This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Behavioural Processes 80 (2009) 60–66 Contents lists available at ScienceDirect Behavioural Processes journal homepage: www.elsevier.com/locate/behavproc The social function of tail up in the domestic cat (Felis silvestris catus) S. Cafazzo a,∗ , E. Natoli b a b Dipartimento di Biologia Evolutiva e Funzionale, Università degli Studi di Parma, Parma, Italy Azienda USL Roma D, Area Dipartimentale Sanità Pubblica Veterinaria, Roma, Italy a r t i c l e i n f o Article history: Received 14 April 2008 Received in revised form 11 September 2008 Accepted 13 September 2008 Keywords: Affiliative behaviour Domestic cat Dominance hierarchy Tail up a b s t r a c t We investigated the social function of tail up in order to verify its possible relationship with the hierarchical organization of a social group. Domestic cats live at higher densities than their ancestor which is a solitary species. Since the signals needed by solitary animals have different properties than those needed by group-living individuals, signalling pattern utilised by the domestic cat has inevitably changed. Kittens displayed the tail up when greeting their mother; this behaviour can also be observed in wild species. But, in domestic cat the tail up can be also observed when an adult individual meets another one and it signals the intention to interact amicably. Rank order affected the display of tail up posture: it was more frequently displayed by low-ranking cats, and high-ranking individuals received it more often than other members of the social group. Then, tail up seems to be a signal by means of which a cat shows the recognition of the higher social status of the individual to whom is directed. We confirmed the association between tail up and other affiliative behavioural patterns and the individual variability in displaying them. Considerations on the evolution of the tail up as a visual signal will be discussed. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Most wild felids are solitary-living, at least in the sense that they do not form social groups of adult animals. This is true also for the two prospective ancestor of domestic cat (Felis silvestris catus): European wildcat (Felis silvestris silvestris) and the African wildcat (Felis silvestris lybica). Nevertheless, during domestication, cats must have adapted to live at higher densities than their ancestor and then subsequently they adopted group-living. Since the signals needed by solitary animals have different properties than those needed by group-living individuals, the changes in the spacing pattern and social organization may have led to an evolutionary change in the signalling pattern utilised by the domestic cat (Bradshaw and Cameron-Beaumont, 2000). In a social group of domestic cats, when an adult individual meets another one, it occasionally approaches the conspecific with the tail raised almost vertically but with the tip often slightly bowed towards the animal being greeted; such a behavioural pattern has been defined “tail up”. This action is sometimes associated with rubbing (a cat rubs its body, head, and neck along the body of the ∗ Corresponding author at: Dipartimento di Biologia Evolutiva e Funzionale, Università degli Studi di Parma, Parco Area delle Scienze 11/A, 43100 Parma, and via Gasperina 300, 00173 Roma, Italy. Tel.: +39 06 72670591. E-mail addresses: simona.cafazzo@inwind.it (S. Cafazzo), enatoli@tiscali.it (E. Natoli). 0376-6357/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.beproc.2008.09.008 other cat) and sniffing nose (two cats sniff each other’s noses). The patterns described fall in the affiliative behaviour category. Thus greeting behaviour in domestic cats can be described as “tail up”, “sniffing nose” and “rubbing”, usually occurring in this sequence if all are displayed. Furthermore, it is possible to hypothesize that the pattern “tail up” has the function to inhibit intraspecific aggressive behaviour, as Cameron-Beaumont (1997) suggested. She presented silhouettes of cats identical to each other apart from the position of the tail to neutered feral cats. The silhouette with the tail raised vertically (tail up silhouette) was significantly more likely to induce tail up when it was first sighted by the responding cat, and was also approached faster than the silhouette with its tail down. On the contrary, the latter induced some aggressive postures in the responding individual. If so, then it is possible to suppose that this signal can be influenced by individual dominance rank and that it is more frequently showed by low-ranking individuals towards cats of higher rank, rather than the other way round. The flow of interactions, especially rubbing, from low-ranking to high-ranking cats has been already proposed by Macdonald