Social Play in the American Black Bear: Its Similarity to Canid Social Play and an Examination of Its Identifying Characteristics

AMER. ZOOI.., 14:371-389 (1974).

Social Play in the American Black Bear: Its Similarity to Canid Social Play and an Examination of its Identifying Characteristics

J. D. HENRY AND S. M. HERRERO

Department of Biology and Faculty of Environmental Design, The University of Calgary, Calgary, Alberta, Canada, T2N 1N4

SYNOPSIS. Bears evolved from a canid stock at quite a recent date (early Miocene) . j-'Cspitc tuis recent origin, ucsrs show substantial morphological, pliySiologiCai, and Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 ecological differences when compared to modern day canids. However, the display be- haviors of Canidae and Ursidae have remained remarkably similar. In this paper, the motor patterns of black bear social play are described in detail. Numerous similarities between canid and ursid social play are pointed out. Agonistic displays common to both families are also pointed out. These behavioral similarities support the principle that social behavior, particularly display behavior, will frequently be conservative in its evolution as compared to the evolution of morphology, anatomy, or ecological adaptations. Beach (1945) stressed the importance of identifying and testing the general char- acteristics of play. A large number of characteristics have been suggested as being diagnostic of play, but these characteristics have received very little testing. Five char- acteristics of social play were tested in this study, and two were found to be only partially valid for black bear social play. Extensive testing of the general characteris- tics of play on as wide a range of species as possible is definitely recommended for future research.

INTRODUCTION show substantial differences (see Papez, 1929, and Davis, 1964, for reviews). For ex- Bears evolved from a canid lineage at ample, Ursidae manifests expansion of cer- quite a recent date. The ursid line is first tain areas in the cerebral cortex which ap- identified in the fossil record during the pears to be related to the enhanced manip- lower Miocene, and the modern day genus ulative abilities of the ursid forelimbs Ursus did not appear until the upper Plio- (Davis, 1949, 1964). Regarding ecological dif- cene (Herrero, 1972). Colbert (1955) states ferences, many ursid species have adopted that, along with Hyaenidae, the family an omnivorous niche. And in cold climates, Ursidae is the youngest and most recent bears have evolved winter lethargy. Folk family of carnivores to differentiate. De- et al. (1972) and Nelson et al. (1973) review spite this recent origin, Ursidae exhibits the physiological adaptations that allow many differences when compared with mod- bears to achieve this state of winter dor- ern day canids. mancy. For example, regarding morphological Despite these morphological, ecological, differences, bears show only a rudiment of and physiological differences, the social dis- the large canid tail. Bears also exhibit a plays of Canidae and Ursidae have re- plantigrade condition and have evolved a mained remarkably similar. This is one of bunodont dentition (Davis, 1964). Even the the main hypotheses examined in this re- brain morphologies of Canidae and Ursidae search. It is examined first by comparing the social play of black bears with that of canids. A subsequent article will look at This research was supported by N. R. C. Grant #69-0734, by the Killam Foundation, and by the agonistic behavior. Environmental Sciences Centre (Kananaskis). The If the social displays of Canidae and co-operation of the National and Historic Parks Ursidae are indeed similar, it illustrates the Branch of Canada and the Calgary Zoo made this principle that social behavior can be rather research possible. We gratefully acknowledge the financial support and co-operation received from conservative in its evolution when com- these organizations. pared with the evolution of morphology, 371 372 J. D. HENRY AND S. M. HERRERO anatomy, or ecological adaptations. Hofer of mammalian behavior, this testing should (1972) and Geist (1974) discuss this prin- lead to an objective and verifiable defini- ciple. Hofer applies it to evolution among tion of play behavior. the primates. The purpose of this paper, then, is two- The preceding statements assume that fold: first, to describe the social play be- behavioral homologies exist between Cani- havior of black bears as part of an effort to dae and Ursidae. Criteria indicating mor- describe the social behavioral repertoire of phological homology were outlined by this species; and, second, to examine which

