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2-1974
Social Play and Play-Soliciting by Infant Canids
Marc Bekoff
University of Missouri, marc.bekoff@gmail.com
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Recommended Citation
Bekoff, M. (1974). Social play and play-soliciting by infant canids. American Zoologist, 14(1), 323-340.
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Social Play and Play-Soliciting by Infant Canids
Marc Bekoff
University of Missouri
ABSTRACT
The development of social interaction was studied in infant coyotes, beagles, and wolves. In this paper,
social play behavior is discussed. Social play may be characterized in a number of ways: (i) actions from
various contexts are incorporated into labile (unpredictable) temporal sequences; (ii) the "play bout" is
typically preceded by a metacommunicative signal which indicates "what follows is play"; these signals
are also observed during the bout; (iii) certain actions may be repeated and performed in an exaggerated
manner; (iv) the activity appears "pleasurable" to the players.
By comparing these three species, some insight into the dynamics of social play may be gained. Coyotes
were the least successful in soliciting play. When they did play, 90% of all bouts had been previously
solicited. Coyotes also tended to use the most successful signals most frequently. This trend was not
observed in the beagles or the wolves. By taking into account the fact that infant coyotes are significantly
more aggressive than either infant wolves or beagles, the differential ontogeny of social play can be
explained. Some of the functions of social play in canids are discussed, and it is concluded that social
play is a valid class of social behavior and lends itself nicely to quantitative study.
"By the very clarity and simplicity of its expression, the play of children is often an excellent
window through which an observer may look upon a culture otherwise concealed by
complexities, suspicion, and the barriers of language." (Gardner and Heider, 1968, p. 63).
Although there have been many recent reviews of social play behavior in various mammals (e.g., Loizos,
1966, 1967; Millar, 1968; Berlyne, 1969; Dolhinow and Bishop, 1970; Muller-Schwarze, 1971; Bekoff,
1972a, 1974), few quantitative data have been amassed concerning this important category of social
behavior. Many workers have concluded that "play" is not a valid class of behavior (e.g., Schlosberg,
1947; Berlyne, 1969; Welker, 1971), because they lump social play behavior together with inanimate
object play and/or exploration. These are not the same behaviors (Hutt, 1970; Müller-Schwarze, 1971).
Social play must be studied in its own right, as involving two (or more) living organisms, capable of
exchanging information about an on-going interaction. The level of study may involve the observation of
gross movements (postures, gestures, facial expressions), the analysis of vocalizations, or the monitoring
of neuromuscular processes (e.g., Welker, 1971). Another source of confusion stems from the fact that
definitions of social play range from being totally uninformative (e.g., play is "any socially directed play
activity, including rough-and-tumble, approach-withdraw, and noncontact play"; Suomi, 1973, p. 73) to
being fairly comprehensive (e.g., Bertrand, 1967, p. 58ff; Müller-Schwarze, 1971; Bekoff, 1972a).
Workers should make every effort to indicate what they mean by "social play behavior" in the organisms
that they are observing.
In canids, there have been few in-depth studies of social play behavior (e.g., Tembrock, 1958; Ludwig,
1965; Zimen, 1971; Bekoff, 1972a,b; Bekoff and Jamieson, unpublished). Social play in canids (and other
mammals) may be characterized as follows: (i) actions from various contexts are incorporated into labile
(unpredictable) temporal sequences; (ii) the "play bout" is typically preceded by a metacommunicative
signal which indicates "what follows is play" (Bateson, 1955); these signals are also observed during the
bout; (iii) certain actions may be repeated and performed in an exaggerated manner; (iv) the activity
appears "pleasurable" to the participants (Bertrand, 1969; Csikszentmihalyi and Bennett, 1971;
1
Csikszentmihalyi, personal communication; Bekoff, 1974; Reynolds, unpublished). There is usually an
initial decrease in distance between the interactants (Bekoff, 1972a), however, this distance may
decrease and then increase, such as during chase and running play.
In this paper I would like to present data which have been collected on pairs of wolves, coyotes, and
beagles, observed under controlled conditions from 3 to 7 weeks of age. This period of life is
characterized by important changes in the central nervous system (Fuller and Fox, 1969), and it is also
during this period of time that the animals form intraspecific (and interspecific) social relations (Mills,
1898; Scott and Fuller, 1965). These three species of canids show very different courses of social
development during early life (Fox, 1969; Bekoff, 1972b), and by following the ontogeny of social play
under standardized conditions, a comparative analysis is possible.
