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Individual predators differ in the level of risk they represent to prey. Because prey incur costs when responding to predators, prey can benefit by adjusting their antipredator behavior based on the level of perceived risk. Prey can potentially assess the level of risk by evaluating the posture of predators as an index of predators’ motivational state. Like other prey species, humans might evaluate predator body posture as a prominent cue for assessing danger. We tested whether human participants adjusted their visual attention based on the postures of predators by presenting participants with photographic arrays of predators (lions) that varied in postures while we recorded the participants’ gaze behavior. The participants searched for a standing lion (representing a high-risk target) among an array of reclining lions (representing low-risk distractors) or searched for a reclining lion among an array of standing lions. They also searched through similar arrays consisting of non-threatening prey (impalas) standing or reclining, rather than predators. Participants detected standing lions and impala faster than reclining lions and impala. Surprisingly, they detected standing lions at similar latencies as standing impala. They detected the reclining lions and impala more slowly because they spent more time looking at the standing lion and impala distractors and looked at more of those distractors. These results show that upright animals, regardless of whether they are predators or prey, attract attention in humans, and this could allow humans to rapidly evaluate predatory threats or the flight readiness of hunted game.

Primates can rapidly detect potential predators and modify their behavior based on the level of risk. The gaze direction of predators is one feature that primates can use to assess risk levels: recognition of a predator's direct stare indicates to prey that it has been detected and the level of risk is relatively high. Predation has likely shaped visual attention in primates to quickly assess the level of risk but we know little about the constellation of low-level (e.g., contrast, color) and higher-order (e.g., category membership, perceived threat) visual features that primates use to do so. We therefore presented human and chimpanzee (Pan troglodytes) participants with photographs of potential predators (lions) and prey (impala) while we recorded their overt attention with an eye-tracker. The gaze of the predators and prey was either directed or averted. We found that both humans and chimpanzees visually fixated the eyes of predators more than those of prey. In addition, they directed the most attention toward the eyes of directed (rather than averted) predators. Humans, but not chimpanzees, gazed at the eyes of the predators and prey more than other features. Importantly, low-level visual features of the predators and prey did not provide a good explanation of the observed gaze patterns. [ABSTRACT FROM AUTHOR]

Even prey that successfully evade attack incur costs when responding to predators. These nonlethal costs can impact their reproductive success and survival. One strategy that prey can use to minimize these costs is to adjust their antipredator behavior based on the perceived level of risk. We tested whether humans adopt this strategy by presenting participants with photographic arrays of predators (lions) that varied in their level of risk. While their eye movements were recorded, the participants searched for a forward-facing predator (signifying potential predator interest; high-risk target) among an array of inattentive predators that were facing away (low-risk distractors) or searched for a predator that was facing away from them among an array of forward-facing predators. As a control, participants also searched through similar arrays that displayed a potential prey species (impalas) rather than predators. Participants detected forward-facing predators more quickly than predators facing away from them. Unexpectedly, they were also quicker at detecting forward-facing prey versus prey facing away from them, but slower to detect these forward-facing prey compared with forward-facing predators. They were slower to detect predators and prey facing away from them because they spent more time looking at the forward-facing distractors and looked at more of those distractors. The results indicate that human attention is drawn toward dangerous predators with forward-facing orientations, and this could allow humans to quickly assess predator intentions. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Predation is a major source of natural selection on primates and may have shaped attentional processes that allow primates to rapidly detect dangerous animals. Because ancestral humans were subjected to predation, a process that continues at very low frequencies, we examined the visual processes by which men and women detect dangerous animals (snakes and lions). We recorded the eye movements of participants as they detected images of a dangerous animal (target) among arrays of nondangerous animals (distractors) as well as detected images of a nondangerous animal (target) among arrays of dangerous animals (distractors). We found that participants were quicker to locate targets when the targets were dangerous animals compared with nondangerous animals, even when spatial frequency and luminance were controlled. The participants were slower to locate nondangerous targets because they spent more time looking at dangerous distractors, a process known as delayed disengagement, and looked at a larger number of dangerous distractors. These results indicate that dangerous animals capture and maintain attention in humans, suggesting that historical predation has shaped some facets of visual orienting and its underlying neural architecture in modern humans.