Remaine and applied to behavioral homol- of the suggested characteristics of social Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 ogy, first, by Baerends (1958) and, more play are valid for black bear social play. recently, by Wickler (1967a). The conclu- sion that social behavioral homologies exist METHODS between Canidae and Ursidae has been made because several of these criteria can Black bear social play was studied prin- be satisfied. First, homology is indicated cipally by observing black bear cubs (Ursus because of the criterion of relative position: arnericanus) under captivity conditions. At namely, many motor patterns occupy the the Calgary Zoo, three cubs (two females, same relative position in the temporal se- one male) were raised together from ap- quencing of canid and ursid social behav- proximately 3 months of age in a 12- x 12- iors. Secondly, the criterion of specific yard arena. As a consequence of feeding and quality is satisfied: There are extensive simi- cage cleaning, the cubs received approxi- larities in the external appearances of motor mately li/2 hr of close contact with humans patterns and displays in canid and ursid per day. All three cubs appeared healthy social behaviors. Finally, the fact that the and showed considerable growth over the same motor patterns and displays occur in summer, but the male cub always remained a large number of closely related canid and somewhat smaller than the two females. ursid species indicates that these motor pat- The male cub did not, however, perma- terns are homologous. Numerous examples nently occupy the lowest position in the illustrating the above three criteria will be hierarchy. given in the descriptions of black bear so- Observations on social play began after cial play. the bears had been housed together for over Beach (1945) states that a definition of a month. From mid-June to the end of July play behavior must be based on its objective 1973 the cubs were observed and a total of characteristics which, when combined, set 508 social play sequences were filmed using off play behavior from non-play behavior. 8 mm cine film. For each filmed sequence, Bekoff (1972) has offered an operational pertinent notes were also taken regarding definition of social play that is, in fact, the exact beginning and end of the se- based on several of play's suggested identify- quence, the precise location of vocalizations ing characteristics (see also Bekoff, 1974). on the film, etc. In slow motion and occa- His definition of social play is used through- sionally frame by frame, these films were out this study. A large number of charafcter- analyzed for social play motor patterns, and istics have been suggested as being diagnos- the films were tested for the identifying tic for solitary and social play (see Meyer- characteristics of black bear social play. Holzapfel, 1956; Tembrock, 1958; Marler, Additionally, for several years, free- 1966; Loizos, 1967), but these characteristics ranging black bears have been observed in have received very little testing (Muller- several Canadian national parks. Bears were Schwarze, 1968, 1971). It is imperative that frequently observed at or around sanitary objective descriptions of play exist from landfills where they congregated to feed on as wide a range of species as possible and refuse, but also were observed occasionally that the suggested identifying characteris- in the backcountry, a number of miles away tics of play be tested on this wide range of from these landfills. Black bears were ob- species. If play is a valid, unitary category served during the summer and fall of 1968 SOCIAL PLAY IN THE AMERICAN BLACK BEAR 373 at the Jasper Landfill in Jasper National B. Interspecific Social Play: The play Park, Alberta, and during the summer and partner is from a different species. fall of 1971 and 1972 at the Waskesiu Land- This paper analyzes intraspecifk social fill in Prince Albert National Park, Sas- play of the black bear which, by definition, katchewan. Aggressive behavior as well as implies an interaction between two or more social play were thoroughly studied at these black bears. An interaction is defined as any times. Seventy-two social play sequences behavioral situation where two or more were filmed in the cub, yearling, and sub- black bears react with each other in such a adult black bears that visited these landfills, way as to disrupt their ongoing patterns of Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 while numerous other social play sequences moving, feeding, or resting (Stonorov and were described, but not filmed. These data Stokes, 1972). Social play was analyzed in from free-ranging black bears are used to terms of sequences. A sequence is simply determine whether the descriptions and an interaction that takes place over time conclusions made about the captive cubs (seconds or minutes). Social play among appear to be valid for the behavior of free- black bears usually occurs in discrete se- ranging black bears. quences, that is, the bears approach, inter- act with each other, and then usually sepa- THE CLASSIFICATION OF SOCIAL PLAY rate bringing the interaction to an end. Sequences are made up of a series of motor Free-ranging black bears, from cubs as patterns. A motor pattern is defined as a young as 4 months old up to sub-adults distinct and frequently repeated spatio- estimated to be 4 years old, commonly temporal pattern of muscular contractions exhibited social play. Social play usually (Hinde, 1970). occurred in one of three social contexts: The sequences of black bear social play (i) among litter mates, (ii) between a mother showed an intensity gradient. This gradient and her offspring, and (ill) among sibling was particularly conspicuous in play fight- or non-sibling sub-adults that have sepa- ing. We tried only to divide this intensity rated from their mothers (see also Meyer- gradient approximately in half and to Holzapfel, 1957). classify sequences into either high or low The entire play repertoire of the black intensity. We did so according to the fol- bear can be classified according to the fol- lowing criterion: if over 50% of the motor lowing system (after Tembrock, 1958): patterns, as measured in seconds, were I. Solitary Play: Play with an inanimate judged to be performed in a high intensity object or body part, (see Leyhausen, manner (fast running, vigorous clawing 1949; Meyer-Holzapfel, 1957). actions, intense biting actions, etc.), the TI. Social Play: Play with a social partner. play sequence was classified as a high- A. Intraspecific Social Play: The social intensity sequence. Otherwise, it was classi- partner is a conspecific. fied as a low-intensity sequence. 1. Play-fighting: Play that involves The 508 social play sequences from the physical contact and consists pri- captive cubs are classified in Table 1. The marily of agonistic-like motor patterns. TABLE 1. Quantitative classification of the 508 social play sequences from the captive cubs. In the third 2. Locomotory Play: Play that con- column, the average time duration and its standard sists mainly of chasing or climb- deviation are listed for each type of social play. ing after another bear and in- % Time duration volves little physical contact. Mo- n occurrence (X ± SD) tor patterns resemble agonistic motor patterns. Play-fighting 428 84% low intensity 228 20.3 •+• 49.6 sec 3. Sexual Play: Play that involves high intensity 200 18.2 ±13.1 sec physical contact and consists pri- Locomotory play 68 14% 9.3 •+• 10.5 sec marily of sexual-like motor pat- Sexual play 12 2% 18.6+ 15.9 sec terns. Totals 508 100% 374 J. D. HENRY AND S. M. HERRERO table shows that black bear intraspecific the sequences showed behavior that com- social play is predominantly play-fighting bined two different types of social play. Of (84% of the sequences). Only 14% of the the four different combinations possible, play sequences were locomotory play, and only two combinations appeared: locomo- only 2% were sexual play. These findings tory play was combined with play-fighting, correlate well with observations from free- and sexual play was combined with play- ranging bears. Among free-ranging cubs fighting. In Table 1, these combination and sub-adults, social play was predomi- sequences were classified according to which nantly play fighting, while locomotory play type of play predominated in the sequence. and sexual play were only occasionally ob- We conclude that play-fighting is by far the Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 served. Social play between a sow and her predominant form of social play among cub usually took the form of low intensity black bears and that the other two forms of play fighting. social play (locomotory play and sexual One way to test the adequacy of a be- play) frequently have at least some play- havioral classification system is to measure fighting behavior associated with them. the amount of overlap between categories THE EAR POSTURES, FACIAL EXPRESSIONS, AND of that system. 86% of the filmed social play VOCALIZATIONS OF SOCIAL PLAY sequences showed behavior from only one category of play (either play-fighting, loco- Ear postures motory play, or sexual play). Only 14% of The pinnas of the black bear are large

HG. 1. The smaller cub shows the relaxed open- cub shows the alert face and frontal alert ears, mouth face and partially flattened ears. The larger SOCIAL PLAY IN THE AMERICAN BLACK BEAR 375 Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021

FIG. 2. One cub exhibits crescent ears. The other cub is face-pawing. and mobile. The pinnas appear especially Crescent posture: The pinnas face ven- large in young black bears. Their conspicu- trad or nearly so, and stand perpendicularly ity appears to be due to differential growth. out from the side of the head (Fig. 2). This Using analysis of variance, Sauer (1966) ear posture can be readily identified by the examined measurements from 129 black crescent-like curve formed by the bear's bears of various ages and found that the pinnas and forehead. In young black bears, pinnas attain adult size when the black the crescent ear posture may have an exag- bear is only 1 or 2 years old. gerated quality due to the special largeness As with many canid species, the pinnas of the pinnas. The crescent ear posture is of the black bear appear to be important observed during active submission, during signals for social communication (Burg- interactions between a sow and her cub, hardt, 1972). Five distinct ear postures are and during social play. recognized in black bear social communica- Flattened posture: During aggressive be- tions. All five ear postures are observed havior, the black bear flattens its ears on its during social play, and a description of each neck, and the pinnas disappear completely follows. from view. Flattening the ears appears to Frontal alert: The pinnas stand erect on be a strong sign stimuli in black bear social the head and face forward (Fig. 1). communication. For example, in social play Laterad: The pinnas face laterad, half- if the physical contact becomes intense, one way between erect and flat on the neck. of the bears may flatten its ears, and this Laterad appears to be the relaxed ear frequently leads to a quick termination of posture. the social play sequence. 376 J. D. HENRY AND S. M. HERRERO Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021

\ A-J FIG. 3. The darker subadult rears bipedally and hibits partially flattened ears and the relaxed open- shows the puckered-lip face. The other subadult ex- mouth face.