METHODS
The animals observed in this study included four coyotes (Canis latrans), four wolves (C. lupus), and four
beagles (C. familiaris). The animals were hand-reared from approximately 10 days of age and were all
treated similarly. Until they were able to chew semi-solid food, all animals were tube-fed liquified Esbilac
(Borden's bitch's milk supplement). In order to regulate social interaction, the animals were housed
separately, and allowed to interact for 15 min per day (at the same time each day, 1 hr after feeding),
from 21 to 50 days of age with a similarly reared littermate in a 1.5-m × 1.5-m four-wall arena. The
animals were housed together in pairs (with the same littermate with whom they had had previous
interaction) after dominance relations were formed or on day 42 (whichever came first), in order to
determine if any changes in behavior would result due to cohabitation (e.g., food competition, increased
proximity).
Thirty-five discrete motor action patterns (body postures, facial expressions, gestures) were catalogued
and coded (Bekoff, 1972a,b). Coding the actions facilitated recording the data. Detailed daily notes were
also taken. During all observation periods I and the same co-observer were present.
DESCRIPTIONS OF ACTIONS USED TO INITIATE SOCIAL PLAY
Bow (B): The soliciting animal crouches on its forelegs and elevates its hind-end (Fig. 1); from this
position the animal is able to perform a wide range of other movements such as leaping, dodging, and
springing back-and-forth.
Exaggerated approach (EA): The soliciting animal approaches its prospective playmate in a "loose,
bouncy" gait, at a speed greater than that observed during normal walking; this has also been called a
"play rush" and "gamboling" in the non-human primate literature; during the approach, the shoulders and
head are frequently moved from side-to-side in an exaggerated fashion.
FIG. 1. A "bow" performed by the dog on the right. (After Bekoff 1972a, with kind permission of the Quarterly
Review of Biology.)
FIG. 2. Face-oriented pawing by the beagle on the right.
Approach/withdrawal (A/W): The soliciting animal approaches its prospective playmate and then
withdraws; withdrawal may involve stepping away slowly, or running away for a few meters and then
approaching (and withdrawing) once again; it is not uncommon to observe the soliciting animal approach,
stop, and then rock back-and-forth in one spot, making intention movements of running away.
FIG. 3. High leaping during play soliciting by a red fox.
General movements (GM ): These include movements of the head and eyes, such as head-tossing and
eye-rolling, and also body movements such as shoulder swaying; stalking of the prospective playmate is
also included--one animal slowly circles its partner, and then slowly, stealthily approaches; the approach
after a stalk may be exaggerated, and may also involve rapid approach/withdrawals.
Face-pawing (FP): This action involves extension of one of the forelimbs toward the face of the other
animal (Fig. 2); it is not uncommon to observe rapid extension and flexion of the forelimb when the
animals are at a few meters from one another (in this case the action is called a "paw intention").
Leap-Leap (LL): This action involves two high-amplitude leaps in which the forelimbs are lifted off the
ground, and hit the ground, simultaneously.
Barking (Bk) : See below.
We have also had the opportunity to observe some red foxes (Vulpes vulpes) (Bekoff and Fox, personal
observation). Some actions which they perform to initiate social play, that are not observed in other
Canidae include high-leaping (Fig. 3), flattening out (the animal lies flat on the ground and moves its head
from side-to-side), and "high-stepping" with the hind-legs.
FIG. 4. The median frequency of occurrence (%) of action patterns observed during both play soliciting and
agonistic interactions, in relation to the total number of actions performed during the stated time periods. t =
animals housed together in pairs at the beginning of this time period; vertical bars = range.
RESULTS
lnterobserver agreement was consistently over 95%. The observed animals demonstrated large
differences in the development of social behavior (Fig. 4). Note the high frequency of agonistic behavior
observed in the coyotes from days 21-28, and the low frequency of play-soliciting during this same time
period. Coyotes typically form their dominance relationships between 25 to 30 days of age (Fox and
Clark, 1971; Bekoff, 1972b; Bekoff and Jamieson, unpublished), and with few exceptions, these social
relations are the outcome of severe, unritualized fights. The beagles show an early ontogeny of play and
play-soliciting and very low levels of agnostic behavior. In fact, the levels indicated on the graph represent
very mild threat behavior and absolutely no fighting at all. Likewise, the wolves initially show low levels of
agonistic behavior and a higher percentage of play-soliciting. As the frequency of agonistic behavior by
the wolves decreased from days 43-50 (the animals were housed together in pairs on day 42), the
incidence of play-soliciting increased. All agonistic behavior consisted of threat, and there was no fighting
at all.
TABLE 1. Play-soliciting by beagles, wolves, and coyotes (days 21-50).
