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Although self-recognition or self-awareness has been studied with the visually-based mirror test, passed by several species, primarily apes, the possibility of a chemically-based analogue is controversial. Prior studies suggested that chemical self-recognition may occur in some squamate reptiles. To evaluate this possibility, we studied 24 individually housed gartersnakes, Thamnophis sirtalis, raised from birth on either earthworm or fish diets and tested 12 male and 12 female snakes with cage liners that were either clean, their own, or from same-sex siblings fed their own or the opposite diet. Tongue flicking and activity were recorded in 30-minute video-recorded trials in a balanced design. After initial habituation to the stimuli, male, but not female, snakes discriminated between their own stimuli and those from littermates fed the same diet. Combined with other data and studies, the possibility that a chemical ‘mirror’ form of self-recognition exists in squamate reptiles is supported.

[Correction Notice: An Erratum for this article was reported in Vol 135(3) of Journal of Comparative Psychology (see record 2021-87304-004). In the article "How Comparative Was (Is) the Journal of Comparative Psychology? A Reptilian Perspective" by Gordon M. Burghardt (Journal of Comparative Psychology. Advance online publication. August 5, 2021. http://doi.org/10.1037/com0000290), the phrase in the introduction that includes the Dewbury (1998) citation also includes an extra word. The phrase should appear as Dewbury (1998) noted that the focus. The year of publication for the Journal of Animal Behavior that appears in the third line of the Method section should appear as (1911-1917). The last sentence in the first paragraph of the Method section should appear as The 8,911 entries over this 110-year period constituted the data analyzed here in detail. The first sentence of the Results section should appear as The Journal of Animal Behavior published 238 articles in its 7-year run. The last phrase of the first paragraph of the Results section should appear as and 8,635 published items of the JCP and JCPP....] Comparative psychology, and particularly the Journal of Comparative Psychology, has been criticized for a lack of taxon diversity. The nature and consequences of the critiques are discussed and assessed by analyzing the representation of nonavian reptiles in the journal over its 100-year existence. Although reptiles are indeed rare in the journal, their representation has greatly increased in recent decades, and especially since about 1980. More interestingly, the mix among the major reptilian groups: turtles, lizards, snakes, and crocodylians, has shifted. First turtles predominated in studies, but in recent decades, snakes were far more prominent. In the last 50 years of the journal, there were 10 times the number of articles on snakes than in the first 50 years, turtles declined, and lizards increased greatly, although their totals remained less than half the number of snake articles. Crocodylians only appeared in the first several volumes in the 1920s and never again. The predominance of snakes, not known for their cognitive prowess, in a journal viewed increasingly as an outlet for work on comparative cognition, is discussed. Finally, it appears that the low representation of reptile behavioral research is not peculiar to the Journal of Comparative Psychology, but animal behavior journals more generally. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

An appreciation of the diverse roots of animal behaviour study is essential for informed teaching and stimulating current research and scholarship. Insights by early seminal authors are often ignored, insights that may have avoided subsequent controversies or spawned productive research. Even with internet access now available for much early work, historical perspectives are increasingly being lost. Animal behaviour textbooks are often misleading and simplistic on historical matters. In this paper, I document how four authors writing 100 or more years ago greatly influenced my research on nonavian reptile behaviour. These four authors, which merit serious re-reading by students of virtually any taxa and topic, are Jakob von Uexkull, Margaret Floy Washburn, James Mark Baldwin and Wallace Craig. There are also current and upcoming challenges and risks impacting animal behaviour research that may affect how today's research will be viewed in historical perspectives 50, 100 or more years from now.

Play is an important and understudied class of phenomena that likely serves a critical role in the ontogeny and maintenance of fitness-enhancing behaviors. Many species exhibit little or no play. Among those animals that do play, some exhibit only very simple forms, while others engage in complex play both solitarily and socially. Likewise, some animals play only as juveniles, while others continue to play as adults. We propose a general framework to explain interspecies variation in the evolution and emergence of simple vs. complex forms of play, supported by both a review of the empirical evidence and a novel mathematical model. The emergence of play requires that initial investment returns benefits that sufficiently compensate the opportunity costs associated with simple play. The subsequent evolution of complex play depends upon the interplay of several life-history factors related to the benefits, costs, and time course of play investment. We conclude with implications for understanding the evolution of play across the animal kingdom.