Partially flattened posture: The pinnas nals (see also Schenkel, 1947; Fox, 1970). are partially flattened on the neck but are It is important to realize that these five still somewhat visible (Figs. 1, 3). Specifi- ear postures graded and changed into one cally, the pinnas are flattened to a point so another, and that it was difficult to deter- that an imaginary straight line can be mine what was communicated by the many drawn from the nose through the eye of the intermediate ear postures observed. We did, bear and along the exterior surface of the however, examine the hypothesis that pinna (Fig. 1). If the pinnas are flattened the ears were clearly crescent or clearly below this imaginary line, the ear posture partially flat at the beginning of the social is classified as flat. Above this line, the ears play sequence. This hypothesis was sup- are classified as laterad. In the black bear, ported by 88% of the high intensity social the partially flat posture is seen during play sequences. The bear that initiated so- flight behavior and also during social play. cial play usually clearly exhibited crescent During social play, this ear posture can be ears. Its partner usually clearly exhibited interpreted as a somewhat defensive, but partially flattened ears. play-permitting signal. Since flattening the Social communications by means of ear ears tended to disrupt the social play se- postures is further supported by the excep- quence whereas partially flattened ears did tions during high intensity social play se- not, these two ear postures are interpreted quences. In 23 sequences, the bear being as distinct, although somewhat related, sig- approached either flattened its ears or SOCIAL PLAY IN THE AMERICAN BLACK BEAR 377 showed frontal alert ears. The other bear, Ear postures in the black bear appear to instead of initiating social play, pivoted be relatively independent of facial expres- and fled in all but two of these sequences. sions. For example, the puckered-lip face is Thus, from the ear postures alone we could associated with frontal alert ears during so- successfully predict whether or not the play cial investigation, crescent or partially flat sequence would be initiated. ears during social play, and flat ears during The ears of both bears were most clearly serious aggression. Judged by the reactions crescent or partially flat at the beginning of the bear receiving the signals, the same of high intensity social play sequences. facial expression combined with different Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 However, black bears tend to exhibit these ear postures appears to have a somewhat two ear postures, although in more variable different message content. A detailed de- forms, continuously during all social play. scription of the puckered-lip face and the These two ear postures, in conjunction with relaxed open-mouth face follows.1 other characteristics, are useful identifying The puckered-lip face (Fig. 3): The eye- characteristics of black bear social play. lids in this facial expression are usually wide open. The skin on the forehead is Facial expressions flexed and a furrow sometimes appears. The Lorenz (1953) suggests that because bears eyebrow regions are usually raised. This are solitary animals and have a thick skin elevation of the eyebrow regions may be covering their head and face that they strike emphasized by the brown eye patches that without warning, that is, without first lay- are located above and mediad to the eyes ing back their ears or giving an agonistic (see Fig. 2). Cubs, yearlings, and sub-adults facial expression. Our observations, how- usually have these brown eye patches, al- ever, suggest that black bears almost always though there are some exceptions; these eye lay their ears back before attacking and that patches frequently disappear in adult boars. facial expressions appear to be of great The bear with a puckered-lip face alternates importance for social communication (see between a quick short stare at the opponent Meyer-Holzapfel, 1957). and a partial looking away. In this facial There appear to be seven distinct facial expression, the mouth is held tightly shut. expressions in the black bear. Bolwig (1964) The upper lip and the corners of the mouth and Fox (1970) have emphasized the simi- are puckered out. This puckering is espe- larity of facial expressions in primate and cially conspicuous in front (see also Meyer- canids, and ursids also show many of these Holzapfel, 1957; Burghardt, 1972). The similarities. Because of these similarities, anterior black color of the upper lip may we adapted our terminology and method of help to emphasize this puckering (see Fig. study from van Hooff (1967) and Fox (1970) 3). Vocalizations usually do not occur with whenever possible. this facial expression, although moaning is In the black bear, there are three closed- sometimes associated with it in cubs. mouth facial expressions which are listed in The puckered-lip face occurs in several order of increasing alertness: the relaxed different social contexts. It is commonly ob- face, the alert face (Fig. 1), and the served during social investigation, during puckered-lip face (Fig. 3). All three are active submission (Schenkel, 1967), during frequently seen during social play. In addi- the terminal phase of agonistic encounters, tion, there are four open-mouth facial ex- and during the initiation and termination pressions that are also listed in terms of of social play. During social play, the increasing alertness: the relaxed open- puckered-lip face appears in a low intensity mouth face (Fig. 1), the jaw-snapping face, form, that is, the forehead is usually not the jaw-gape face, and the biting face. Of furrowed, the eyebrow regions are fre- these four, only the relaxed open-mouth 1 face is commonly seen during social play. In a subsequent article, the other five facial ex- pressions will be described, and a diagram illustrat- The other three are observed during ag- ing all the facial expressions and ear postures of the gressive behavior. black bear will be provided. 378 J. D. HENRY AND S. M. HERRERO quently not raised, and the eyelids may ap- and biting intention movements than it pear partially closed. does in many canid and primate species (see The relaxed open-mouth face (Figs. 1, 3): Bolwig, 1964; van Hooff, 1967; Fox, 1970). This facial expression is related to the The "play face" in bears is not observed aggressive jaw-gape face, but the two are during locomotory play nor is it usually distinct because of subtle differences in the observed during the play-soliciting ap- eyelids, forehead, and ears. proach (see below). In many canid and pri- In the relaxed open-mouth face, the eye- mate species, the "play face" is observed lids are partially closed, and the forehead during both of these contexts. Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 and eyebrow ridges are relaxed. The ears are either crescent or partially flat. The mouth Vocalizations is held open from 20° to 60°, and the corners of the mouth are slightly elevated. The Play in the black bear is distinguished by upper lip is puckered out but not as exten- its lack of vocalizations, that is, during soli- sively as in the puckered-lip face. The lower tary and social play no vocalizations are lip is also puckered out and, along its sides, given except for respiratory sounds, such as hangs down away from the teeth. The lower panting and breathing sounds. Serious ago- canines are usually clearly visible. No vo- nistic behaviour is the antithesis of social calizations except for breathing sounds are play in that it is marked by numerous and normally associated with this facial expres- frequent vocalizations (Darwin, 1872). sion. The relaxed open-mouth face is usually Burghardt (1972) also observed that dur- observed during social play in the following ing black bear play silence was the rule and context: Prior to biting, one bear assumes stated that "this distinguishing characteristic this facial expression and stares directly at of true play was virtually without excep- the opponent. This is quickly followed by tion." Silence during play-fighting was ob- reaching to bite at the opponent, or by served in captive sloth bears (Mclursus head-ducking as the opponent bites or paws ursinus), Himalayan black bears (Selenarc- first. Occasionally a bear will assume this tos thibetanus), and polar bears (Ursus facial expression and maintain it for up to maritimus) at the Calgary Zoo. Free-ranging 30 sec without biting. During this time the sub-adult grizzlies (Ursus arctos) in Banff bears paw and play-wrestle with each other. National Park were also observed to be si- The aggressive jaw-gape differs from the lent during play-fighting. The rule of silence relaxed open-mouth face in a number of may differentiate the social play of Ursidae subtle ways. In both, the mouth is held from that of Canidae. Bekoff (1972) reports open 20° to 60°. In the jaw-gape face, how- that in the domestic dog play-soliciting ever, the eyelids are wide open, instead of gestures, such as the play bow, are often partially open; the eyebrow regions are accompanied by an attention-getting bark. raised instead of relaxed; and the ears are Although social play is silent, it may be flat on the neck, instead of crescent or par- terminated by one of the bears moaning. tially flat. The jaw-gape face is usually When physical contact in social play became associated with the aggressive body posture intense, one bear frequently oriented of arching the back and strongly flexing the towards the other bear and moaned. Moan- head and neck down. This challenge pos- ing was followed by a quick termination of ture is rarely observed during social play. social play in 22 out of the 34 sequences in Thus, these two facial expressions can be which moaning occurred. In those sequences distinguished on the basis of subtle differ- where contact play continued, the moaning ences in their external appearances. bear frequently flattened its ears and aggres- The relaxed open-mouth face is only ob- sively attacked its social partner. served during play behavior and can be In conclusion, social play in the black considered a "play face" in the black bear. bear can be identified by two constant ac- In the black bear this "play face" appears companying features: (i) no vocalizations more closely associated with biting actions are given except for respiratory sounds, and SOCIAL PLAY IN THE AMERICAN BLACK BEAR 379