Beagles
Action
S(#)
a
U(#)
a
Wolves
a
P(P/S)
S(#)
U(#)
Coyotes
P(P/S)
S(#)
U(#)
P(P/S)
B
67
42
.61
29
27
.52
12
27
.36
EA
70
17
.80
11
3
.26
5
21
.19
A/W
77
35
.69
29
111
.21
10
29
.26
GM
54
13
.81
11
4
.73
31
51
.38
FP
32
2
.96
7
10
.41
2
8
.20
LL
37
9
.80
---
---
---
---
---
---
BK
29
33
.56
---
---
---
---
---
---
�
X=
.77
b,c
S.D. =
.12
rho =
‒.48
d
.43
.28
.05
.09
‒.70
+.87
a
S = frequency of occurrence of successful play solicits. U = frequency of occurrence of unsuccessful play solicits.
P(P/S) = given that there was a play-signal (S), what was the probability that social play (P) resulted. In other
words, P(P/S) is equal to the success of soliciting social play.
b
� for beagles based on all 7 actions = .75, S.D. = .13.
Based on first 5 actions; X
c
See figure 5 for "P" values (levels of significance).
d
Correlation between success of an action (P(P fS)) and the frequency of occurrence of that action.
Table 1 presents data concerning the relative success (P{P/S}) of each of the actions used to initiate
social play. The beagles were successful greater than 56% of the time, using any of the actions. In the
wolves and coyotes, general movements were most successful, and bows, second-most. Figure 5 shows
the total number of play bouts observed, the overall success (P{P/S}) rates, the levels of significance for
the differences observed, the Spearman rank-order correlation (rho) for the relationship between the
success of a particular action and the frequency of its occurrence, and the frequency with which bouts
were solicited (P{S/P}). The beagles were significantly more successful than either the wolves (df = 8, t =
3.42, P < .01) or the coyotes (df = 8, t = 6.7, P < .001), and the wolves more successful than the coyotes
(df = 8, t = 2.20, P < .05). Exaggerated approaches and face-pawing were least successful in the coyotes.
The low success of approach/withdrawals in the wolves was due to the inactivity and lack of "playfulness"
on the part of one of the animals (see below). It is also interesting that the correlations between success
of a particular action and the frequency of occurrence of that action was negative in both the beagles and
the wolves, and highly positive in the coyotes. That is, coyotes tended to use the most successful actions
most frequently.
Table 2 shows the frequency of occurrence of "sexual" behaviors during play bouts. The male beagles
performed more of these actions than did the females; mounting and thrusting were first observed on day
27. No "sexual" behaviors were observed in any of the coyotes, and one female wolf mounted her brother
on day 45.
FIG. 5. The success with which beagles (B), wolves (W), and coyotes (C) initiated social play.
P(play/soliciting)--see Table 1 for explanation; P (soliciting/play)--see Table 6 for explanation. The small
numbers on the left-hand graph (e.g., .01) indicate levels of significance (see text). The small numbers on the
right-hand graph indicate the individual scores for each member of each pair of animals. (1 applies to the
first pair of animals and 2 to the second pair--see Table 6). Rho = the correlation between the success of a
particular action and the frequency with which it was used. Bouts = the total number of play bouts observed.
TABLE 2. Frequency of occurrence of mounting (M), clasping (CL), and pelvic thrusting (PT) by beagles
a
during play.
Males
a
Females
Days
M
CL
PT
M
CL
PT
21-35
3
7
2
0
1
0
36-50
3
12
5
0
3
0
6
19
7
0
4
0
No mounts, clasps, or thrusts were observed in the coyotes; on day 45, one female wolf mounted her brother.
Table 3 shows the frequency of occurrence of head-shaking (side-to-side shaking of the head while
biting), face-pawing and also the frequency of occurrence of biting directed to various parts of the body.
The beagles did more face-pawing (it was very successful in soliciting play) and this action persisted
throughout the course of observations. In the coyotes and the wolves, the frequency of face-pawing
began to decrease on approximately day 35. The wolves performed more head-shaking and also more
scruff-biting, while the beagles bit more at the face and the body (legs, flank, and back).
Individual differences
Coyote pair 1. In this pair there was a severe, unritualized fight (uninhibited biting accompanied by
vigorous head-shaking) on day 25, U female emerging dominant. On this day there was no play-soliciting
by either animal, and there was a large increase in self-directed play (tail-chasing) by the subordinate
male (Fig. 6). There was a further increase on self-directed play on day 26. Similarly, on days 45 and 46,
when there was an increase in aggression by the dominant female, there was an increase in self-directed
play by her subordinate brother. Overall, the subordinate male (C) performed significantly more selfdirected play behavior than his dominant sister (135:33; P < .005, sign-test). Usually this behavior either
followed an unsuccessful play-solicit (28%) or occurred in the absence of any play-soliciting (in vacuo)
(67%). On a number of occasions, tail-chasing occurred, and then the male briefly stopped and looked at
his sister, and then commenced chasing once again. Between days 21-42 there were only 17 bouts of
play, and between days 45-50, there were 23 bouts. The animals did not get more successful in soliciting
play as length of time with social experience increased.
TABLE 3. Frequency of occurrence of various actions and bite orientation (days 21-50).