et al. (1987). Domestic cats are very flexible regarding their ability to live solitary and in groups, and there seems to be a clear correlation with food dispersion. They live solitary at very low density (less than 5 cats per km2 ), depending on dispersed natural prey (mainly rabbits and rodents), whereas they form small groups of closely related females at higher densities (up to 250 cats per km2 in rural areas), depending on clumped food provided by human beings (i.e. farm Author's personal copy S. Cafazzo, E. Natoli / Behavioural Processes 80 (2009) 60–66 cat) or clumped natural prey such as colonies of ground-nesting seabirds (i.e. rural feral populations) (Liberg et al., 2000). Higher densities (up to 2000 cats per km2 ) were found only in urban areas where cats fed on rich supplies of refuse or were fed daily by large numbers of “cat lovers”, i.e. people not owning the cats, but who frequently placed cat food at traditional places (Izawa et al., 1982; Natoli, 1985; Liberg et al., 2000). In the urban environment, and more rarely in rural environment, the domestic cat lives in large multimale–multifemale social groups where it is possible to observe clearly the hierarchical relationship between the two sexes. Recently, Natoli et al. (2001) found a significant linear dominance hierarchy among males and females in a social group of rural cats, based on the outcome of agonistic encounters. Subsequently Bonanni et al. (2007) demonstrated the existence of a transitive hierarchy in an urban cat colony between males and females. In this species the dominance is maintained mainly via overt aggression and subordinates are regularly threatened by dominants. Bonanni et al. (2007) found a positive correlation between rank order and aggressions given, and a negative correlation between rank order and aggressions received. Practically the higher cats were in rank, the more aggressions they gave to other cats, and the less aggressions they received from other cats. Since the tail up signals the intention to interact amicably, it might inhibit an aggressive behaviour of another individual; if so, as already said, one might hypothesize that this signal is more frequently showed by low-ranking individuals to ones of higher rank. The aim of this study was to investigate the social function of tail up in order to verify the hypothesis that the vertical tail is an affiliative behaviour directed from subordinates to dominants, therefore it would signal both amicably intentions and recognition of the social status of another member belonging to the social group. 61 be handled. However, even the most elusive cats were visible and observations could be carried out at a distance of about 10 m. Cats were dependent on food provided directly by human beings; they fed on food found in refuse and hunted very rarely. 2.3. Experimental procedure The study was carried out in the city of Rome, in a large courtyard (about 6000 m2 ) situated in a popular quarter called “Garbatella”. The area was delimited by a boundary wall and completely isolated from road traffic. The Courtyard contained eleven buildings, several areas of spontaneous vegetation, trees and bushes, cultivated flowerbeds and floored places. Cats had free access to every part of the courtyard but they established their “core area” in a partially wire-fenced sector located in the south side of the courtyard. Here, thick spontaneous vegetation offered a good shelter for animals. The study began in October 2002 and lasted until the half of June 2003. Data were collected by the focal animal sampling method (Altmann, 1974) for a total of 427.65 h of recording. Each individual’s observations were equally distributed over the time period, as well as over daytime between 08:00 and 19:00 h. Agonistic behaviour (including aggressive and submissive behaviour) was recorded by “all occurrences” method (Altmann, 1974). Aggressive behaviour included the following: (1) threats (striking with a paw, biting, assuming a threatening posture, pointing, staring at, baring of the canines), (2) chasing, (3) ritualised vocal duels and (4) actual fighting. Submissive behaviour included the following: (1) crouching with the ears flattened, (2) avoiding, (3) retreating, (4) fleeing and (5) hissing at. Also affiliative behaviour was recorded by “all occurrences” method (Altmann, 1974) and included the following: (1) sniffing nose, (2) rubbing and (3) tail up (for description see Section 1). The individual scores of all behaviour patterns were corrected for animal observation time because the latter varied between individuals. In order to determine the dominance hierarchy, the outcomes of aggressive and submissive interactions were ranked in two different squared matrices with winners on one axis and losers on the other, so as to minimize the