(ii) the ears are continuously either in the TABLE 2. The motor patterns of black bear social play. crescent or partially flattened ear postures. Motor patterns of play-fighting: No other type of black bear social behavior Playful approach that we have observed shows these two fea- Rearing Head butting * tures continuously during the behavioral Pawing * sequence. Face-pawing * Lunging * Clawing THE MOTOR PATTERNS OF SOCIAL PLAY Inhibited clawing Hind-leg-clawing Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 Rolling over Table 2 enumerates 30 different motor Play bites patterns that are frequently observed during Biting intention movement Inhibited bite black bear social play. Twenty-two of these Neck-bite-hold motor patterns are similar to motor patterns Head shake observed in various canids (Tembrock, Muzzle seizure Standing over 1958; Fox, 1969, 1970, 1971; Bekoff, 1972). Looking away This fact illustrates the extensive similarity Licking-cut-off between canid and ursid social behaviors. Head and neck extension This section describes the motor patterns Motor patterns of locomotory play: Play nip characteristic of locomotory play, play fight- Running chase ing, and sexual play in that order. Climbing chase Seizing the object Motor patterns of locomotory play Motor patterns of sexual play: Vulva stimulation Shoulder-scruff-bite In the black bear, there are two types of Clasping with forepaws Pelvic thrusts locomotory play. The first kind involves Mounting chasing after a conspecific. The second type Inguinal presentation involves seizing an object. * Indicates that motor pattern is also observed in Chasing usually begins by one animal canid species (see text). walking up to another animal from behind and play nipping that animal. The play nip The second type of locomotory play in- is a quick, painful bite usually delivered to volves seizing an object. This type of loco- the flank, rump, or hindlimb of the op- motory play has been described in several ponent (see Table 3). The attacking bear other carnivore species. Chrisler (1958) de- immediately flees. The bear that was bitten scribed it among young semi-captive wolves, usually pivots around, obviously aroused by and Schaller (1972) described it between a the bite and makes high intensity biting or lioness and two cubs. In the captive bear clawing actions at the fleeing bear. About cubs, the object seized was usually a new 25% of the time, it chases after the attacker. object in the arena. It was usually chewable, Alternately, chasing was initiated by one but not edible, for example, a bone, a bear running at a second bear who fled be- branch, or a feather. Specifically, one cub fore physical contact was made. The first approached another cub that was chewing bear then simply continued to chase after on a new object. The cub approached at a the fleeing bear. During chasing behavior, walk and then gently pawed or smelled at both bears exhibit the alert or puckered-lip the object in the other bear's mouth. The face. The fleeing bear usually has partially object was seized when it dropped to the flat ears while the chasing bear usually has ground, or it was seized directly from the crescent ears. Chasing sequences among mouth of the other bear. The bear then free-ranging sub-adults have been observed fled with the object and began to chew on to last for over 2 min. Infrequently, a climb- it. The second bear usually did not im- ing chase was observed while both bears mediately chase after the fleeing bear, but were in a tree. within a few minutes it approached and 380 J. D. HENRY AND S. M. HERRERO seized the object back in a similar manner. others. During one occurrence involving a feather, Motor patterns associated with biting ac- reciprocal seizing of the object continued tions. During play-fighting, different kinds off and on between the three captive cubs of biting actions were observed. The neck- for over 20 min. bite-hold was the most intense type of biting observed and differs from the ordinary play- Motor patterns of play-fighting bite in a number of features. During the neck-bite-hold, the opponent's neck was bit-

