Behavioral Ecology最新文献

Alternative reproductive phenotypes involve polymorphic behaviors and forms within sexes. Testing whether behavioral variants such as alternative tactics (eg sneaking or satellite behavior) are initially co-expressed or decoupled from morphological polymorphisms (eg weapon size or color pattern) can provide insight into the origins of reproductive diversity. In Hawaiian field crickets (Teleogryllus oceanicus), an eavesdropping parasitoid fly selected for rapid, parallel evolution of male wing mutations that reduce acoustic signals. Two of these, "flatwing" and "curly-wing", co-occur in populations alongside ancestral "normal-wing" males that can sing. These convergent alternative morphs may both rely on satellite tactics in which nonsinging males position themselves near calling males to intercept females, rather than attracting mates directly by producing a conspicuous song. Here, we test whether flatwing and curly-wing vary in their tendencies to express satellite behavior using playback experiments with virgin, unmanipulated males simulating natural conditions. Surprisingly, flatwing males were significantly less likely to behave as satellites than normal-wing or curly-wing males. Normal-wing males with poorer body condition were more likely to behave as satellites, consistent with theory and previous findings, but the reduced-sound morphs showed no such condition dependence. Our findings suggest that morph-specific variation in the tendency to adopt satellite behavior may contribute to the maintenance of convergent male reproductive morphs; future work would benefit from testing whether such variation is driven by acoustic self-assessment. A decoupled relationship between behavioral reproductive tactics and morphological reproductive strategies may promote diversification of alternative mating morphs in nature.

Our understanding of visual camouflage has increased dramatically in recent years, however we know less about anti-predator defenses that exploit senses other than vision. Low light habitats, such as leaf litter, are more commonly dominated by predators that rely on chemical, tactile, and other nonvisual cues. Passive debris cloaking is a trait found in several arthropod groups that reside in low light habitats and appears as a layer of environmental debris that covers the cuticle. This debris accumulates passively as the organism moves through its habitat, generally via the secretion of adhesive compounds through specialized pores. We hypothesized that passive debris cloaking is a form of non-visual camouflage, and tested this experimentally using zopherid beetles as a model. Zopherid beetles are highly diverse in Aotearoa New Zealand and include many species that exhibit passive debris cloaking. By exposing zopherids with varying degrees of cuticular debris to colonies of foraging predatory ants, we found that passive debris cloaking (1) reduces detection by ants, (2) reduces the probability of attack if detected, and (3) is most effective when interactions occur on natural backgrounds. Our results provide evidence that passive debris cloaking is a highly effective form of non-visual camouflage, suggesting non-visual camouflage may be more prevalent in low light habitats than currently appreciated.

In animals living in groups, stress-induced changes in behavior can be a source of social information, and stressed individuals can potentially become stressors for other social partners, with important consequences for social and population dynamics. Here, we studied stress transmission from experimentally stressed chicks to both their parents and neighbors in the yellow-legged gull (Larus michahellis), a seabird that forms large breeding colonies. To do this, we experimentally increased the level of a stress hormone by corticosterone implant in 2 first-hatched chicks of the brood and observed its effects on their parents and both adults and chicks in the neighboring nests. Two days after the implant, corticosterone-implanted chicks showed reduced basal corticosterone levels, probably due to a physiological feedback response. Exogenous corticosterone promoted behavioral changes in the corticosterone-implanted chicks, showing faster responses to a potential predator attack than the placebo-treated chicks. Eight days after implantation, not only the corticosterone-implanted chicks but also the neighboring chicks showed elevated corticosterone levels after a standardized handling stress compared with the placebo-implanted chicks and their neighbors. The parents and neighbor adults of the corticosterone-implanted chicks showed increased mobbing behavior but reduced aggressive and resting behaviors in comparison with the adult gulls living close to the placebo-implanted chicks. Overall, our results suggest that individual physiological stress in a colony may be socially transmitted within families and neighbors, with potential consequences for colony dynamics.

