Z. Tierpsychol., 39, 126-140 (1975) @ 1975 Verlag Paul Parey, Berlin und H a m b u r g ISSN 0044-3573/ASThI-Coden ZETIAG
Max-Planck-Institut f i i Verhaltensphysiologie, ~ Seewiesen
Observations on Fighting Behaviour of Male Mice (Mus muscuhs L.)
BY
R. G. BEILHARZ and V. C. BEILHARZ
Received: 13. 11. 1974
Abstract Fighting behaviour of male mice was compared in 8 wild, 2 unselccted laboratory and 6 laboratory mice from a population bred from winners of fights. Behaviour was recorded when all 16 mice were allowed to fight in all possible pairs in a neutral test box, and when 5 selected mice fought in pairs in the home cages of one o r the other. The occurrence of self-grooming, tail rattle and squealing are discussed. Different occurrences of behaviour in the different strains are explained as a result of genetic selection responses.
Introduction The normal environment of house mice includes human habitations. “Artificial” laboratory situations, in which behaviour can most readily be observed, need not therefore be an unnatural environment even for a wild house mouse. Fighting behaviour of house mice has been reviewed several times (EIBL-EIBESFELDT 1950, SCOTTand FREDERICSON 1951, SCOTT1966). In much of the work laboratory strains have been used. Such strains often have genetically unique genotypes (BAKNETT 1969, SMITH1972, St. JOHN 1973). Conclusions derived from such strains apply strictly only to mice of those strains. In his review SCOTT(1966) stated that “agonistic behaviour is yet to be analysed in breeding experiments in rats and mice”. Since then LAGERSPETZ and LAGERSPETZ (1971) have selected laboratory mice for and against aggressiveness for 19 generations. They recorded the aggressiveness of d d o n a 7-point scale after they had been reared in isolation from weaning onwards. 99 were not tested as they failed to show signs of aggressiveness in contacts with each other (LAGERSPETZ 1969). The strains differed significantly in male aggression from the second generation. After the 7th generation there has been no further response. Clearly, in these mice aggression has been modified genetically. At Melbourne University we have also selected laboratory mice for “aggression” in both sexes since 1967. The selection response seems to be still continuing after 20 generations of selection. The fighting behaviour of some
Observations on Fighting Behaviour of Male Mice
127
individuals of this strain was observed and compared with that of unselected white laboratory mice and of captured wild mice.
Methods Stock mice. b'rom 28/9/71 to 26/1 1/71, 16 wild house mice (9 c3, 7 were caught in and around several of the buildings of the institute at Seewiesen. They were placed in various types of cages but eventually in 4 glass tanks covered by wire, as they continually escaped from more conventional mouse cages. With one csception the groups of individuals scttled down well after some initial fighting. The mice showed no evidence of serious wounding. The exception was a young 6 who was killed on the day in which he was placed in cage 3 , which had already contained 2 older 6 & and 1 matiire for at least 9 days. S e e w e s e n mice. T w o 3 ~3 and 5 all young adults, were obtained from a population of white mice maintained by colony breeding at Seewiescn. This population was said to be non-aggressive. I t had existed at Seewiesen since 1968. The 7 mice were all housed in one cage. Their coats showed no evidence of fighting. Melbourne mice. 8 (3 8 and 12 from generation 1 8 of population 7 b of the mice being bred at the School of Agriculture, University of Melbourne, were sent by air to arrive at Seewiesen o n 13/11/71. This population has been bred since generation 5 from those male and female mice that had won the most fights with strange mice of the same sex, in neutral boxes ( B E I L H A R1972). Z The 8 8 6 had been reared as 1 group since 3 weeks of age. One 6 was de5troyed on arrival because he had been wounded by the others during the flight. The other mice, mature but so far unmated, were placed in 5 cages each containing 1 o r 2 6 6 and 1 to 3 In each of the 2 cages containing 2 6 6 one (3 was badly wounded when seen 2 days later. O n e of these (No. 766) was removed to a new c.ige with a I n cage 26 t w o ($ (3 were allowed t o remain together. The wounded 8 (No. 429) died on 28/11/71 after gradually deteriorating in health. Fucilities: The mice were kept in a room about 1 m by 3 m in floor area. The room was heated in winter but not to a constant temperature. With 1 exception all holes through which mice could leave the room were blocked. Above the door the wood that should have sealed the space between the brickwork and the doorframc was not tight. Despite efforts t o seal this hole, mice continued to find refuge there. However, as the mice that escaped from their cages always turned up again in this room, we assume that there was no way o u t of the room. Most observations were made in a test box 98 cm long, 39 cm wide and 39 cm high. The box had previously been a fish tank. It had a glass front on one long side, and on the inside, a frame where a glass partition had previously divided the tank across its length into halves. This central frame protruded 5 cm upward from the floor and 7 cm inward from the front and rear walls. The floor of the box was covered with wood shavings which were not removed between observations. Every mouse must thus have smelled the previous presence of other mice in the test box. Very rarely a wild mouse jumped out of the box. The central frame provided an opportunity for climbing without, however, allowing escape. Description of Experiments: The following behaviours were recorded with a 20-bar event recorder for individual mice in the experiments described below.