Play-fighting sequences started with one ten and held for up to 10 sec, instead of Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 bear approaching another bear, usually in a being immediately released as in the play- walk (80% of the sequences), infrequently bite. Pawing actions, attempting to pin the in a run (20%). This bear exhibited a opponent to the ground, were observed with puckered-lip face with ears usually crescent neck-bite-holds, but not with ordinary play- (63%), infrequently partially flat (37%). bites. Vigorous head shaking was often ob- The bear approached and, when close to served just prior to the release of the neck- the other bear, pawed, bit, head butted, or bite-hold. Head shaking was only infre- reared bipedally. The other bear, almost quently associated with ordinary play-bites. simultaneously, reared, bit, or pawed back Also the orientation of the neck-bite-hold at the initiator. was quite regular: 74% weie oriented The playful approach followed by paw- towards the lateral neck surface of the op- ing, biting, head butting, or rearing appears ponent (Table 3). The orientation of the to be the play soliciting gesture of the black play-bite was more variable: 14 different bear. The black bear does not show the play body parts were bitten in 146 different play- bow, exaggerated approach, or play dance bites (Table 3). that are play-soliciting behaviors in canids Biting attempts are complete biting ac- (Fox, 1970; Bekoff, 1972). tions where the animal missed or had its Play-fighting sequences ended with both head blocked by the opponent. Biting at- bears shutting their mouths, assuming a low tempts are to be distinguished from biting intensity puckered-lip face, and walking or intention movements. Biting intention running away from each other. In 50% of movements are incomplete biting actions, the play-fighting sequences, this moving performed once or repeatedly, but always in apart was preceded or accompanied by a an incomplete manner. They usually con- cut-off or submissive display, for example, sisted of one bear opening its mouth and looking away, licking cut-off, head and, neck orienting it towards, without reaching to extension, or shrugging away (see Fox, 1970, bite, the other bear. At their highest degree for a description of these behaviors in of completion, biting intention movements canids). take the form of the inhibited bite. In the The 20 different motor patterns com- inhibited bite, the jaws are placed around monly observed during play-fighting are the opponent's neck or limb but are not described under two headings. These head- shut or are shut very gently. The jaws are ings relate to the double weapon system of held there for 1 to 2 sec, and then with- the black bear. Canid species use only the drawn. Inhibited biting is also observed teeth to inflict injuries during social combat during serious agonistic encounters in the (Fox, 1969, 1970). Ursid species, on the other black bear. Bekoff (1972) suggests that in hand, are equipped with two weapon sys- canids inhibited biting appears to be a par- tems for social combat, the teeth and the tially learned response as a result of a con- claws. This dual weapon system of the bears flict situation: the animal wishes to bite but has influenced the appearance of both seri- fears a counter-attack (see also Poole, 1966; ous agonistic behavior and play-fighting. Fox, 1971). The dual weapon system has apparently led During play-fighting, young black bears to the development of new motor patterns also show muzzle seizure behavior (Fig. 4). while modifying the external forms of During this behavior, two bears come to- SOCIAL PLAY IN THE AMERICAN BLACK BEAR 581 Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021

FIG. 4. Two of the captive cubs engage in muzzle seizure behavior. gether in a face-to-face orientation, inter- the forequarter and forepaws. He supports lock their jaws, and hold them interlocked this statement by describing in detail the for up to 15 sec. Gentle squeezing actions morphological adaptations exhibited by are frequently observed. bears for this increased manipulation of the Muzzle seizure is observed in the wolf and forepaws. coyote (Fox, 1970, 1971). In the wolf, it During play-fighting, increased manipu- serves a number of different functions, for lative ability of the forepaws is evident in example, a greeting behavior, a dominance both pawing and clawing actions. Pawing display, a play activity among young wolves, actions are variable, low intensity arm move- and a form of "ritualized aggression" (Fox, ments that are often aimed at knocking the 1971). In the black bear, muzzle seizure has opponent's head or arm out of the way and never been observed to form a type of "ritu- thus blocking an attack. Figure 2 shows alized aggression." It is usually observed face-pawing, a type of pawing frequently only during low intensity play-fighting observed during black bear social play, and amng cubs and sub-adults, or infrequently often used to initiate the social play as a greeting behavior between a sow and sequence. her cub. Pawing actions also occur during lunging Motor patterns associated with pawing when one bear extends his forelimbs and and clawing actions. Davis (1949, 1964) lunges at the opponent's shoulder region in states that bears, as compared to canids, an attempt to knock the social partner over. show an increased manipulative ability of Knocking the social partner over is also 382 J. D. HENRY AND S. M. HERRERO accomplished by head butting. In this mo- Rearing occurs when the bear lifts its fore- tor pattern, one bear walks into the other paws off the ground, and while standing bear with its forehead and gives a quick on its hind legs, or sitting, holds its fore- head lift movement trying to knock the paws free of the ground for up to 20 sec other bear off balance. Head butting is fre- (see Fig. 3). Rearing frees the forepaws for quently observed at the initiation of the manipulative actions, and rearing and paw- social play sequence. ing are closely associated in many play- Clawing actions as compared to pawing fighting sequences. For example, repeatedly actions are vigorous swiping movements during a sequence, both bears may rear Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 aimed at various parts of the opponent's and paw at each other trying to knock body (Table 3). Observations support that each other over (Meyer-Holzapfel, 1957). clawing actions can inflict serious injuries. These extended rearing-pawing matches are During several aggressive encounters, we one of the most common activities during observed an adult bear inflict 4- to 6-inch- play-fighting, but they have never been long cuts in the side or rump of a rival bear. observed during serious agonistic en- During play fighting, the black bear ap- counters. pears to use a form of inhibited clawing. Rearing also frequently precedes stand- In this clawing, the claws are not flexed ing over. Standing over occurs when a bear down, and the opponent (or the observer's approaches a conspecific from the side, hand) is consistently hit with the foot pad rears, and places its paws on the conspeci- instead of with the claws. fic's shoulder or back. Fox (1971) describes We have described the neck-bite-hold standing over in various canids. Among observed during play-fighting. In order to the captive black bear cubs, standing over break the neck-bite-hold the bear frequently usually preceded play fighting, but in four rolls over. Hip slamming which many canids sequences standing over led to sexual play. use to break neck-bite-holds (Fox, 1970, By way of summary, the typical play- 1971) has not been observed in the black fighting sequence usually exhibits four bear. If rolling over does not break the phases: initiation, pushing-pulling, biting- hold, hind-leg-clawing is frequently ob- clawing, and finally, termination. One bear served. Specifically, the bear that has rolled approaches another bear and initiates play over lifts its hind feet and alternately claws by rearing, pawing, biting, head butting, at the forehead of the opponent. Hind-leg- or, infrequently, lunging at that animal. clawing is similar to a motor pattern seen Frequently, both animals rear and an ex- in the domestic cat (Leyhausen, 1973), but tended pawing match follows. The purpose this claw-related motor pattern has never of pawing appears to be to knock the social been described in canid species. partner off balance so that a biting or claw- Burghardt and Burghardt (1972) describe ing action can be delivered. Biting inten- rolling over as a play-invitation behavior tion movements and face-pawing actions in black bears. We observed rolling over are repeatedly observed during these ex- used in the context of breaking neck-bite- tended rearing-pawing matches. Once the holds. We also infrequently observed it social partner is pushed or pulled into when a larger bear playing with a smaller a vulnerable position, a play-bite or neck- bear rolled over apparently to assume a bite-hold is frequently delivered. The bitten subordinate role. In both of these contexts, animal then rolls over and may hind-leg- rolling over did not occur until well after claw in order to break the neck-bite hold. the play sequence had begun. In less than Once freed, both bears frequently return 1% of the sequences (3 out of 508) was to the rearing-pushing-pulling phase until rolling over observed at the initiation of one of the bears once again becomes vul- the social play sequence. nerable to a bite or clawing action. This In many play-fighting sequences, reamig alternation between the pushing-pulling initiates the sequence but it may also ap- and biting-clawing phases continues on the pear repeatedly throughout the sequence. average for about 20 sec (see Table 1) until SOCIAL PLAY IN THE AMERICAN BLACK BEAR 383

TABLE 3. The orientation of 200 biting actions and 200 clawing actions during black bear play fighting. Number in parentheses is percentage of actions oriented towards that specific body region.