Wallace Craig's "Appetites and Aversions as Constituents of Instincts," one of the seminal articles in animal behavior, comparative psychology, and ethology, appeared 100 years ago this year. The influence of this classic article is continuing and perhaps even expanding. Here we review the major ideas Craig offered in the article, provide a brief sketch of his scientific career and historical context, and examine the impact of the article on ethological and instinct theory. We also review some current applications of his work in diverse areas and discuss why it is cited more now than in earlier decades, especially in articles on causal mechanisms. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

The Illusion of God’s Presence is an important book on the spiritual quest from an ethological perspective filtered through an updated Freudian lens. Ethology is the naturalistic study of behavior ...

Play behavior and playfulness may be major factors in behavioral and cultural evolution in animals, and especially people. Although play is largely ignored by scholars and scientists dealing with human cultural evolution, this chapter argues that it is an ancient and deep phenomenon that has appeared repeatedly throughout evolution, is at the root of many behavioral and social phenomena, and ignoring it fosters a myriad of often incompatible scenarios. For example, play and ritual seem to be disparate phenomena, one focused on freedom and variety, the other on formality and rigidity. In reality, they have many common elements, and play may be a source for not only rituals in animals, but also cultural attainments in humans including language, tools and other innovations, morality, religion, science, as well as other aspects of our lives typically viewed through an anthropocentric lens. Surplus Resource Theory helps explain the organismal and setting conditions for play behavior in many species and the cultural attainments of humans and thus aids integration across academic fields. The playful origin of religion, as posited by Robert Bellah in his treatise Religion in Human Evolution, is highlighted.

One of the most eventful periods in the study of animal behavior was from the end of WWI to the awarding of the Nobel Prize in Physiology or Medicine to three of the major contributors to the field during that period. It was a time during which the traditional zoological natural history, ethology, animal psychology, and comparative psychology traditions developed along different conceptual and methodological lines and diverged considerably; then began a reconciliation that continued even as new approaches and methods came to the fore.

Social play is a fundamental aspect of behavioral development in many species. Social play deprivation in rats alters dendritic morphology in the ventromedial prefrontal cortex (vmPFC) and we have shown that this brain region regulates responses to social defeat stress in Syrian hamsters. In this study, we tested whether play deprivation during the juvenile period disrupts dendritic morphology in the prefrontal cortex and potentiates the effects of social defeat stress. At weaning, male hamsters were either group-housed with peers or pair-housed with their mother, with whom they do not play. In adulthood, animals received acute social defeat stress or no-defeat control treatment. The hamsters were then tested for a conditioned defeat response in a social interaction test with a novel intruder, and were also tested for social avoidance of a familiar opponent. Brains were collected for Golgi-Cox staining and analysis of dendritic morphology in the infralimbic (IL), prelimbic (PL), and orbitofrontal cortex (OFC). Play-deprived animals showed an increased conditioned defeat response and elevated avoidance of a familiar opponent compared with play-exposed animals. Furthermore, play-deprived animals showed increased total length and branch points in apical dendrites of pyramidal neurons in the IL and PL cortices, but not in the OFC. These findings suggest that social play deprivation in juvenile hamsters disrupts neuronal development in the vmPFC and increases vulnerability to the effects of social stress in adulthood. Overall, these results suggest that social play is necessary for the natural dendritic pruning process during adolescence and promotes coping with stress in adulthood. (PsycINFO Database Record

Our knowledge of the biology of neonatal snakes has lagged behind that of adult animals, mostly due to the difficulty of finding and studying neonatal snakes in the wild. Traditional approaches view neonatal reptiles as miniature replicates of their adult counterparts. In this contribution, we present data on the natural history of neonatal Green Anacondas from opportunistic captures in the wild over a 17-year period, as well as from a brief study on captive-born radio-tagged individuals. Both approaches converge in presenting a picture of the ecology of neonatal anacondas showing many similarities between their natural history and that of adult anacondas in spite of the great size difference. The neonates' biology resembles that of adults, especially males, in their preference for birds in their diet, the relative prey size they choose, slow growth rates they experience, low feeding frequency, little mobility, and preference for similar habitats of stagnant, shallow water covered by aquatic vegetation. T...

