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Primates are the most visually adapted order of mammals. There is a rich history within anthropology of proposed explanations for the adaptive significance of binocular vision, especially pertaining to primate origins and evolution. Depth perception and orbit morphology have been hypothesized to be functionally related to specialized locomotor or f...
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The plenary session of the XVI Asociacion Iberica de Limnologia (AIL) congress was devoted to remembering Professor Margalef on the occasion of the 10th anniversary of his death. Based on the main theme of the congress, i.e., "Understanding the resilience of aquatic ecosystems, basis for a sustainable future", I take the occasion to review the main...
Swarming agents are interconnected organisms or agents. As is well known in our information age, a key benefit of being connected is access to information. We have discovered and observed this interconnectivity from the biological standpoint in Chap. 2, then analyzed it from the physical viewpoint in Chap. 3, and thoroughly studied its network stru...
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... Notably, the discontinuity between an animal's body and its background generates distinct visual clues even with backgrounds with high-fidelity color and texture matching, facilitating predator detection and identification (Thayer, 1918). Furthermore, the evolution of binocular vision and the ability to detect depth and 3D observation of the surroundings increased a predator's ability to detect the shape and presence of prey (Heesy, 2009;Julesz, 1971). ...
Animal camouflage serves a dual purpose in that it enhances both predation efficiency and anti‐predation strategies, such as background matching, disruptive coloration, countershading, and masquerade, for predators and prey, respectively. Although body size and shape determine the appearance of animals, potentially affecting their camouflage effectiveness, research over the past two centuries has primarily focused on animal coloration. Over the past two decades, attention has gradually shifted to the impact of body size and shape on camouflage. In this review, we discuss the impact of animal body size and shape on camouflage and identify research issues and challenges. A negative correlation between background matching effectiveness and an animal's body size has been reported, whereas flatter body shapes enhance background matching. The effectiveness of disruptive coloration is also negatively correlated with body size, whereas irregular body shapes physically disrupt the body outline, reducing the visibility of true edges and making it challenging for predators to identify prey. Countershading is most likely in larger mammals with smaller individuals, whereas body size is unrelated to countershading in small‐bodied taxa. Body shape influences a body reflectance, affecting the form of countershading coloration exhibited by animals. Animals employing masquerade achieve camouflage by resembling inanimate objects in their habitats in terms of body size and shape. Empirical and theoretical research has found that body size affects camouflage strategies by determining key aspects of an animal's appearance and predation risk and that body shape plays a role in the form and effectiveness of camouflage coloration. However, the mechanisms underlying these adaptations remain elusive, and a relative dearth of research on other camouflage strategies. We underscore the necessity for additional research to investigate the interplay between animal morphology and camouflage strategies and their coevolutionary development, and we recommend directions for future research.
... Notably, the discontinuity between an animal's body and its background generates distinct visual clues even with backgrounds with high-fidelity color and texture matching, facilitating detection and identification by predators (Thayer, 1918). Simultaneously, the evolution of binocular vision and the ability to detect depth and 3D observation of the surroundings facilitate the detection of presence and shape of animals by predators (Julesz, 1971;Heesy, 2009). ...
Animal camouflage serves the dual purpose of enhancing predation or anti-predation efficiency through strategies such as background matching, disruptive coloration, countershading, masquerade, and motion dazzle. Although body size and shape determine the visual appearance of animals, potentially affecting their camouflage effectiveness, research over the past two centuries has primarily focused on animal coloration. Over the past two decades, attention has gradually shifted to the impact of body size and shape on camouflage. In this review, we analyze the impact of animal body size and shape on camouflage based on existing research and identify research issues and challenges. The results of existing studies indicate a negative correlation between background matching effectiveness and an animal’s body size, whereas flatter body shapes enhancing background matching. The effectiveness of disruptive coloration is also negatively correlated with body size, whereas irregular body shapes physically disrupt the body outline, reducing the visibility of true edges and making it challenging for predators to identify prey. Countershading is more likely to occur in larger mammal groups with smaller individuals, whereas body size is unrelated to countershading in smaller animal groups. Different body shapes also contribute to variations in countershading effectiveness. Animals employing masquerade achieve camouflage by resembling inanimate objects in their habitats in terms of body size and shape. The camouflaging effect of motion dazzle is negatively correlated with body size; however, the impact of body shape on motion dazzle remains unknown. A significant research gap exists in examining correlations between various camouflage strategies and body size and shape. Further, insufficient exploration of these strategies warrants thorough investigation in the future to better understand the mechanisms and evolutionary factors influencing camouflage in animals. Our review provides a theoretical foundation for the development of novel camouflage strategies.