Previous research on individual differences in the acoustic structure of vocalizations and vocal recognition has largely focused on the contexts of parent-offspring interactions, territory defense, sexual interactions, and group cohesion. In contrast, few studies have examined individual differences in the acoustic structure of mobbing and alarm calls. The purpose of this study was to explore individual differences in the acoustic structure of the inflected alarm caw of the American Crow (Corvus brachyrhynchos). The alarm caws of 15 wild, marked individuals were recorded and 25 acoustic measurements were made automatically using customized software. A stepwise discriminant function analysis showed that 20 of the 25 variables were important in discriminating among individuals, with 65% classification success. We used factor analysis to reduce the large number of variables to a set of seven meaningful call features. All of these features differed among individuals, suggesting that American Crows have the potential to discriminate among individual birds on the basis of call structure alone. Five of the features differed between the sexes, with call frequency being the most significant. One clearly subordinate male clustered with the females, raising the possibility that social status partially determines the sex-based differences. Encoding of individual identity in alarm contexts may be adaptive if receiver vigilance and approach urgency depend on the status, reliability, or family membership of the alarm signaler. Key words: acoustic feature analysis, alarm vocalization, call classification, individual signature call. Las investigaciones anteriores sobre las diferencias individuales en la estructura acustica de las vocalizaciones y sobre el reconocimiento individual se han centrado principalmente en los contextos de interacciones entre padres e hijos, defensa de territorios, interacciones sexuales y cohesion de grupo. En contraste, pocos estudios han examinado las diferencias individuales en la estructura acustica de las llamadas de alarma y de acoso a los depredadores. El proposito de este estudio fue explorar las diferencias individuales en la estructura acustica del llamado declinado de alarma de Corvus brachyrhynchos. Se grabaron las llamadas de alarma de 15 individuos silvestres marcados y se realizaron automaticamente 25 mediciones acusticas utilizando un programa de computacion disenado para este proposito. Un analisis de funciones discriminantes por etapas demostro que 20 de las 25 variables fueron importantes para la discriminacion entre individuos, con un exito de clasificacion del 65%. Utilizamos un analisis de factores para reducir el amplio numero de variables a un grupo de siete caracteristicas significativas de los llamados. Todas estas caracteristicas variaron entre individuos, lo cual sugiere que los individuos de C. brachyrhynchos pueden potencialmente distinguirse con base en tan solo la estructura de la llamada. Cinco de las caracteristicas variaron entre sexos, siendo la frecuencia de la llamada la mas significativa. Los llamados de un macho claramente subordinado se agruparon con los de las hembras, sugiriendo que el estatus social puede ser un determinante parcial de las diferencias entre sexos. La codificacion de la identidad individual en contextos de alarma podria ser adaptativa si la vigilancia y la urgencia de aproximacion del receptor dependen del estatus, fiabilidad, o membresia familiar de quien emite la alarma.

Males often exhibit elaborate ornamentation that contributes to their fitness. Similarly, females can also exhibit elaborate ornamentation, but we have a relatively limited understanding of its function. Recent studies have demonstrated that female ornamentation can function in both intrasexual competition and male mate choice, but few studies have been conducted on lekking species. We therefore investigated the possibility that female ornamentation provides information about the dominance status of the bearer, which could mediate intrasexual competition. We examined this possibility using Indian peafowl (Pavo cristatus), a sexually dimorphic lekking species in which females exhibit elaborate ornamentation in the form of iridescent green neck plumage. We tested whether female ornamentation predicts dominance status using an information theoretic model averaging approach. We found that females with brighter ornamentation are more socially dominant than females with darker ornamentation. These results suggest that female ornamentation in this species provides social information about the dominance status of the bearer. This study provides insight into the evolution of conspicuous female traits by suggesting a potential role for female ornamentation in intrasexual competition in a lekking species. [ABSTRACT FROM AUTHOR]