number of dominance reversals. The dominant animal of each dyad was the one that gave more aggressions to the other than it received from the opponent, or received more submissions from the other than it gave. Hissing was excluded from the matrix based on submissive interactions because it was considered an ambiguous behaviour. We tested the transitivity of dominance relationships between the members of the social group, based either on aggressive or on submissive patterns separately, by applying an improved test of linearity developed by de Vries (1995) that is based on Landau’s linearity index, but that takes into account unknown and tied relationships between group members. After the rank order was determined, we used the Landau’s linearity index h′ (corrected for unknown relationships) (de Vries, 1995) as a measure of the dominance hierarchy degree of linearity. We performed non-parametric statistical tests using STATISTICA 99 edition (StatSoft, 1999) and the Landau’s linearity index h′ , as well as the improved linearity test, by mean of MATMAN (Noldus, 1998). All statistical tests are two tailed. 2.2. Cat group 3. Results The group studied consisted of domestic cats (Felis silvestris catus). All adult cats belonging to the colony (four males and five females) were already neutered when the study started, whereas the only juvenile male (cats were considered to be juveniles up to the age of 11 months and to be adults afterwards) was intact. The age of the subjects was obtained by inquiries to the “cat lovers”, or estimated according to Pascal and Castanet (1978) method. All the animals being study were easily distinguished by their coat colour and pattern, hair length and size. The sex of cats was already known at the start of the research since others studies were conducted on the same social group. All individuals belonging to the colony had no constraints placed on movements by human and some cats were tame enough to 3.1. Tail up and dominance hierarchy 2. Materials and methods 2.1. Study area A significantly linear dominance hierarchy based both on direction of aggressive behaviour (improved linearity test: h′ = 0.557, P = 0.047; N = 50 aggressive interactions; Table 1) and on direction of submissive behaviour (except hissing) (improved linearity test: h′ = 0.618, P = 0.021; N = 62 submissive interactions; Table 2) was found. The rank order was the same for both dominance hierarchies. Landau’s linearity index h′ was higher for dominance hierarchy based on direction of submissive behaviour (h′ = 0.62) than for dominance hierarchy based on direction of aggressive behaviour (h′ = 0.56). In fact on the basis of previous studies (Natoli et al., 2001; Bonanni et al., 2007), aggressions were not expected to show Author's personal copy 62 S. Cafazzo, E. Natoli / Behavioural Processes 80 (2009) 60–66 Table 1 Dominance relationships among cats, based on aggressive interactions. Individual rank order increases from left to right. Cats ANT SON LAV PIC RIG CLA FIA SPO RUG FLY TOTr PIC RIG CLA FIA SPO RUG 1 5 1 3 2 2 4 1 1 2 1 1 1 ANT SON LAV 2 3 1 3 FLY 2 3 1 1 1 2 3 1 1 5 12 1 3 2 0 1 7 7 6 7 TOTp 19 9 9 3 1 1 3 3 2 0 Males in italic letters. TOTp: total aggressions performed, TOTr: total aggressions received. Table 2 Dominance relationships among cats, based on submissive interactions (except hissing). Individual rank order increases from left to right. Cats ANT SON LAV PIC RIG CLA FIA SPO RUG FLY TOTr ANT 1 3 2 8 6 1 6 1 28 SON LAV PIC RIG CLA FIA SPO RUG FLY 0 1 3 3 10 14 5 10 5 11 1 1 2 3 2 1 1 10 1 2 1 5 1 5 1 1 1 6 2 2 1 4 5 2 1 3 1 2 TOTp 0 Males in italic letters. TOTp: total submissions performed, TOTr: total submissions received. the same high degree of linearity as reported for submissions. However the level of linearity was not very high probably due to incompleteness of information about the relationships concerning a relatively high percentage of dyads (42.22% in the matrix based on direction of aggressive behaviour and 37.78% in the matrix based on direction of submissive behaviour). Nevertheless, no dyads were characterized by an individual dominating another higher in rank, and then no interactions were reversals against the hierarchy. The top positions of this hierarchy were occupied by two adult males, whereas the only juvenile male was at the bottom (Tables 1 and 2). The rank order was positively correlated with each individual’s rate of aggressive behaviour (Rs = 0.815, N = 10, P = 0.004). In other words, the higher the cats were in rank, the more aggressions they directed to other cats. A significantly difference in aggressive behaviour between adult males and females was not found (Mann–Whitney U test: U = 6, N1 = 4, N2 = 5, P = 0.327); they scored about the same values (mean ranks: 4 for adult males and 4.2 for females). Age affected