Video © Marc Bekoff
Play has been postulated to serve a variety of functions, including practice of life skills, provision of benefits associated with exercise and cognitive development, reinforcement of social bonds, and enhanced familiarity with the animal’s environment. While the exact function is difficult to determine, it is critical that individuals engaging in social play interpret acts of their partner as play, and not as aggression. Here, a dog exhibits the familiar canine “play bow,” which serves as a form of metacommunication (communication about communication), indicating that all acts to follow should be interpreted in the context of play. Indeed, domestic dogs often engage in rambunctious play that involves growling, baring teeth, and ritualized biting, all of which are commonly perceived by partners as play and not aggression when preceded by a play bow.
FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 13, “Communication”; chap. 16, “Play, Aging and Disease, Animal Personalities.” L. A. Dugatkin and M. Bekoff, “Play.” Behavioural Processes 60 (2003), pp. 209–214
Courtesy Serge Pellis
Play fighting in rodents is typified by elements resembling adult sexual behavior (e.g., play mounting) and aggression (e.g., attacks on the nape of the neck). Males exhibit a higher frequency of these behaviors than females as a result of the masculinizing effects of testosterone over the course of development. In addition to the direct role of testosterone, however, the aromatization of testosterone to estrogen in developing males also acts to promote sex differences in play behavior.
FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 3, “Hormones and Neurobiology”; chap. 16, “Play.” E. F. Field, I. Q. Whishaw, S. M. Pellis, and N. V. Watson, “Play fighting in androgen-insensitive tfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense,” Developmental Psychobiology 48 (2006), pp. 111–120.
Diane Mollaghan/Sam Gosling
This clip presents extremes along the dimension of fearfulness. We see a highly fearful dog that is cowering, flinching at sounds produced by conspecifics, holding its tail low, closing its mouth, and avoiding eye contact, in contrast to a nonfearful dog that is rising to greet a human visitor, engaging that individual with its eyes, wagging its tail, and vocalizing with its mouth loosely held open.
FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 17, “Animal Personalities.” A. C. Jones and S. D. Gosling, “Temperament and personality in dogs (Canis familiaris): A review and evaluation of past research,” Applied Animal Behaviour Science 95 (2005), pp. 1–53.
Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 17, “Animal Personalities.” A. C. Jones and S. D. Gosling, “Temperament and personality in dogs (Canis familiaris): A review and evaluation of past research,” Applied Animal Behaviour Science 95 (2005), pp. 1–53.
Research into animal personalities has revealed that like humans, non-human animals show behavioral propensities that are more or less stable within individuals over time and within different environmental contexts. In fact, the same major dimensions used to describe and quantify human personality have been applied to non-human animals, and explain the majority of behavioral variation among individuals in several species (e.g., in spotted hyenas, Crocuta crocuta, those scales explain 75 percent of the total variation in behavior). Beyond its theoretical importance, research addressing animal personality can be applied to improve animal welfare and can facilitate matching companion/service animals to both the temperament and tasks desired by their human partners. This clip contrasts two dogs in terms of aggressiveness, with the first individual showing high aggression, and the second low aggression. The aggressive individual lunges at a human visitor; its overall posture is high and stiff, its ears are laid back against its head, its eyes are set in a fixed stare, its teeth are bared, and it growls and barks. The nonaggressive individual approaches the human visitor with its tail wagging, its ears in neutral position, and its mouth intermittently open with the tongue licking the lips.
FURTHER READING: Diane Mollaghan/Sam Gosling
Individuals placed in the same situation often show dramatically different behavior, and yet within a given individual, behavior may be remarkably consistent across different contexts, suggesting a more or less stable personality type. Here, red squirrels (Tamiasciurus hudsonicus) are tested in an open field as a component of assessing their underlying personality. While one individual is quite active, and it devotes a considerable amount of its time to escape-related behavior, another individual placed in the same open field essentially remains inactive throughout its trial. Work on red squirrels reveals that populations are composed of individuals manifesting a range of personalities, as the fitness consequences of personality are context-dependent, and the environment varies extensively from year to year. In years with an abundance of food, more active individuals are able to channel the foraging benefits of their lifestyle into more rapid offspring growth, but when food is limited, offspring of passive mothers benefit disproportionately, as energy is not lost to excessive activity.
FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 17, “Animal Personalities.” A. K. Boon, D. Reale and S. Boutin, “The interaction between personality, offspring fitness and food abundance in North American red squirrels,” Ecology Letters 10 (2007), pp. 1094–1104.
Allison M. Bell
A three-spined stickleback (Gasterosteus aculeatus) is presented with a potential predator (a northern pike—Esox lucius) behind a Plexiglas™ divider to assess its boldness under apparent predation risk. Relatively bold individuals approach and inspect predators, while shy individuals take refuge under available cover. Work on behavioral syndromes typically reveals positive correlations between activity levels, boldness, and aggression, suggesting not only the existence of general personality types, but also that the non-independence of behaviors across different functional contexts may constrain the evolutionary modification of a given behavior should environmental change occur. Research performed by Allison Bell, however, examining behavioral correlations and the heritability of behavioral traits in sticklebacks derived from populations exposed to different levels of predation risk, suggests that behavioral syndromes don’t always act as evolutionary constraints.
FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 12, “Antipredator Behavior”; chap. 17, “Animal Personalities.” A. M. Bell, “Behavioural differences between individuals and two populations of stickleback (Gasterosteus aculeatus),” Journal of Evolutionary Biology 18 (2005), pp. 464–473.