The coexistence of species within the same guild is promoted by ecological and behavioral mechanisms, particularly niche differentiation. When niches overlap, coexistence may be maintained through spatial segregation, achieved through interspecific territoriality. Most research has focused on pairs of species, with little attention given to complex multispecies guilds. This study investigates the role of interspecific territoriality in promoting the coexistence of 5 sympatric tit species during the breeding season in northern Italy. These species are commonly grouped into "broadleaf" (great tit, blue tit, marsh tit) and "conifer species" (crested tit, coal tit), based on their habitat preferences. Indeed, in the study area, previous observations have shown that their breeding territories are spatially segregated. We experimentally tested whether aggressive territorial behaviors occurred in response to heterospecific playback stimuli, and if they were more intense against heterospecific intruders sharing the same, rather than a different habitat. Our findings revealed that this was the case for all "broadleaf species," indicating convergent adaptative heterospecific song recognition driven by competition for shared resources. In contrast, "conifer species" did not show such patterns, suggesting possible resource partitioning at a microhabitat scale or differences in breeding territory densities among habitats. This study enhances our understanding of intra-guild interactions and of the mechanisms facilitating coexistence in ecological communities.

To balance the basic needs of organisms, internal and external cues are used to inform the optimal behavioral strategy. Some of the best-studied related cognitive rules have emerged in predator-prey contexts, such as the threat-sensitivity hypothesis, which postulates that prey should adjust their antipredator behavior in accordance with the level of risk. Extending this theory, the risk allocation hypothesis posits that under long-term sustained high predation risk, individuals should decrease their antipredator responses towards risky stimuli so as to meet their energetic demands. Evidence for the risk allocation hypothesis has been mixed in invertebrates, particularly in gastropods, which are classic model systems for antipredator responses. This may be due to past studies frequently lacking sham controls and/or sufficient certainty about the risk regime. The present study in the aquatic gastropod Physella acuta controls for these factors by crossing long-term background risk, ie lifelong consistent exposure to conspecific alarm cues, which reliably signal high predation risk (high-risk), or a water control (low-risk) with exposure to a high-risk or low-risk stimulus. Crawl-out behavior is an adaptive antipredator response in gastropods. In accordance with threat-sensitivity, high-risk stimuli induced increased crawl-out behavior independent of background risk. Providing partial support for risk allocation, high background risk induced lower responsivity to both low-risk and high-risk chemical stimuli. This may be because cue addition also provided tactile cues that could be considered risky by high background risk snails. Altogether, the present well-controlled research contributes novel data to the hitherto mixed evidence for risk allocation in gastropods.

Changes in environmental conditions impact predator-prey interactions by altering behavior through sensory and non-sensory (eg metabolic or cognitive) pathways. Elevated water temperature and turbidity are known to alter activity levels and anti-predator responses in prey fish, and are increasing globally as a result of anthropogenic activities. Less is known about how temperature and turbidity impact predators' ability to detect prey directly, or indirectly via changes to prey behavior. We quantified the detectability of Trinidadian guppies (Poecilia reticulata) free-swimming in a large arena from the perspective of a stationary visual predator (simulated as an underwater camera). We used a fully factorial experimental design testing the independent and combined effects of increased temperature and turbidity. We found that both stressors had a strong influence on the appearance of prey (objectively quantified as the mean magnitude of the optical flow in the videos). As expected, turbidity reduced the frequency of detection between the guppies and the simulated predator, ie the magnitude of optical flow exceeded the threshold for a "detection event" more often in clear water. Events were also shorter in duration in turbid water, reducing the time available for a predator to detect the prey. However, during an event, prey were more detectable in warmer water (ie the mean magnitude was greater). Although we found no evidence of interactive effects of turbidity and temperature on the response variables, their cumulative main effects suggest an antagonistic effect between the two stressors on the predator-prey dynamic overall.

