KeywordsPersonality Trait Parenting Style Bottlenose Dolphin Wild Chimpanzee African Elephant
The examination of the relationship between social factors and animal personality.
Research on animal personality has blossomed over the past few decades with a variety of species being studied. While the genesis of animal personality is debatable, many would agree that social factors play a role. Therefore, social mammals make especially good subjects for personality research as they are presented with many opportunities for individual variation within contexts such as mate choice, parenting style, competition, and cooperation. Additionally, a given personality trait can be adaptive to the presenting individual, the entire social group, or both. For instance, the trait of boldness can lead to an increase in mating success for the presenting individual (e.g., Godin and Dugatkin 1996; Nettle 2006), whereas an especially creative individual may develop a novel solution to a problem from which other group members can also benefit (Matsuzawa 2003). Overall, personality traits and social factors seem to be closely related. This chapter will highlight the relationship between animal personality and social factors in three widely studied social mammals: chimpanzees, dolphins, and elephants.
Chimpanzees (Pan troglodytes) live in fission-fusion societies in which the composition of the social group changes for different situations (Nishida 1968). For example, females will change membership from one group to another when seeking mates. Adult males will often forage alone or form a small hunting party. Male chimpanzees (and females to an extent) present a dominance hierarchy with one individual as the alpha and the rest falling in a fairly linear fashion (Noe et al. 1980). Short- and long-term alliances are often maintained with food sharing and grooming behaviors. Consequently, chimpanzee communities are dynamic and provide many opportunities for individual differences to present themselves. For example, researchers studying wild chimpanzees observed an adult male repeatedly using a probe to open up his blocked nasal passages (Nishida and Nakamura 1993). The researchers noted that it was curious that no other chimpanzees were observed exhibiting this behavior and suggested that sticking an external object into such a delicate place may be considered to be too bold for the other members (Nishida 2003). Another creative solution was seen when an alpha male exhibited a novel behavior where he wiped his mouth with leaves and branches while eating juicy lemons (Nishida 2003). This leaf napkin behavior then appeared to spread to at least nine other chimpanzees in the group. In this case, the creative individual provided a new strategy for the group. These observations support the idea that personality traits can be adaptive in animal societies.
More formal investigations of chimpanzee personality have also been made. One of the first examinations of chimpanzee personality had human raters assess wild chimpanzees on 45 paired-word traits (Buirski et al. 1978). The ratings revealed consistent, reliable patterns in personality for both male and female chimpanzees across multiple raters. Additionally, personality seemed to be related to the dominance ranking of individuals, with more dominant animals demonstrating more aggressive personalities and less dominant animals demonstrating more timid personalities. These early findings may suggest that personality factors can serve a role in various chimpanzee social interactions as well as influence aspects of group living in a socially cohesive species.
While much research has been conducted since to refine and further disseminate the presence of chimpanzee personality and its parallels to human personality (e.g., King and Figueredo 1997), there are several key studies which examine the implications of personality on components of chimpanzee social behavior and their role in a chimpanzee society. For example, Koski (2011) investigated how social networks influence variation in personality expression in chimpanzees. Personality was measured for 75 captive chimpanzees across three zoos that exhibited high repeatability on several social behaviors. All repeatable behaviors were then analyzed with factor analysis, which resulted in five emergent personality traits specifically oriented toward social components of chimpanzee behavior: sociability, positive affect, equitability, anxiety, and activity. Chimpanzees exhibited variation in trait expression between zoos, emphasizing the importance of accounting for a variety of external forces that influence personality in social and nonsocial contexts. Moving forward, it would be valuable to examine if certain socially organized chimpanzee personality traits led to higher evolutionary fitness. For example, in humans there is a correlation between high levels of extraversion and likelihood of having children (Jokela et al. 2009) and size of social networks (Swickert et al. 2002). Studies of this nature with chimpanzees would allow for evolutionary comparisons of how personality and social factors influence each other.
Another social factor in which personality can play a role is friendship. For instance, human children have friends with whom they share significant similarities in temperament, and these similarities precede the formation of such friendships (Dunn and Cutting 1999; Rubin et al. 1994). Massen and Koski (2014) similarly assessed the role of personality in chimpanzee friendships. Results indicated friends were significantly more similar on personality factors sociability and boldness when compared to dyads of non-friends. However, it has yet to be determined whether chimpanzees choose friends based upon having similar personalities or if the similar personalities develop by chance. Chimpanzee dyads with similarities in boldness and sociability may be adaptive due to their function in cooperative situations among unrelated individuals. Further research is needed to assess the role and development of personality in chimpanzees and what function such individual differences serve in other social roles that exist for chimpanzees.
Much like chimpanzees, bottlenose dolphins (Tursiops truncatus) possess a broad and diverse behavioral repertoire, providing ample opportunity for individual differences. They also exhibit a fission-fusion social structure and engage in numerous social associations and interactions, which include mating alliances, group foraging, pair bonds, and alloparental relationships (Shane et al. 1986). The type of associations and relationships an individual engages in could be indicative of their individual personality.
For example, dolphins have been observed around the world engaging in a variety of feeding strategies such as schooling prey, searching the sand for prey, or even beaching themselves to obtain fish (Mann et al. 2000). In particular, observations were made of two groups of bottlenose dolphins near the coast of Florida that used a specialized cooperative technique to acquire fish which involved one animal using fluke slaps to herd or drive fish toward the other members of the group. It was determined that the identity of the driver in each group remained the same during each fishing bout (Gazda et al. 2005). Although it is unclear why these individuals developed this specialized role, personality may be a factor.
