RESUMO

Although numerous studies about camouflage have been conducted in the last few decades, there is still a significant gap in our knowledge about the magnitude of protective value of different camouflage strategies in prey detection and survival. Furthermore, the functional significance of several camouflage strategies remains controversial. Here we carried out a comprehensive meta-analysis including comparisons of different camouflage strategies as well as predator and prey types, considering two response variables: mean predator search time (ST) (63 studies) and predator attack rate (AR) of camouflaged prey (28 studies). Overall, camouflage increased the predator ST by 62.56% and decreased the AR of prey by 27.34%. Masquerade was the camouflage strategy that most increased predator ST (295.43%). Background matching and disruptive coloration did not differ from each other. Motion camouflage did not increase ST but decreases AR on prey. We found no evidence that eyespot increases ST and decreases AR by predators. The different types of predators did not differ from each other, but caterpillars were the type of prey that most influenced the magnitude of camouflage's effect. We highlight the potential evolutionary mechanisms that led camouflage to be a highly effective anti-predatory adaptation, as well as potential discrepancies or redundancies among strategies, predator and prey types.

Assuntos

RESUMO

The intensity of mate competition is often influenced by predation pressure. The threat-sensitive predator avoidance hypothesis predicts that prey should precisely adjust their fitness-related activities to the level of perceived acute predation risk and this effect should be stronger under high background risk. Individuals should compensate during periods of moderate risk for lost opportunities during high risk. Our study examined the interaction between acute and background predation risk on mate competition. Under laboratory conditions, we explored the effects of acute risk (low vs. high) using chemical alarm cue (AC; control (results presented in Chuard et al. (2016)) The effects of adult sex ratio on mating competition in male and female guppies (Poecilia reticulata) in two wild populations. Behav Process 129:1-10), 25 % concentration, and 100 % concentration), and population of origin (low vs. high background risk) on mate competition in guppies (Poecilia reticulata). Surprisingly, males favored courtship over forced mating under acute predation risk irrespective of background risk, potentially benefiting from a female preference for bold males. We discuss our results in the context of chemical threat-sensitivity and resource differences in defendability (e.g. mates vs. food).

Assuntos

RESUMO

Systematic reviews and meta-analyses often examine data from diverse taxa to identify general patterns of effect sizes. Meta-analyses that focus on identifying generalisations in a single taxon are also valuable because species in a taxon are more likely to share similar unique constraints. We conducted a comprehensive phylogenetic meta-analysis of flight initiation distance in lizards. Flight initiation distance (FID) is a common metric used to quantify risk-taking and has previously been shown to reflect adaptive decision-making. The past decade has seen an explosion of studies focused on quantifying FID in lizards, and, because lizards occur in a wide range of habitats, are ecologically diverse, and are typically smaller and differ physiologically from the better studied mammals and birds, they are worthy of detailed examination. We found that variables that reflect the costs or benefits of flight (being engaged in social interactions, having food available) as well as certain predator effects (predator size and approach speed) had large effects on FID in the directions predicted by optimal escape theory. Variables that were associated with morphology (with the exception of crypsis) and physiology had relatively small effects, whereas habitat selection factors typically had moderate to large effect sizes. Lizards, like other taxa, are very sensitive to the costs of flight.

Assuntos

RESUMO

When confronted by predators, prey need to make an economic decision between continuing their current activity or flee. Flight Initiation Distance (FID), the distance at which an organism begins to flee an approaching threat, has been used to indicate an animal's fearfulness level and a way to examine factors influencing escape decisions. Here we investigated how the FID of the barber surgeonfish, Acanthurus bahianus, responds to the presence of spearfishers in a fishing site in northeast Brazil. Specifically, we examined whether the FID was influenced by body and group size; by the heterogeneity of species in groups formation; and the distance to shelter. Significant differences in FID were observed with increasing body size. We found no significant relationship of FID with size or group formation, neither with distance to shelter. Preferences in forming groups with A. bahianus were seen among some species, and a higher FID was associated with less sheltered substrates. Results obtained here support theories suggesting that spearfishers do influence fish behavior. We highlight that future research should focus on the indirect impacts of spearfishing on the structure of marine communities, emphasizing the anti-predator behaviour of juvenile and adult target fishes.