Hsh
Beagles
a
FP
126
389
(26)
Coyotes
b
229
61
319
325
158
1141
(46)
237
(67)
544
(35)
GB
193
(287)
(16)
(68)
a
SB
1182
(90)
(59)
Wolves
FB
713
(57)
502
(130)
(259)
(180)
881
(115)
(246)
Hsh = side-to-side head-shaking accompanying a bite
FP = face-pawing
FB = face-biting
GB = general biting (flank, body, tail)
b
Median
FIG. 6. The relationship between self-directed play and play-soliciting by the subordinate male in coyote pair
1. The star indicates that on day 25, dominance relations were formed (see text).
TABLE 4. Day of first occurrence of actions used to initiate social play.
Coyotes
Beagles
(1)
(2)
C
B
c
U
Female
b
49
28
(27)
EA
---
28
(30)
32
GM
30
FP
---
LL
---
B
---
41
(26)
b
c
29
37
(26)
---
25
(30)
(27)
(27)
27
(26)
23
23
21
21
26
37
---
(23)
27
(38)
(37)
(23)
--28
(28)
30
(35)
(27)
---
---
-----
--30
(29)
(43)
---
---
30
(25)
(42)
37
-----
---
---
29
---
(41)
(43)
(26)
-----
---
40
---
(26)
(26)
---
---
(43)
28
27
--45
(34)
(26)
24
---
27
25
(34)
(38)
(27)
(24)
(24)
28
29
26
---
34
23
26
(27)
(23)
(39)
(24)
35
32
30
25
40
---
26
24
(24)
(31)
26
26
(28)
(33)
(26)
48
24
23
27
(42)
(30)
(30)
(30)
---
21
30
(28)
(26)
(25)
23
23
(40)
(29)
---
(28)
23
24
22
35
(28)
U
Male
-----
29
(33)
C
Female
---
---
---
U
Male
28
---
-----
a
---
---
C
Female
(27)
---
---
W
Female
22
32
---
B
Male
(29)
(29)
(29)
---
�
X
30
(35)
W
23
49
(2)
Female
(28)
(31)
(1)
B
(27)
(25)
(2)
Male
25
27
30
34
Female
(32)
(26)
(27)
a
30
24
(46)
(26)
U
Male
31
28
(46)
A/W
C
a
Male
Wolves
(1)
--36
(31)
Dominant animal.
Day of first success. ( ) = day of first failure.
See text for code.
The subordinate male first successfully solicited social play on day 28 after having been unsuccessful on
days 24, 26, and 27 (Table 4). The dominant female first successfully solicited social play on day 28. On
day 32 there was an increase in social play by the female, and on day 33, the longest fight of all was
observed. Overall, play-soliciting resulted in an aggressive response only four times, the remainder of the
unsuccessful solicitations being responded to with "indifference" by the recipient. On day 45, when there
was an increase in aggressive behavior by the female, the male approached her after play soliciting and
she did not respond. Ten seconds later, he approached once again without previously signalling a "play
intention," and she responded aggressively. It is also important to point out that of 40 attempts to initiate
chase play by the dominant female, only I was successful, and this was the only one which was preceded
by a play signal (general movements) (Table 5).
Table 6 presents the data dealing with the success (P{P/S}) of play-soliciting and also the probability that
a bout had been previously solicited (P{S/P}. The dominant female of this pair was both less successful
and less solicitous than her brother, and when play did occur, the probability that the subordinate male
had previously solicited playful interaction was higher than that observed for his sister. A total of 90% of
all bouts were signalled by either animal (see also Fig. 5).
Play bouts typically consisted of wrestling, jaw-wrestling, and inhibited biting. "Role reversals" were also
observed, the dominant female allowing her subordinate brother to "dominate" her. On a few occasions,
play fighting did lead to real fighting. On day 40, for example, the animals were engaged in a reciprocal
bout of wrestling and play-fighting, when all of a sudden the dominant female aggressively vocalized and
(38)
began attacking her brother. He rolled over into a passive-submissive posture (Bekoff, 1972b) and
remained motionless until she stopped attacking. Eye-contact by the female was sufficient to induce flight
and turning away by the male (Fig. 7).
TABLE 5. Chase sequences in coyotes.
Response by subordinate male
Turning-away
Rolling-over
Def. threat
No reaction
Play
20
14
3
2
1
Chase by dominant female
a
Total
a
40
The only instance in which chase was preceded by a play-signal
a
TABLE 6. Play-soliciting by individual animals observed in pairs.