We investigated the influence of relatedness on the function of dyadic butting contests over access to a food resource (plant phloem) in the group-living horned aphid Astegopteryx bambusae on bamboo leaves. Relatedness between dueling pairs did not differ significantly from that of randomly selected aphid pairs. Microsatellite genotyping showed that the average genetic relatedness between a dueling pair was 0.79 ± 0.12 (mean ± SD, N = 75), with 56% (42/75) of duels occurring between clonal pairs. Butting contests observed in the field lasted longer when the competing aphids were of similar age and when the attacker won, but they involved low costs in terms of time or injury. Neither the duration nor outcome of the contests was associated with the pairwise relatedness, suggesting that there was no kin-discrimination in the butting pair of aphids. 83% (50/60) of the contests between aphids of different ages were won by the older and larger aphid. These results suggest that the aphids discriminate between their opponents on the basis not of relatedness but of size or age. We suggest that the duels in these Astegopteryx aphids are not an aggressive fight for resources between different genotypes, but a low-cost method by which the aphids assess each other's reproductive value, providing an indirect fitness benefit for losing younger individuals that yield a feeding site to older kin. This provides a selective context for the evolution of the young, rather than old, altruistic soldiers that are observed in the open colonies of many cerataphidine species.

Social groups in which some individuals forgo reproduction and others reproduce, are one of the most remarkable products of evolution. To fully understand these social groups, we must understand both why non-breeders tolerate their situation and why breeders tolerate non-breeders. In general, breeders tolerate non-breeders because they help provision the breeders' offspring or the breeders themselves, but in some vertebrate societies the benefits that breeders accrue from non-breeders are surprisingly hard to detect. This raises the question: why do breeders tolerate non-breeders in such societies? Here, we test the hypothesis that breeders of the clown anemonefish (Amphiprion percula) will tolerate non-breeders because they are distant relatives who go on to inherit the territory. We use 40 polymorphic microsatellite loci to assess the pairwise relatedness of 683 individuals from 203 groups. We show that the mean pairwise relatedness among individuals from the same group is effectively zero, and no different from that found among individuals from the same reef or that found among individuals from the population at large. Further, we show that the mean pairwise relatedness found among breeder/breeder dyads is no different from that found among breeder/non-breeder dyads or that found among non-breeder/non-breeder dyads. We conclude that kin selection does not explain why breeders tolerate non-breeders in the clown anemonefish, and suggest that the explanation must lie with other, as yet untested, hypotheses: within-generation bet-hedging or mutualist-mediated benefits.

Wind is an important abiotic factor that influences an array of biological processes including animal behavior, but it is rarely considered in plant-pollinator interactions. Here, we investigate the impact of wind speed on plant-pollinator community structure under natural conditions. In our field experiment we observed threefold greater abundance of pollinators and double the species richness under low (< 0.5 m/s) versus moderate (> 2.5 m/s) wind speeds. Significant differences in plant-pollinator community structure were also observed, with Diptera most abundant under low wind conditions, and Hymenoptera predominant and Lepidoptera absent in windier conditions. Across three plant species, the foraging rates of both honey and bumble bees were 15% greater at low versus moderate wind speeds. Lastly, at greater wind speeds bees made more movements between plants, suggesting that wind may improve yield for crops that require cross-pollination. Overall, our findings show that wind is an important factor in determining which pollinator groups are active and that eusocial bees, which are often the most important pollinators, were little affected by moderate wind speeds. Our results raise several important issues for further study and suggest that the use of linear features such as trees and hedges that act as windbreaks may be beneficial to crop pollination and conservation efforts.

Birds that migrate from temperate areas to the Arctic to breed lose their strongest Zeitgeber of circadian organization when they cross the Arctic circle in spring - the 24h light-dark cycle. Under continuous daylight, diverse behavioral and physiological patterns have been detected in both free-ranging and laboratory animals. To better understand the evolution of plasticity in circadian clocks, it is essential to study behavioral and physiological rhythmicity in the context of a species' ecology. Employing a multifaceted approach, which included wildlife cameras, accelerometers, and noninvasive sampling of hormone metabolites, we investigated activity patterns and corticosterone rhythmicity in a migratory herbivore, the barnacle goose (Branta leucopsis), during its Arctic breeding season on Svalbard. We found that females showed a combination of both ultradian and diel rhythmicity in nest recesses and sleep during incubation. In both parents, these rhythms in activity continued also during the gosling rearing phase. During molt, many geese aligned activity with the prevailing tidal rhythm. Barnacle geese showed weak diel rhythmicity in excreted corticosterone metabolites (CORTm). This suggests that while Arctic geese may adopt an alternative Zeitgeber during the Arctic summer to maintain a diel rhythm, ultradian rhythmicity remains essential, allowing the geese to flexibly adjust their rhythms to environmental conditions.