Object play occurs in diverse animals in addition to birds and mammals. Although many carnivores engage in object play in a predatory context, many non-predators do so also. Conjectures over the years on the motivation to play are reviewed dealing with intrinsic, developmental, and stimulus factors. We then report on quantitative studies of the play of puppies from 6 litters (3 breeds) when given 5 different toys with different sensory and functional properties at half week intervals from 3 to 7 weeks of age. The propensity to engage with objects begins early, play complexity increases rapidly, the structure of the play is similar to adult object play, and breed differences were found. Object play with predatory characteristics appears before weaning, suggesting that hunger is not the primary motivation. Studying the development of object play in different dog breeds may be useful in addressing questions of domestication and play evolution.

In several rodent species social play appears to be necessary for proper deployment of species-specific patterns of aggressive and reproductive behavior. Specifically, in male Syrian hamsters (Mesocricetus auratus), play has been linked to the development of adult aggression. We quantified several types of social play behavior in same-sex peer groups of Syrian hamsters three times per week for three consecutive weeks after weaning, which included postnatal days 22–42 (PD22 to PD42). Male hamsters increased playful contact during PD36-PD42, whereas females showed peak playful contact during PD29-PD35. These findings suggest that the motivation for social play increases during mid-adolescence in males, but dissipates in females. To investigate the effects of social play deprivation, one hamster per litter remained pair-housed with its mother for three weeks after weaning its littermates. In adulthood, both play-deprived and play-exposed animals received acute social defeat stress followed by social interaction testing. Play deprivation led to increased defeat-induced social avoidance in both males and females. In males, play deprivation increased fighting back during social defeat stress, whereas in females it reduced aggressive behavior during conditioned defeat testing. We suggest that social play deprivation disrupts neural circuits regulating aggression in a sex-specific manner, perhaps related to sex differences in territorial defense, but has similar effects on neural circuits regulating stress responsivity. Overall, these findings suggest that juvenile social play functions to promote coping with stress and appropriate social behavior in adulthood.

Juvenile animals of many species engage in social play, but its functional significance is not well understood. This is especially true for a type of social play called fair play. Social play often involves behavioral patterns similar to adult behaviors (e.g., fighting, mating, and predatory activities), but young animals often engage in fair play behaviors such as role-reversals and self-handicapping, which raises the evolutionary problem of why fair play exists. A long-held working hypothesis, tracing back to the 19th century, is that social play provides contexts in which adult social skills needed for adulthood can be learned or, at least, refined. On this hypothesis, fair play may have evolved for adults to acquire skills for behaving fairly in the sense of equitable distribution of resources or treatment of others. We investigated the evolution of fair play using an evolutionary agent-based model of populations of social agents that learn adult fair behavior by engaging in fair play as juveniles. In our model, adults produce offspring by accumulating resources over time through foraging. Adults can either behave selfishly by keeping the resources they forage or they can pool them, subsequently dividing the pooled resources after each round of foraging. We found that fairness as equitability was beneficial especially when resources were large but difficult to obtain and led to the evolution of fair play. We conclude by discussing the implications of this model, for developing more rigorous theory on the evolution of social play, and future directions for theory development by modeling the evolution of play.

Although play occurs in a wide variety of animals, models of the origins of play behavior are lacking. We propose a novel computational model exploring the evolution of non-social frivolous play. Asexually reproducing semelparous animals can either rest or forage. Foraging occurs when an organism is below an energy threshold. Success is determined by the combination of skill and availability of resources, which declines over time but replenishes for each generation. Play was introduced as a mutant strategy: a frivolous activity that uses energy and increases the probability of dying over resting with no direct fitness benefit. Simulations show that play behavior becomes fixed in the population and the time spent playing is maintained at a low rate in spite of its costly nature. When play behavior is functional by increasing foraging ability, it evolves quickly and the time individuals spend playing increases, but eventually the population of players collapses and play disappears. We suggest a mechanism underlying the origins of adaptive play from non-adaptive behavior when resources expand. Initially play acts as a spiteful behavior in that playing individuals suffer a direct cost to their fitness, but also may incur even greater costs to other individuals in the population.