Play bites Bite-and-holds Play nips Clawings Lateral face 45 (31%) 5 (12%) 56 (28%) Forehead 9 (6) 52 (26) Lateral neck 19 (13) 29 (74) 28 (14) Shoulder 4 (3) 3 (8) 1 (7%) 50 (25) Ear 5 (3) 1 (7) Ventral neck 1 ( 1) / 9\ Chest 2 ( 1) 6 \ *V Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 Foieliiu'u 4 ( 3) Abdomen 2 Lateral body 9 1 (3) 2 (13) 5 (3) Dorsal body 3 (218) 1 (3) Rump 9 (6) 5 (33) 3 < 1) Hindlimb 11 (8) 4 (27) Foot 23 (16) 2 (13) Total 146 (100%) 39 (100%) 15 (100%) 200 (100%) one of the bears closes its mouth, frequently biting actions and 200 clawing actions ob- gives a cut-off display, pivots, and flees. served during play-fighting in the captive Flight behavior by one of the bears usually cubs. Table 4 examines the orientation of terminates the play-fighting sequence. The 129 biting actions and 42 clawing actions initiation and termination phases of the observed during aggressive behavior in play-fighting sequences are comparatively adult black bears. Adult aggressive be- regular. The pushing-pulling phase alter- havior was identified by the complete flat- nating with the biting-clawing phase shows tening of the ears and numerous vocaliza- a great amount of variability in the tem- tions that accompanied it. Complete biting poral sequencing of motor patterns. actions are relatively rare in adult black Many of the canid motor patterns that bear aggressive behavior. Thus, the biting black bears do not show are highly cur- actions contained in Table 4, are composed sorial ones, for example, hip slamming, the of 100 high intensity biting intention play dance, the play bow, and the exag- movements, 17 inhibited bites, and 12 com- gerated approach (Fox, 1970; Bekoff, 1972). plete, uninhibited bites. These may represent motor patterns of In the black bear, there appears to be a more recent origins that evolved in Canidae strong tendency to bite at the side of the after the ursid line had differentiated (see face or the lateral neck surface of the op- Lorenz, 1941, for an evolutionary study of ponent. In play-fighting 49% of the biting motor patterns in Anatinae). actions (98 out of 200) were directed to- Table 3 examines the orientation of 200 wards these two regions. The remaining biting actions in play-fighting were dis- TABLE 4. The orientation of 129 biting actions and tributed among 12 other body regions. 42 clawing actions during adult black bear aggres- Within the limitations of the comparison, sive behavior. Number in parentheses is percentage of actions oriented towards that body region. Table 4 suggests that this tendency to bite at the side of the face or lateral neck surface Biting Clawing appears even stronger in adult aggressive actions actions behavior; 91% of the biting actions in ag- Lateral face 90 (70%) 4 (10%) gression were oriented towards these two Lateral neck 28 (21) 3 ( 7) body regions. Biting actions during adult Shoulder 2 (2) 22 (52) Forelimb 2 (2) aggressive behavior, therefore, appear to be Lateral body 4 (10) less variable in their orientation than biting Rump 3 (2) 8 (19) actions during social play. Hindlimb 4 (3) Foot 1 (2) In play-fighting, there appears to be a Total 129 (100%) 42 (100%) strong tendency to claw at the side of the 384 J. D. HENRY AND S. M. HERRERO face, forehead, or shoulder region of the quently showed standing over by placing social partner. These three body regions his forepaws on the littermate's back. Next, account for 79% of the clawing actions ob- the male cub moved into mounting posi- served during play-fighting. Four other tion, bit the littermate's shoulder scruff- body regions received the remainder of the skin, and, finally, clasped the littermate clawing actions. In adult aggressive be- bilaterally with his forepaws. At this point, havior, one body region of the opponent, the littermate usually rolled over on its the shoulder region, received 52% of the back and initiated play-fighting by pawing aggressive clawing actions. Thus, as with and biting at the male cub's face. Infre- Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 biting actions, clawing during adult aggres- quently, pelvic thrusts were seen during sive behavior appears less variable in its sexual play. Since the baculum of cubs is orientation than it does during social play. short and weighs appi'oximately half a Fox (1969) suggests that canid aggressive gram (Rausch, 1961), it is doubtful that behavior is ritualized because the attacker intromission ever takes place. tends to bite at certain, restricted body re- Vulva stimulation was also observed dur- gions of the opponent. The above data sug- ing sexual play. The male cub usually gest that this may also be true for black approached a female littermate from be- bear aggressive behavior. Also the data sug- hind and smelled the base of her tail and gest that the side of the face, forehead, rump without touching them. Then the lateral neck, and shoulder regions of the male cub moved his nose ventrad and black bear should be examined for defense smelled and gently bit and licked the vulva mechanisms against aggressive clawing and region of the female. Frequently, the fe- biting. male cub was lying on her side and, when Defense mechanisms may take the form the male cub touched her vulva, the female of thick dermal shields (see Geist, 1964), cub inguinal presented, that is, she rolled or long, thick protective coats of hair (see one leg laterad exposing the inguinal re- Schallar, 1972). The long thick fur on the gion (see Fox, 1971, for a description of dorsal and lateral surfaces of the bear's inguinal presentation in canids). In adult neck may function as such a defense mecha- sexual behavior, vulva stimulation has al- nism. ways been observed to precede the first mounting attempt. In sexual play, mount- Motor patterns of sexual play ing was often attempted without vulva stimulation preceding it. In the black bear, as in many species, Littermates usually responded to mount- sexually immature animals on occasion ing and vulva stimulation by initiating exhibit sexual behavior, and this type of play-fighting. They frequently sat or rolled behavior has been termed sexual play. We over on their backs in order to break the may validly ask if sexual play is really play mounting attempt. Then they pawed and behavior; and, if so, by what criteria and bit at the male cub's face in a low intensity characteristics is it identified as such. We manner. Rolling over and pawing at the will examine this question by comparing male's face are also observed in non-recep- the sexual behavior shown by black bear tive adult females in response to the serious cubs with the sexual behavior as shown by mounting attempts of adult boars. The adult black bears. non-receptive adult female during this re- Sexual play was infrequently observed in action frequently shows partially flat ears, the social play of black bear cubs and sub- a lack of vocalizations, and the relaxed adults (see, for example, Table 1). During open-mouth face. It is one of the few con- the sexual play of captive and free-ranging sistent occurrences of play-like behavior in cubs, a male cub usually tried to mount a the behavioral repertoire of adult black male or female littermate. The male cub bears. approached, ears crescent, giving no vocali- From the above descriptions, it is appar- zation. The male cub then reared and fre- ent that the sexual behavior shown by SOCIAL PLAY IN THE AMERICAN BLACK BEAR 385 cubs exhibits a number of features only same motor patterns as they appear in non- observed in other types of social play. For playful behavior. We will discuss three of example, the male cub in approaching a these hypotheses. littermate gives no vocalization and his ears Hypothesis 1: Motor patterns during are usually clearly crescent. During adult play often have an incomplete appearance sexual behavior, the boar approaching a when compared to their appearance during female frequently makes a throat-clunking non-playful behavior. For example, during vocalization and his ears, although variable, play-fighting, in dogs, snarling may be dis- are frequently frontal or laterad. Further- sociated from the piloerection which in- Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 more, during sexual play the male cub evitably accompanies it during true fight- usually performs only part of the normal ing (Marler, 1966). adult sexual sequence; for example, mount- This hypothesis appears valid for much ing is frequently attempted without vulva of black bear social play. The following stimulation preceding it. Marler (1966) examples illustrate this point. First, the states that partially performed sequences above example about piloerection appears are frequently a characteristic of social play. valid for black bear social play. In black These characteristics support the conclu- bears, piloerection of the dorsal and lateral sion that the sexual behavior shown by neck fur is occasionally observed during cubs is indeed a form of social play. real fighting but has never been observed during play-fighting. Second, during black HYPOTHESIS TESTING AND DISCUSSION bear social play many behaviors lack the Beach (1945) stresses that play must be vocalizations that normally accompany defined according to its general, objective these behaviors during non-playful be- characteristics. A number of researchers havior (see p. 378). Third, many threat have speculated about what the general displays are omitted from play-fighting. characteristics of play might be (see Meyer- For example, in an adult agonistic en- Holzapfel, 1956; Tembrock, 1958; Marler, counter, an approaching bear frequently 1966; Loizos, 1967). Muller-Schwarze (1968) stops abruptly and paw swats the ground showed the value of testing this specula- (see also Jonkel and Cowan, 1971). Later tion. He found that several of the charac- in the encounter, both bears usually display teristics as put forth by Meyer-Holzapfel the challenge postiure (see p. 378). At the (1956) were not valid for the social play of end of the encounter, a bear moving away blacktailed deer (Odocoileus hemionus co- frequently jaw snaps repeatedly at the op- lumbianns). Extensive testing of this specu- ponent. These three threat displays are lation over a wide range of species is neces- rarely observed during play-fighting. Poole sary if the valid diagnostic characteristics (1966) also observed that in the play-fight- of play are to be identified. In this section, ing of polecats (Putorius putorins) most five suggested characteristics are tested for agonistic behaviors were present except their validity in black bear social play. four threat behaviors which were omitted. Hypothesis about the characteristics of Thus, in at least two species of Carnivora, social play can be grouped under two head- certain threat displays appear to be se- ings: (i) characteristics about the motor lectively omitted from play-fighting be- patterns of social play, and (ii) character- havior. istics about the sequencing of social play. The above examples serve to illustrate The following five hypotheses are examined that the first hypothesis appears valid for under these two headings. much of black bear social play: many motor patterns are given in an incomplete manner Characteristics of the motor patterns of when compared to their appearance during social play non-playful behavior. Hypotheses about the motor patterns of Hypothesis 2: Social play may be identi- social play compare the appearance of the fied by certain motor patterns which are motor patterns during social play to the observed only during social play (Marler, 386 J. D. HENRY AND S. M. HERRERO