Ao serem confrontadas por predadores, as presas precisam tomar decisões econômicas, escolhendo entre continuar com sua atividade atual ou fugir. Distância Inicial de Fuga (DIF), a distância à qual um organismo começa a fugir de uma ameaça que se aproxima, tem sido utilizada para indicar o nível de medo do animal e um modo para se examinar fatores que influenciam nas decisões de fuga. Aqui nós investigamos como a DIF do peixe cirurgião, Acanthurus bahianus , responde à presença de pescadores subaquáticos em uma tradicional área de pesca no nordeste do Brasil. Especificamente, investigamos se a DIF foi influenciada pelo tamanho do corpo e do grupo; pela heterogeneidade das espécies na formação de grupos; e pela distância para refúgio. Diferenças significativas na DIF foram observadas com o aumento no tamanho do corpo. Nós não encontramos nenhuma relação significativa da DIF com o tamanho ou formação do grupo, nem com a distância para refúgio. Preferências na formação de grupos com A. bahianus foram observadas entre algumas espécies,e maiores DIF foram associadas com substratos menos abrigados. Resultados obtidos aqui suportam teorias sugerindo que pescadores subaquáticos influenciam no comportamento dos peixes. Nós destacamos que pesquisas futuras devem focar nos impactos indiretos da pesca subaquática na estrutura das comunidades marinhas, enfatizando o comportamento anti-predador de peixes juvenis e adultos alvo da pesca.

Assuntos

RESUMO

When confronted by predators, prey need to make an economic decision between continuing their current activity or flee. Flight Initiation Distance (FID), the distance at which an organism begins to flee an approaching threat, has been used to indicate an animal's fearfulness level and a way to examine factors influencing escape decisions. Here we investigated how the FID of the barber surgeonfish, Acanthurus bahianus, responds to the presence of spearfishers in a fishing site in northeast Brazil. Specifically, we examined whether the FID was influenced by body and group size; by the heterogeneity of species in groups formation; and the distance to shelter. Significant differences in FID were observed with increasing body size. We found no significant relationship of FID with size or group formation, neither with distance to shelter. Preferences in forming groups with A. bahianus were seen among some species, and a higher FID was associated with less sheltered substrates. Results obtained here support theories suggesting that spearfishers do influence fish behavior. We highlight that future research should focus on the indirect impacts of spearfishing on the structure of marine communities, emphasizing the anti-predator behaviour of juvenile and adult target fishes.(AU)

Ao serem confrontadas por predadores, as presas precisam tomar decisões econômicas, escolhendo entre continuar com sua atividade atual ou fugir. Distância Inicial de Fuga (DIF), a distância à qual um organismo começa a fugir de uma ameaça que se aproxima, tem sido utilizada para indicar o nível de medo do animal e um modo para se examinar fatores que influenciam nas decisões de fuga. Aqui nós investigamos como a DIF do peixe cirurgião, Acanthurus bahianus , responde à presença de pescadores subaquáticos em uma tradicional área de pesca no nordeste do Brasil. Especificamente, investigamos se a DIF foi influenciada pelo tamanho do corpo e do grupo; pela heterogeneidade das espécies na formação de grupos; e pela distância para refúgio. Diferenças significativas na DIF foram observadas com o aumento no tamanho do corpo. Nós não encontramos nenhuma relação significativa da DIF com o tamanho ou formação do grupo, nem com a distância para refúgio. Preferências na formação de grupos com A. bahianus foram observadas entre algumas espécies,e maiores DIF foram associadas com substratos menos abrigados. Resultados obtidos aqui suportam teorias sugerindo que pescadores subaquáticos influenciam no comportamento dos peixes. Nós destacamos que pesquisas futuras devem focar nos impactos indiretos da pesca subaquática na estrutura das comunidades marinhas, enfatizando o comportamento anti-predador de peixes juvenis e adultos alvo da pesca.(AU)

Assuntos