What factors in animal life history facilitate or reduce the probability that a species will perform play behavior? While some relationships are known within species and across individuals, it is not obvious that such relationships can be used to explain differences and similarities in amount and type of play across large taxonomic groupings of animals, let alone transitions among them. Primates encompass a relatively large assemblage of species that differ in numerous dietary, habitat, reproductive, and physiological processes. While all juvenile primates engage in social play, far fewer primate species engage in social play as adults. Here, derived from theory and more small-scale comparisons, we explore several biological and behavioral phenomena that differ among nonhuman primates and which may explain differences in the occurrence of adult–adult social play. We used phylogenetic logistic regression to assess the correlation of adult play with various life-history, metabolic and socioecological variables. Although the main contribution of our paper is demonstrating use of phylogenetic methods in the context of play evolution, suggestive but not significant evidence was found that adult sexual and nonsexual social play is influenced by diet, habitat, reproductive, and metabolic factors, sometimes in opposite directions, that we discuss along with needed future analyses involving improved data and interactions among traits.

Casualties and impediments inflicted on consumers by defended prey, and vice versa, may be averted by vocalizations, postures, coloration, scents, and other warning, or so-called aposematic, displays. The existence of aposematic signals has challenged biologists who have sought plausible mechanisms for their evolution. Here, we elaborate on the rationale for the hypothesis that aposematic signals arise via concurrent reciprocal selection (CRS) enacted between inimical signal receivers and signal emitters, where signal emitters, e.g., defended prey, select against non-discriminating signal receivers, e.g., predators, and signal receivers select against unrecognized signal emitters. It is postulated that this mutual selective interaction culminates in the survival of discriminating signal receivers that avoid signal emitters, and recognized (distinctive) signal emitters that are avoided by signal receivers. A CRS hypothesis for the evolution of aposematism, therefore, maintains that distinctive features of prey arise in response to selection imposed by consumers, and that avoidances of those features by consumers arise in response to selection imposed by defended prey. We discuss the plausible inception of aposematism via CRS in light of related hypotheses, and describe points of concordance with previous observations and suggestions on the origin of aposematism. Aposematism arising via CRS is not contingent upon the relatedness of signallers, aversions acquired by learning, or other conditions postulated for some other evolutionary hypotheses. CRS is a credible alternative hypothesis for the evolution of warning signals in diverse consumer-prey interactions.

Rough-and-tumble play (RT) is a widespread phenomenon in mammals. Since it involves competition, whereby one animal attempts to gain advantage over another, RT runs the risk of escalation to serious fighting. Competition is typically curtailed by some degree of cooperation and different signals help negotiate potential mishaps during RT. This review provides a framework for such signals, showing that they range along two dimensions: one from signals borrowed from other functional contexts to those that are unique to play, and the other from purely emotional expressions to highly cognitive (intentional) constructions. Some animal taxa have exaggerated the emotional and cognitive interplay aspects of play signals, yielding admixtures of communication that have led to complex forms of RT. This complexity has been further exaggerated in some lineages by the development of specific novel gestures that can be used to negotiate playful mood and entice reluctant partners. Play-derived gestures may provide new mechanisms by which more sophisticated communication forms can evolve. Therefore, RT and playful communication provide a window into the study of social cognition, emotional regulation and the evolution of communication systems.

When I was in the midst of writing my conceptual and empirical overview of play in animals, Brian Sutton-Smith published, in 1997, his compact and magisterial work, The Ambiguity of Play. I immedia...

Animals that depend on defensive chemicals acquired from food may face a decision when attempting to deter predatory attacks: Should they exhibit antipredator behavior that relies on the toxicity of the sequestered chemicals or should they adopt other behaviors that can avoid predation without using the chemical defense, such as flight? Thus, it is reasonable to assume that animals that sequester prey toxins have evolved the ability to flexibly change their antipredator responses according to the amount of toxin-resource they have consumed. We tested this hypothesis using an Asian snake, Rhabdophis tigrinus, that sequesters toxins from toads consumed as food and stores them in specialized organs back of the head, called nuchal glands. We reared hatchling snakes from toad-free and toad-rich islands on controlled diets and examined their subsequent antipredator responses after 3 and 6 month feeding. Juveniles from a toad-free island that had been fed a diet including toads for 3 months showed antipredator displays associated with the nuchal glands more frequently than those that had been fed a diet without toads. They showed a similar, but less clear, tendency after 6 months feeding. Juveniles from the toad-rich island did not show a clear tendency of dietary effect. We discuss possible reasons for the different dietary effects between the 2 populations and between the ages. Our results, along with previous related phenomena in other animals, suggest that the ability of self-toxicity-recognition may be widespread in animals that sequester defensive toxins from facultative food. (PsycINFO Database Record