... A wider potential field of more accurate depth perception offered by more forward-facing eyes may allow the animals to more accurately gauge the distance to their landing substrate. However, it has been suggested that stereopsis may not function over the distances crossed during potential grasp-leaping in the earliest crown primates (Heesy, 2009). It is also possible that either a narrow binocular field or the numerous depth cues available through the entire visual field (including motion parallax, perspective cues, etc) could have been sufficient to facilitate the type of leaping behavior used by the earliest crown primates and their immediate ancestors (Rock, 1984;Kandel, 1991;Heesy, 2009). ...
... However, it has been suggested that stereopsis may not function over the distances crossed during potential grasp-leaping in the earliest crown primates (Heesy, 2009). It is also possible that either a narrow binocular field or the numerous depth cues available through the entire visual field (including motion parallax, perspective cues, etc) could have been sufficient to facilitate the type of leaping behavior used by the earliest crown primates and their immediate ancestors (Rock, 1984;Kandel, 1991;Heesy, 2009). Even if either of these scenarios regarding depth cue importance for leaping and ancestral primates is correct, the increased light sensitivity, increased contrast discrimination, improved acuity and potential optical flow improvements afforded within the binocular field by forward-facing eyes may also have played a potentially important role in facilitating leaping behavior in a nocturnal arboreal crown primate ancestor. ...
... However, even when the effects of these adjustments are controlled statistically, subjects exhibited decreased landing performance under the reduced binocular field condition as indicated by their increased probability of experiencing adverse landings and requiring additional grasp adjustments. This importance of binocular visual cue availability for subjects' ability to execute precise landings runs counter to the suggestion that leaping behavior could not have selected for more forward-facing eyes in primates because landing substrates were outside of the functional range of stereopsis at the start of a leap (Heesy, 2009). Instead, the effect of binocular cue availability on landing precision regardless of launch adjustments suggests that even if early primates were engaging in leaps long enough that the range of stereopsis at take-off would not include the landing substrate, stereopsis could still have been important in facilitating preparation for a coordinated landing while the animal is in the air. ...
Multiple competing hypotheses attribute the evolution of the suite of traits that distinguish primates from their closest relatives, including forward-facing eyes which create a wide field of binocular vision, to specific behavioral and ecological factors. The Grasp-Leaping Hypothesis suggests that the evolution of these traits in basal primates was driven by the demands of a form of leaping locomotion unique to primates. Whether the Grasp-Leaping Hypothesis provides a viable mechanism for the evolution of primates’ forward-facing eyes remains untested. To determine whether grasp-leaping locomotion may have contributed to driving the evolution of primates’ forward-facing eyes, the importance of vision within the binocular field for this type of leaping was evaluated experimentally in Cheirogaleus medius, one of the cheirogaleid primate species considered reasonable living analogues of the earliest primates. Availability of binocular visual cues was experimentally restricted using a head-mounted blinder that narrowed binocular visual field without altering the total visual field. Animals altered their launch behavior, reduced their horizontal leap speed, and were significantly more likely to select paths that offered the shortest available leaps when their binocular field was restricted. Restriction of binocular cue availability also significantly increased the probability of adverse landings even when statistically controlling for potentially confounding variables such as leap distance, horizontal leap speed, learning effects, etc. These results suggest a functional mechanism by which selection for improved grasp-leaping could also have contributed to the evolution of forward-facing eyes in the earliest crown primates.
... However, while the reactions of jays and human participants to the fast pass effect are similar, they are unlikely to be homologous. This is because there are staggering differences between the corvid and the primate visual system (Heesy 2009, Martin 2007, with the corvid visual system having a flicker rate that is far superior to that of primates (Bobrowicz & Osvath 2019, Boström et al. 2016). Moreover, corvids are able to switch between binocular and monocular vision (Koboroff et al. 2008, Rogers & Kaplan 2006. ...
Magic is an art form that has fascinated humans for centuries. Recently, the techniques used by magicians to make their audience experience the impossible have attracted the attention of psychologists, who, in just a couple of decades, have produced a large amount of research regarding how these effects operate, focusing on the blind spots in perception and roadblocks in cognition that magic techniques exploit. Most recently, this investigation has given a pathway to a new line of research that uses magic effects to explore the cognitive abilities of nonhuman animals. This new branch of the scientific study of magic has already yielded new evidence illustrating the power of magic effects as a psychological tool for nonhuman animals. This review aims to give a thorough overview of the research on both the human and nonhuman perception of magic effects by critically illustrating the most prominent works of both fields of inquiry.