99)
Wild
99,
9
99
99.
9.
A : Mouse in 1 spot (hind feet) but not still. A includes all behaviour in 1 spot not specified elsewhere. B: Normal movement over the ground, as in exploration. B includes all behaviour not I-pecified elsewhere, while the mouse is moving over the ground. C: Freezing. Mouse does not even move whiskers. When a mouse stopped suddenly and iroze, the first reaction of the observer was often t o press A. As it became clear that C was involved C was pressed and a note made on the record paper to enable correct evaluation. D: Grooming of self, ranging from a short rub of nose and whiskers by the front paws to complete scquences of grooming of all parts of the fur. E : Grooming of another mouse. This behaviour graduates imperceptibly into biting of the other mouse (SCOTTand FREDERICSON 1951; CLARK and SCHEIN1966). E was recorded t o the point where the other mouse gave an indication that it had been bitten. F: Digging. This includes all forms of pushing floor material (shavings) with front or hind legs. I: also includes the rare periods spent under shavings after digging. G : Handling or nosing of floor materials (shavings). The mouse may be moving slowly or may remain in 1 spot. H : Eating. This includes the holding or handling of food with front paws. I : Sniffing genitals of another mouse.
R. G. BEILHARZ and V. C. BEILHARZ
128 J:
Running away rapidly, as in fright.
K : Jumping. L: Stiff movement over the ground usually seen in tens? situations such as before and between periods of fighting. This behaviour, while distinguishable from B in laborator) mice, was hard to separate from B in wild mice. In the latter the records d o not provide a clear separation of L and B. L is probably the same as “mincing” (SCOTT 1966) and “humping” (CLARKand SCHEIN1966). M : Climbing. The mouse has all feet off the ground. N : Tail rattling. This is a stereotyped rapid and rhythmic movement of the tail (SCOTTand FREDERICSON 1951). 0: Biting of another mouse. P: Squealing. This was only recorded when the mouse that squealed could be clearly identified. Thus more squealing occurred than appears in the records. Q: Mouse in a defensive or submissive position. The mouse stands still, its movement clearly inhibited. The head is high, the front paws are held in the direction of (push away) the other mouse which is moving freely usually with its head towards the lower parts of the 1951; “Demutbody of the submissive mouse, where it may bite (SCOTT and FREDERICSON stellung” EIBL-EIBESFELDT 1950). Rarely, a mouse assumes a position similar to this before attacking or almost attacking. In such a c a e it sccms to us that the mouse is in conflict between balancing tendencies to attack and to run away. Thus, on rare cccasions a recorded Q indicates such a conflict rather than clear submission. R : Rolling, scratching and biting. This is a clearly recognizable fighting involving 2 mice. S : Sniffing of a n y part of the body of another mouse excluding the genitals. S includes, for tense situations, the “sniffing” a t another mouse from distances u p to 1.5 cm. T: Running away from another animal. This is seen after, o r as a n alternative to, fighting. U: Chasing another animal. This also occurs only with fighting. V : Climbing o n the wire at the top of a cage. T h e records of behaviour were made o n paper marked at 4-sec intervals. For each interval the behaviour present longest was determined. The intervals assigned to each behaviour were added over whole observation periods to obtain bchavioural profiles. Where required, the time that elapsed to first evidence of fighting (shown by behaviours 0, Q, R, T o r U) and other criteria were found directly from the records. Preliminary Experiment: When the 16 6 6 available (Wild mice 1, 4, 5, 6, 9, 10, 13, 14; Seewiesen mice 1001, 1002; and Melbourne mice 432, 444, 445, 446, 763, 766) were placed for their first time, singly, in the test box, their behaviour was recorded for 10 min. This took place from 3/12/71 to 10/12/71. I n error No. 763 was recorded f o r only 5 min. The proportion of time spent in thc various activities was estimated and the strains of mice were compared. Experiment 1 : From 10/12/71 to 25/1/72 the same 16 6 8 were placed in the test box t w o a t a time and observed for 15 min or until one mouse clearly exhibited behaviour Q (submission). The observations were repeated until all mice had met every other mouse once. No pairs were repeated. The allocation of opponents was made a t random within the group of mice not yet met. No mouse was put into the test box more than once per day. The behaviour of only one mouse out of each pair was recorded. Initially, and whenever both opponents had a n equal number of records, the choice of which mouse to record was made at random. Later, the mouse which had fewer records was recorded in order to obtain a roughly equal number of records for each mouse. When it was possible, the “winner” and “loser” (the mouse that showed submission) were recorded. Where no mouse was submissive a “tie” was recorded. Where none of the behaviours 0, Q, R, T or U were seen “ n o aggression” was recorded. Experiment 2: From 11/4/72 5 to 18/4/72 5 8 8 (445, 1001, 5 and 10) were used in a 2nd test. Each subject was chosen at random o u t of one of the following classifications based o n the results of Experiment 1 : 1. Most dominant pair of Melbourne mice, 2. least dominant pair of Melbourne mice, 3. Seewiesen mice, 4. most dominant pair of wild mice, 5. least dominant pair of wild mice. The subjects were tested in all possible pairs twice, first in the home cage of one of them, then some days later in the cage of the other. The period of observation was 3 min or until one mouse showed clear submission (Q), whichever was the later. If submission had not occurred by 10 min observation was stopped a n d a “tie” recorded. Allocations of opponents, and choice of cage for the 1st encounter for each pair, were made a t random. No mouse was tested more than once in any morning or afternoon.
Observations on Fighting Behaviour of Male Mice
129
The behaviour of the mouse not in its home cage was recorded in all cases. The “winner”, “loser” or “tie” was found for each encounter.
Results General Observations: The wild mice periodically escaped from their cages by gnawing through the wire at the top corners of their glass tanks. They were recaptured either immediately or after having disappeared for some time. Disappearances did not follow a random pattern, however. For example, during the period from 20/12/71 to 3/1/72, when d‘ No. 1 was out of his cage, wild dd from other cages in which a hole had been gnawed were found either just on the wire or still within their cage, while 99 had disappeared to be recaptured later. The dates of escapes and recaptures show that a t no time had dd from different cages disappeared simultaneously. I t seems that an escaped 0“ by taking the whole room over as his territory, prevented other dcr”from leaving their cages. $29were not affected in this way.This explanation is consistent with the findings of MACKINTOSH (1970). Wild mice reentered their own cages on recapture without causing fighting. If a wild mouse of either sex was placed into the wrong cage fighting broke out. Preliminary Experiment: The proportions of time that the subjects spent in the one spot (behaviours A or C) and moving (B, F, G, J, K, L or M) were Table 1: Proportion of time spent in the one spot and moving when in the test box f o r the first time
I
I
Strain of mice
0.L5 0.41
.
Table 2: Results of encounters in the test box
-
I
Moving
0.6L
Seewiesen Melbourne
Subject
I
In one spot
Wild
Opponent LLL
LL5 432 766 763 [ LL6 1001 1002
-- 5
LLL LL5 432 7 66 763 LL6
w
w
W
L
w w -
w w w
L
-
1001 1002
w
w
L
NS
L
L L L L NS L L L
L NS L L L L L L
NS W L L NS NS NS L
5 1L 6 1 10 13 9
L -
W W W W L L
W W W W W NS W L L NS NS L L NS L
1 4 1 6
1
10
13
9
L
DV
‘
w w w w 90 W W W W 6 9 W W W W 69 W 63 W W W N S W W W 53 51 W W W W
w
w
W W W W W
W W W W N S
NS W
L W
W NS
W NS
NS W
NS W
NS NS
W W
L7 43
-
N A W NA NA NA NS
W NA
-
NS
-
VI W W NS
L NA NS L
L L L NS
NS NA NS NA
-
W NA W NA NA
NA NS L
-
W NS W NS NS W
L FIA
-
W W NS NA W NA W
L
-
43 39 35 29 29 29 29 18
NA L L L L L L
-
w
w
W W W W W
W W W W W
W : Win over opponent; L: Loss to opponent; NS: “Tie” with aggression; NA: No aggression D V (Dominance value): Angular transform of proportion of enccunters won (NS NA W/2) ~
7:
Z. Tierpsychol. Bd. 39, Heft 1-5
9
R. G . BEILHARZ and V. C . BEILHARZ
130
Subject in home cage
LL5
446
5
10
LL5 LL6
LL5 LL6
445 446
1001
1001
LL5
LL5 4L6
LL6
1001
1001
1001
5
5
5
10
10
10
-
Subject in opponent’s cage 1001
5’
NS 10
NS
calculated, The angular transforms (arc sin) of these proportions were analysed. There were significant differences between strains in both measures (p < .05). Mean values, transformed back to proportions, are given in Table 1. Clearly laboratory mice of both strains spent much more time moving than wild mice when in the test box for the first time. Subjective assessment of experiments Experiment I : Table 2 gives the results of encounters between pairs of mice in the test box. The following findings emerge clearly. 1. I t is widely accepted that of 2 animals the one that wins an aggressive encounter is or becomes dominant (SCOTT1966). The 16 dd can be ranked in an almost linear dominance order with Melbourne mice most dominant, Seewiesen mice intermediate and wild mice least dominant. Although weights were not taken, the laboratory mice were much larger than wild mice. Dominance differences between laboratory and wild mice could thus be mainly a
j
Interval (length
=
Table 4 : 4 sec) in which 1st evidence of fighting (behaviours 0, Q, R, Opponent
Subject
0.821
T, U)
occurred’se
-
41
L
12
2L
6
15
21 10 2
12
30 3
55 39
12
2L 26
3 34
1002 1001
1.259 -
-
16
1.201)-
25 13
81 18
5 136
21 L8
6 60
15 70
L1 50
-
2LO
33
28 81 28
75
240
8L 16 16 61 104
240 70 61
- 2LO
-
0.967
I 1
1.401
1.803 -
17 15
-
-
32 138 115 77 2.40 2LO 119 L7 - 72
44
The maximum duration of observation (240 intervals) was used where no evidence of fighting occurred (no aggression). * Below the diagonal are shown the mean values of the logarithms of the values in the equivalent part of the table above the diagonal.
O b s e r v a t i o n s o n F i g h t i n g B e h a v i o u r of M a l e M i c e
Subject in home cage
445
LL5 LL6 1001 5 10
Mean
LL6
0.00
Subject in opponent’s cage 1001 5
0.00 0.00
1.11 0.00 1.49
0.00 1.18 0.30 0.70
1.OL 0.60 1.00
0.L8 0.30
0.L8
0.5L
0.66
0.20
0.77
131
10
0.00 0.00 1.15 1.11
Mean
0.28 0.00 1.22 0.62 0.62
0.56
result of weight differences rather than of differences in intrinsic “aggression”. Dominance could also, of course, reflect differences between mice in speed of attack and readiness to show submission. 2. The near linearity of dominance (only 4 wins below the diagonal) suggests that outcomes of encounters were not affected greatly by results of previous encounters in which “winning” or “losing” could have been learned. These results are comparable with those of SCOTTand FREDERICSON (1951) who discussed methods of training mice to fight, run away, or be peaceful, based on experiences of winning or losing fights, and of LEVINE et al. (1965). In the present work encounters were stopped as soon as one of the mice showed clear submission. Apparently, no subject was so badly defeated as to prejudice his future chances of winning. 3. In all 75 encounters involving Melbourne mice, aggression (shown by behaviours 0, biting: Q, submission; R, rolling scratching fight; T, running away; U, chasing) occurred. I11 only 3 encounters, involving the 2 least doniinant Melbourne mice with other strains, did neither mouse become submissive in 1 5 min. In contrast, while aggression was present in all 29 encounters involving Seewiesen mice, no submission occurred in 8 of them. The encounters involving wild mice showed another difference. In 8 out of 28 encounters involving wild mice only, no aggression occurred at all. In a further 6 of these 28 encounters and in a total of 23 out of all 92 encounters involving wild mice, no submission occurred. Clearly, in the neutral box, wild mice generally showed least aggression, and only they were able not to show aggression a t all. All encounters without aggression involved the subjects 13, 1 4 and 1, which had been judged to be young or sub-adult a t capture. 4. Of 6 encounters that iiivolved cage mates only 1 was non-aggressive. The 2 mice involved (13 and 14) also showed non-aggression towards other mice. Conditions in the test box must, therefore, have been such (so “tensc”, or so full of aggression-eliciting stimuli) that even familiar mice were attacked.
Subject in home cage
LL5 LL6 1001 5 10 Mean
LL5
LL6
0.a 0.00 0.00
Subject in opponent’s cage 1001 5
0.60 0 30
0.90 0.L8 0.30
0.00
0.00 0.60 0.00
0.30 0.30
1.61
0.08
0.27
0.38
0.82
0.30
10
Mean
0.70 1.18 1.52 1.71
0.67 0.L9 0.L6 0.73 0.L8
1.28
R. G. BEILHARZ and V. C. BEILHARZ
132
Subject in home cage
Subject in opponent’s cage LL5
146
1001
5
10
Mean
0.48
0.60 0.30
1.30 0.L8 1.51
0.70 1.18 1.66 1.80
0.77 0.L9 1.35 0.93 0.95
LL5 LL6 1001 5 10
0.00 1.18 0.L8 0.70
1.0L 0.85 1.00
0.60 0.L8
1.63
Mean
0.59
0.8L
0.50
1.23
1.3L
Observations on Fighting Behaviour of Male Mice
133
Table 8 : Number of records showing presence or absence of behaviour N (tail rattle) in Experiment 1 Jirain of mice
After Before 1st evidence of fighting
Type of encounter
Wild
Win
Loss or Melbourne
tie
Present
Absent
Present
Absent
3 3
8 24
L
8 9
23
Win
Loss or tie
I
I
Win
!Iieewiesen Loss or tie
owner was. Subject 5 also fought a long time in subject 10’s cage. It is remarkable that the “aggressive” Melbourne mice submitted so much more quickly once attacked, than the wild mice when in the opponent’s cage, while clearly maintaining their speed of attack and dominance in their own cage. Table 7 is a composite of the previous 2 tables. Total time to first evidence of submission was very markedly affected ( p .O1) by the mouse in the home cage. Melbourne mice achieved submission in their opponents slightly raster than wild mice. The Seewiesen mouse, however, was much slower. There was significant variation ( p .05) between mice when in the opponent’s cage also. The Seewiesen mouse had the shortest total time to submission followed Ly the Melbourne mice. Wild mice took longest. Strain Differences in Behaviour: The proportion of records in Experiment 1 with behaviour C (freeling) present was very much higher in wild mice than in both strains of laboratory mice. Clearly, freezing is a behaviour which has been almost completely lost in laboratory mice. This finding confirms that of SMITH(1972). Behaviour N (tail rattle) was much more prevalent in Melbourne mice than in Seewiesen or wild mice. ST. JOHN (1973) also found big differences in frequency of tail rattle between different laboratory strains and their crosses. Behaviour L (“mincing”) was prevalent in both strains of laboratory mice but absent from the records of wild mice. As previously indicated, it seems impossible to define a separate type of stiff movement (L) for wild mice, although the 2 types of movement arc clearly distinguishable for
Max-Planck-Institut f i i Verhaltensphysiologie, ~ Seewiesen
Observations on Fighting Behaviour of Male Mice (Mus muscuhs L.)
BY
R. G. BEILHARZ and V. C. BEILHARZ
Received: 13. 11. 1974
Abstract Fighting behaviour of male mice was compared in 8 wild, 2 unselccted laboratory and 6 laboratory mice from a population bred from winners of fights. Behaviour was recorded when all 16 mice were allowed to fight in all possible pairs in a neutral test box, and when 5 selected mice fought in pairs in the home cages of one o r the other. The occurrence of self-grooming, tail rattle and squealing are discussed. Different occurrences of behaviour in the different strains are explained as a result of genetic selection responses.
Introduction The normal environment of house mice includes human habitations. “Artificial” laboratory situations, in which behaviour can most readily be observed, need not therefore be an unnatural environment even for a wild house mouse. Fighting behaviour of house mice has been reviewed several times (EIBL-EIBESFELDT 1950, SCOTTand FREDERICSON 1951, SCOTT1966). In much of the work laboratory strains have been used. Such strains often have genetically unique genotypes (BAKNETT 1969, SMITH1972, St. JOHN 1973). Conclusions derived from such strains apply strictly only to mice of those strains. In his review SCOTT(1966) stated that “agonistic behaviour is yet to be analysed in breeding experiments in rats and mice”. Since then LAGERSPETZ and LAGERSPETZ (1971) have selected laboratory mice for and against aggressiveness for 19 generations. They recorded the aggressiveness of d d o n a 7-point scale after they had been reared in isolation from weaning onwards. 99 were not tested as they failed to show signs of aggressiveness in contacts with each other (LAGERSPETZ 1969). The strains differed significantly in male aggression from the second generation. After the 7th generation there has been no further response. Clearly, in these mice aggression has been modified genetically. At Melbourne University we have also selected laboratory mice for “aggression” in both sexes since 1967. The selection response seems to be still continuing after 20 generations of selection. The fighting behaviour of some
Observations on Fighting Behaviour of Male Mice
127
individuals of this strain was observed and compared with that of unselected white laboratory mice and of captured wild mice.
Methods Stock mice. b'rom 28/9/71 to 26/1 1/71, 16 wild house mice (9 c3, 7 were caught in and around several of the buildings of the institute at Seewiesen. They were placed in various types of cages but eventually in 4 glass tanks covered by wire, as they continually escaped from more conventional mouse cages. With one csception the groups of individuals scttled down well after some initial fighting. The mice showed no evidence of serious wounding. The exception was a young 6 who was killed on the day in which he was placed in cage 3 , which had already contained 2 older 6 & and 1 matiire for at least 9 days. S e e w e s e n mice. T w o 3 ~3 and 5 all young adults, were obtained from a population of white mice maintained by colony breeding at Seewiescn. This population was said to be non-aggressive. I t had existed at Seewiesen since 1968. The 7 mice were all housed in one cage. Their coats showed no evidence of fighting. Melbourne mice. 8 (3 8 and 12 from generation 1 8 of population 7 b of the mice being bred at the School of Agriculture, University of Melbourne, were sent by air to arrive at Seewiesen o n 13/11/71. This population has been bred since generation 5 from those male and female mice that had won the most fights with strange mice of the same sex, in neutral boxes ( B E I L H A R1972). Z The 8 8 6 had been reared as 1 group since 3 weeks of age. One 6 was de5troyed on arrival because he had been wounded by the others during the flight. The other mice, mature but so far unmated, were placed in 5 cages each containing 1 o r 2 6 6 and 1 to 3 In each of the 2 cages containing 2 6 6 one (3 was badly wounded when seen 2 days later. O n e of these (No. 766) was removed to a new c.ige with a I n cage 26 t w o ($ (3 were allowed t o remain together. The wounded 8 (No. 429) died on 28/11/71 after gradually deteriorating in health. Fucilities: The mice were kept in a room about 1 m by 3 m in floor area. The room was heated in winter but not to a constant temperature. With 1 exception all holes through which mice could leave the room were blocked. Above the door the wood that should have sealed the space between the brickwork and the doorframc was not tight. Despite efforts t o seal this hole, mice continued to find refuge there. However, as the mice that escaped from their cages always turned up again in this room, we assume that there was no way o u t of the room. Most observations were made in a test box 98 cm long, 39 cm wide and 39 cm high. The box had previously been a fish tank. It had a glass front on one long side, and on the inside, a frame where a glass partition had previously divided the tank across its length into halves. This central frame protruded 5 cm upward from the floor and 7 cm inward from the front and rear walls. The floor of the box was covered with wood shavings which were not removed between observations. Every mouse must thus have smelled the previous presence of other mice in the test box. Very rarely a wild mouse jumped out of the box. The central frame provided an opportunity for climbing without, however, allowing escape. Description of Experiments: The following behaviours were recorded with a 20-bar event recorder for individual mice in the experiments described below.
99)
Wild
99,
9
99
99.
9.
A : Mouse in 1 spot (hind feet) but not still. A includes all behaviour in 1 spot not specified elsewhere. B: Normal movement over the ground, as in exploration. B includes all behaviour not I-pecified elsewhere, while the mouse is moving over the ground. C: Freezing. Mouse does not even move whiskers. When a mouse stopped suddenly and iroze, the first reaction of the observer was often t o press A. As it became clear that C was involved C was pressed and a note made on the record paper to enable correct evaluation. D: Grooming of self, ranging from a short rub of nose and whiskers by the front paws to complete scquences of grooming of all parts of the fur. E : Grooming of another mouse. This behaviour graduates imperceptibly into biting of the other mouse (SCOTTand FREDERICSON 1951; CLARK and SCHEIN1966). E was recorded t o the point where the other mouse gave an indication that it had been bitten. F: Digging. This includes all forms of pushing floor material (shavings) with front or hind legs. I: also includes the rare periods spent under shavings after digging. G : Handling or nosing of floor materials (shavings). The mouse may be moving slowly or may remain in 1 spot. H : Eating. This includes the holding or handling of food with front paws. I : Sniffing genitals of another mouse.
R. G. BEILHARZ and V. C. BEILHARZ
128 J:
Running away rapidly, as in fright.
K : Jumping. L: Stiff movement over the ground usually seen in tens? situations such as before and between periods of fighting. This behaviour, while distinguishable from B in laborator) mice, was hard to separate from B in wild mice. In the latter the records d o not provide a clear separation of L and B. L is probably the same as “mincing” (SCOTT 1966) and “humping” (CLARKand SCHEIN1966). M : Climbing. The mouse has all feet off the ground. N : Tail rattling. This is a stereotyped rapid and rhythmic movement of the tail (SCOTTand FREDERICSON 1951). 0: Biting of another mouse. P: Squealing. This was only recorded when the mouse that squealed could be clearly identified. Thus more squealing occurred than appears in the records. Q: Mouse in a defensive or submissive position. The mouse stands still, its movement clearly inhibited. The head is high, the front paws are held in the direction of (push away) the other mouse which is moving freely usually with its head towards the lower parts of the 1951; “Demutbody of the submissive mouse, where it may bite (SCOTT and FREDERICSON stellung” EIBL-EIBESFELDT 1950). Rarely, a mouse assumes a position similar to this before attacking or almost attacking. In such a c a e it sccms to us that the mouse is in conflict between balancing tendencies to attack and to run away. Thus, on rare cccasions a recorded Q indicates such a conflict rather than clear submission. R : Rolling, scratching and biting. This is a clearly recognizable fighting involving 2 mice. S : Sniffing of a n y part of the body of another mouse excluding the genitals. S includes, for tense situations, the “sniffing” a t another mouse from distances u p to 1.5 cm. T: Running away from another animal. This is seen after, o r as a n alternative to, fighting. U: Chasing another animal. This also occurs only with fighting. V : Climbing o n the wire at the top of a cage. T h e records of behaviour were made o n paper marked at 4-sec intervals. For each interval the behaviour present longest was determined. The intervals assigned to each behaviour were added over whole observation periods to obtain bchavioural profiles. Where required, the time that elapsed to first evidence of fighting (shown by behaviours 0, Q, R, T o r U) and other criteria were found directly from the records. Preliminary Experiment: When the 16 6 6 available (Wild mice 1, 4, 5, 6, 9, 10, 13, 14; Seewiesen mice 1001, 1002; and Melbourne mice 432, 444, 445, 446, 763, 766) were placed for their first time, singly, in the test box, their behaviour was recorded for 10 min. This took place from 3/12/71 to 10/12/71. I n error No. 763 was recorded f o r only 5 min. The proportion of time spent in thc various activities was estimated and the strains of mice were compared. Experiment 1 : From 10/12/71 to 25/1/72 the same 16 6 8 were placed in the test box t w o a t a time and observed for 15 min or until one mouse clearly exhibited behaviour Q (submission). The observations were repeated until all mice had met every other mouse once. No pairs were repeated. The allocation of opponents was made a t random within the group of mice not yet met. No mouse was put into the test box more than once per day. The behaviour of only one mouse out of each pair was recorded. Initially, and whenever both opponents had a n equal number of records, the choice of which mouse to record was made at random. Later, the mouse which had fewer records was recorded in order to obtain a roughly equal number of records for each mouse. When it was possible, the “winner” and “loser” (the mouse that showed submission) were recorded. Where no mouse was submissive a “tie” was recorded. Where none of the behaviours 0, Q, R, T or U were seen “ n o aggression” was recorded. Experiment 2: From 11/4/72 5 to 18/4/72 5 8 8 (445, 1001, 5 and 10) were used in a 2nd test. Each subject was chosen at random o u t of one of the following classifications based o n the results of Experiment 1 : 1. Most dominant pair of Melbourne mice, 2. least dominant pair of Melbourne mice, 3. Seewiesen mice, 4. most dominant pair of wild mice, 5. least dominant pair of wild mice. The subjects were tested in all possible pairs twice, first in the home cage of one of them, then some days later in the cage of the other. The period of observation was 3 min or until one mouse showed clear submission (Q), whichever was the later. If submission had not occurred by 10 min observation was stopped a n d a “tie” recorded. Allocations of opponents, and choice of cage for the 1st encounter for each pair, were made a t random. No mouse was tested more than once in any morning or afternoon.
Observations on Fighting Behaviour of Male Mice
129
The behaviour of the mouse not in its home cage was recorded in all cases. The “winner”, “loser” or “tie” was found for each encounter.
Results General Observations: The wild mice periodically escaped from their cages by gnawing through the wire at the top corners of their glass tanks. They were recaptured either immediately or after having disappeared for some time. Disappearances did not follow a random pattern, however. For example, during the period from 20/12/71 to 3/1/72, when d‘ No. 1 was out of his cage, wild dd from other cages in which a hole had been gnawed were found either just on the wire or still within their cage, while 99 had disappeared to be recaptured later. The dates of escapes and recaptures show that a t no time had dd from different cages disappeared simultaneously. I t seems that an escaped 0“ by taking the whole room over as his territory, prevented other dcr”from leaving their cages. $29were not affected in this way.This explanation is consistent with the findings of MACKINTOSH (1970). Wild mice reentered their own cages on recapture without causing fighting. If a wild mouse of either sex was placed into the wrong cage fighting broke out. Preliminary Experiment: The proportions of time that the subjects spent in the one spot (behaviours A or C) and moving (B, F, G, J, K, L or M) were Table 1: Proportion of time spent in the one spot and moving when in the test box f o r the first time
I
I
Strain of mice
0.L5 0.41
.
Table 2: Results of encounters in the test box
-
I
Moving
0.6L
Seewiesen Melbourne
Subject
I
In one spot
Wild
Opponent LLL
LL5 432 766 763 [ LL6 1001 1002
-- 5
LLL LL5 432 7 66 763 LL6
w
w
W
L
w w -
w w w
L
-
1001 1002
w
w
L
NS
L
L L L L NS L L L
L NS L L L L L L
NS W L L NS NS NS L
5 1L 6 1 10 13 9
L -
W W W W L L
W W W W W NS W L L NS NS L L NS L
1 4 1 6
1
10
13
9
L
DV
‘
w w w w 90 W W W W 6 9 W W W W 69 W 63 W W W N S W W W 53 51 W W W W
w
w
W W W W W
W W W W N S
NS W
L W
W NS
W NS
NS W
NS W
NS NS
W W
L7 43
-
N A W NA NA NA NS
W NA
-
NS
-
VI W W NS
L NA NS L
L L L NS
NS NA NS NA
-
W NA W NA NA
NA NS L
-
W NS W NS NS W
L FIA
-
W W NS NA W NA W
L
-
43 39 35 29 29 29 29 18
NA L L L L L L
-
w
w
W W W W W
W W W W W
W : Win over opponent; L: Loss to opponent; NS: “Tie” with aggression; NA: No aggression D V (Dominance value): Angular transform of proportion of enccunters won (NS NA W/2) ~
7:
Z. Tierpsychol. Bd. 39, Heft 1-5
9
R. G . BEILHARZ and V. C . BEILHARZ
130
Subject in home cage
LL5
446
5
10
LL5 LL6
LL5 LL6
445 446
1001
1001
LL5
LL5 4L6
LL6
1001
1001
1001
5
5
5
10
10
10
-
Subject in opponent’s cage 1001
5’
NS 10
NS
calculated, The angular transforms (arc sin) of these proportions were analysed. There were significant differences between strains in both measures (p < .05). Mean values, transformed back to proportions, are given in Table 1. Clearly laboratory mice of both strains spent much more time moving than wild mice when in the test box for the first time. Subjective assessment of experiments Experiment I : Table 2 gives the results of encounters between pairs of mice in the test box. The following findings emerge clearly. 1. I t is widely accepted that of 2 animals the one that wins an aggressive encounter is or becomes dominant (SCOTT1966). The 16 dd can be ranked in an almost linear dominance order with Melbourne mice most dominant, Seewiesen mice intermediate and wild mice least dominant. Although weights were not taken, the laboratory mice were much larger than wild mice. Dominance differences between laboratory and wild mice could thus be mainly a
j
Interval (length
=
Table 4 : 4 sec) in which 1st evidence of fighting (behaviours 0, Q, R, Opponent
Subject
0.821
T, U)
occurred’se
-
41
L
12
2L
6
15
21 10 2
12
30 3
55 39
12
2L 26
3 34
1002 1001
1.259 -
-
16
1.201)-
25 13
81 18
5 136
21 L8
6 60
15 70
L1 50
-
2LO
33
28 81 28
75
240
8L 16 16 61 104
240 70 61
- 2LO
-
0.967
I 1
1.401
1.803 -
17 15
-
-
32 138 115 77 2.40 2LO 119 L7 - 72
44
The maximum duration of observation (240 intervals) was used where no evidence of fighting occurred (no aggression). * Below the diagonal are shown the mean values of the logarithms of the values in the equivalent part of the table above the diagonal.
O b s e r v a t i o n s o n F i g h t i n g B e h a v i o u r of M a l e M i c e
Subject in home cage
445
LL5 LL6 1001 5 10
Mean
LL6
0.00
Subject in opponent’s cage 1001 5
0.00 0.00
1.11 0.00 1.49
0.00 1.18 0.30 0.70
1.OL 0.60 1.00
0.L8 0.30
0.L8
0.5L
0.66
0.20
0.77
131
10
0.00 0.00 1.15 1.11
Mean
0.28 0.00 1.22 0.62 0.62
0.56
result of weight differences rather than of differences in intrinsic “aggression”. Dominance could also, of course, reflect differences between mice in speed of attack and readiness to show submission. 2. The near linearity of dominance (only 4 wins below the diagonal) suggests that outcomes of encounters were not affected greatly by results of previous encounters in which “winning” or “losing” could have been learned. These results are comparable with those of SCOTTand FREDERICSON (1951) who discussed methods of training mice to fight, run away, or be peaceful, based on experiences of winning or losing fights, and of LEVINE et al. (1965). In the present work encounters were stopped as soon as one of the mice showed clear submission. Apparently, no subject was so badly defeated as to prejudice his future chances of winning. 3. In all 75 encounters involving Melbourne mice, aggression (shown by behaviours 0, biting: Q, submission; R, rolling scratching fight; T, running away; U, chasing) occurred. I11 only 3 encounters, involving the 2 least doniinant Melbourne mice with other strains, did neither mouse become submissive in 1 5 min. In contrast, while aggression was present in all 29 encounters involving Seewiesen mice, no submission occurred in 8 of them. The encounters involving wild mice showed another difference. In 8 out of 28 encounters involving wild mice only, no aggression occurred at all. In a further 6 of these 28 encounters and in a total of 23 out of all 92 encounters involving wild mice, no submission occurred. Clearly, in the neutral box, wild mice generally showed least aggression, and only they were able not to show aggression a t all. All encounters without aggression involved the subjects 13, 1 4 and 1, which had been judged to be young or sub-adult a t capture. 4. Of 6 encounters that iiivolved cage mates only 1 was non-aggressive. The 2 mice involved (13 and 14) also showed non-aggression towards other mice. Conditions in the test box must, therefore, have been such (so “tensc”, or so full of aggression-eliciting stimuli) that even familiar mice were attacked.
Subject in home cage
LL5 LL6 1001 5 10 Mean
LL5
LL6
0.a 0.00 0.00
Subject in opponent’s cage 1001 5
0.60 0 30
0.90 0.L8 0.30
0.00
0.00 0.60 0.00
0.30 0.30
1.61
0.08
0.27
0.38
0.82
0.30
10
Mean
0.70 1.18 1.52 1.71
0.67 0.L9 0.L6 0.73 0.L8
1.28
R. G. BEILHARZ and V. C. BEILHARZ
132
Subject in home cage
Subject in opponent’s cage LL5
146
1001
5
10
Mean
0.48
0.60 0.30
1.30 0.L8 1.51
0.70 1.18 1.66 1.80
0.77 0.L9 1.35 0.93 0.95
LL5 LL6 1001 5 10
0.00 1.18 0.L8 0.70
1.0L 0.85 1.00
0.60 0.L8
1.63
Mean
0.59
0.8L
0.50
1.23
1.3L
Observations on Fighting Behaviour of Male Mice
133
Table 8 : Number of records showing presence or absence of behaviour N (tail rattle) in Experiment 1 Jirain of mice
After Before 1st evidence of fighting
Type of encounter
Wild
Win
Loss or Melbourne
tie
Present
Absent
Present
Absent
3 3
8 24
L
8 9
23
Win
Loss or tie
I
I
Win
!Iieewiesen Loss or tie
owner was. Subject 5 also fought a long time in subject 10’s cage. It is remarkable that the “aggressive” Melbourne mice submitted so much more quickly once attacked, than the wild mice when in the opponent’s cage, while clearly maintaining their speed of attack and dominance in their own cage. Table 7 is a composite of the previous 2 tables. Total time to first evidence of submission was very markedly affected ( p .O1) by the mouse in the home cage. Melbourne mice achieved submission in their opponents slightly raster than wild mice. The Seewiesen mouse, however, was much slower. There was significant variation ( p .05) between mice when in the opponent’s cage also. The Seewiesen mouse had the shortest total time to submission followed Ly the Melbourne mice. Wild mice took longest. Strain Differences in Behaviour: The proportion of records in Experiment 1 with behaviour C (freeling) present was very much higher in wild mice than in both strains of laboratory mice. Clearly, freezing is a behaviour which has been almost completely lost in laboratory mice. This finding confirms that of SMITH(1972). Behaviour N (tail rattle) was much more prevalent in Melbourne mice than in Seewiesen or wild mice. ST. JOHN (1973) also found big differences in frequency of tail rattle between different laboratory strains and their crosses. Behaviour L (“mincing”) was prevalent in both strains of laboratory mice but absent from the records of wild mice. As previously indicated, it seems impossible to define a separate type of stiff movement (L) for wild mice, although the 2 types of movement arc clearly distinguishable for