dominance among individuals belonging to the group: rank order was positively correlated with age of cats (Rs = 0.821, N = 10, P = 0.004). All tail-up events registered during the focal animal sampling (N = 109) were enclosed in a squared matrix (Table 3) where individuals were ordered following the rank. Tail up occurred in 16 male–female dyads, in 6 male–male dyads and in 1 female–female dyad. This pattern was more frequently directed from a subordinate individual towards a dominant one, rather than the other way round. In fact, the only exception was an adult female, LAV, who directed the tail up also to an adult subordinate male, RIG. The rank order was negatively correlated with the frequency of tail up (Rs = −0.819, N = 10, P = 0.004): lower ranking cats were more likely to show this pattern. Moreover the tail up was shown prevalently by females and lower ranking males, whereas it was never observed in higher ranking males. Independently from the sex and the rank of the cat that showed the tail up, the latter was more frequently directed towards two higher ranking males, ANT and SON. The correlations between Table 3 Tail-up interactions among cats. Individuals are in rank order. Cats ANT SON LAV PIC RIG CLA FIA SPO RUG FLY TOTr ANT SON 6 14 6 1 2 1 7 31 15 9 12 6 48 LAV PIC RIG CLA FIA SPO RUG FLY 0 0 14 14 0 0 16 20 22 23 2 3 3 3 9 1 1 0 4 1 1 2 Males in italic letters. TOTp: total acts of tail up performed, TOTr: total acts of tail up received. 4 4 5 5 10 1 1 TOTp 0 Author's personal copy 63 S. Cafazzo, E. Natoli / Behavioural Processes 80 (2009) 60–66 Table 4 Tail-up events followed by sniffing nose between cat dyads. Individuals are in dominance rank order. Cats ANT SON LAV PIC RIG CLA FIA SPO RUG FLY TOTr ANT SON LAV PIC RIG CLA FIA SPO RUG FLY 1 1 3 1 2 0 0 0 1 0 3 0 0 TOTp 0 0 0 1 0 0 0 4 1 0 0 Males in italic letters. TOTp: total acts of tail up performed, TOTr: total acts of tail up received. rank and frequency of tail up received failed to reach a statistically significant level, although showed a clear tendency (Rs = −0.619, N = 10, P = 0.056). Nevertheless by gathering all individuals into three classes, “high-rank” (ANT, SON, LAV), “medium-rank” (PIC, RIG, CLA, FIA) and “low-rank” (SPO, RUG, FLY), it has been possible to underline that these classes differ significantly in tail up received (Kruskal–Wallis test: H2 = 6.46, P = 0.039): the frequency of tail up was higher for the individuals belonging to the “high-rank” class (mean ranks: high-rank 9, medium-rank 3, low-rank 4.75). 3.2. Relation between tail up and other affiliative behaviours All tail-up events, preceded or accompanied by rubbing (N = 18) and sniffing nose (N = 6) respectively, were enclosed in two squared matrices where individuals are arranged in rank order. The tail up was shown more frequently alone, rather than in association with other affiliative behaviours; only the 22.73% of interactions of tail up was associated with sniffing nose or rubbing (Tables 4 and 5). Rubbing was often preceded from tail up, although there was an evident individual variability (e.g. an adult female, FIA often showed rubbing with tail up, whereas other cats rarely showed it); on the other hand the sniffing nose was rarely shown together with tail up (only an adult male, SPO, showed sniffing nose always together with tail up) (Figs. 1 and 2). Considering all rubbing (N = 29) and sniffing nose (N = 18) interactions sampled during focal animal sampling, the percentage of rubbing interactions associated with tail up was 65.52%, whereas the percentage of sniffing nose interactions associated with tail up was 33.33%. The direction of affiliative behaviour among the different age–sex classes showed an interesting pattern. Among adult cats, females were responsible for 69.05% of all affiliative behaviour and mainly of rubbing and tail up, whereas for sniffing nose were mostly adult males who took the initiative. Most of affiliative interactions (81.75%) were observed between adult females and adult males. The interactions between cats of the same sex were more frequently Fig. 1. Rubbing events performed by each cats. Individuals are in rank order. Fig. 2. Sniffing nose events performed by each cats. Individuals are in rank order. Table 5 Tail-up events preceded or followed by rubbing, between cat dyads. Individuals are in rank order. Cats ANT SON LAV PIC RIG CLA FIA SPO RUG FLY TOTr ANT SON 2 2 1 7 3 3 1 13 LAV PIC RIG CLA FIA SPO RUG FLY 0 0 5 0 0 0 8 3 0 2 1 0 0 1 0 Males in italic letters. TOTp: total acts of tail up performed, TOTr: total acts of tail up received. 0 1 1 TOTp 0 0 Author's personal copy 64 S. Cafazzo, E. Natoli / Behavioural Processes 80 (2009) 60–66 recorded in males (14.29%) than in females (3.97%), although mostly of these were directed by an adult male, SPO, towards other adult ones. Finally, the only juvenile cat, FLY, directed more affiliative behaviour towards adult males (76.7%) rather than adult females (23.3%). 