RESUMO

Interactions between humans and nature have profound consequences, which rarely are mutually beneficial. Further, behavioral and environmental changes can turn human-wildlife cooperative interactions into conflicts, threatening their continued existence. By tracking fine-scale behavioral interactions between artisanal fishers and wild dolphins targeting migratory mullets, we reveal that foraging synchrony is key to benefiting both predators. Dolphins herd mullet schools toward the coast, increasing prey availability within the reach of the net-casting fishers, who gain higher foraging success-but only when matching the casting behavior with the dolphins' foraging cues. In turn, when dolphins approach the fishers' nets closely and cue fishers in, they dive for longer and modify their active foraging echolocation to match the time it takes for nets to sink and close over mullets-but only when fishers respond to their foraging cues appropriately. Using long-term demographic surveys, we show that cooperative foraging generates socioeconomic benefits for net-casting fishers and ca. 13% survival benefits for cooperative dolphins by minimizing spatial overlap with bycatch-prone fisheries. However, recent declines in mullet availability are threatening these short- and long-term benefits by reducing the foraging success of net-casting fishers and increasing the exposure of dolphins to bycatch in the alternative fisheries. Using a numerical model parametrized with our empirical data, we predict that environmental and behavioral changes are pushing this traditional human-dolphin cooperation toward extinction. We propose two possible conservation actions targeting fishers' behavior that could prevent the erosion of this century-old fishery, thereby safeguarding one of the last remaining cases of human-wildlife cooperation.

Assuntos

RESUMO

Sexual segregation is widely reported among sexually dimorphic species and generally attributed to intraspecific competition. Prey diversity and human activities can reinforce niche segregation by increasing resource heterogeneity. Here, we explored trophic and spatial sexual segregation in the only avian scavenger that exhibits pronounced sexual size dimorphism (up to 50% difference in body mass) and a highly despotic social system, the Andean condor (Vultur gryphus). We predicted that larger and dominant males would exclude smaller and subordinate females from high-quality resources, leading to sexual segregation particularly in human-dominated landscapes showing increased prey diversity. We compared resource use between females and males across six sites in Argentina featuring a range of prey diversity via stable isotopes analysis of molted feathers (n = 141 individuals). We then focused on two sites featuring contrasting levels of prey diversity and quantified assimilated diet via stable isotopes and space use via GPS monitoring (n = 23 and 12 tagged individuals). We found no clear differences in isotopic niche space, individual variation in isotopic signature, or assimilated diet between females and males. However, there were differences in foraging locations between sexes, with females apparently using areas of fewer food resources more frequently than males. Local conditions defined the dynamics of fine-scale sexual differences in foraging sites; yet, unpredictable and ephemeral carrion resources likely prevent segregation by sexes at the landscape scale. Our study highlights complex dynamics of sexual segregation in vultures and the relevancy of analyses under multiple spatial-temporal scales to explore segregation in social species.

Assuntos

RESUMO

In a collective foraging situation, we assessed the distribution of search responses of Wistar rats relative to the size of the group. For both, small and large groups, the number of production opportunities per capita was equal. Foraging strategies were classified as either production (opening gates with food) or scrounging (following conspecifics). Small groups showed a higher proportion of producers than large groups and required less time to deplete the food. The proportion of producing and scrounging responses yields to equilibrium between their payoffs. Producing and scrounging were highly correlated with different prior responses. Also, the relative frequency of producing and scrounging associated activities correlated with the time spent consuming food procured by each activity. It is possible that a simple outcome-strategy feedback mechanism mediates the choice of prior activities and procurement responses.

Assuntos

RESUMO

Extractive foraging is a skill young capuchin monkeys learn over time. A key unknown is whether unskilled individuals occupy spatial positions that increase their opportunities to learn. We observed the spatial positions of individuals in a group of capuchin monkeys in Northeastern Brazil. To improve our understanding of the relationship between learning by young capuchin monkeys and inter-individual distance, we investigated the associations between the proximity of individuals and their age, activity, and proficiency at extractive foraging. To do this, we used one form of extractive foraging, opening palm nuts, as an index of proficiency at all types of extractive foraging. Our results indicate that, in the subset of the data where dyads consisted of one proficient individual and a partner with any level of proficiency, the distance between individuals was predicted by their foraging activity (i.e., extractive foraging, other foraging, or not foraging). In those dyads, the proficiency of the partner did not significantly improve prediction of inter-individual distances, indicating that spatial proximity of proficient individuals to others does not function primarily to increase opportunities for unskilled individuals to observe extractive foraging. Dyads in which both individuals were engaged in similar foraging activities (e.g., both "extractive foraging") exhibited the shortest inter-individual distances. Proximity between individuals engaged in similar foraging activities may result from the spatial distribution of resources or from social learning mechanisms, such as local or stimulus enhancement.

Assuntos

RESUMO

Differences in distribution, prey species, season and social learning opportunities influence the feeding tactics used by marine mammals. Here, we analyze the coordinated feeding behavior of the Guiana dolphin, Sotalia guianensis (Van Bénéden, 1864, Delphinidae) and its relation to seasonality and the presence of calves. In a total of 201 feeding bouts, we observed four types of coordinated feeding tactics, which differed in frequency and in mean number of engaged individuals. Tactics in which dolphins used their bodies to herd and capture prey were the most frequent, presenting a higher frequency and engaging a higher number of individuals, suggesting that these tactics are better for capturing fishes which form larger schools. Furthermore, the seasons influenced the feeding behavior used by dolphins. During spring-summer, a longer duration of bouts and a larger number of individuals engaged in the feeding tactics was observed, which may be related to the seasonal spawning of larger schooling fish, such as Sardinella brasiliensis (Steindachner, 1879). Calves were present in 95% of all coordinated feeding tactic occurrences. This study indicates a complete preference of dolphins for coordinating their actions to capture prey and for the first time reports the presence of calves in the coordinated tactics and jumps. This broadens the current knowledge of the Guiana dolphin feeding tactics.

RESUMO

Differences in distribution, prey species, season and social learning opportunities influence the feeding tactics used by marine mammals. Here, we analyze the coordinated feeding behavior of the Guiana dolphin, Sotalia guianensis (Van Bénéden, 1864, Delphinidae) and its relation to seasonality and the presence of calves. In a total of 201 feeding bouts, we observed four types of coordinated feeding tactics, which differed in frequency and in mean number of engaged individuals. Tactics in which dolphins used their bodies to herd and capture prey were the most frequent, presenting a higher frequency and engaging a higher number of individuals, suggesting that these tactics are better for capturing fishes which form larger schools. Furthermore, the seasons influenced the feeding behavior used by dolphins. During spring-summer, a longer duration of bouts and a larger number of individuals engaged in the feeding tactics was observed, which may be related to the seasonal spawning of larger schooling fish, such as Sardinella brasiliensis (Steindachner, 1879). Calves were present in 95% of all coordinated feeding tactic occurrences. This study indicates a complete preference of dolphins for coordinating their actions to capture prey and for the first time reports the presence of calves in the coordinated tactics and jumps. This broadens the current knowledge of the Guiana dolphin feeding tactics.

RESUMO

Differences in distribution, prey species, season and social learning opportunities influence the feeding tactics used by marine mammals. Here, we analyze the coordinated feeding behavior of the Guiana dolphin, Sotalia guianensis (Van Bénéden, 1864, Delphinidae) and its relation to seasonality and the presence of calves. In a total of 201 feeding bouts, we observed four types of coordinated feeding tactics, which differed in frequency and in mean number of engaged individuals. Tactics in which dolphins used their bodies to herd and capture prey were the most frequent, presenting a higher frequency and engaging a higher number of individuals, suggesting that these tactics are better for capturing fishes which form larger schools. Furthermore, the seasons influenced the feeding behavior used by dolphins. During spring-summer, a longer duration of bouts and a larger number of individuals engaged in the feeding tactics was observed, which may be related to the seasonal spawning of larger schooling fish, such as Sardinella brasiliensis (Steindachner, 1879). Calves were present in 95% of all coordinated feeding tactic occurrences. This study indicates a complete preference of dolphins for coordinating their actions to capture prey and for the first time reports the presence of calves in the coordinated tactics and jumps. This broadens the current knowledge of the Guiana dolphin feeding tactics.