There is also evidence of individual differences from studies of maternal care and infant behaviors in dolphins. For example, Hill et al. (2007) found that dolphin mothers demonstrate consistent individual differences in parenting styles. The most apparent difference was the mothers’ use of discipline in controlling and herding their calf. Parental care is costly, and individual differences in maternal care patterns may have important evolutionary implications. Individual differences have also been observed in studies of the early social development of wild bottlenose dolphins (Gibson and Mann 2008). Wild-born calves differed in terms of their independence and time spent near their mom, which could be an early indicator of the bold-shy continuum (Mann 1997).
The first empirical evidence of personality in bottlenose dolphins was by Highfill and Kuczaj (2007). Human ratings of dolphin personality were examined before and after drastic changes to the subjects’ physical and social environments due to Hurricane Katrina. It was found that the personality traits of 12 of the 15 dolphins remained consistent from assessment 1 to assessment 2. Kuczaj et al. (2012) investigated the importance of context and temporal stability in personality characteristics by assessing specific traits across three contexts (interactions with the physical world, interactions with other dolphins, and interactions with humans). Four of the subjects were stable in all traits across all contexts, while the remaining 16 dolphins’ ratings were variable across contexts, supporting the notion that context affects personality expression and should be accounted for in future assessments.
Personality in social contexts in particular has been thought to serve a function in different social roles, such as dolphin hierarchy social rank. In a recent assessment, Frick (2016) examined the relationship between personality and rank within the dominance hierarchy for a semi-captive and socially housed group of 24 bottlenose dolphins. Scores for all personality factors were correlated to each dolphin’s ranked position for both the males and females. The results suggest that a relationship between personality and an individual’s social status is present, yet complex. For example, the most dominant male may not necessarily be the most aggressive or most bold animal. Individuals ranked at both extremes of the hierarchy (highest and lowest) appear to exhibit a more correlative relationship between personality and social status. However, other factors appear to influence and vary this relationship for middle-ranked dolphins. For example, the calves of a dominant female dolphin who exhibit a cosseting maternal style affect both how her calves behaviorally develop and how others (including more dominant animals) behave toward them. Thus, these results suggest that factors such as age, strength of associations between individuals, maternal style, and interactions between male and female hierarchies all influence how personality is expressed in different contexts.
Asian (Elephas maximus), African savannah (Loxodonta africana), and African forest (L. cyclotis) elephant species exhibit complex social structures that differ between the sexes. Adult males travel alone or in bachelor herds, only interacting with the female groups for reproduction. Adult females and calves live in societies based on matrilineal groups that persist for several generations. Elephant societies are characterized by a high degree of social facilitation, observed through alloparenting, cooperation among adults, helping behaviors, and an interest in ailing individuals (Schulte 2000).
In particular, the variety of behavioral responses exhibited in response to a change in the social group, such as the death of a matriarch, suggests that elephants may display a wide range of individual differences in terms of behavior, personality, and temperament. Such individual differences may serve an important role in the formation and maintenance of elephant social hierarchies. Freeman et al. (2004) found that for both Asian and African elephants, dominance status was positively correlated with surveys of temperament (score range included most submissive to aggressive). Studies by Lee (2011) and Lee and Moss (2012) were the first to explicitly investigate personality traits within the same familial group of wild African elephants. Ratings of 28 adjectives on 11 female elephants found individual differences present on factors leadership, playfulness, gentleness, and constancy. Scores for leadership were positively correlated to social rank, with the suggestion that leadership illustrates the respect accorded to individuals as a function of their problem-solving ability.
Highfill et al. (2013) assessed the stability of personality traits after a significant social disruption, the death of the matriarch. Personality ratings were collected twice, with the second collection approximately 28 months later, during which time the matriarch has passed away. Despite this disruption to the social group, all remaining elephants exhibited stable personality factors. Horback et al. (2013) also found individual differences in personality in elephants from utilizing both ratings and coding methodologies. All of the traits for each elephant were found to be temporally stable, which suggests that human raters with extensive knowledge of the subjects’ behavioral repertoire can provide a valid description of personality, which could be utilized in future assessments of social factors.
This chapter highlighted three well-studied social mammal species, but the connection between social behaviors and personality can be observed in many other species. For other social species of primates, such as rhesus macaques (Macaca mulatta), there is research that parallels the role of personality in various aspects of social behavior, including friendship (Weinstein and Capitanio 2008, 2012). Personality and temperament are extensively studied in canines (for review, see Jones and Gosling 2005) with preliminary links to social contexts. For example, wolf (Canis lupus) leadership behaviors are related to dominance and breeding status (Peterson et al. 2002). In another example, sheep (Ovis aries) that are considered more “bold” are more likely to split the foraging group into smaller subgroups to decrease intergroup competition for resources (Michelena et al. 2009). These examples further support the need for increased research into the role of personality in social mammals. It is only recently that more attention is being paid to the relationship between the presentation of a personality trait and its relevance in a social context (e.g., Coleman and Wilson 1998; Dingemanse and De Goede 2004). As our understanding of social mammals increases, research detailing the role of personality in social contexts will become important for our understanding of the variation present for a behaviors’ communicative purpose and function.
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