4. Discussion 4.1. Social function of tail up Tail up is not simply a greeting behaviour. In this study we have found that tail up was more frequently displayed by low-ranking cats, and that high-ranking individuals received it more often than others members of social group. Therefore, rank order affects the display of tail up posture. Nevertheless, there is an evident individual variability in showing this pattern: some cats display tail up more willingly towards certain individuals rather than other ones. During a study carried out in a colony of neutered cats, CameronBeaumont (1997) found that tail up was particularly associated with rubbing on and sniffing of another colony member. Also in the present study tail up has resulted associated with others affiliative behaviours even if not very often; in fact, rubbing and sniffing nose occurred in only 22.73% of the whole tail up interactions. This difference could be set down to a clearly individual variability in showing these patterns. Nevertheless, the tail up posture is the lowest intensity but most commonly observed component of greeting behaviour, as observed by Dards (1983) too. Moreover, Cameron-Beaumont (1997) demonstrated that tail up signals an intention to interact amicably probably to avoid the possible aggression from a cat whose intentions are unknown. This result agrees with the hypothesis of the rank influence, especially if we bear in mind that in the present study a positively correlation between rank order and frequency of aggression was found. Thus, low-ranking cats could display tail up to signal their amicably intentions, to acknowledge social status and to inhibit aggressiveness of the other one. An interesting result is the direction of affiliative behaviour analysed: tail up and rubbing were generally displayed by females towards males; on the contrary, sniffing nose was more often displayed by males towards females; altogether females took the initiative in the affiliative interactions more often than males because tail up and rubbing were more frequent than sniffing nose. A female bias in initiation of affiliative interactions was also found by Macdonald et al. (1987). Dards (1983) investigated the same affiliative behaviours in a group of adult feral cats not neutered; she found similar results but she never observed this behaviour between mature males. Conversely, during this research amicable interactions between adult males were observed and they were even more frequently than those observed between females. However, it should be underlined that in the most of affiliative interactions between males the initiative were taken by a particular male, Spotted (SPO), the youngest among all adult males and the lower ranking one. Moreover, amicable interactions between males were never observed in the same colony before cats were neutered (Bonanni et al., 2007); during that period Spotted was yet a young cat. The sterilisation involves the decrease both of frequency and intensity of agonistic interactions among adult cats, especially between males, as found during a study carried out in the same social group (Cafazzo et al., in preparation), probably as a consequence of a drop of level of testosterone. Then, the decrease of levels of competition between adult males could have allowed the beginning of affiliative interactions between them. Brown and Bradshaw (1996), during a research carried out on a small colony of neutered feral cats, observed affiliative interactions among males. Neville and Remfry (1984) found a decrease of aggressive behaviours between adult males as a consequence of sterilisation, but they did not observe amicable interactions between them. During a previous study carried out on free-roaming rural cats, who were not neutered (Laundré, 1977), males resulted the initiators of affiliative behaviours more frequently than females; however, in this case, tail up was not sampled but only rubbing and sniffing were collected; this could explain the different result in comparison with the present research. Laundré (1977) observed amicable interactions between males more frequently rather than between females, although the former involved mainly two individuals, one of which was a young cat. Also in the present study the only young male belonging to the colony (FLY) showed affiliative behaviours mainly towards adult males. The age of individuals, after all, could influence the direction of affiliative behaviour, thus, it could involve a general tendency of younger cats to display this interactions towards older ones. Further studies are required to verify this hypothesis. In conclusion, this study confirms some results found during other researches (Macdonald et al., 1987; Dards, 1983; Brown and Bradshaw, 1996; Bernstein and Strack, 1996; Cameron-Beaumont, 1997), as the association between tail up and other affiliative behaviours (rubbing and sniffing nose), the direction of these behaviours and, finally, the individual variability in displaying them. Nevertheless, even more important is the evidence yielded by this study that tail up is a signal by means of which a cat shows not only its amicable intentions but also the recognition of the higher social status of the individual to whom is directed. 