S(#)
Coyote 1:
Coyote 2:
Beagle 1:
Beagle 2:
Wolf 1:
Wolf 2:
C
Male
b
26
U(#)
36
b
b
b
P(P/S)
# Bouts
(P(S/P)
.42
40
.65
U
Female
c
10
30
.25
40
.25
C
Female
19
37
.34
29
.66
U
Female
7
34
.17
29
.24
B
Male
86
40
.68
243
.35
W
Female
76
17
.82
243
.31
c
B
Male
127
51
.71
237
.54
W
Female
95
33
.74
237
.40
C
Female
15
56
.21
85
.18
U
Male
13
44
.23
85
.15
C
Female
56
79
.42
78
.72
U
Male
6
7
.46
78
.08
a
Based on the total frequency of play-soliciting actions
b
See Table 1 for legend concerning S, U, and P(P/S); P(S/P) = given that there was play (P), what was the
probability that it was preceded by a play-signal(s). In other words, P(S/P) is equal to the % of solicited play bouts.
c
Dominant animal
Coyote pair 2. In this pair of coyotes, C appeared to be dominant over her sister (U) between 26 and 30
days of age. There was no fight and the relationship was not as clear-cut as had been observed in coyote
pair 1. On day 30, U began asserting dominance over C and controlling their interactions from then on. Of
the 24 periods in which there appeared to be an assertion of dominance by one of the animals, U was
clearly dominant during 20 (83%).
From 3 to 4 weeks of age, there was little difference in their success of soliciting play and their
"playfulness," C attempting to solicit play eight times, and U attempting to solicit play six times. After U
began asserting dominance on day 30, C became more successful in soliciting social play. The animals
were housed together on day 35, and between days 36-42, there were no bouts of play, as U became
more aggressive. On day 42 there was a dominance fight, U clearly dominant over C. Between days 4350, C was clearly more solicitous, attempting to initiate social play 21 times to her sister's 8. U was less
successful overall, and more bouts were preceded by a play signal sent by her subordinate sister (Table
6). A total of 90% of all play bouts were preceded by a play signal sent by either animal (Table 6).
Beagle pairs 1 and 2. It is not misleading to clump the data for the beagles, since the individual animals
did not display individual differences as large as those observed in the coyotes or the wolves. In both
dyads, no dominance relations were formed, and there was a lot of reciprocal interaction. The beagles
were the most solicitous and playful of the animals (engaging in 483 bouts of play) and successfully
solicited play earlier than their congeners (Table 4). The frequency of occurrence of play bouts for any
seven-day period (e.g., 21 to 28, 29 to 35 days of age) ranged from 45 to 69. In the first pair, when W
female was inactive between days 29-35, B male engaged in self-directed play 112 times. Typical
sequences of beagle play are illustrated in Figures 7 and 8. During play bouts, more "sexual" actions
were noted in the beagles. Also, the beagles were the only animals which barked during the solicitation of
social play. (We also observed barking at inanimate objects such as the food bowl and water bucket.)
None of the beagles were as successful as the subordinate coyotes (Table 6).
FIG. 7. Some typical sequences of social play in the beagles and coyotes. EA = exaggerated approach; TA =
turning away; CH = chase; GB = general body biting; hsh = side-to-side head shaking accompanying the
biting; RO = rolling over; A = approach; CR = chin rest; NR = no response; ISO = incomplete stand-over; AJW
= approach/withdrawal; PS = play solicitations. For pictoral representations and full descriptions of these
actions see Bekoff, 1972b.)
Play consisted of reciprocal chase, wrestling, inhibited biting, and rearing and pushing with the forepaws.
A breed-typical action pattern, the leap-leap, was performed in its highest frequency by the beagles
(mean = 165), and it was highly successful in the initiation of social play (Table 1). It was never observed
in the coyotes and very rarely in the wolves (mean = 9). When it occurred in the wolves, the leaps were of
lesser amplitude.
Wolf dyad 1. The wolves in this pair behaved very much alike and there was a good deal of reciprocal
play interaction. No dominance relations were formed. Between days 21-28 and days 29-35, there were
33 bouts of play during each period. The frequency of occurrence of social play precipitously decreased
between days 36-42 to 9, and between days 43-50 to 10. Play consisted of chase and wrestling.
FIG. 8. This sequence of photos shows a play sequence between two 30-day old beagles. The beagle on the
right performs a bow (A) and his littermate approaches (B). As she approaches he makes direct eye-contact
and she turns her head away for a brief moment (C). D, the female (on the left) rears and leaps off the ground;
E, the male responds by moving closer. A play bout consisting of wrestling, rolling, and inhibited face-biting
occurred (F).
Wolf dyad 2. As in pair 1, no dominance relations were formed during the course of observation. Although
both animals were approximately equally successful in soliciting play (P{P/S}) (Table 6), there were large
individual differences in "playfulness," U male attempting to solicit social play only 13 times. Unlike pair 1,
there was a great deal of play from days 35-50, there being 28 bouts from days 36-42 and 29 bouts from
days 43-50. The large difference in P(S/P) was due to U's inactivity. C female performed significantly
more self-directed play when U was inactive and unresponsive (38:8; P < .05, sign-test).