... The influence of activity pattern on primate biology has been a major focus of research in evolutionary anthropology because of its perceived importance for understanding the clade's early evolutionary history and the origin of crown Anthropoidea (Allman, 1977;Cartmill, 1992;Ross, 1996Ross, , 2000Ross, 2001, 2004;Kirk and Kay, 2004;Ravosa and Savakova, 2004). Numerous studies have demonstrated correlations between activity pattern and aspects of the visual system across primates (Kay and Cartmill, 1977;Kay and Kirk, 2000;Ross, 2004;Kirk, 2006aKirk, , 2006bRoss and Kirk, 2007;Heesy, 2008Heesy, , 2009), but the ecological consequences of diurnality and nocturnality are likely to be pervasive (Charles-Dominique, 1975;Clutton-Brock and Harvey, 1977; van Schaik and Kappeler, 1996;Kronfeld-Schor and Dayan, 2003). ...
Activity pattern has played a prominent role in discussions of primate evolutionary history. Most primates are either diurnal or nocturnal, but a small number are active both diurnally and nocturnally. This pattern—cathemerality—also occurs at low frequency across mammals. Using a large sample of mammalian species, this study evaluates two macroevolutionary hypotheses proposed to explain why cathemerality is less common than diurnality and nocturnality: (1) that cathemeral lineages have higher extinction probabilities (differential diversification), and (2) that transitions out of cathemerality are more frequent, making it a less persistent state (differential state persistence). Rates of speciation, extinction, and transition between character states were estimated using hidden-rates models applied to a phylogenetic tree containing 3013 mammals classified by activity pattern. The models failed to detect consistent differences in diversification dynamics among activity patterns, but there is strong support for differential state persistence. Transition rates out of cathemerality tend to be much higher than transition rates out of nocturnality. Transition rates out of diurnality are similar to those for cathemerality in most clades, with two important exceptions: diurnality is unusually persistent in anthropoid primates and sciurid rodents. These two groups combine very low rates of transition out of diurnality with high speciation rates. This combination has no parallels among cathemeral lineages, explaining why diurnality has become more common than cathemerality in mammals. Similarly, the combination of rates found in anthropoids is sufficient to explain the low relative frequency of cathemerality in primates, making it unnecessary to appeal to high extinction probabilities in cathemeral lineages in this clade. These findings support the hypothesis that the distribution of activity patterns across mammals has been influenced primarily by differential state persistence, whereas the effect of differential diversification appears to have been more idiosyncratic.
... The two ecological factors considered here, diet and locomotion, have previously been shown as significantly associated with cranial variation for the whole skull [2,73,102,[128][129][130][131][132][133][134][135][136][137][138]. Here, we show that these associations are supported in roughly half of the cranial elements, with diet influencing slightly more elements, and with stronger effect, than does locomotion [73,137]. ...
The placental skull has evolved into myriad forms, from longirostrine whales to globular primates, and with a diverse array of appendages from antlers to tusks. This disparity has recently been studied from the perspective of the whole skull, but the skull is composed of numerous elements that have distinct developmental origins and varied functions. Here, we assess the evolution of the skull's major skeletal elements, decomposed into 17 individual regions. Using a high-dimensional morphometric approach for a dataset of 322 living and extinct eutherians (placental mammals and their stem relatives), we quantify patterns of variation and estimate phylogenetic, allometric and ecological signal across the skull. We further compare rates of evolution across ecological categories and ordinal-level clades and reconstruct rates of evolution along lineages and through time to assess whether developmental origin or function discriminate the evolutionary trajectories of individual cranial elements. Our results demonstrate distinct macroevolutionary patterns across cranial elements that reflect the ecological adaptations of major clades. Elements derived from neural crest show the fastest rates of evolution, but ecological signal is equally pronounced in bones derived from neural crest and paraxial mesoderm, suggesting that developmental origin may influence evolutionary tempo, but not capacity for specialisation.
This article is part of the theme issue ‘The mammalian skull: development, structure and function’.
... 5b-d, 6a, c). Arboreal species rely mostly on vision for perceiving their environment 89 , which enables them to locate important objects such as food sources or predators at a distance and has, alongside the evolution of binocular colour vision and consequent depth perception, led to the complexification of cortical visual processing. This is reflected in our data by a selective expansion of occipital and dorsolateral aspects of the cerebral cortex in association with arboreality. ...
Studies in comparative neuroanatomy and of the fossil record demonstrate the influence of socio-ecological niches on the morphology of the cerebral cortex, but have led to oftentimes conflicting theories about its evolution. Here, we study the relationship between the shape of the cerebral cortex and the topography of its function. We establish a joint geometric representation of the cerebral cortices of ninety species of extant Euarchontoglires, including commonly used experimental model organisms. We show that variability in surface geometry relates to species’ ecology and behaviour, independent of overall brain size. Notably, ancestral shape reconstruction of the cortical surface and its change during evolution enables us to trace the evolutionary history of localised cortical expansions, modal segregation of brain function, and their association to behaviour and cognition. We find that individual cortical regions follow different sequences of area increase during evolutionary adaptations to dynamic socio-ecological niches. Anatomical correlates of this sequence of events are still observable in extant species, and relate to their current behaviour and ecology. We decompose the deep evolutionary history of the shape of the human cortical surface into spatially and temporally conscribed components with highly interpretable functional associations, highlighting the importance of considering the evolutionary history of cortical regions when studying their anatomy and function.