4.2. Evolution of tail up The most striking aspects of many animals are signals. Signals evolved to communicate information and manipulate receivers to the signaller’s benefit. Similarly, the receiver’s response to signals is under selection to promote its fitness (Ryan and Cummings, 2005). According to Wilson (1975) we observe an event of communication whenever an individual modifies or alters the behaviour of another one in the adaptive sense for one or both of them. Undoubtedly the tail up is a signal of communication; it is associated with other behaviours that signal amicable intentions, but, above all, it has an its own role as a visual signal independently from other affiliative behaviours. From the results of this study, and those of previous researches, emerged that an individual who displays tail up transmits to the receiver a precise information: he acknowledges the higher rank of the receiver and signals to him the intentions to interact amicably. Then the receiver can decide not to answer and the interaction ends, or he can answer displaying itself the tail up; if he does so, there will be a high probability that the interaction proceeds and that other affiliative behaviours occur. Thus, the intensity of interaction increases and the individuals could display sniffing nose and reciprocal rubbing. To our knowledge tail up, at least as we have described it so far, has never been observed in other species of felids (with the exception of the lion: see below); therefore which could be the evolutionary origin of this signal? As already said, cat domestication could have caused an evolutionary change in the signalling patterns used by this species. In fact, during the gradual and dynamic process of domestication, cats have been adapted to living in different ecological conditions, and they have adopted group-living. Signals can be derived originally from a great variety of ordinary activity by ritualisation. The ritualisation is an evolutionary process by which behaviour patterns become modified to serve a communication function (Mainardi, 1992). During this process nat- Author's personal copy S. Cafazzo, E. Natoli / Behavioural Processes 80 (2009) 60–66 ural selection operates to transform a behavioural pattern into a more reliable and conspicuous form of communication. Differences between signals used by the domestic cat and undomesticated felids may have been caused by domestication, both by altering the circumstances in which intraspecific behaviour is expressed (e.g. high local population densities) and by introducing a need for inter-specific (i.e. cat–human) communication (Bradshaw and Cameron-Beaumont, 2000). Therefore tail up as affiliative behaviour might be derived originally either from nonsignal movements (tail raised during urine spraying) or from signal showed in another context that has assumed a second function, but remains structurally unchanged (tail held vertically during the “presentation ritual” or when kittens meet their mother), by ritualisation. Then we consider three hypotheses: (1) the evolution of tail up from the action of urine spraying, thus from a non-signals behaviour (Bradshaw and CameronBeaumont, 2000); (2) the evolution of tail up, and in general the evolution of greeting behaviours, from sexual behaviour by ritualisation (Schaller, 1972; Leyhausen, 1979); (3) the evolution of tail up from a raising tail by kitten when they approach their mother. In the last two cases the tail up should originate from signals already used for communication but in other context. 