1966). There is evidence, therefore, to conclude In the black bear there are several motor that certain motor patterns during social patterns that are observed almost exclu- play are less economical in their orientation sively during social play. These are head than they are during adult non-playful butting, muzzle seizure, the play nip, and behavior. hind-leg-clawing. These four motor pat- Regarding the enlarged or prolonged terns which are frequently observed during quality of motor patterns, our observations black bear play-fighting are extremely rare suggested that the majority of social play

in the agonistic behavior of cubs, sub- motor patterns were not performed in an Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 adults, or adult black bears. Marler (1966) enlarged manner when compared to the gives several examples of motor patterns same motor pattern in adult non-playful unique to social play, and all of the ex- behavior. We tested this point by timing amples are play-soliciting behaviors. In the the filmed motor patterns. We selected and black bear, only head butting and the play timed six motor patterns that appear in nip appear to serve as play-soliciting be- both high intensity adult aggressive be- haviors (see p. 380). The other two motor havior and in high intensity play-fighting patterns unique to black bear social play (Table 5). Filmed sequences were selected usually do not occur until well after the by random numbers, and 30 timings for social play sequence has begun. each motor pattern were obtained. The Hypothesis 3: Social play is character- means and standard deviations for each ized by the exaggerated and uneconomical motor pattern are reported in Table 5. Dif- quality of the motor patterns involved ferences between means were tested for (Loizos, 1967). Loizos states that this exag- using the Student's t test (2 tail test, gerated and uneconomical quality of the a = .05). From these tests (see Table 5.), motor patterns is "what all playful activity we conclude that motor patterns in play has in common." fighting do not show a consistent increased duration when compared to their adult ag- There is an important need to state more gressive counterparts. objectively what "exaggerated" and "un- economical" mean in terms of observable Loizos' hypothesis, therefore, appears behavior. These terms are vague and some- only partially valid for black bear social what subjective, and, therefore, difficult to play. Certain motor patterns appear more test (Beach, 1945). We interpreted "uneco- variable in their orientation during social nomical" to mean that motor patterns dur- play, but our tests and observations suggest ing social play are more variable in their that motor patterns are not performed in orientation than they are during non-play- an enlarged or prolonged manner in social ful behavior. We interpreted "exaggerated" play when compared to the same motor to mean that social play motor patterns are patterns in adult non-playful behavior. performed in an enlarged or prolonged manner as compared to non-playful motor patterns. From this enlarged or prolonged TABLE 5. The duration of motor patterns in black quality, we would expect social play motor bear play fighting and aggressive behavior (in sec). patterns to exhibit an increased time dura- Play Conclusion tion as compared to non-playful motor pat- fighting Aggression a = 0.05 terns. Biting 1.47 -t- 1.00 1.16 -i- 0.38 P.F. = Agg. Tables 3 and 4 offer evidence that during Clawing 0.58 •+• 0.16 0.59 •+• 0.18 P.F. = Agg. social play biting and clawing actions are Rearing 3.16 ± 2.42 2.13 ± 1.49 P.F. > Agg. Looking- more variable in their orientation than away 1.76 ± 0.65 2.03 ± 1.01 P.F. = Agg. are adult aggressive bitings and clawings Licking- (see p. 383). Mounting also appears more cut-off 1.35 ± 0.90 1.98 ± 1.28 P.F. < Agg. Biting- variable in its orientation during sexual intention- play than during adult sexual behavior. movement 1.27 ± 0.26 2.34 ±1.29 P.F. < Agg. SOCIAL PLAY IN THE AMERICAN BLACK BEAR 387

