A bird's-eye view on turbulence: seabird foraging associations with evolving surface flow features

Understanding physical mechanisms underlying seabird foraging is fundamental to predict responses to coastal change. For instance, turbulence in the water arising from natural or anthropogenic structures can affect foraging opportunities in tidal seas. Yet, identifying ecologically important localized turbulence features (e.g. upwellings approximately 10–100 m) is limited by observational scale, and this knowledge gap is magnified in volatile predators. Here, using a drone-based approach, we present the tracking of surface-foraging terns (143 trajectories belonging to three tern species) and dynamic turbulent surface flow features in synchrony. We thereby provide the earliest evidence that localized turbulence features can present physical foraging cues. Incorporating evolving vorticity and upwelling features within a hidden Markov model, we show that terns were more likely to actively forage as the strength of the underlying vorticity feature increased, while conspicuous upwellings ahead of the flight path presented a strong physical cue to stay in transit behaviour. This clearly encapsulates the importance of prevalent turbulence features as localized foraging cues. Our quantitative approach therefore offers the opportunity to unlock knowledge gaps in seabird sensory and foraging ecology on hitherto unobtainable scales. Finally, it lays the foundation to predict responses to coastal change to inform sustainable ocean development.

Facing death together: heterospecific aggregations of blowfly larvae evince mutual benefits

Heterospecific aggregations and foraging associations have been observed between different species, from apes to birds to insects. Such associations are hypothesized to result in a mutually beneficial relationship entailing benefits that are not apparent in conspecific groupings. Therefore, the objectives of the present study were to investigate 1) how 3 blowfly species, namely, Calliphora vicina, Calliphora vomitoria, and Lucilia sericata, aggregate according to species, and 2) if developmental benefits are linked to heterospecific aggregation. For objective (1), larvae of 2 species were placed between 2 conspecific aggregates, each with a different species (i.e., a binary choice test). After 20 h, the positions of all larvae were determined. On average, 98% of the maggots added later settled together on one of the 2 pre-existing aggregations, demonstrating a collective choice. The aggregation spot with C. vicina was preferred against others, indicating different attractiveness of different species. To relate this behavior to its benefits (objective ii), C. vicina and L. sericata larvae were raised from first instar to adult in con- and heterospecific conditions, and their development time, mortality rates, and morphometrics were measured. Thereby, mutual and asymmetric consequences were observed: specifically, there were significant increases in size and survival for L. sericata and faster development for C. vicina in heterospecific groups. These results indicate that the predilection for heterospecific association leads to mutual developmental benefits. This heterospecific aggregation behavior may be a resource-management strategy of blowflies to face carrion-based selection pressure.

Hunting associations of American badgers (Taxidea taxus) and coyotes (Canis latrans) revealed by camera trapping

Interspecies foraging associations occur in a wide variety of vertebrate taxa and are maintained through gains in foraging efficiency and (or) predator avoidance. Despite their advantages, foraging associations often are variable in space and time and benefits may not accrue equally to all participants. In mammals, interspecies associations between solitary mammalian carnivores are rare. Coyotes (Canis latrans Say, 1823) and American badgers (Taxidea taxus (Schreber, 1777)) occasionally form hunting associations in pursuit of ground squirrels (Spermophilus armatus Kennicott, 1863), yet spatiotemporal variation in this association may be substantial. Better documentation of coyote–badger interactions across space and time will improve our understanding of the environmental drivers of this relationship and its benefit to both species. We used a broad-scale camera trapping array to document coyote–badger hunting associations. Out of 46 detections of badgers, we found five instances of hunting associations with coyotes, all of which occurred in mid- to late summer when ground squirrels were most active. Given our high rate of detection, these interactions are likely common on our study area. Habitat characteristics of the regions where we document coyote–badger interactions may have increased the likelihood of hunting associations. Our study demonstrates the effectiveness of camera traps for documenting this association and suggests that the coyote–badger system may be ideal for studying drivers of spatiotemporal variation in foraging associations.

REEF FISH FORAGING ASSOCIATIONS AT MALPELO ISLAND, COLOMBIA (TROPICAL EASTERN PACIFIC)

Varias especies de animales marinos establecen temporalmente asociaciones de caza interespecíficas, en las cuales especies oportunistas siguen a otras especies llamadas nucleares mientras estas buscan alimento pues disturban el substrato. Este tipo de comportamiento ha sido observado entre algunas especies de peces arrecifales en la isla Malpelo en el Pacífico colombiano. La morena Gymnothorax dovii y el jurel Caranx melampygus fueron identificados como especies nucleares mientras cazaban dentro del sitio conocido como El Arrecife. Estas especies fueron acompañadas por algunos meros Dermatolepis dermatolepis y Mycteroperca olfax, jurel Seriola rivoliana, pez corneta Aulostomus chinensis, la vieja Bodianus diplotaenia y en algunas ocasiones por el jurel Caranx melampygus, que tuvo ambos comportamientos (nuclear/seguidor). Este tipo de interacción alimentaria es un importante componente en la estructura trófica de las comunidades arrecifales que ocurren en todos los mares.