4.3. The evolution of tail up from a non-signal behaviour The tail is raised vertically during urine spraying and then immediately lowered (Schaller, 1972; Smith et al., 1989; Mellen, 1993; Wemmer and Scow, 1977). This action is thought to occur in all species of felids, domestic and undomesticated. Obviously the tail up differs from the raised tail that occurs during urine spraying in both context, being linked to affiliative behaviours, and structure, occurring for prolonged periods of time, often remaining upright during locomotion (Cameron-Beaumont, 1997). CameronBeaumont (1997) investigated the point at which the tail up might have evolved by looking for its presence in undomesticated felids. She found no evidence of the presence of tail up in any of the three species analysed, thus Oncifelis geoffroyi, Caracal caracal and Felis chaus, who are representatives from all three evolutionary lineages: ocelot lineage, Panthera lineage and domestic cat lineage. On the contrary of what we observe in domestic cats, all three species display rubbing without raising their tail. On the basis of the studies carried out by Wemmer and Scow (1977), Mellen (1993), and Bradshaw and Cameron-Beaumont (2000) asserted that tail up evolved as an affiliative signal from a non-signal behaviour during domestication, perhaps consecutively to the increased sociality that may have caused the necessity of an additional visual signal, as we have already said. However the authors underlined that it cannot be ruled out that the tail up may have evolved at an early stage, possibly amongst one of the undomesticated species of Felis silvestris. There are few behavioural studies on the subspecies of F. silvestris, particularly on the African subspecies, which may account for the absence of any mention of tail up (Bradshaw and CameronBeaumont, 2000). 4.4. The evolution of tail up from a sexual behaviour In the “Serengeti Lion” Schaller (1972) wrote: “The greeting pattern, including circling, rubbing, raising the tail (. . .), has a striking similarity to the sexual behaviour of the female. (. . .) there seems to be little doubt that rubbing was derived from it, that the greeting behaviour is a ritualised form of sexual behaviour”. This idea was 65 also suggested by Leyhausen (1979). He defined the moment during the courtship when a female, with her back slightly arched over and her tail raised, pushes her vulva against the nose of the male, as “presentation ritual” and so he explained how in the most mammals the “presentation ritual” has become a greeting behaviour. Leyhausen asserted that during an affiliative interaction between two individuals, it is impossible to establish the rank of both cats solely considering the intensity of the “presentation ritual” or taking into account the animal that starts the interaction. It is difficult to confirm if it is really possible to consider the tail up as a ritualised form of sexual behaviour, however it is opportune to bear in mind that the assertion by Leyhausen (1979) is denied from the results of this research. 4.5. The evolution of tail up from raising tail occurring during mother–kitten interactions When kittens greet their mother, they approach her with the tail held vertically and rub their forehead and then their upper part of the head, against her chin. This sequence is often associated with food require. It is possible that, this behavioural pattern has evolved a further social function as an inhibitory of the potential aggressiveness of adult cats besides the mother. In fact, in the social group of domestic cat, kittens display greeting behaviour and thus the tail up, also when they approach other adult individuals. Moreover during domestication this infantile behaviour might has been preserved in the adult cat to inhibit the aggressive intentions of another one, as a consequence of the increase of social interactions. The domestic cat might have evolved the ability to utilise infantile behaviour when adult (neoteny) both in intraand inter-specific communication: in fact tail up occurs also during cat–human interactions. 4.6. Comparison with the greeting behaviour of lion The lion (Panthera leo) is the only other felid that has been proven to be able to live socially. In fact both lion (Schaller, 1972; Packer et al., 1991; Pusey and Packer, 1994) and domestic cat (Macdonald et al., 1987, 2000; Liberg et al., 2000) form social groups composed of genetically related females, their offspring and some males. Up to now, the only other felid for whom it has been reported that social rubbing can occur with the tail raised is lion (Schaller, 1972): during head-rubbing and sniffing contacts, the tail is raised almost vertically but tipped limply towards the animal being greeting. Therefore both in lions and in cats tail up occurs as affiliative behaviours. The function of tail up in lions may even be similar to that in the domestic cats, thus as an affiliative signal. In conclusion, the fact that the tail up as affiliative behaviour occur only in the domestic cat and in lion, that come from different evolutionary lineages, may suggest that this signal has evolved separately in the two species, possibly as a result of similar selective pressures acting only on the two most social species of cats (Bradshaw and Cameron-Beaumont, 2000). Acknowledgements We wish to thank Antonio Buogo, the cat care-taker of the colony studied, for his help during the study. 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