Characteristics of social play sequences TABLE 6. The frequency of motor patterns in black bear play fighting and aggressive behavior. The number in the parentheses indicates that the sam- We have examined three hypotheses con- ple size was different from 30. cerning the motor patterns of social play. A number of other hypotheses concerning Play Conclusion the sequences of social play have also been fighting Aggression a = 0.05 advanced. We will examine two of these Biting 3.87 ± 3.08 1.64 ± 0.93 P.F. > Agg. (n - 19) hypotheses. Clawing 3.77 ±3.80 1.71 ±1.61 P.F. > Agg.

Hypothesis 4: A characteristic of play is (n = 23) Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 that certain motor patterns are repeated Rearing 2.53 ± 2.31 1.70 ± 1.40 F.F. = Agg. (n = 23) more frequently in the play sequences than Looking- during the non-play sequences (Meyer-Hol- away 2.30 ± 1.66 2.07 ±1.11 P.F. = Agg. Licking- zapfel, 1956; Loizos, 1967). cut-off 1.68 ±0.49 1.33 ±0.76 P.F. > Agg. We tested this hypothesis in the follow- Biting- ing way: Motor patterns that occur more intention- than once in either a play-fighting sequence moveraent 6.27 ± 6.64 2.75 ±2.11 P.F. > Agg. or in an adult aggressive sequence are listed in Table 6. Biting and clawing actions in display. It appears that greater repetition this table include both inhibited and unin- of the motor patterns was not due to the hibited types of biting and clawing. Filmed play-fighting sequences lasting longer than sequences were chosen at random and used the adult aggressive sequences. We con- once. This included both play sequences clude, therefore, that, within the limita- from cubs and aggressive sequences from tions of the test, greater repetition of certain adult black bears. For each sequence, one motor patterns appears to be a valid char- of the motor patterns from Table 6 was acteristic of black bear social play. chosen and the frequency of it in the se- Hypothesis 5: In play, normal temporal quence was counted. For each motor pat- groupings of functionally related motor tern 30 non-zero frequencies were obtained patterns break down, so that different kinds (with 3 exceptions for adult aggressive be- of behaviors intermingle in the same se- havior; see Table 6). The means and stan- quence; for example, prey capture behavior dard deviations of these frequencies are and sexual behavior may be combined in presented in Table 6. Using a Student's t the same play sequence (Meyer-Holzapfel, test (Li, 1961), we tested for differences be- 1956). tween means (2 tail test, a = .05). We con- Predatory behavior is rarely observed in clude that four of the six motor patterns adult black bears, and it also appears to be examined are repeated significantly more rare in black bear social play. Thus, there frequently during play-fighting than dur- is only one possible way that black bears ing adult aggression. could manifest this characteristic, namely, Greater frequency of a motor pattern per by combining sexual motor patterns with sequence may result simply because play- agonistic motor patterns. We examined the fighting sequences last longer than aggres- filmed sequences from the captive cubs and sive sequences. To test this point, we from adult black bears for this combination. recorded the time duration of each play Regarding sexual behavior, the sample and aggressive sequence used. Using a t size is small, but a general trend appears test (2 tail test, a = .05), we found that in to be indicated. Three-fourths of the sexual five out of the six tests play-fighting se- play sequence (9 out of 12) combined sexual quences did not last significantly longer motor patterns with agonistic motor pat- than sequences of adult aggression. The one terns. However, about three-fourths of the exception involved the looking away be- adult sexual sequences (10 out of 12) also havior: Play-fighting sequences that showed showed this combination. As mentioned looking away last significantly longer than earlier, this is because both cubs and non- adult aggressive sequences that showed this receptive adult females respond to courting 388 J. D. HENRY AND S. M. HERRERO males by initiating play-fighting. Thus, the and social play are to be known. Beach combination of sexual with agonistic motor (1945) and Marler (1966) have correctly patterns cannot be used to differentiate stressed the need for this type of research. sexual play in cubs from sexual behavior in Repeatedly during this paper we have adult black bears. pointed out similarities between canid and Regarding agonistic behavior, only 0.4% ursid social behavior. Geist (1974), among of adult black bear agonistic sequences others, has stated that social behavior, and (1 out of 247) showed sexual motor patterns particularly display behavior, can be ex- combined with agonistic motor patterns. pected to be rather conservative in its evo- Downloaded from https://academic.oup.com/icb/article/14/1/371/2066821 by guest on 02 October 2021 The one sequence that showed this combi- lution. The conservatism of black bear nation involved an agonistic encounter display behavior is illustrated by the fol- between an adult male and an adult female lowing example. Black bear and canids black bear. The male emerged from the en- share the following active submissive dis- counter dominant, and immediately after plays: face-pawing, licking intention move- the encounter, tried to mount the female. ments, and nose-stab movements oriented His attempt was unsuccessful because the towards the dominant animal's mouth (Fox, female fled. Since only 1 out of 247 se- 1971). These displays in Canidae have been quences showed sexual behavior combined derived from soliciting behaviors, that is, with agonistic behavior, we may conclude from when young canids beg food from that this combination is almost non-existent their parents (Fox, 1971). Bears have re- in adult black bear agonistic behavior. It tained these active submissive displays even also appears that black bears do not use a though the regurgitation response of Cani- ritualized mounting behavior as a domi- dae has been lost from the bear's behavioral nance display. This type of dominance dis- repertoire. play is frequently observed in primate spe- The extensive similarities between canid cies (see Wickler, 19676). and ursid displays tend to support the prin- In black bear cubs, 3.9% of the play- ciple of the evolutionary conservatism of fighting sequences (17 out of 428) showed social behavior. This principle has im- agonistic behavior combined with sexual portant implications for behavioral research behavior. We, therefore, conclude as fol- and ultimately for our understanding of lows: Agonistic motor patterns combined man's future societies. The principle de- with sexual motor patterns is almost non- serves to be thoroughly tested. existent in adult black bear agonistic be- havior. In cub play-fighting, the vast ma- REFERENCES jority of the sequences (411 out of 428) show Baercnds, G. P. 1958. 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