DISCUSSION
In canids, play may be characterized as indicated in the introduction to this paper (see Tembrock, 1958;
Ludwig, 1965; Eisfeld, 1966; Altmann and Recker, 1971; Bekoff, 1972a,b). To an observer familiar with
the species or individuals under study, it is usually not difficult to differentiate social play from other
categories of social behavior. Miller (1973) has correctly written that an ". . . observer who 'knows' he
sees play, even if he doesn't know what it 'is', is not necessarily talking off the top of his head" (p. 89).
By observing pairs of animals, much may be learned about the dynamics of social interaction in a
particular species (Kalmus, 1969; Poole, 1972). In order to gain insight into social ontogeny, conditions of
captivity provide a good setting, since individuals may be identified at an early age. In canids in the wild,
much behavior occurs inside the den during the first weeks of life, and in coyotes in particular, many
valuable data would be lost. Recent observations of an intact litter of coyotes, reared in captivity with their
mother, indicated that between days 18 and 35, 85-90% of all social activity took place within the nest
box, or directly in front of it (Bekoff and Jamieson, unpublished).
A most difficult aspect of the analysis of social play is the study of the temporal sequencing of the actions
which are incorporated into a play bout. Most of these actions originate in other contexts. Preliminary
analysis (Bekoff, in progress) indicates that the probability that an action will occur during a bout is very
little dependent on the nature of the preceding event. The sequences appear more random and less
predictable than those observed during actual fighting, courtship, or prey-killing. This is especially true for
the beagles and wolves. In mathematical terminology, it appears that most play sequences would be
categorized as zeroth-order Markov chains (Slater, 1973). That is, after one animal delivers a bite to the
rear leg of another animal, side-to-side head-shaking occurs as frequently as biting the other leg, scruffbiting, or rapid withdrawal. This lability of temporal sequencing has also been observed in free-roaming
dogs (Ludwig, 1965; Bekoff et al., in progress), and in wolves (Zimen, 1971). Slater (personal
communication) has suggested that perhaps different rules apply at different points in the play bout, and
that the analysis of temporal sequences is complicated by the fact that two interacting organisms are
involved. I do not agree with Lazar and Beckhorn (1974) that " ... play activities are seen to be
exaggerated, out of sequence, incomplete ... only when viewed with respect to adult behavior patterns."
Fox (1969) and this author have observed infant coyotes perform normal species-typical predatory
sequences as well as engage in true agonistic encounters. When these actions are performed by the
same animals during social play, there is exaggeration, lack of sequencing, and incompleteness of action.
Thus, play need not be characterized only by reference to adult behavior. Furthermore, I do not agree
with Tobach and Schneirla (I 968) that "play is a term for immature undifferentiated behavior patterns in
the process of organization ... " for the above reasons, and for the more obvious reason that adult animals
do engage in social play.
Species and individual differences
The early ontogeny of agonistic behavior in coyotes which results in clear-cut dominance relations (Fox
and Clark, 1971; Bekoff, 1972b; Bekoff and Jamieson, unpublished) clearly differentiates coyotes from
beagles and wolves. Overall, the beagles were seven times as playful as the coyotes and three times as
playful as the wolves. (In the domestic dog, breed differences are also evident [Ludwig, 1965; Scott and
Fuller, 1965] and whether or not these breed differences are reflected in early ontogeny would be
interesting to study [Ewer, 1968].) There were virtually no instances in which we were unable to
differentiate play-fighting from real fighting, and I feel that rather than labeling play-fighting as "quasiagonistic" (McGrew, 1972), I would retain the label "play-fighting." This is because, at least in canids, both
the sequencing of the actions and the outcome of the interaction differ from that observed during true
fighting. Poole (1973) has recently differentiated true fighting from play-fighting in polecats.
Recent data collected on a litter of coyotes (Bekoff and Jamieson, unpublished) suggest that the
differences in ontogeny which are evident in the early life of canids, may be useful in understanding later
adult social organization. And, as has been suggested for various mammals (Etkin, 1963; Baldwin and
Baldwin, 1974), it appears that "animals which play together, tend to stay together." Animals which play
less appear to have weaker social ties to their group.