... For instance, Cooper's Hawks (Accipiter cooperi), a closed habitat species, have a wider binocular field, a longer vertical extent of the binocular field (above the head), and a narrower blind area than Red-Tailed Hawks (Buteo jamaicensis), an open habitat species, likely to improve visual performance in vertically complex environments (O'Rourke et al. 2010a). Wide binocular fields have been suggested to increase contrast discrimination (Heesy 2009) and provide stereoscopic cues in arboreal habitats (Changizi and Shimojo 2008). Binocular vision in raptors have been suggested to be involved in depth perception via stereopsis (Pettigrew and Konishi 1976;Fox et al. 1977;Pettigrew 1978;van der Willigen et al. 1988;Wagner and Frost 1994), but others have suggested that it would mainly be involved in topic flow-field information (Martin 2009). ...
We describe for the first time the visual fields of the largest tropical raptor, the Harpy Eagle (Harpia harpyja), a powerful keystone species that hunts almost exclusively in forested habitats. They have the largest blind area described to date of any diurnal raptor species, and relatively narrow binocular fields, which together may help explain the way they interact with their prey in the visually complex environments they inhabit. As a top predator, their spatial visual sampling is likely driven more by foraging needs than predator detection, and they thus serve as an excellent study species for understanding the tradeoffs between visually guided foraging and anti-predatory behaviors. Further studies on the position and the projection of retinal foveae, visual acuity, and color vision will improve our understanding of their visual capabilities and could play important roles in conservation of a vulnerable Neotropical species.
... In addition to retinal, cortical, and other soft-tissue mechanisms for integrating visual sensory fields (e.g., 2 and references therein), certain cranial modifications are thought to enhance the ability to collect visual imagery. Foremost among these is the presence of forward-facing (or convergent) bony orbits [1][2][3][4] . A high level of orbital convergence enables significant visual field overlap, which is fundamental for neurological processing of depth information [1][2][3][4][5] . ...
... Foremost among these is the presence of forward-facing (or convergent) bony orbits [1][2][3][4] . A high level of orbital convergence enables significant visual field overlap, which is fundamental for neurological processing of depth information [1][2][3][4][5] . ...
The evolution of mammalian vision is difficult to study because the actual receptor organs-the eyes-are not preserved in the fossil record. Orbital orientation and size are the traditional proxies for inferring aspects of ocular function, such as stereoscopy. Adaptations for good stereopsis have evolved in living predaceous mammals, and it is reasonable to infer that fossil representatives would follow the same pattern. This applies to the sparassodonts, an extinct group of South American hypercarnivores related to marsupials, with one exception. In the sabertooth Thylacosmilus atrox, the bony orbits were notably divergent, like those of a cow or a horse, and thus radically differing from conditions in any other known mammalian predator. Orbital convergence alone, however, does not determine presence of stereopsis; frontation and verticality of the orbits also play a role. We show that the orbits of Thyla-cosmilus were frontated and verticalized in a way that favored some degree of stereopsis and compensated for limited convergence in orbital orientation. The forcing function behind these morphological tradeoffs was the extraordinary growth of its rootless canines, which affected skull shape in Thylacosmilus in numerous ways, including relative orbital displacement.
... Other orders (e.g., rodents and scandentia) also show a preference for sitting during precursory use of skilled forelimb movements (Whishaw et al., 1998), and they may rely on similar mechanisms, although body-eye-hand coordinate transformation was little documented in nonprimates. One potential difference between primates and nonprimates is that object reaching and handling could involve different sensory modalities, such as chemosensation in mice (Galiñanes et al., 2018) versus vision in primates (Heesy, 2009). Another distinction is that primates uniquely combined vertical posture with other task-related adaptations, such as binocular vision for 3D/depth perception, high visual acuity (Heesy, 2009), and forelimb musculoskeletal features associated with graspingrelated functional properties (e.g., independent finger movements and opposable thumbs; Molnar et al., 2017). ...
... One potential difference between primates and nonprimates is that object reaching and handling could involve different sensory modalities, such as chemosensation in mice (Galiñanes et al., 2018) versus vision in primates (Heesy, 2009). Another distinction is that primates uniquely combined vertical posture with other task-related adaptations, such as binocular vision for 3D/depth perception, high visual acuity (Heesy, 2009), and forelimb musculoskeletal features associated with graspingrelated functional properties (e.g., independent finger movements and opposable thumbs; Molnar et al., 2017). These gave way to greater manipulation complexity and visuomotor processing skills, which had to be translated into multiple coordinate systems. ...
