The Effects of Population Density and Sociality on Scent Marking in the Yellow Mongoose

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Le Roux, A; Cherry, M I; Manser, M B (2008). The effects of population density and sociality on scent marking in the yellow mongoose. Journal of Zoology, 275(1):33-40. Postprint available at: http://www.zora.uzh.ch University of Zurich Posted at the Zurich Open Repository and Archive, University of Zurich. Zurich Open Repository and Archive http://www.zora.uzh.ch Originally published at: Journal of Zoology 2008, 275(1):33-40.

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Year: 2008

The effects of population density and sociality on scent marking in the yellow mongoose

Le Roux, A; Cherry, M I; Manser, M B

Posted at the Zurich Open Repository and Archive, University of Zurich. http://www.zora.uzh.ch

Originally published at: Journal of Zoology 2008, 275(1):33-40. The effects of population density and sociality on scent marking in the yellow mongoose

Abstract

We investigated scent marking behaviour in the yellow mongoose Cynictis penicillata, focusing on a low-density population where all offspring dispersed upon reaching sexual maturity. Dominant males appeared to be the main territory defenders and demarcators, with offspring foraging and marking only near the territory cores. The cheek-marking rates of dominant males increased during the breeding season and may have been involved in olfactory mate guarding. We compared our low-density population with a high-density population displaying natal philopatry. The two populations differed markedly in terms of individual contributions to territorial marking, as subordinate group members in the low-density population performed almost no territorial marking or defence, but were the primary scent-markers and territory defenders in the high-density population. We discuss scent-marking distinctions between populations in the context of ecological and social differences. 1 Journal of Zoology (2008), 275: 33-40 2 doi: 10.1111/j.1469-7998.2007.00404.x 3 4 5 The effects of population density and sociality on scent marking in the yellow 6 mongoose 7 8 Aliza Le Roux1, Michael I. Cherry1, Marta B. Manser2 9 10 1. Department of Botany and Zoology, University of Stellenbosch, South Africa 11 2. Animal Behaviour, Department of Zoology, University of Zurich 12

14 We investigated scent marking behaviour in the yellow mongoose Cynictis penicillata,

15 focusing on a low-density population where all offspring dispersed upon reaching sexual

16 maturity. Dominant males appeared to be the main territory defenders and demarcators,

17 with offspring foraging and marking only near the territory cores. The cheek-marking

18 rates of dominant males increased during the breeding season and may have been

19 involved in olfactory mate guarding. We compared our low-density population with a

20 high-density population displaying natal philopatry. The two populations differed

21 markedly in terms of individual contributions to territorial marking, as subordinate group

22 members in the low-density population performed almost no territorial marking or

23 defence, but were the primary scent-markers and territory defenders in the high-density

24 population. We discuss scent-marking distinctions between populations in the context of

25 ecological and social differences.

27 Keywords: mate guarding, population density, scent marking, territory, yellow

28 mongoose

1 1 Introduction

3 Scent-marking forms an integral part of the communicative repertoire of many

4 mammals (Eisenberg & Kleiman, 1974; Gorman & Trowbridge, 1989). Marking rates

5 typically increase around the onset of puberty (e.g. Woodmansee et al., 1991), and many

6 mammals are able to discriminate between individuals' scents (Swaisgood, Lindburg &

7 Zhou, 1999; Mendl, Randle & Pope, 2002; Mateo, 2006). In solitary animals, age,

8 gender and territory ownership appear to be the main determinants of scent-marking rates

9 (e.g. in honey badgers Mellivora capensis Begg, du Toit & Mills, 2003), whereas social

10 mammals are, additionally, affected by position in the dominance hierarchy, relative

11 contributions to territory defence, and the frequency of aggressive interactions (e.g.

12 coyotes Canis latrans Gese & Ruff, 1997). Although the dominant male in a group is

13 usually the primary scent marker, subordinate adult group members often contribute

14 substantially to marking and defence (Gese & Ruff 1997; Jordan 2007). Additionally,

15 males may overmark females’ scent, as a form of olfactory mate guarding (e.g. Brashares

16 & Arcese, 1999) or other males’ scents, indicating intrasexual dominance (e.g. Rich &

17 Hurst, 1999). Within a social group, allomarking – marking other individuals – often

18 occurs, probably to maintain a ‘familiar’ group smell and tolerance between group

19 members (e.g. in European badgers Meles meles Buesching, Stopka & MacDonald,

20 2003).

21 Olfactory communication is involved in a variety of functions as diverse as dominance

22 advertisement (e.g. in guinea pigs, Carla porcellus, Drickamer & Martan, 1992) and the

23 marking of food caches (e.g. in in the short-tailed shrew, Blarina brevicauda, Robinson

2 1 & Brodie, 1982). However, in solitary as well as social mammals, scent marks are usually

2 implicated in two primary functions, i.e. territory demarcation and sexual advertisement.

3 Territory holders typically mark and actively defend their home ranges (Ralls, 1971).

4 Scent marks serve as information exchange points (Eisenberg & Kleiman, 1974),

5 containing, inter alia, information on the ability of an owner to defend its territory (Rich

6 & Hurst, 1999). During the breeding season, this information may include indications of

7 oestrus in females (e.g. in kangaroo rats, Dipodomys spectabilis, Randall, 1986), and

8 males may also increase signaling during this season as a form of sexual advertisement

9 (Kappeler, 1998). In some species, the male may attempt to mask the female’s sexual

10 advertisement by overmarking her scent marks, thereby performing mate guarding (e.g.

11 Roberts & Dunbar, 2000; Lewis, 2005).

13 As there may be great intraspecific variation in territory size, group composition

14 and degree of sociality in vertebrates (Lott, 1991), scent marking behaviour within a

15 species is potentially variable. For example, the scent marking strategies of hyenas can be

16 strongly affected by territory size. Whereas marks were concentrated in the territory core

17 of large territories (the ‘hinterland’ marking strategy), they were concentrated along the

18 borders (border marking strategy) of smaller territories (Gorman & Mills, 1984). These

19 distinct strategies are seen as the most economical means of marking a territory, ensuring

20 that intruders will come across a scent mark before reaching the protected territory core.

21 However, relatively few studies have performed intraspecific comparisons of scent

22 marking behaviour between populations with different territory sizes, and in particular we

3 1 found no intraspecific comparisons between populations that show different social

2 structures.

4 The yellow mongoose Cynictis penicillata dens together with conspecifics in

5 groups ranging between two and 13 individuals in size, but individuals typically forage

6 alone or in pairs (Rasa et al., 1992; Cavallini, 1993). Females are polyestrous,

7 occasionally giving birth to two litters per season, and young typically disperse during

8 spring (Rasa et al., 1992). Similar to many mammals (Ralls, 1971; Gorman &

9 Trowbridge, 1989), the yellow mongoose is territorial and uses various forms of marking

10 in its territory (Earlé, 1981; Wenhold & Rasa, 1994). Yellow mongoose mark vegetation

11 and other prominent objects using anal marks, cheek marks (‘cheek wipes’) and body

12 rubs (‘sidewipes’) (after Earlé, 1981; Wenhold & Rasa, 1994). Body rubbing appears to

13 be a form of self-anointing with odours (including own scent marks) from the

14 environment, rather than the actual deposition of scent, as yellow mongooses lack scent

15 glands on their flanks (Pocock, 1916). Urination and defecation are considered to be

16 secondary forms of marking (e.g. Wenhold & Rasa, 1994), and we have not included the

17 analysis of defecation and urination in this study as there was no evidence of a primary

18 communicative function (le Roux 2007).

20 Scent marking in the yellow mongoose has been described in varying degrees of

21 detail in populations of intermediate to high densities [23 – 26 individuals per km2

22 (Balmforth, 2004) to 133 – 200 individuals per km2 (Earlé, 1981; Wenhold & Rasa,

23 1994)]. Of these studies, only Wenhold and Rasa’s (1994) quantified the marking

4 1 behaviour of a group of mongooses (n = 13 group members) and tested specific

2 hypotheses. They presented individuals' marking rates as averages over nine months

3 (April – December) (Wenhold & Rasa, 1994). Whereas Wenhold and Rasa (1994)

4 showed that subordinate adults were the primary territory defenders and markers, Earlé

5 (1981) found in the same Big Island (BI) population in the Vaal Dam (26º52’S, 28

6 º11’E), South Africa, that the dominant males played the main role in this respect.

8 We focused our research on a low-density population of yellow mongooses at the

9 Kuruman River Reserve (KRR) in South Africa. The mated pair constituted the only

10 adult members of each group and offspring were not involved in raising new litters but

11 dispersed on reaching sexual maturity. Similar to other low-density populations

12 (Cavallini, 1993), aggression between family members and neighbours was low. In

13 contrast, groups in the BI population consisted of the mated pair, recent offspring and

14 related adults that cooperated in the rearing of young and aggressive territory defence

15 (Earlé, 1981; Wenhold, 1990; Wenhold & Rasa, 1994).

17 Here we describe the scent marking behaviour of the KRR population and

18 compare it with the scent marking behaviour of the BI population (Wenhold & Rasa,

19 1994). We predicted that, as in many mammals (Ralls, 1971), the dominant male would

20 be the main territory defender in terms of scent marking and active defence. As territory

21 sizes were much larger in the KRR than the BI population, the KRR population may use a

22 hinterland-marking strategy. We did not expect the adult females or offspring to show

23 strongly territorial behaviour. We predicted that offspring would show no evidence of

5 1 sexual advertisement, as they rarely encountered potential mates before dispersal, and did

2 not stay in the natal territory as adults.

5 Materials and Methods

7 We studied a habituated population of wild yellow mongooses at the Kuruman River

8 Reserve (28°58’S, 21°49’E), South Africa (le Roux, Cherry & Manser, in press). The

9 study area included the dry Kuruman River bed and surrounding dune areas, primarily

10 covered in low shrubs, Acacia trees and grasses (Clutton-Brock et al., 1998). The field

11 site had a large number of bolt-holes and potential sleeping burrows (Manser & Bell,

12 2004) maintained and used by yellow mongooses, meerkats Suricata suricatta and Cape

13 ground squirrels Xerus inauris. During the study period from February 2004 to March

14 2006 we collected data for six adult (dominant) males, 10 of their offspring (four male,

15 six female) and one adult (dominant) female. Offspring were classified as pups (0 – 3

16 months), juveniles (3 – 6 months) and sub-adults (up to 12 months), and adults were older

17 than one year of age. In each group one adult animal was radio collared with collars from

18 Sirtrack© (Havelock North, New Zealand), and non-collared individuals were identified

19 through non-permanent, renewable dye-marks on their fur (for more details, see le Roux

20 et al., in press). We were able to follow all these habituated animals at a distance of less

21 <5 m. We obtained the following number of sessions for individuals: adult males: 30 +

22 2.9 (mean + SE); offspring: 19 + 6.7 and adult female: 14.

6 1 During active foraging periods, we recorded the position of focal animals at 10-

2 min intervals and the location of all scent marks, using all-occurrence sampling, on an

3 eTrex Garmin ® (Olathe, KS, USA) global positioning system (GPS), to an accuracy of

4 <10 m. Observational data were collected using a handheld computer (Psion organiser II

5 model LZ64, Bourne End, UK). Each scent marking act was typically preceded by

6 sniffing the object to be marked. We described the object (or individual) marked and

7 whether or not it was within 2m of a bolt-hole or sleeping burrow. During morning

8 observation sessions we noted all marking acts from the time of emergence, but hourly

9 marking rates were determined using only data from active foraging periods away from

10 the sleeping burrow in the morning and afternoon. Some marking occurred at the sleeping

11 burrow before foraging trips, and these data were included in the ArcView GIS data

12 which we used to determine scent-mark densities.

14 Spatial data were analysed using ArcView GIS and its animal movements

15 extension (Hooge, Eichenlaub & Solomon, 1999). Using all coordinates recorded at t10-

16 minute intervals, we determined home-range sizes as the 95% kernel, with least-squares

17 cross-validation smoothing factors (Worton, 1989; Seaman et al., 1999). Although

18 autocorrelation between successive data points may reduce the accuracy of home range

19 estimations (Swihart & Slade, 1985), we used a data collection protocol that allowed us

20 to retain all these data in our calculations. The effect of autocorrelation is typically

21 addressed by subsampling the spatial dataset (e.g. Jordan, Cherry & Manser, 2007).

22 However, de Solla, Bonduriansky & Brooks (1999) demonstrated that using the entire

23 dataset could improve home range estimations substantially, compared to sub-sampling,

7 1 if data were collected with a constant sampling interval over an extended period of time.

2 Our regular data collection spanning several months satisfied these recommendations and

3 the number of GPS points per individual (adult males: 310 + 64.3 (mean + SD);

4 offspring: 115 + 60.2; dominant female: 80 points) exceeded the recommended minimum

5 of 50 points for home range estimations (Seaman et al., 1999).

9 65% (territory core) # ## # # # # # 85% (kernel border) # # ## 95% (territory border) ## # # # # # # 10 # # # # # # # # # ## # # ## # # # # 11 # # # # ## ### # # # # # # #### # ## # ### # # # # # # # # # 12 # ## # ### # ### # # ## # # # ## # ###### ## # # ##### # # # # # ############ # # # # ########### # # ## ### # # # ## # # # # # # # # # ### # # # # # ### # # # # 13 # # # ## # #### ## # ### ## ################ # # # ## ############# # # # # # ### #### # # # ##### ######## # # # # # # # ################### # # # ## ### # # # ## # ### ###### # ### # ########## # ### # ##### ## # # # ###### ## ## ############### ## ############## # ######### 14 # ######### ########### ## ### # # ## ## ####### # # ######### # ############# # 15 # Overlap zone between neighbouring territories

N 16 W E

0.7 0 0.7 1.4 Kilometers 17 S

19 Fig. 1. The main subdivisions of territory areas are shown for dominant male CM03. 20 Anal marks indicated by filled circles. The density of anal marks appears higher in the 21 area where neighbouring territories overlapped. 22

24 We defined adult males’ home ranges as territories, as these areas were defended

25 against intruders from other groups (Maher & Lott, 1995). The undefended areas

8 1 occupied by offspring and the dominant female were termed home ranges, as we never

2 observed intruder defence in these locations. We defined core and border areas (Fig. 1)

3 following Jordan et al.s’ (2007) categorization of meerkat territory areas at the same

4 study site. The area between the 85% and 95% kernel was the ‘territory border’ and the

5 65% kernel was the ‘territory core.’ The area between the territory border and core was

6 the ