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An ethogram of social interaction patterns in group-housed dry sows
Applied Animal Ethology, 6 (1980) 341-350 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
341
AN ETHOGRAM OF SOCIAL INTERACTION PATTERNS IN GROUPHOUSED DRY SOWS
PER JENSEN Swedish University of Animal Hygiene
of Agricultural Sciences, Faculty of Veterinary with Furrier’s School, Skara (Sweden)
Medicine,
Department
(Accepted for publication 8 October 1979)
ABSTRACT Jensen, P., 1980. An ethogram of social interaction patterns in group-housed dry sows. Appl. Anim. Ethel., 6: 341-350. Several papers on social behaviour in the domestic swine have been published. However, no detailed description of the interaction patterns have been presented. The social behaviour is usually referred to as “aggression “, “threat”, etc. The aim of the present paper is to provide a pure description, an ethogram, of social behaviour in group-housed dry sows, without any attempt to interpret the significance of the behaviours. A total of 17 dry sows, in three groups, were observed for a total time of 70 hours, equally spread out between 06.00 a.m. and 06.00 p.m. The observed interaction patterns were registered and recorded with video equipment. The ten main interaction patterns observed were: parallel pressing, inverse parallel pressing, head-to-head knock, head-to-body knock, levering, nose-to-nose, nose-to-body, anal-genital nosing, head tilt and withdrawing. Which of the described interactions were actually used in previous works by other authors to determine “aggression “, “threat” and “attacks” is discussed. The question of whether submissive behaviour exists in the domesticated pig is also briefly discussed. The author concludes that non-interpretative descriptions, like the ones in the paper, have to be made before interpretations like “aggressive behaviour”, etc., are discussed. Such interpretations have to be based on carefully designed observations and experiments.
INTRODUCTION
The social behaviour of the adult tame swine has been dealt with in a number of works, mainly during the last ten years. The studies have been concerned with several aspects of social behaviour and hierarchy: the general patterns (Rasmussen et al., 1962; Signoret, 1969; Meese and Ewbank, 1972, 1973a; van Putten, 1978), the role of different senses in social behaviour (Ewbank et al., 1974; Meese and Baldwin, 1975), the influence of stocking rate and group size upon social behaviour (Bryant and Ewbank, 1972; Ewbank and Bryant, 1972), the relationship between social behaviour and leadership and exploratory behaviour (Meese and Ewbank, 1973b), the qualities and growth of the individuals in relation to social behaviour (McBride et al., 1964; Beilhartz and Cox, 1967) and social behaviour in relation to manage-
342
ment in husbandry (Ewbank and Meese, 1971; Fraser, 1974). It remains, however, somewhat unclear exactly which behaviour patterns have been studied. Rasmussen et al. (1962) describe the aggressive display as pushing and biting, biting being directed mainly towards the head and ears. McBride et al. (1964) describe a fighting behaviour with mouth-toneck attacks and thrusts sideways and upwards. They also stress that attacks on the body other than the neck seem to be ignored. Beilhartz and Cox (1967) use the fact that one pig replaces the other at the feeding trough as the only measured interaction, but mention that biting and pushing occurred in defence of a position at the trough. Ewbank and Bryant (1972) use the term “threat” and mention that the mere approach of a dominant animal was enough to cause submission, but that threatening was expressed more commonly through blows against the neck, head and shoulder. They also point out that the intensity varied from a soft tap to a vigorous bite. In another work, the same authors use the term “threat/attack” (Bryant and Ewbank, 1972). Meese and Ewbank (1972) show that “aggression” varies within the same group of swine independently of general variations in activity. No definition as to what has been considered as “aggression” is given. Ewbank and Meese (1971) describe three different social patterns used in their work. Attack is defined as an aggressive interaction including physical contact, a threat as an aggressive interaction without physical contact and replacement as the action when one pig replaces another at the feeding trough. These definitions are used in several later works (Meese and Ewbank, 1973a, 1973b; Ewbank et al., 1974; Meese and Baldwin, 1975). Fraser (1974) defines in more detail the interaction patterns used by him: butting, chasing, running to the partner, running away, moving away, vigorous biting, mild biting, mounting and mutual pushing. Whether any submissive behaviour exists or not is also unclear in the literature. Bryant and Ewbank (1972) mention that submission is shown by withdrawal or retreat, and that generally all encounters contain a submission. The same authors (Ewbank and Bryant, 1972) stress that submissive behaviour is shown through retreat, and Meese and Ewbank (1973a) mention that no obvious submissive behaviour seems to exist in the swine. However, no analyses are presented for any of these statements. It is obviously very difficult to interpret the results of the earlier studies mentioned because it is not clear what behaviour patterns have been studied and what significance these behaviours may have in terms of communication. For an interpretation of any observations of social behaviour in animals the following studies must first be carried out: (1) A pure description of the behaviour patterns under study, an ethogram, has to be made. Each pattern must be carefully described, if necessary with drawings or photographs, and should be given a descriptive term without any attempt of interpretation (see e.g. Stevenson and Poole, 1976). Therefore, terms like “aggression”, “threat” or “aggressive sidedisplay” should be avoided. The ethogram should also contain measurements
343
of the organization and frequency of different patterns, notes on specificity (e.g. “performed only by males “, “performed only at nest site”, etc.) and other comments that are necessary for the reader to understand clearly what behaviour patterns are studied. (2) Using the ethogram, the next step is to make an analysis of the behaviour patterns. The aim of such an analysis is to make it possible statistically to predict a sequence of behaviours; e.g. if Animal A performs Behaviour 1 against Animal B, then there is a great possibility that A will perform Behaviour 2, and B will perform Behaviour 3 (see e.g. Grant, 1963). Such predictions can make it possible to interpret the behaviour patterns of the ethogram in terms of “aggression”, “submission”, etc., and can therefore be helpful in applied behaviour studies where one wishes to understand, e.g., different effects of environmental factors on the social behaviour of the species studied. Normally, the ethogram and the analysis can be integrated, especially in well studied species. However, in spite of numerous reports on social behaviour in domestic swine, no ethogram fulfilling the demands listed above has been presented. Therefore, the present study has only been concerned with description and naming. It is a pure ethogram with an attempt to discuss what interaction patterns have actually been measured in earlier papers on domestic swine. In a later paper, an analysis of the behaviour patterns will be presented. MATERIALS
AND METHOD
A total of 17 dry sows, in three groups, were studied. The animals were housed in lying boxes with straw (245 X 300 cm). A common dunging area (140 X 245 cm) and individual feeding stalls (180 X 50 cm) were provided. All groups studied contained both Swedish Landrace and cross-breeds with Swedish Landrace and Yorkshire. All observations were made on animals in lying boxes from a point about 1.5-2 m above ground and a maximum distance of 4 m from the sows. All behaviour patterns performed by one sow, and directed against another sow, i.e. behaviour patterns involving at least two animals, were defined as social interactions and were recorded with the emitter and receiver specified. No recording of vocalization was made. Continuous observations were carried out for a total of 70 h. The observation periods, lasting 2-4 h, were spread out equally between 06.00 a.m. and 06.00 p.m. More than 1000 interactions were observed during these 70 h, and a sample of each distinguishable pattern was recorded on video-recorder and analysed with a frame-by-frame technique (see e.g. Jenssen and Hover, 1976). Only behaviour patterns performed without space limitations through physical environment or pen-mates were analysed. The temporal organization of the interactions was measured from the recordings. No statistical approach was used in this study, and measurements
344
were made on the interactions as discrete events regardless of the animals involved. If, e.g., Animal A performed Behaviour 1 against Animal B, and Animal B or Animal A then performed Behaviour 2, the transition 1 -+ 2 was scored. The terms were chosen so that they would give the best possible description of the body-movements of the sows during the interaction without any attempt to interpret the significance of the interaction. RESULTS
From the observed behaviours, 10 main patterns of social interaction were distinguished. Four of these were also performed with “bite” as accessory feature. Three of the behaviours were of very low frequency which complicated a satisfactory frame-by-frame analysis. The recorded patterns of social interactions are listed below, without any attention paid to the situations in which they were performed. 1. (4 observations) Parallel pressing. The sows stand side by side and push hard with the shoulders against each other, throwing the head against the neck or head of the other. Parallel pressing-cum-bite. As above but with bites directed towards, head, ears and flanks of the other. 2. (5 observations) Inverse parallel pressing. The sows face front to front and then push their shoulders hard against each other, throwing the head against the neck and flanks of the other. 3. (>50 observations) Head-to-head knock. A rapid thrust upwards or sideways with the head or snout against the neck, head or ears of the other. The performer’s mouth is shut. Head-to-head knock-cum-bite. As above, but with bites directed towards head, ears or neck. Performer’s mouth is open. 4. (>50 observations) Head-to-body knock. A rapid thrust upwards or sideways with the head or snout against any part of the body behind the ears. Most of the knocks are performed against the front half of the receiver. The performer’s mouth is shut. Head-to-body knock-cum-bite. As above but with bites. Performer’s mouth is open. 5. (7 observations) Levering. The sow puts its snout under the body of another sow (in all observed cases from behind), and lifts it up in the air. 6. (>50 observations) Nose-to-nose. The nose of the sow approaches the nose, head or ears of another sow, and usually there is at least a short physical contact. 7. (>50 observations) Nose-to-body. The nose of a sow approaches any part of the body behind the ears, apart from the genital region, of another sow. Usually there is at least a short physical contact. 8. (>50 observations) Anal-genital nosing. The nose of a sow approaches
345
the genital region of another sow. Usually physical contact. observations) Head tiIt. The sow lowers its head and moves it sideways in the direction of another sow. Usually it retains this position for a few seconds. 10. (>50 observations) Withdrawing. The sow moves away from another sow rapidly with head high. The movement is often accompanied by a shrill scream. 9. (>50
Drawings, made from the video-recording, are shown in Fig. 1. (Behaviours 3,4,6, 7,8). Figure 2 shows a sequence from a frame-by-frame analysis of nose-to-nose followed by head tilt, and Fig. 3 shows a sequence with nose-to-nose followed by withdrawing. Very often the interaction patterns were obviously organized into sequences like the ones in Figs. 2 and 3. Figure 4 is made without any statistical approach but gives an indication of the temporal relationships between the different behaviours. The following limits were subjectively chosen: continuous lines indicate that the behaviours were seen to follow immediately
hb
-w nn
nb
“9
Fig. 1. The recorded interaction patterns of dry sows: hh = head-to-head knock; hb = head-to-body knock; nn = nose-to-nose; nb = nose-to-body; ng = anal-genital-nosing.
346
VI
v) 0)
.-E c
0
6
347
L--------
1 nb
1
1 ng
1
1 nn
c--_----A
Fig. 4. The relationship between different interaction patterns. The direction of the arrow shows in what order the interactions are performed in relation to each other. A continuous line indicates that the behaviour patterns were seen to follow closely after each other more than 20 times, and a dotted line that they were seen to follow each other more than 5 times but less than 20. pp/ip = parallel/inverse-parallel pressing; hh = head-to-head knock; hb = head-to-body knock; 1 = levering; ht = head-tilt; w = withdrawing; nn = noseto-nose; nb = nose-to-body; ng = anal-genital nosing.
after each other, in the direction of the arrow, more than 20 times and a dotted line indicates that they were observed following each other more than 5 times but less than 20. It is noted that anal--genital nosing was not followed by other behaviours. It is further noted that withdrawing and head tilt were typical “following behaviours”, but that withdrawing also occurred immediately before head-to-body knock more than 20 times, and that head tilt was not seen to be followed by any other interaction. DISCUSSION
The aim of the present paper is to provide a pure description of the interaction patterns observed in dry sows housed in groups. No interpretation as to what the behaviours are, e.g. “aggressive”, “non-aggressive” or “subordinate”, can be made without a careful analysis. Obviously, the parallel pressing and inverse parallel pressing are, by definition, aggressive behaviour, but no such interpretation of, e.g., nose-to-nose or head tilt is possible from the present material. Therefore, the discussion will deal mainly with those of the interactions described here that earlier papers on social behaviour in domestic swine may have recorded and referred to widely as, e.g., “aggression” or “threat”. Although the interactions mentioned here are not described earlier in detail, it is likely that these behaviour patterns are the ones used in several earlier works. The interactions described by Fraser (1974) have much in
348
common with those of this paper. “Butting” is probably the same as head-tohead and head-to-body knock and possibly also the same as levering. “Running away” and “moving away” are likely to be the same as withdrawing. “Vigorous biting “, “mild biting” and “mutual pushing” could be the same as different types of parallel and inverse parallel pressing. Rasmussen et al. (1962) describe the “aggressive display” as “pushing and biting”, which also seems to be the same as parallel and inverse parallel pressing. The same is reported by McBride et al. (1964) and Beilhartz and Cox (1967). The statement of McBride et al. that attacks against any other part than the neck seem to be ignored is contradictory to the findings in this study, as shown in Fig. 4. Van Putten (1978) and Signoret (1969) describe fighting in terms of “pressing” and “biting”. In all patterns reported in this paper, it was very difficult to distinguish between interactions with or without physical contact. Also, when such a distinction was possible, no obvious differences were seen in the receiving animal’s reaction, so the division of interactions into attack and threat by means of the presence or absence of physical contact in aggressive encounters, by Ewbank and Meese (1971), seems difficult to use in studies on dry sows. No comments are given as to how the interactions are interpreted as “aggressive”. These definitions are used in several later works (Meese and Ewbank, 1973a, 197313; Ewbank et al., 1974; Meese and Baldwin, 1975). The event of replacement that is used to determine dominance relationships in several works (Beilhartz and Cox, 1967; Ewbank and Meese, 1971; Meese and Ewbank, 1973a, 1973b; Ewbank et al., 1974; Meese and Baldwin, 1975) could be a result of many of the interaction patterns described in this paper. The replacing pig could reach its place solely by pushing itself into place without any obvious displays or defineable interactions, and thereby exclude one pen-mate. The replacement could also be a result of a parallel pressing with or without bite, or head-to-body or head-to-head knock or levering closely followed by withdrawing of the other animal. As long as the different interaction patterns are not carefully studied and investigated, it is difficult to draw any conclusions about the dominance relationship between the replacing and the replaced animal. For both the European Wild Boar (Sus scrofu) and the African Warthog (Phacochoerus aethiopicus) it is reported that replacement at feeding places is performed by both dominant and subordinate animals (Beuerle, 1975; Fddrich, 1965). The question about submissive behaviour in the domestic pig is also unanswered. Bryant and Ewbank (1972) and Ewbank and Bryant (1972) state that all interactions appear to result in submission, performed as withdrawal or retreat, while Meese and Ewbank (1973a) dre of the opinion that no obvious submissive behaviour exists. Van Putten (1978) describes a submissive behaviour where the submissive animal displays its throat, something that was never observed in this study. In this paper, it is shown that withdrawing often followed all interactions except anal--genital nosing, but that withdrawing then was often followed by a head-to-body knock (Fig. 4). Head
349
tilt, which frequently followed nose-to-nose, was not seen to be followed by any knocks at all. This could possibly mean that head-tilt inhibits any further knocks, and in this sense it could be a submissive behaviour. Such a conclusion can, however, not securely be drawn from the material presented. Nose-to-nose, nose-to-body and anal-genital nosing are briefly described by van Putten (1978) and Signoret (1969). Ewbank et al. (1974) mention that pigs recently put together examined each other closely in the facial region, which could be the nose-to-nose. Meese and Baldwin (1975) measured to what extent bulbectomized pigs examined a newcomer on 10 determined parts of the body. Their results indicate that the examination on belly, flank and rump (nose-to-body) does not solely play a role in individual recognition. The results of this paper concerning the anal-genital nosing, that no reaction was observed by the receiving animal, indicates that the function of that behaviour could be purely individual recognition. Most of the interaction patterns found in this paper are also reported for other, wild-living Suidae. Gundlach (1968) describes a snout thrust in Sus scrofa, that is performed towards all parts of the body. A short, hardly noticeable, intention thrust is interpreted as a threat. This could possibly be the same behaviour used by Ewbank and Meese (1971) and several others, but it is not clearly shown by the authors what is actually meant. Beuerle (1975) also reports the same thrusts for Sus scrofu, but describes the threat as non-directed bite movements. Levering is reported as part of the fighting behaviour by the same author. The same patterns of thrusts and threats are described for Phacochoerus aethiopicus (Fradrich, 1965). Inverse parallel pressing, with bites as the one animal retreats, is mentioned for the African Giant Forest Hog, Hylochoerus meinerthzugeni, (Donhoff, 1942). Frldrich (1974) states that the main parts for olfactory inspection in Suidae are the face and the genital area. In general terms, this paper shows that social behaviour in swine is not easily put into brief terms like “aggression” or “threat”. Certainly some, by definition obviously aggressive behaviours, are distinguishable, but social interaction in animals involves many more, less easily interpreted behaviour patterns. A descriptive ethogram, like the one presented, can be of help in making statistically safe interpretations of less obvious interaction patterns. A method for such an analysis will be presented in a later paper.
REFERENCES Beilhartz, R.G. and Cox, D.F., 1967. Social dominance in swine. Anim. Behav., 15: 117-122. Beuerle, W., 1975. Freilandsuntersuchungen zum Kampf und Sexualverhalten des europlischen Wildschweines (Sus scrofa L.). Z. Tierpsychol., 39: 211-258. Bryant, M.J. and Ewbank, R., 1972. Some effects of stocking rate and group size upon agonistic behaviour in groups of growing pigs. Br. Vet. J., 128: 64-70. Donhoff, C.G., 1942. Zur Kenntnis des afrikanischen Waldschweines (Hylochoerus meinertzhageni Thos.). Zool. Gart.. 6: 192-200.
350 Ewbank, R. and Bryant, M.J., 1972. Aggressive behaviour amongst groups of domestic pigs kept at various stocking rates. Anim. Behav., 20: 21-28. Ewbank, R. and Meese, G.B., 1971. Aggressive behaviour in groups of domestic pigs on removal and return of individuals. Anim. Prod., 13: 685-693. Ewbank, R., Meese, G.B. and Cox, J.E., 1974. Individual recognition and the dominance hierarchy in the domestic pig. The role of sight. Anim. Behav., 22: 473-480. (Phacochoerus Friidrich, H., 1965. Zur Biologie und Ethologie des Warzenschweines des Verhaltens anderen Suiden. Z. Tieraethiopicus Pallas) unter beriicksichtigung psychol., 22: 328-393. Friidrich, H., 1974. A comparison of behaviour in Suidae. IUCN Publ. New Ser., 24: 133-143. Fraser, D., 1974. The behaviour of growing pigs during experimental social encounters. J. Agric. Sci., 82: 147-163. Grant, E.C., 1963. An analysis of the social behaviour of the male laboratory rat. Behaviour, 21: 260-281. Gundlach, H., 1968. Brutfiirsorge, Brutpflege, Verhaltenssontogenese und Tagesperiodik beim europiiischen Wildschwein (Sus scrofu L.). Z. Tierpsychol., 25: 955-995. Jenssen, T.A. and Hover, E.L., 1976. Display analysis of the signature display of Anolis limifrons (Sauria: Iguanidae). Behaviour, 52: 227-240. McBride, G., James, J.W. and Hodgens, N., 1964. Social behaviour of domestic animals. IV: Growing pigs, Anim. Prod., 6: 129-140. Meese, G.B. and Baldwin, B.A., 1975. The effects of ablation of the olfactory bulbs on aggressive behaviour in pigs. Appl. Anim. Ethol., 1: 251-262. Meese, G.B. and Ewbank, R., 1972. A note on instability of the dominance hierarchy and variation in level of aggression within groups of fattening pigs. Anim. Prod., 14: 359-362. Meese, G.B. and Ewbank, R., 1973a. The establishment and nature of the dominance hierarchy in the domestic pig. Anim. Behav., 21: 326-334. Meese, G.B. and Ewbank, R., 1973b. Exploratory behaviour and leadership in the domestic pig. Br. Vet. J., 129: 251-259. Putten, G., van, 1978. Schwein. In: H.R. Sambraus (Editor), Nutztierethologie. Paul Parey, Berlin, Hamburg, pp. 168-213. Rasmussen, O.G., Banks, E.M., Berry, J.H. and Becker, D.E., 1962. Social dominance in gilts. J. Anim. Sci., 21: 520-522. Signoret, J.P., 1969. Verhalten von Schweine. In: E. Porzig (Editor), Das Verhalten Landwirtschaftlicher Nutztiere. Deutscher Landwirtschaftsverlag, Berlin, 430 pp. Stevenson, M.F. and Poole, T.B., 1976. An ethogram of the common marmoset (Calithrix jacchus jacchus): general behavioural repertoire. Anim. Behav., 24: 428-451.
341
AN ETHOGRAM OF SOCIAL INTERACTION PATTERNS IN GROUPHOUSED DRY SOWS
PER JENSEN Swedish University of Animal Hygiene
of Agricultural Sciences, Faculty of Veterinary with Furrier’s School, Skara (Sweden)
Medicine,
Department
(Accepted for publication 8 October 1979)
ABSTRACT Jensen, P., 1980. An ethogram of social interaction patterns in group-housed dry sows. Appl. Anim. Ethel., 6: 341-350. Several papers on social behaviour in the domestic swine have been published. However, no detailed description of the interaction patterns have been presented. The social behaviour is usually referred to as “aggression “, “threat”, etc. The aim of the present paper is to provide a pure description, an ethogram, of social behaviour in group-housed dry sows, without any attempt to interpret the significance of the behaviours. A total of 17 dry sows, in three groups, were observed for a total time of 70 hours, equally spread out between 06.00 a.m. and 06.00 p.m. The observed interaction patterns were registered and recorded with video equipment. The ten main interaction patterns observed were: parallel pressing, inverse parallel pressing, head-to-head knock, head-to-body knock, levering, nose-to-nose, nose-to-body, anal-genital nosing, head tilt and withdrawing. Which of the described interactions were actually used in previous works by other authors to determine “aggression “, “threat” and “attacks” is discussed. The question of whether submissive behaviour exists in the domesticated pig is also briefly discussed. The author concludes that non-interpretative descriptions, like the ones in the paper, have to be made before interpretations like “aggressive behaviour”, etc., are discussed. Such interpretations have to be based on carefully designed observations and experiments.
INTRODUCTION
The social behaviour of the adult tame swine has been dealt with in a number of works, mainly during the last ten years. The studies have been concerned with several aspects of social behaviour and hierarchy: the general patterns (Rasmussen et al., 1962; Signoret, 1969; Meese and Ewbank, 1972, 1973a; van Putten, 1978), the role of different senses in social behaviour (Ewbank et al., 1974; Meese and Baldwin, 1975), the influence of stocking rate and group size upon social behaviour (Bryant and Ewbank, 1972; Ewbank and Bryant, 1972), the relationship between social behaviour and leadership and exploratory behaviour (Meese and Ewbank, 1973b), the qualities and growth of the individuals in relation to social behaviour (McBride et al., 1964; Beilhartz and Cox, 1967) and social behaviour in relation to manage-
342
ment in husbandry (Ewbank and Meese, 1971; Fraser, 1974). It remains, however, somewhat unclear exactly which behaviour patterns have been studied. Rasmussen et al. (1962) describe the aggressive display as pushing and biting, biting being directed mainly towards the head and ears. McBride et al. (1964) describe a fighting behaviour with mouth-toneck attacks and thrusts sideways and upwards. They also stress that attacks on the body other than the neck seem to be ignored. Beilhartz and Cox (1967) use the fact that one pig replaces the other at the feeding trough as the only measured interaction, but mention that biting and pushing occurred in defence of a position at the trough. Ewbank and Bryant (1972) use the term “threat” and mention that the mere approach of a dominant animal was enough to cause submission, but that threatening was expressed more commonly through blows against the neck, head and shoulder. They also point out that the intensity varied from a soft tap to a vigorous bite. In another work, the same authors use the term “threat/attack” (Bryant and Ewbank, 1972). Meese and Ewbank (1972) show that “aggression” varies within the same group of swine independently of general variations in activity. No definition as to what has been considered as “aggression” is given. Ewbank and Meese (1971) describe three different social patterns used in their work. Attack is defined as an aggressive interaction including physical contact, a threat as an aggressive interaction without physical contact and replacement as the action when one pig replaces another at the feeding trough. These definitions are used in several later works (Meese and Ewbank, 1973a, 1973b; Ewbank et al., 1974; Meese and Baldwin, 1975). Fraser (1974) defines in more detail the interaction patterns used by him: butting, chasing, running to the partner, running away, moving away, vigorous biting, mild biting, mounting and mutual pushing. Whether any submissive behaviour exists or not is also unclear in the literature. Bryant and Ewbank (1972) mention that submission is shown by withdrawal or retreat, and that generally all encounters contain a submission. The same authors (Ewbank and Bryant, 1972) stress that submissive behaviour is shown through retreat, and Meese and Ewbank (1973a) mention that no obvious submissive behaviour seems to exist in the swine. However, no analyses are presented for any of these statements. It is obviously very difficult to interpret the results of the earlier studies mentioned because it is not clear what behaviour patterns have been studied and what significance these behaviours may have in terms of communication. For an interpretation of any observations of social behaviour in animals the following studies must first be carried out: (1) A pure description of the behaviour patterns under study, an ethogram, has to be made. Each pattern must be carefully described, if necessary with drawings or photographs, and should be given a descriptive term without any attempt of interpretation (see e.g. Stevenson and Poole, 1976). Therefore, terms like “aggression”, “threat” or “aggressive sidedisplay” should be avoided. The ethogram should also contain measurements
343
of the organization and frequency of different patterns, notes on specificity (e.g. “performed only by males “, “performed only at nest site”, etc.) and other comments that are necessary for the reader to understand clearly what behaviour patterns are studied. (2) Using the ethogram, the next step is to make an analysis of the behaviour patterns. The aim of such an analysis is to make it possible statistically to predict a sequence of behaviours; e.g. if Animal A performs Behaviour 1 against Animal B, then there is a great possibility that A will perform Behaviour 2, and B will perform Behaviour 3 (see e.g. Grant, 1963). Such predictions can make it possible to interpret the behaviour patterns of the ethogram in terms of “aggression”, “submission”, etc., and can therefore be helpful in applied behaviour studies where one wishes to understand, e.g., different effects of environmental factors on the social behaviour of the species studied. Normally, the ethogram and the analysis can be integrated, especially in well studied species. However, in spite of numerous reports on social behaviour in domestic swine, no ethogram fulfilling the demands listed above has been presented. Therefore, the present study has only been concerned with description and naming. It is a pure ethogram with an attempt to discuss what interaction patterns have actually been measured in earlier papers on domestic swine. In a later paper, an analysis of the behaviour patterns will be presented. MATERIALS
AND METHOD
A total of 17 dry sows, in three groups, were studied. The animals were housed in lying boxes with straw (245 X 300 cm). A common dunging area (140 X 245 cm) and individual feeding stalls (180 X 50 cm) were provided. All groups studied contained both Swedish Landrace and cross-breeds with Swedish Landrace and Yorkshire. All observations were made on animals in lying boxes from a point about 1.5-2 m above ground and a maximum distance of 4 m from the sows. All behaviour patterns performed by one sow, and directed against another sow, i.e. behaviour patterns involving at least two animals, were defined as social interactions and were recorded with the emitter and receiver specified. No recording of vocalization was made. Continuous observations were carried out for a total of 70 h. The observation periods, lasting 2-4 h, were spread out equally between 06.00 a.m. and 06.00 p.m. More than 1000 interactions were observed during these 70 h, and a sample of each distinguishable pattern was recorded on video-recorder and analysed with a frame-by-frame technique (see e.g. Jenssen and Hover, 1976). Only behaviour patterns performed without space limitations through physical environment or pen-mates were analysed. The temporal organization of the interactions was measured from the recordings. No statistical approach was used in this study, and measurements
344
were made on the interactions as discrete events regardless of the animals involved. If, e.g., Animal A performed Behaviour 1 against Animal B, and Animal B or Animal A then performed Behaviour 2, the transition 1 -+ 2 was scored. The terms were chosen so that they would give the best possible description of the body-movements of the sows during the interaction without any attempt to interpret the significance of the interaction. RESULTS
From the observed behaviours, 10 main patterns of social interaction were distinguished. Four of these were also performed with “bite” as accessory feature. Three of the behaviours were of very low frequency which complicated a satisfactory frame-by-frame analysis. The recorded patterns of social interactions are listed below, without any attention paid to the situations in which they were performed. 1. (4 observations) Parallel pressing. The sows stand side by side and push hard with the shoulders against each other, throwing the head against the neck or head of the other. Parallel pressing-cum-bite. As above but with bites directed towards, head, ears and flanks of the other. 2. (5 observations) Inverse parallel pressing. The sows face front to front and then push their shoulders hard against each other, throwing the head against the neck and flanks of the other. 3. (>50 observations) Head-to-head knock. A rapid thrust upwards or sideways with the head or snout against the neck, head or ears of the other. The performer’s mouth is shut. Head-to-head knock-cum-bite. As above, but with bites directed towards head, ears or neck. Performer’s mouth is open. 4. (>50 observations) Head-to-body knock. A rapid thrust upwards or sideways with the head or snout against any part of the body behind the ears. Most of the knocks are performed against the front half of the receiver. The performer’s mouth is shut. Head-to-body knock-cum-bite. As above but with bites. Performer’s mouth is open. 5. (7 observations) Levering. The sow puts its snout under the body of another sow (in all observed cases from behind), and lifts it up in the air. 6. (>50 observations) Nose-to-nose. The nose of the sow approaches the nose, head or ears of another sow, and usually there is at least a short physical contact. 7. (>50 observations) Nose-to-body. The nose of a sow approaches any part of the body behind the ears, apart from the genital region, of another sow. Usually there is at least a short physical contact. 8. (>50 observations) Anal-genital nosing. The nose of a sow approaches
345
the genital region of another sow. Usually physical contact. observations) Head tiIt. The sow lowers its head and moves it sideways in the direction of another sow. Usually it retains this position for a few seconds. 10. (>50 observations) Withdrawing. The sow moves away from another sow rapidly with head high. The movement is often accompanied by a shrill scream. 9. (>50
Drawings, made from the video-recording, are shown in Fig. 1. (Behaviours 3,4,6, 7,8). Figure 2 shows a sequence from a frame-by-frame analysis of nose-to-nose followed by head tilt, and Fig. 3 shows a sequence with nose-to-nose followed by withdrawing. Very often the interaction patterns were obviously organized into sequences like the ones in Figs. 2 and 3. Figure 4 is made without any statistical approach but gives an indication of the temporal relationships between the different behaviours. The following limits were subjectively chosen: continuous lines indicate that the behaviours were seen to follow immediately
hb
-w nn
nb
“9
Fig. 1. The recorded interaction patterns of dry sows: hh = head-to-head knock; hb = head-to-body knock; nn = nose-to-nose; nb = nose-to-body; ng = anal-genital-nosing.
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VI
v) 0)
.-E c
0
6
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L--------
1 nb
1
1 ng
1
1 nn
c--_----A
Fig. 4. The relationship between different interaction patterns. The direction of the arrow shows in what order the interactions are performed in relation to each other. A continuous line indicates that the behaviour patterns were seen to follow closely after each other more than 20 times, and a dotted line that they were seen to follow each other more than 5 times but less than 20. pp/ip = parallel/inverse-parallel pressing; hh = head-to-head knock; hb = head-to-body knock; 1 = levering; ht = head-tilt; w = withdrawing; nn = noseto-nose; nb = nose-to-body; ng = anal-genital nosing.
after each other, in the direction of the arrow, more than 20 times and a dotted line indicates that they were observed following each other more than 5 times but less than 20. It is noted that anal--genital nosing was not followed by other behaviours. It is further noted that withdrawing and head tilt were typical “following behaviours”, but that withdrawing also occurred immediately before head-to-body knock more than 20 times, and that head tilt was not seen to be followed by any other interaction. DISCUSSION
The aim of the present paper is to provide a pure description of the interaction patterns observed in dry sows housed in groups. No interpretation as to what the behaviours are, e.g. “aggressive”, “non-aggressive” or “subordinate”, can be made without a careful analysis. Obviously, the parallel pressing and inverse parallel pressing are, by definition, aggressive behaviour, but no such interpretation of, e.g., nose-to-nose or head tilt is possible from the present material. Therefore, the discussion will deal mainly with those of the interactions described here that earlier papers on social behaviour in domestic swine may have recorded and referred to widely as, e.g., “aggression” or “threat”. Although the interactions mentioned here are not described earlier in detail, it is likely that these behaviour patterns are the ones used in several earlier works. The interactions described by Fraser (1974) have much in
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common with those of this paper. “Butting” is probably the same as head-tohead and head-to-body knock and possibly also the same as levering. “Running away” and “moving away” are likely to be the same as withdrawing. “Vigorous biting “, “mild biting” and “mutual pushing” could be the same as different types of parallel and inverse parallel pressing. Rasmussen et al. (1962) describe the “aggressive display” as “pushing and biting”, which also seems to be the same as parallel and inverse parallel pressing. The same is reported by McBride et al. (1964) and Beilhartz and Cox (1967). The statement of McBride et al. that attacks against any other part than the neck seem to be ignored is contradictory to the findings in this study, as shown in Fig. 4. Van Putten (1978) and Signoret (1969) describe fighting in terms of “pressing” and “biting”. In all patterns reported in this paper, it was very difficult to distinguish between interactions with or without physical contact. Also, when such a distinction was possible, no obvious differences were seen in the receiving animal’s reaction, so the division of interactions into attack and threat by means of the presence or absence of physical contact in aggressive encounters, by Ewbank and Meese (1971), seems difficult to use in studies on dry sows. No comments are given as to how the interactions are interpreted as “aggressive”. These definitions are used in several later works (Meese and Ewbank, 1973a, 197313; Ewbank et al., 1974; Meese and Baldwin, 1975). The event of replacement that is used to determine dominance relationships in several works (Beilhartz and Cox, 1967; Ewbank and Meese, 1971; Meese and Ewbank, 1973a, 1973b; Ewbank et al., 1974; Meese and Baldwin, 1975) could be a result of many of the interaction patterns described in this paper. The replacing pig could reach its place solely by pushing itself into place without any obvious displays or defineable interactions, and thereby exclude one pen-mate. The replacement could also be a result of a parallel pressing with or without bite, or head-to-body or head-to-head knock or levering closely followed by withdrawing of the other animal. As long as the different interaction patterns are not carefully studied and investigated, it is difficult to draw any conclusions about the dominance relationship between the replacing and the replaced animal. For both the European Wild Boar (Sus scrofu) and the African Warthog (Phacochoerus aethiopicus) it is reported that replacement at feeding places is performed by both dominant and subordinate animals (Beuerle, 1975; Fddrich, 1965). The question about submissive behaviour in the domestic pig is also unanswered. Bryant and Ewbank (1972) and Ewbank and Bryant (1972) state that all interactions appear to result in submission, performed as withdrawal or retreat, while Meese and Ewbank (1973a) dre of the opinion that no obvious submissive behaviour exists. Van Putten (1978) describes a submissive behaviour where the submissive animal displays its throat, something that was never observed in this study. In this paper, it is shown that withdrawing often followed all interactions except anal--genital nosing, but that withdrawing then was often followed by a head-to-body knock (Fig. 4). Head
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tilt, which frequently followed nose-to-nose, was not seen to be followed by any knocks at all. This could possibly mean that head-tilt inhibits any further knocks, and in this sense it could be a submissive behaviour. Such a conclusion can, however, not securely be drawn from the material presented. Nose-to-nose, nose-to-body and anal-genital nosing are briefly described by van Putten (1978) and Signoret (1969). Ewbank et al. (1974) mention that pigs recently put together examined each other closely in the facial region, which could be the nose-to-nose. Meese and Baldwin (1975) measured to what extent bulbectomized pigs examined a newcomer on 10 determined parts of the body. Their results indicate that the examination on belly, flank and rump (nose-to-body) does not solely play a role in individual recognition. The results of this paper concerning the anal-genital nosing, that no reaction was observed by the receiving animal, indicates that the function of that behaviour could be purely individual recognition. Most of the interaction patterns found in this paper are also reported for other, wild-living Suidae. Gundlach (1968) describes a snout thrust in Sus scrofa, that is performed towards all parts of the body. A short, hardly noticeable, intention thrust is interpreted as a threat. This could possibly be the same behaviour used by Ewbank and Meese (1971) and several others, but it is not clearly shown by the authors what is actually meant. Beuerle (1975) also reports the same thrusts for Sus scrofu, but describes the threat as non-directed bite movements. Levering is reported as part of the fighting behaviour by the same author. The same patterns of thrusts and threats are described for Phacochoerus aethiopicus (Fradrich, 1965). Inverse parallel pressing, with bites as the one animal retreats, is mentioned for the African Giant Forest Hog, Hylochoerus meinerthzugeni, (Donhoff, 1942). Frldrich (1974) states that the main parts for olfactory inspection in Suidae are the face and the genital area. In general terms, this paper shows that social behaviour in swine is not easily put into brief terms like “aggression” or “threat”. Certainly some, by definition obviously aggressive behaviours, are distinguishable, but social interaction in animals involves many more, less easily interpreted behaviour patterns. A descriptive ethogram, like the one presented, can be of help in making statistically safe interpretations of less obvious interaction patterns. A method for such an analysis will be presented in a later paper.
REFERENCES Beilhartz, R.G. and Cox, D.F., 1967. Social dominance in swine. Anim. Behav., 15: 117-122. Beuerle, W., 1975. Freilandsuntersuchungen zum Kampf und Sexualverhalten des europlischen Wildschweines (Sus scrofa L.). Z. Tierpsychol., 39: 211-258. Bryant, M.J. and Ewbank, R., 1972. Some effects of stocking rate and group size upon agonistic behaviour in groups of growing pigs. Br. Vet. J., 128: 64-70. Donhoff, C.G., 1942. Zur Kenntnis des afrikanischen Waldschweines (Hylochoerus meinertzhageni Thos.). Zool. Gart.. 6: 192-200.
350 Ewbank, R. and Bryant, M.J., 1972. Aggressive behaviour amongst groups of domestic pigs kept at various stocking rates. Anim. Behav., 20: 21-28. Ewbank, R. and Meese, G.B., 1971. Aggressive behaviour in groups of domestic pigs on removal and return of individuals. Anim. Prod., 13: 685-693. Ewbank, R., Meese, G.B. and Cox, J.E., 1974. Individual recognition and the dominance hierarchy in the domestic pig. The role of sight. Anim. Behav., 22: 473-480. (Phacochoerus Friidrich, H., 1965. Zur Biologie und Ethologie des Warzenschweines des Verhaltens anderen Suiden. Z. Tieraethiopicus Pallas) unter beriicksichtigung psychol., 22: 328-393. Friidrich, H., 1974. A comparison of behaviour in Suidae. IUCN Publ. New Ser., 24: 133-143. Fraser, D., 1974. The behaviour of growing pigs during experimental social encounters. J. Agric. Sci., 82: 147-163. Grant, E.C., 1963. An analysis of the social behaviour of the male laboratory rat. Behaviour, 21: 260-281. Gundlach, H., 1968. Brutfiirsorge, Brutpflege, Verhaltenssontogenese und Tagesperiodik beim europiiischen Wildschwein (Sus scrofu L.). Z. Tierpsychol., 25: 955-995. Jenssen, T.A. and Hover, E.L., 1976. Display analysis of the signature display of Anolis limifrons (Sauria: Iguanidae). Behaviour, 52: 227-240. McBride, G., James, J.W. and Hodgens, N., 1964. Social behaviour of domestic animals. IV: Growing pigs, Anim. Prod., 6: 129-140. Meese, G.B. and Baldwin, B.A., 1975. The effects of ablation of the olfactory bulbs on aggressive behaviour in pigs. Appl. Anim. Ethol., 1: 251-262. Meese, G.B. and Ewbank, R., 1972. A note on instability of the dominance hierarchy and variation in level of aggression within groups of fattening pigs. Anim. Prod., 14: 359-362. Meese, G.B. and Ewbank, R., 1973a. The establishment and nature of the dominance hierarchy in the domestic pig. Anim. Behav., 21: 326-334. Meese, G.B. and Ewbank, R., 1973b. Exploratory behaviour and leadership in the domestic pig. Br. Vet. J., 129: 251-259. Putten, G., van, 1978. Schwein. In: H.R. Sambraus (Editor), Nutztierethologie. Paul Parey, Berlin, Hamburg, pp. 168-213. Rasmussen, O.G., Banks, E.M., Berry, J.H. and Becker, D.E., 1962. Social dominance in gilts. J. Anim. Sci., 21: 520-522. Signoret, J.P., 1969. Verhalten von Schweine. In: E. Porzig (Editor), Das Verhalten Landwirtschaftlicher Nutztiere. Deutscher Landwirtschaftsverlag, Berlin, 430 pp. Stevenson, M.F. and Poole, T.B., 1976. An ethogram of the common marmoset (Calithrix jacchus jacchus): general behavioural repertoire. Anim. Behav., 24: 428-451.