur la DF, nous avons comparé des estimations de la répétabilité à deux échelles temporelles (durant une même journée et sur plusieurs jours). Des DF semblables pour des mesures obtenues le même jour et pour les mâles et les femelles indiquent l'absence de désensibilisation à court terme et d'effets du sexe. Par contre, la DF diminuait pour des mesures prises sur plusieurs jours et de l'est vers l'ouest, ce qui pourrait refléter une habituation à la présence d'humains ou d'autres processus temporels ou spatiaux. La répétabilité était élevée (0,42 ± 0,06), mais tendait à diminuer pour des intervalles de temps plus grands. L'étude fait ressortir le potentiel que présente la DF pour l'étude reposant sur les individus de l'écologie et la dynamique de l'évolution de l'...