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9156384463537987891 9156384463537987891 Document Transcript

  • EthologyScent-Marking Behaviour in a Pack of Free-Ranging DomesticDogsSimona Cafazzo*, Eugenia Natoli† & Paola Valsecchi* `* Dipartimento di Biologia Evolutiva e Funzionale, Universita degli Studi di Parma, Parma, Italy† Azienda USL Roma D, Area Dipartimentale Sanita Pubblica Veterinaria, Rome, Italy `Correspondence AbstractSimona Cafazzo, Dipartimento di Biologia `Evolutiva e Funzionale, Universita degli Studi Most mammals scent-mark, and a variety of hypotheses have been putdi Parma, via G.P. Usberti 11/A, 43100 Parma, forward to explain this behaviour. Most of our knowledge about scentItaly, and via Gasperina 300, 00173 Rome, marking in domestic dogs comes from studies carried out on laboratory orItaly. companion dogs, while few studies have been carried out on free-rangingE-mail: simona.cafazzo@inwind.it dogs. Here, we explored the functional significance of different scent- marking behavioural patterns in a pack of free-ranging domestic dogs byReceived: June 20, 2011 testing two non-exclusive hypotheses: the indirect territorial defenceInitial acceptance: September 16, 2011 and the dominance/threat hypotheses. Through direct observation, weFinal acceptance: July 5, 2012 recorded the locations of dog scent marks (urination, defecation and(M. Herberstein) ground scratching) and information regarding the identity and posture ofdoi: 10.1111/j.1439-0310.2012.02088.x the marking animal. We found evidence that markings are used by dogs to form a ‘property line’ and to threaten rivals during agonistic conflicts. Both males and females utilized scent marking to assert dominance and probably to relocate food or maintain possession over it. Raised-leg urina- tion and ground scratching probably play a role in olfactory and visual communication in both males and females. Urinations released by females, especially through flexed-leg posture, may also convey informa- tion about their reproductive state. Finally, our observations suggest that defecation does not play an essential role in olfactory communication among free-ranging dogs and that standing and squat postures are associ- ated with normal excretion. Our results suggest that many of the proposed functions of marking behaviours are not mutually exclusive, and all should be explored through detailed field and laboratory studies. are more likely than females to direct their urine atIntroduction specific targets (Martins & Valle 1948; Bekoff 1979a;Scent marking may be defined as the deposition of Ranson & Beach 1985). In addition, adult males typi-odour by urination, defecation or the release of glan- cally raise a hind leg to urinate, while adult femalesdular secretions (Kleiman 1966). Scent marking may usually squat (Martins & Valle 1948; Beach 1974).communicate detailed information about the scent While urination clearly has the physiological functionsource, including social status, age, sex and reproduc- to empty the bladder in both sexes, its role in scenttive state, group composition and individuality (e.g. marking is thought to be more important in male dogsRalls 1971; Gorman & Trowbridge 1989; Smith et al. than in female dogs (Martins & Valle 1948; Bekoff2001). 1979a; Pal 2003). Indeed, Kleiman (1966) suggested Most of our knowledge about scent marking in that female dogs mark with urine only around thedomestic dogs (Canis lupus familiaris) comes from stud- time they are in oestrus. Lisberg & Snowdon (2009,ies carried out on laboratory or companion dogs. 2011) observed that, outside of oestrus, both high-Urinary behaviour in domestic dogs is sexually dimor- status males and females urinated, investigated urinephic (Beach 1974; Ranson & Beach 1985). Adult and countermarked more than same-sex dogs withmales urinate more frequently than do females and lower status. Moreover, males and females wereEthology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH 955
  • Scent-Marking Behaviour in Domestic Dogs S. Cafazzo, E. Natoli & P. Valsecchiequally likely to countermark and investigate urine intruder to identify the territory owner by matching(Lisberg & Snowdon 2011). scent marks encountered in the territory with the A study (Pal 2003) carried out using direct observa- scent of individuals encountered (Gosling (1982).tion of urine-marking behaviour of free-ranging Identification of the territory owner by the intruderdomestic dogs further showed that urine marking was can help to avoid escalated conflicts between themdisplayed especially during territorial defence. Ques- and thus is beneficial to both parties (Gosling &tions remain, however, regarding the function of Roberts 2001). If the costs of scent-marking the terri-urine-marking behaviour and other scent-marking tory (in terms of time and energy and perhapsbehaviours, especially in relation to different social increased vulnerability to predators) are lower thanclasses within a pack. the costs of attacking an intruder, scent marking In the current study, we explored the functional becomes an economic strategy for territorial defencesignificance of different scent-marking behaviours in (Gosling 1982, 1986; Gosling & Roberts 2001).a pack of free-ranging domestic dogs living in a subur- According to both scent fence and scent-matchingban environment. We focused on three different mechanisms, scent marking should be concentratedbehavioural patterns of marking: urination, defeca- in areas where scent marks are most likely to betion and ground scratching. Scent marking by urina- encountered by an intruder, that is, along the territo-tion is a common