Play-soliciting
Animals have to be able to differentiate play from "not play." Before the play bout commences, one
organism may "metacommunicate" (Bateson, 1955) its intention to play by using various signals. These
signals are usually clear and unambiguous, and some appear to be specific to the context of social play
(Bekoff, 1972a; Sade, 1973). Furthermore, when two seemingly contradictory signals are given, one of
which is a play-soliciting action, priority is most usually given to the play signal (Loizos, 1966; Bekoff,
1972a). In a previous paper I have discussed metacommunication in more depth (Bekoff, 1972a), and I
also suggested that some of the play-signals in canids were specifically used to initiate social play. I was
referring to the "bow." It still appears that although the bow and other movements are also observed in
other contexts (during courtship for example) "play intention" cannot be ignored. Christie and Bell (1972)
present quantitative data showing that there is an increase in male-female play during both pre-estrous
and estrous in domestic dogs. We have observed courtship between a male malemute and a female wolf
(Lockwood, Shideler, Bekoff, and Fox, unpublished) and observed numerous bows, along with other
actions used to initiate play. Perhaps play serves to strengthen the bond between the courting animals
and reduces flight tendencies.
After the bout is underway, there is continual feedback between the interactants, and it appears possible
that the animals "know" that they are playing because of the changes in the temporal sequencing
(Chevalier-Skolnikoff, 1973). Therefore, when an observer does not perceive a play signal, he does not
have to feel that he has necessarily missed something, for the "signal" may be in the sequencing itself.
On the other hand, a signal may be given which is so subtle as to be almost undetectable to the human
observer. By doing frame-by-frame analysis of movie film shot at the "eye level" of the interacting animals,
we have observed very slight eye and head movements directed toward the prospective playmate, and at
the moment, can only assume that they are of some import to the animals (Bekoff and Jamieson, in
progress).
The coyotes were significantly less successful than the beagles or the wolves in initiating play. However,
when play did occur, 90% of the time it was preceded by a play invitation signal. The subordinate animals
were more playful than their dominant partners. Furthermore, in the coyotes, there was a high positive
correlation (rho) between the success of a particular action and the frequency with which it was used.
That is, coyotes showed a strong tendency to use the more successful signals more frequently, while in
the beagles and the wolves there were negative correlations. (In an ongoing study of free-roaming
domestic dogs, we have found a correlation of rho = ‒.04.) These facts fit in nicely with what has already
been discussed concerning the differences in social development between these three species. Since in
the coyote there is an "aggressive atmosphere" prevailing, and during social play the actions observed
are usually those otherwise seen in true aggression, it would be important for an animal to communicate
its intention to engage in social play and that this intention be perceived and shared by the recipient. In
the coyotes, the least ambiguous signals (at least to the observers) were the most successful. The
importance of the signal in coyotes is also indicated by the fact that if play did occur after a signal was
sent, it was most usually the subordinate who had solicited the interaction, in a sense, assuring the most
dominant sib that "what follows is play, and not an attempt to overthrow you!" Similarly, when the
dominant female in pair 1 attempted to initiate chase play without previously communicating play
intention, she failed 39 out of 39 times. The only successful initiation of chase play occurred after she had
sent a play signal. Loizos (1969), in her study of chimpanzee social play, found that in order for chase to
result in play, and not flight, the subordinate had to do the chasing.
In the wolves, exaggerated head and body movements (e.g., head-tossing and side-to-side swaying of
the shoulders) were most successfully used to initiate play. In the beagles, all actions were successful
more than 56% of the time. High-pitched barking by the beagles was also successful in initiating an
approach by the partner and subsequent play 56% of the time, and it was often combined with another
play-soliciting action. Barking may be a way in which an animal calls attention to itself and play signals
may also serve as attention-getting devices (Steiner, 1971), in addition to intention movements. Beer
(1973) has written that "an effective signal is one that gets attention and is unambiguous" (p. 69).
Sex differences
In the present study, no sex differences in social play were observed with respect to the "roughness" of
the playing. It is possible that this was due to the fact that the animals were not reared with their mothers,
however, observations of other canids reared with their mothers (Bekoff and Jamieson, unpublished,
Bekoff, personal observation) indicate no sex differences during 3 to 8 weeks of age. The only sex
differences involved the frequency of occurrence of "precocious" sexual behavior by the male beagles.
Rheingold (1963) points out that only male dogs were observed to mount other animals during the course
of her observations.
Self-directed play
Qualitative observations of the development of social behavior in various canids led Fox (1971, p. 52) to
suggest that self-directed play might serve as a substitute for social play when the possibility for social
play was blocked. Rather than block social play using experimental techniques (e.g., Miiller-Schwarze,
1968; Chepko, 1971; Reynolds, Oakley, and Noble, personal communication) we found that this occurs
naturally. It appeared that an animal could be "play deprived" even in the presence of a partner(s), if that
partner was unresponsive to play solicitations and/or generally inactive. Being unable to successfully
solicit play, an organism might then redirect its play towards its own body.