practice in the family Canidae (e.g. rial boundary (Gosling 1982). Studies on differentScott & Fuller 1965; Kleiman 1966; Beach 1974; Fox mammalian taxa have supported this prediction (e.g.et al. 1975; Peters & Mech 1975; Dunbar 1977, 1978; wolves, Peters & Mech 1975; Rothman & Mech 1979;Bekoff 1979a; Wells & Bekoff 1981; Gese & Ruff 1997; Zub et al. 2003; tigers, Panthera tigris: Smith et al.Allen et al. 1999; Pal 2003; Zub et al. 2003). Defeca- 1989; marmots, Marmota spp.: Boero 1995; Blumsteintion and ground scratching can also serve as scent & Henderson 1996; blind mole-rats, Spalax ehrenbergi,marking in canids (e.g. wolves, Canis lupus: Peters & Zuri et al. 1997; coyote, Wells & Bekoff 1981; Gese &Mech 1975; Barja & De Miguel 2004; coyote, Canis la- Ruff 1997; Allen et al. 1999; ethiopian wolves, Canistrans: Wells & Bekoff 1981; Gese & Ruff 1997). Scats simensis, Sillero-Zubiri & Macdonald 1998).often are left in conspicuous locations, such as on Ralls (1971) hypothesized that social mammals tendrocks, plants and trail junctions, probably increasing to mark frequently in any situation where they aretheir effectiveness as visual and olfactory marks. both intolerant of and dominant to other members ofGround scratching often occurs after defecation or the same species. In other words, they mark whenraised-leg urination, and it may serve as a chemical they are likely to attack another member of the samesignal and as a visual signal (Peters & Mech 1975; species and are likely to win if they do attack. SuchBekoff 1979b; Bekoff & Wells 1986). The chemical behaviour may occur in territorial defence, but it willcomponent may involve either scent deposited from not necessarily be restricted to territorial situations. Ininterdigital glands or the dispersion of olfactory cues fact, scent marking may function to communicatefrom deposited urine or faeces (Peters & Mech 1975; dominance status among group members, thus reduc-Fox & Cohen 1977). The visual component may ing the need for costly fights. The dominance/threatinvolve the act of ground scratching or the marks left hypothesis has received support from several studieson the ground by such scratching (Kleiman & Eisen- on scent marking in mammals (e.g. Walther 1978;berg 1973; Bekoff 1979b). Ground scratching has not Gosling & Roberts 2001; Miller et al. 2003; Bonannibeen reported to follow squat urination and appears et al. 2007).to be performed predominantly by high-ranking In this study, we aim to test the general predictionmales (e.g. wolves: Peters & Mech 1975; coyotes: Gese that, if scent marking is used to communicate indirect& Ruff 1997). defence of territory (territorial defence hypothesis), dogs Our aim was to test two non-exclusive hypotheses would mark more frequently along the periphery of therelated to the function of scent marking by free-rang- territory than in its interior (prediction 1a); moreover,ing domestic dogs: the ‘indirect territorial defence dogs are expected to mark more frequently at strategichypothesis’ and the ‘dominance/threat hypothesis’. places, such as crossroads, where potential intruders are Animals may scent-mark for the purpose of defend- most likely to encounter marks (prediction 1b).ing food resources or territories, thereby reducing According to the dominance/threat hypothesis, wefights with conspecifics (indirect territorial defence predicted that dominant animals would mark morehypothesis). Scent marks could work as a chemical frequently than subordinate animals (prediction 2a).‘keep out sign’, which would deter or intimidate We also may predict a positive correlation betweenintruders (Wyatt 2003), or scent marks allow an scent marking and aggressive behaviour (prediction956 Ethology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH
  • S. Cafazzo, E. Natoli & P. Valsecchi Scent-Marking Behaviour in Domestic Dogs2b) and an increase in marking rate prior to or during Observations of this pack of dogs began in Mar.agonistic interactions than during non-agonistic 2005. We had direct knowledge of age in dogs 2 yrencounters (prediction 2c). and younger. The ages of the remaining dogs were Finally, to confirm and extend the results of previ- assessed by estimating body size and general appear-ous research, in this study, we also asked the follow- ance (e.g. white hair on the muzzle) as well as toothing questions: is the rate and posture of scent marking wear (e.g. Gier 1968) and eruption (Kirk 1977) duringinfluenced by sex of dogs? Do dogs scent-mark at capturing and immobilization procedure (see Cafazzodifferent rates in different social contexts and in differ- et al. 2010 for details of age estimation). Dogs wereent places? Do female dogs use urination, ground thus reliably classified as juveniles (6 mo to 1 yr),scratching and defecation to mark their territory or to subadults (1–2 yr) and adults (more than 2 yr). Atindicate dominance? the start of the research, the dog pack consisted of 27 individuals. Owing to some deaths, births and disap- pearances of some individuals during the period ofMethods observation (see. Cafazzo et al. 2010 for a detailed description), the pack size ranged from 25 to 42 indi-Study area viduals. The final statistical analysis was applied to 27The research was carried out in a suburban environ- dogs: six adult males, five adult females, four subadultment situated in the south-western outskirts of Rome, males, one subadult female, six juvenile males andItaly (41°50′N, 12°23′W; elevation: about 60 m). The five juvenile females.study area was about 300 ha and was delimited to thenorth, west and south by roads with heavy traffic and Behavioural observationsto the east by cultivated areas. The south-west sector was urbanized, although The study began in Apr. 2005 and lasted until the endnot densely populated. The north-east sector was of May 2006. Data were collected in three differentmainly occupied by a nature reserve called ‘Tenuta contexts: in the presence of food, when receptivedei Massimi’. females were courted by males (and food was not The habitat in the reserve consists mainly of open present), and in the absence of sources of competitiongrasslands with interspersed wooded areas (see (i.e. when food was not present and outside the oes-Bonanni et al. 2010a for a more detailed description). trus period) for a total of 282.53 h of recording. Data All dog packs had free access to virtually every part collection was carried out following Altmann’s (1974)of the study area. Nevertheless, the individuals of the methods: focal animal sampling method was used inpack studied mainly frequented the area of the Natu- the absence of sources of competition, whereas theral Park where the dense vegetation of the wooded focal subgroup sampling method was used in theareas offered good shelter for the animals, especially presence of food and receptive females.for lactating females and their puppies. However, they For each urination, defecation and ground scratch-frequently approached a central road crossing the ing performed by the focal animals, the type, time andstudy area, especially in the early morning, to feed location of the behaviour were recorded. According toon the food (mainly meat from a slaughterhouse) Kleiman (1966), urinations were classified as scent-brought every day by volunteer dog caretakers. marking events rather than eliminations; when urine was released in small quantity following olfactory investigation, it was orientated towards a conspicuousSubjects substrate (plants, rocks, food, walls, car wheels, etc.),The dog pack studied belonged to a population of elicited by familiar landmarks, novel odours or objectsabout 100 adult animals inhabiting the study area. All and conspecifics marks (usually dogs marked just overdogs were mediumsized to large mongrels, and there or some distance away from investigated spots). Uri-was not a recognizable predominant breeding type nation posture recorded included: (1) raised-leg uri-(Cafazzo 2007). With very few exceptions, dogs were nation (one hind leg is raised off the ground, whethernot socialized to humans although they were depen- or not there is a vertical target); (2) flexed-leg urina-dent on humans for food provisioning. All dogs of the tion (the dog squats and elevates one hind leg slightlypack were individually recognized by coat colour and forward or directly under the body); (3) standing uri-pattern, hair length and body size; they were sexed by nation (dogs do not squat but they stand with theirgenital morphology (for a detailed description, see hind legs straight); (4) squat urination (the dog’s hindCafazzo et al. 2010 and Bonanni et al. 2010a,b). part is lowered, the hind legs are bent under the bodyEthology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH 957
  • Scent-Marking Behaviour in Domestic Dogs S. Cafazzo, E. Natoli & P. Valsecchiand the urogenital region comes close to the ground). To test the predictions generated from the indirectWe also recorded all events of defecation. Scats were territorial defence hypothesis, we expressed the indi-considered as true marking cues if they were depos- vidual marking rate as the number of markingsited following olfactory investigation at conspicuous recorded in each zone divided for the time spent inor raised sites (Kleiman 1966). Finally, we also the same zone. Then, we compared the individualrecorded all events of ground scratching, the alternate marking rate displayed along territorial boundaries (atmovements of the legs through which the dog crossroads or not) with those displayed both outsidescratches the ground, sending grass and earth flying (about 100 m beyond the territorial boundaries) andbackward; it often occurs after raised-leg urination inside the territorial area. A scent mark was classifiedand defecation (Rothman & Mech 1979; Zub et al. as a boundary mark when it occurred within 50 m of2003). the territorial boundaries. We also compared the The individual measure of behavioural patterns hourly rate of scent markings observed at denningwas corrected for animal observation time because sites, feeding sites (when no food was present) andthe latter varied between individuals. somewhere else to analyse the spatial distribution of In the absence of sources of competition, we also scent marking inside the territorial area. For theserecorded the location of the focal animal using the analyses, we only considered the scent markingsinstantaneous- sampling method (60-s intervals) recorded in the absence of sources of competition(Altmann 1974). Thus, we could estimate for each (scent marking that occurred during territorial conflictdog, the time spent in the following zones: along the or in the presence of food or oestrus females were notterritorial boundaries, outside the territory, at feeding included) because the spatial distribution of scentsites, at denning sites and somewhere else in the marking observed in the other two contexts (duringterritorial area. feeding and courting) was influenced by the location of feeding sites and by movements of receptive females.Home range and territory sizes As in this dog pack the dominance rank, the rate ofTo analyse the spatial distribution of scent marking, aggressive behaviour and the age of the individualswe calculated the sizes of the home range and of the were correlated (see Cafazzo et al. 2010), we applieddefended area by applying the minimum convex poly- a principal components analysis (PCA) to replace thegon method (Southwood & Henderson 2000). Home mentioned three original variables with new uncorre-range was examined by plotting the locations of the lated component variables, linear combinations of theanimals sighted covering fixed paths everyday twice original variables, called principal components or fac-per day. We totalled 150.65 ± 19.95 sightings for each tors. Then, we tested the dominance/threat hypothe-dog during 197 days of observation. Home range size sis by correlating the hourly rate of markingwas estimated by drawing a convex polygon connect- behaviours to the PCA components that explaineding the outermost sightings and computing its area, most of the variation in the data.including inner buildings and fenced areas. By comparing the rate of scent marking during an As a counterevidence of the territory size esteem, agonistic conflict with the rate of marking duringthe locations where pack members clearly won the non-agonistic interactions, we verified the relationterritorial fights against intruders were plotted. A ter- between marks and the aggressive motivation towardsritorial fight was defined as an agonistic encounter other dogs. For this analysis, we separately consideredbetween pack members under study and dogs belong- interactions between pack members and with dogsing to neighbouring social packs. The pack members from other packs.were considered winning the agonistic encounter We tested the hypotheses and investigated thewhen they managed to drive away the intruders. relationship between scent marking and sex and social context using two-tailed non-parametric sta- tistical tests [Wilcoxon signed-ranks test (t), Mann–Statistical analysis Whitney U-test, and Spearman rank correlationBy using data on the direction of submissive behav- (rs)], (STATISTICA 7.1 edition, StatSoft Italy s.r.l.iour observed between dogs, we could arrange all 2005). Probability level for rejection of the nullindividuals belonging to the pack studied in a linear hypothesis was set at p < 0.05. Media and rangedominance hierarchy whose details are described of behavioural patterns analysed are listed inelsewhere (Cafazzo et al. 2010). Table 1.958 Ethology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH
  • S. Cafazzo, E. Natoli & P. Valsecchi Scent-Marking Behaviour in Domestic DogsTable 1: Media and range of hourly rates of behavioural patterns the incidence of simple elimination (Wilcoxon signedconsidered rank test: t = 1.00, z = 3.46, n = 16, p = 0.0005). On N Media Minimum Maximum the contrary, females more frequently displayed normal excretion than marking (t = 7.00, z = 2.09,Urination marking displayed 16 0.72 0.13 2.67 n = 11, p = 0.04). by males Of 89 defecations recorded, only nine scats haveUrination marking displayed 11 0.27 0.00 0.72 by females been considered to have a communicative functionGround-scratching displayed 27 0.11 0.00 0.48 because they were deposited following investigation by all dogs on raised sites (on rocks or plants); moreover, theseStanding urination displayed 16 0.07 0.00 0.22 nine scats were deposited at crossroads. The incidence by males of scent marking via urination was greater thanSquat urination displayed 11 0.47 0.12 0.71 the incidence of scent marking via defecation. by females The proportion of different postures displayed dur-Defecation displayed by 27 0.11 0.03 0.19 all dogs ing urination varied among the two sexes. Males typically performed raised-leg urination (N = 581; 94.01%), while they rarely displayed standing urina- tion posture (N = 36; 5.83%); only a juvenile maleResults was observed displaying a squat posture (N = 1, 0.16%). Females rarely displayed raised-leg urinationHome range and territory (N = 8, 4.88%), while they usually displayed flexed-Although some subgroups sometimes covered longer leg (N = 52, 31.71%) and squat urination posturesdistances than other subgroups, pack members usu- (N = 104; 63.42%).ally moved all together throughout the area, and indi- The sex of dogs influences the frequency of scentviduals’ home ranges clearly overlapped within the marking via urination: the marking rate via urinationpack. The home range pack size was calculated as  of x was higher for males than for females (Mann–the individuals’ home ranges (N = 27), and it aver- Whitney U-test: U = 42.5, n1 = 16, n2 = 11, p =aged 60.98 ± 9.18 ha. 0.023). Females included a different representation of Territorial boundaries were assumed to be the age categories than males because only one subadultsame for all members of the pack because it has female was observed. As this could skew the results,been observed that all pack members cooperated for we also compared only adult dogs when looking atterritorial and resources defence against intruders male vs. female marking, and we found again thatfrom other neighbouring social packs (Bonanni et al. males marked via urination more frequently than2010a). Group territory size measured 22.14 ha and females (U = 2.37, n1 = 6, n2 = 5, p = 0.017).its boundaries were inside the boundaries of the home The hourly rate of raised-leg urination displayed byrange. We defined the periphery of the territory as a males was higher during feeding than in the presencezone within 50 m of the territorial boundaries. This of receptive females; although the male raised-leg uri-periphery or boundary zone comprised about 21% of nation rate was higher in the absence of sources ofthe area of territory. All dens, resting and feeding sites competition than in the presence of food, the differ-were located inside the territory and never in the ence was not significant (Table 2). Male raised-legperiphery. urination rate was also higher in the absence of sources of competition than in the presence of recep- tive females (Table 2). Males ground-scratched moreScent-marking behaviours: influence of sex and frequently in the presence of food than in the pres-context ence of receptive females and even more frequentlyWe recorded a total of 782 urinations, 143 ground in the absence of sources of competition (Table 2).scratches and 89 defecations during 282.53 h of Standing urination was never observed in the pres-observation. Of 782, 589 were raised-leg, 52 flexed- ence of receptive females and its hourly rate did notleg, 36 standing and 105 were squat urinations. differ across the other two social contexts (Table 2). All squat and standing urinations were identified as Females displayed flexed-leg urination more fre-simple eliminations because they were never pre- quently during their oestrus than in the presence ofceded by olfactory investigation, and they were food and in the absence of sources of competition;released on inconspicuous substrates (the ground). moreover, the hourly rate of flexed-leg urination wasFor males, the incidence of marking was greater than higher in the presence of food than in the absence ofEthology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH 959
  • Scent-Marking Behaviour in Domestic Dogs S. Cafazzo, E. Natoli & P. ValsecchiTable 2: We used the Wilcoxon signed-ranks test to compare the hourly rates of raised-leg urination, ground scratching and standing urinationperformed by males, among three competitive contexts: in the absence of sources of competition, in the presence of food and during courting ofreceptive females Raised-leg urination Ground scratching Standing urination t z p t z p t z pAbsence of sources of competition vs. presence of food (n = 16) 49 0.98 0.32 5.00 2.07 0.04 36 0.66 0.50Presence of food vs. during courting (n = 16) 0.00 3.40 0.001 1.00 2.38 0.02 a a aAbsence of sources of competition vs. during courting (n = 16) 0.00 3.40 0.001 0.00 2.67 0.01 a a aaStanding urination was never observed in the presence of receptive females.sources of competition (Table 3). Squat urination urine-marking rate was higher at feeding sites thanhourly rate did not differ among the three social con- somewhere else the difference was not significanttexts (Table 3). All ground scratchings and raised-leg (Table 5). On the contrary, the urine-marking rate ofurinations performed by females were recorded in the males was higher at feeding sites than denning sitesabsence of sources of competition. and somewhere else (Table 5), while it did not differ between denning sites and somewhere else (Table 5). Males ground-scratched along territorial boundariesTest of predictions at a higher frequency compared with the insidePrediction 1 (t = 0.00, z = 2.67, n = 16, p = 0.007) and outside ofMales scent-marked more frequently along territorial territory (t = 0.00, z = 2.64, n = 16, p = 0.006), but noboundaries and in the interior of the territory than difference was found between the ground-scratchingin rest of their home range (Table 4), while females rate recorded inside and outside the territory (t =were never observed marking outside the territorial 11.00, z = 1.21, n = 16, p = 0.36). Females scratchedarea. the ground only along territorial boundaries following The hourly rate of scent marking via urination raised-leg urination.along territorial boundaries vs. the interior was Scent marking via defecation was displayed only byinfluenced by the sex of dogs. Males scent-marked the alpha male along territorial boundaries. Of 11via raised-leg urination along territorial boundaries events of defecation displayed by the alpha male, 9at a higher frequency compared with the interior (81.82%) were deposited along territorial boundaries(Table 4) and mainly at the crossroads along territo- at crossroads and mainly on conspicuous or highrial borders (t = 5.00, z = 2.98, n = 16, p = 0.003). In substrates (rocks and plants; N = 7, 77.78%).contrast, females scent-marked via flexed-leg urina- All elimination events and the 80 events of defeca-tion more frequently inside the territorial area than tions identified as normal excretions were randomlyalong the boundaries (Table 4). All events of raised- distributed: along territorial boundaries, in the inte-leg urination by females (N = 8) were observed along rior of the territory and in the rest of the home rangethe periphery at the crossroads. Also males scent- (Table 6).marked via raised-leg urination mainly at the cross-roads along territorial borders (t = 5.00, z = 2.98, Prediction 2n = 16, p = 0.003). Inside the territory, females scent-marked more frequently at denning sites than at feed- For males, the first factor of the PCA alone explaineding sites and somewhere else (Table 5), even if the 86.66% of the total variance in the data (Fig. 1a):Table 3: We used the Wilcoxon signed-ranks test to compare the hourly rates flexed-leg urination and squat urination performed by females amongthree competitive contexts: in the absence of any sources of competition, in the presence of food and during courting by males Flexed-leg urination Squat urination t z p t z pAbsence of sources of competition vs. presence of food (n = 11) 3.00 2.10 0.04 15.00 1.60 0.11Presence of food vs. during courting (n = 7) 0.00 2.37 0.002 11.00 0.50 0.51Absence of sources of competition vs. during courting (n = 7) 0.00 2.36 0.002 5.00 1.52 0.13960 Ethology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH
  • S. Cafazzo, E. Natoli & P. Valsecchi Scent-Marking Behaviour in Domestic DogsTable 4: We used the Wilcoxon signed-ranks test to compare the hourly rate of raised-leg urination displayed by males (n = 16) and the hourly rateof flexed-leg urination displayed by females (n = 11) outside and inside of the territory and along territorial boundaries Raised-leg urination (n = 16) Flexed-leg urination (n = 11) t z p t z pOutside of the territory vs. territorial boundaries 0.00 3.52 0.0004Territorial boundaries vs. inside of the territory 0.00 3.51 0.0004 0.00 2.20 0.03Outside of the territory vs. inside of the territory 1.00 2.85 0.0004Table 5: We used the Wilcoxon signed-ranks test to compare the hourly rate of urine marking displayed by males (n = 16) and females (n = 11)inside the territory at different sites: denning sites, feeding sites and somewhere else Raised-leg urination (n = 16) Flexed-leg urination (n = 11) t z p t z pDenning sites vs. feeding sites 0.00 2.98 0.003 0.00 2.22 0.02Denning sites vs. somewhere else 10.00 1.12 0.26 0.00 2.18 0.04Feeding sites vs. somewhere else 0.00 2.91 0.004 0.00 1.83 0.07Table 6: We used the Wilcoxon signed-ranks test to compare the hourly rate of standing urination displayed by males (n = 16), squat urinationdisplayed by females (n = 11) and defecation displayed by all dogs (n = 27) outside and inside of the territory and along territorial boundaries Standing urination (n = 16) Squat urination (n = 11) Defecation (n = 27) t z p t z p t z pOutside of the territory vs. territorial boundaries 13.00 0.17 0.87 7.00 1.18 0.24 103.00 0.76 0.45Territorial boundaries vs. inside of the territory 3.00 1.86 0.07 30.00 0.27 0.79 135.00 1.30 0.19Outside of the territory vs. inside of the territory 10.00 1.12 0.26 11.00 1.95 0.06 158.00 0.45 0.66males characterized by high negative scores on this component. The rate of scent marking via urinationfactor were high-ranking older individuals who displayed by females was negatively correlated to thedisplayed a higher frequency of aggressive behaviour. first factor (rs = À0.88, n = 11, p = 0.0004), but itThe second factor of the PCA explained just 12.01% was not correlated to the second factor (rs = 0.28,of the variance (Fig. 1a). n = 11, p = 0.41). The first factor was negatively correlated with both Males scent-marked via urination more frequentlyurine scent-marking hourly rate (rs = À0.95, n = 16, during agonistic than non-agonistic interactions withp = 0.000001) and ground-scratching hourly rate both other pack members and dogs from other packs(rs = À0.67, n = 16, p = 0.005) displayed by males. (Table 7). Moreover, the rate of marking during ago-Therefore, high-ranking old dogs were more aggres- nistic interactions with pack members was lower thansive and displayed scent-marking behavioural pat- during agonistic interactions with dogs from otherterns more frequently than juveniles or subadults. packs (t = 0.00, z = 3.30, n = 16, p = 0.001). Females For females, the first factor of the PCA alone also scent-marked via urinations (both flexed-leg andexplained 73.90% of the total variance in the data raise-leg urinations) more often during agonistic than(Fig. 1b); the second factor of the PCA explained non-agonistic interactions with both other pack mem-24.48% of the variance. Thus, females characterized bers and dogs from other packs (Table 7). However,by high negative scores for the first factor were high- for them, the rate of marking during agonistic interac-ranking old individuals who displayed a higher fre- tions with pack members and with dogs from otherquency of aggressive behaviour. Females with high packs did not differ (t = 5.00, z = 0.67, n = 11,negative scores on the second factor displayed a p = 0.5). Finally, the rate of ground scratching washigher frequency of aggressive behaviour (Fig. 1b). higher during agonistic than non-agonistic interac-Moreover, these dogs were also younger, on average, tions with both pack members and dogs from otherthan those that had high negative scores on the first packs (Table 7). Dogs ground-scratched at higher rateEthology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH 961
  • Scent-Marking Behaviour in Domestic Dogs S. Cafazzo, E. Natoli & P. Valsecchi (a) Discussion Indirect territorial defence hypothesis Our results provide evidence that scent marking by free-ranging domestic dogs may serve as demarcation of territorial boundaries according to the territorial defence hypothesis. Male dogs, as other species of canids (wolves: Harrington 1981; Asa et al. 1985a,b, 1990; Harrington & Asa 2003; Peters & Mech 1975; Zub et al. 2003; coyotes: Wells & Bekoff 1981; Gese & Ruff 1997; Allen et al. 1999), appear to delimit their territory by means of urine and scratching. Dogs, as wolves (Zub et al. 2003) and coyotes (Wells & Bekoff 1981), were observed scent-marking especially at crossroads, where the intrusion of other dogs from neighbouring packs might be more likely. Neverthe- less, whether scents alone (i.e. the scent-fence hypothesis) or the matching between scents and sig- (b) nallers (territory owners; i.e. the scent-matching hypothesis) would keep out intruders needs to be explored. Moreover, as we did not study the scent- marking distribution pattern of neighbouring dog packs, we cannot exclude that the concentration of scent marking along territorial boundaries could also be caused by dogs countermarking unfamiliar conspecifics’ urine; this does not necessarily indicate territory defence as the main function of urine marking. Wolves have been observed depositing and accu- mulating scats at strategic sites (e.g. crossroads, con- spicuous substrates), probably to increase their effectiveness as visual and olfactory marks (Barja et al. 2004). In our dog pack, only the alpha male was observed scent-marking by means of faeces at cross- roads, but a real accumulation of scats in this place has never been observed. As group members collec- tively defended the territory in agonistic encountersFig. 1: Principal components analysis (PCA) results for males (a) and with intruders, if scats functioned in territorialfemales (b). The circles shows the correlation between the original vari- defence, a group-wide (rather than ‘alpha only’) useables and the two new components. (a) Pearson correlations between of scats along boundaries, especially at crossroads,factor 1 of the PCA and the original variables were: À0.95 (Age), À0.97 should be expected. It is not clear why it was per-(Hierarchical rank), À0.86 (Rate of aggressive behaviour). Pearson corre-lations between factor 2 and the original variables were: À0.27 (Age), formed only by the alpha male.0.17 (Hierarchical rank), À0.50 (Rate of aggressive behaviour). (b) Pear- Contrary to males, female dogs scent-markedson correlations between factor 1 of the PCA and the original variables mainly in the interior of the territory. Nevertheless,were: À0.90 (Age), À0.98 (Hierarchical rank), À0.68 (Rate of aggressive the findings that both females and males scent-behaviour). Pearson correlations between factor 2 and the original vari- marked inside the territory suggest that informationables were: 0.42 (Age), 0.12 (Hierarchical rank), À0.74 (Rate of aggres- was also conveyed via these internal marks.sive behaviour). Dominance/threat hypothesisduring agonistic interaction with dogs from other Our results are also consistent with the dominance/pack than with pack members (t = 0.00, z = 3.06, threat hypothesis (Ralls 1971). High-ranking individ-n = 27, p = 0.002). uals are more likely to display marking behaviour.962 Ethology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH
  • S. Cafazzo, E. Natoli & P. Valsecchi Scent-Marking Behaviour in Domestic DogsTable 7: We used the Wilcoxon signed-ranks test to compare the hourly rate of urine marking displayed by males (n = 16) and by females (n = 11)and the hourly rate of ground scratching by all dogs (n = 27) during agonistic and non-agonistic interactions with both other pack members and dogsfrom other packs Urine marking by males Urine marking by Ground scratching (n = 16) females (n = 11) (n = 27) t z p t z p t z pAgonistic interactions vs. non-agonistic interactions with other 0.00 3.52 0.0004 2.50 2.17 0.03 0.00 2.93 0.003 pack membersAgonistic interactions vs. non-agonistic interactions with dogs 2.5 3.14 0.001 0.00 2.67 0.008 0.00 3.29 0.001 from other packsMoreover, the frequency of scent marking was clearly Influence of sexrelated to aggressive behaviour given that dogsmarked more frequently during agonistic interactions The rate of marking was higher in males than inthan non-agonistic interactions between both pack females as observed in other studies carried out onmates and dogs from other packs. A higher frequency free-ranging dogs (Bekoff 1979a; Pal 2003), laboratoryof territorial marking behaviour performed by high- (Dunbar 1977, 1978) and companion dogs (Lisberg &ranking individuals was also found in wolves (Mech Snowdon 2011) as well as on wolves (Mech 2006).1999, 2000; Peterson et al. 2002) and coyotes (Gese & Moreover, older individuals marked at higher ratesRuff 1997), as well as in high-status companion dogs than younger as reported in previous studies on(Lisberg & Snowdon 2011). domestic dogs (Wirant & McGuire 2004; Wirant et al. Males urinated raising a leg at higher rates during 2007) as well as on wolves (Sillero-Zubiri & Macdon-conflicts with other dogs, especially against intruders ald 1998) and coyotes (Gese & Ruff 1997). Actually,and along territorial boundaries; females displayed adults dominated over subadult dogs and subadultsraised-leg urinations only along territorial boundaries dominated over juveniles; males dominated overand more often during agonistic interactions with females in each age classes (see Cafazzo et al. 2010).intruders. These findings support the idea that this Therefore, high-ranking adult males scent-markedbehavioural pattern may serve both as a mechanism more frequently than other age/sex categories.of border enforcement (as suggested for other species Raised-leg urination posture was exhibited by malesof canids: coyotes, Gese & Ruff 1997; wolves, Barja and rarely by females, which used mainly flexed-leget al. 2004) and as a visual cue to display dominance urination posture. Our results suggest that differentor threat to opponents. postures might be correlated with certain behaviours and contexts: flexed-leg urination appeared to be associated with reproductive state and with theThe functions of ground scratching defence of dens and food; raised-leg urination seemsMales scratched the ground mainly after raised-leg to be mainly associated with aggression and demarca-urinations along territorial boundaries; females were tion of territorial boundaries in both males andobserved scratching the ground only after raised-leg females.urinations. Both of them displayed this behaviour,especially during territorial conflicts. Finally, high- Influence of the contextranking older individuals scratched the ground moreoften than low-ranking younger dogs. These results In free-ranging dogs in India, a higher rate of scenthighlight the role of ground scratching as a display of marking has been reported during the oestrus periodsocial dominance and as a means of territorial (Pal 2003). Although we observed females scent-defence. In fact, scents dispersed during ground marking more often during oestrus, males scent-scratching may identify the social status of the signal- marked mainly during feeding and in the absence ofler and inform intruders of territorial boundaries. sources of competition than in the presence ofTherefore, from our results, ground scratching in receptive females. Agonistic interactions amongdomestic dogs appears to be an additional visual mark male dogs were more frequent in the presence ofto reinforce the olfactory cue of urine marking and to receptive females than in the absence of sources ofintimidate opponents. competition and even more frequent in the presenceEthology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH 963
  • Scent-Marking Behaviour in Domestic Dogs S. Cafazzo, E. Natoli & P. Valsecchiof food (see Cafazzo et al. 2010). Although scent through detailed field and laboratory studies of allmarking is linked to aggressive interactions and the types of marks.rate of aggressions was high in the presence ofreceptive females, males marked more frequently in Acknowledgementsthe absence of sources of competition and in thepresence of food than in the presence of receptive We are grateful to the caretakers, Annamaria Andre-females. In the absence of sources of competition, ozzi and Mirella De Paolis, for their availability todogs marked mainly along territorial boundaries; answer all our questions about dogs and to Dr Gius-therefore, the use of scent marking during inter- eppe Cariola working at the Veterinary Hospital ofgroup competition for territorial defence might have Rome for his help and assistance during the study.a predominant role with respect to the use of scent Special thanks are due to Mark Bekoff for providingmarking during competition for receptive females. relevant literature and to Roberto Bonanni who criti-As for males, we observed a higher level of competi- cally read the drafts of this paper and improved itstion among females in the presence of food than in quality. Finally, we are thankful to the editor and thethe absence of sources of competition (see Cafazzo referees whose suggestions improved the manuscript.et al. 2010). The higher frequency of scent marking This research was partially funded by the Departmentby both males and females during feeding may be of Education, University and Research of Italianlinked to the high level of competition for food Government (PRIN 2004 to P.V.), and by Universityamong pack members. Moreover, dogs often marked of Parma (FIL 2005 to P.V.).on food after taking their meals and before leavingthe feeding site, also when sufficient food still Literature citedremained there. According to Pal (2003), it may behypothesized that scent marking may facilitate relo- Allen, J. J., Bekoff, M. & Crabtree, R. L. 1999: An observa-cation of food resources, as also observed in red tional study of coyote (Canis latrans) scent-marking andfoxes, wolves and coyotes (Henry 1977; Harrington territorialiy in Yellowstone National Park. Ethology 105,1981, 1982); although from our data, we cannot 289—302.exclude that dog scent marking during feeding in Altmann, J. 1974: Observational study of behavior:order to guard this resources instead. sampling methods. Behaviour 48, 227—265. Scent marking by females during their oestrus likely Asa, C. S., Peterson, E. K., Seal, U. S. & Mech, L. D. 1985a:functions, at least in large part, as a declaration of Deposition of anal-sac secretions by captive wolves (Canis lupus). J. Mammal. 66, 89—93.their reproductive state (Beach & Gilmore 1949; Asa, C. S., Mech, L. D. & Seal, U. S. 1985b: The use ofEisenberg & Kleiman 1972; Fox & Cohen 1977; Pal urine, faeces and anal-secretions in scent-marking by a2003); on the other hand, the lowest frequency of captive wolf (Canis lupus) pack. Anim. Behav. 33,marking behaviour displayed by males in the presence 1034—1036.of receptive females might suggest their scent marks Asa, C. S., Mech, L. D., Seal, U. S. & Plotka, E.D. 1990:are not directly associated with the courtship of The influence of social and endocrine factors on urine-females, in contrast to what reported by Pal (2003). marking by captive wolves (Canis lupus). Horm. Behav.Nevertheless, we cannot exclude that females gain 24, 497—509.information about the quality of potential mates from Barja, I. & De Miguel, F. J. 2004: Variation in stimulus,the quality of their odours released by markings, as seasonal context and response to urine marks byobserved in other species (Brown & Macdonald 1985; captive Iberian wolves (Canis lupus signatus). Acta Ethol.Rich & Hurst 1998, 1999). 7, 51—57. ´ Barja, I., De Miguel, F. J. & Barcena, F. 2004: Importance of the crossroads in faecal marking behaviour of theConclusion wolves (Canis lupus). Naturwissenschaften 91, 489—These results provide further support for the idea that 492.free-ranging dogs still retain some features of the Beach, F. A. 1974: Effects of gonadal hormones on urinarysocial organization and communication of their behavior in dogs. Physiol. Behav. 12, 1005—1013.wild ancestor, the wolf, that evolved before domesti- Beach, F. A. & Gilmore, R. W. 1949: Responses of malecation (Bonanni et al. 2010a, b; Cafazzo et al. 2010; dogs to urine from females in heat. J. Mammal. 30,Bonanni et al. 2011). They also remind us that many 391—392.of the proposed functions of marking behaviours are Bekoff, M. 1979a: Scent-marking by free-ranging domesticnot mutually exclusive, and all should be explored dogs. Biol. Behav. 4, 123—139.964 Ethology 118 (2012) 955–966 © 2012 Blackwell Verlag GmbH
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