When the possibility for social play was blocked, due either to the intolerance of one animal for the
proximity of its partner (coyotes) or to one animal's inactivity (beagles and wolves), there were substantial
increases in self-directed play behavior by the more active animal. Kruijt (1971) wrote that the most
important influence of social experience appears to be that it guides the responses of the organism
toward social companions, and in the absence of such partners, the animal forms relationships with its
own body. Mason (1965) suggested that in the absence of social companions, an animal disposed toward
social play would engage in strenuous motor activities. As mentioned above, absence does not
necessarily imply physical absence, but can also refer to unresponsiveness. While the animals we
studied did not have the opportunity to play with inanimate objects during observation sessions,
observations of free-roaming dogs has indicated that it is not uncommon to observe an unsuccessful
solicitor immediately begin playing with an inanimate object. Finally, in-cage observations of these and
other canids that have been housed individually for methodological purposes have shown that these
animals perform very little self-directed play during this limited social isolation at this age (Bekoff and Fox,
personal observation). The presence of another animal appears to serve as a stimulus.
Self-directed play does not always follow an unsuccessful play solicitation. After a period of time, selfdirected play occurred without a prior play soliciting. Since animals adjust their actions to the "expected"
actions of others (McFarland, 1966; Bindra, 1969), an animal may learn not to expect another animal to
play. After repeated "play deprivation," it may forego soliciting play and engage in self-directed play
without prior play soliciting. Bindra (1969) has discussed the above idea in terms of the central motive
state (CMS). The CMS occurs through an interaction between physiological states and incentive stimuli.
Indeed, more studies are needed concerning the physiological state of playing animals (Müller-Schwarze,
1971).
Why play?
Space does not allow me to go into a full discussion of why animals play. Various authors have
considered the functional aspects of social play (Beach, 1945; Millar, 1968: Dolhinow and Bishop, 1970;
Müller-Schwarze, 1971; Bekoff, 1972a), and no one theory of play has been found to be applicable to all
animals (Lowenfeld, 1936; Beach, 1945). Indeed, ecological factors are important to consider when
discussing even a single species (e.g., Barash, 1973). Animals obviously get physical exercise while
playing (Brownlee, 1954), and they may also acquire skills which will increase the facility with which they
can move through their environment (Ripley, 1967).
There have also been repeated assertions that social play experience is necessary for animals to become
"socialized" to conspecifics (Harlow, 1969; Jolly, 1972). In an earlier paper, I overenthusiastically (and
perhaps naively) accepted this point of view. There is some evidence that it is not mandatory for animals
to have had social play experience in order to acquire species-typical social communicatory skills
(Baldwin and Baldwin, 1974) and that methods which have been used to experimentally deprive animals
of social play behavior have not specifically affected only social play experience. However, social play
experience does appear to lead to an increase in flexibility of an individual's behavior repertoire (Miller,
1973) and in the subtlety of social cues to which it can appropriately respond (Baldwin and Baldwin,
1974).
It has also been suggested that animals play in order to pre-exercise "instincts" which will be needed in
later life (Groos, 1898). Suffice it to say, this theory has not been supported in various mammalian groups
(Poole, 1966; Fox, 1969; Welker, 1971; Bekoff, 1972a). What appears to be the case is that play
experience increases the "smoothness" of carrying out certain sequences of behavior, but that it is not
necessary for achieving the consummatory phase of the sequence (e.g., the killing of prey) (see Beach,
1968).
In canids, play appears to be important in learning to control the intensity of the bite and in facilitating the
formation and continued maintenance of social relationships within a group. In coyotes (and red foxes)
play does not usually occur until after dominance relations are formed, while in wolves, play appears
before dominance fights. That the more social canids play more earlier in life is interesting, and there
appears to be some relationship between social ontogeny and later social organization in Canidae,
namely, that "animals that play together, tend to stay together" (Bekoff and Jamieson, unpublished).
Tembrock (1958) wrote that the frequency of play between two individuals was a measure of "fondness."
Finally, animals may play because it is a "pleasurable" experience (Bertrand, 1969; Bekoff, 1974). Young
animals devote a lot of time and energy to social play, and perhaps this good "feeling" is indicated by the
looseness of their gait, the bouncy movements observed during play, and the "smile-like" facial
expression. External cues are frequently used by ethologists and other behavioral scientists to infer mood
(e.g., Darwin, 1872; Hebb, 1946; Vine, 1970; Dittmann, 1972; Ekman, 1973), and the overt behavior
associated with social play indicates a "pleasurable" experience. Neurophysiological studies may provide
some further support for this contention (e.g., Lindsley, 1951; Clynes, 1973).
In conclusion, social play appears to be an important category of social behavior and should not be
dispensed with as being a "wastebasket" into which unmanageable concepts are deposited. Data which
have been and are currently being collected on a wide range of animals are providing evidence that social
play may be studied in its own right.
NOTES
1
The interested reader may contact M. Csikszentmihalyi at the University of Chicago for a copy of his
paper entitled "Flowing: A general model of intrinsically rewarding experiences."
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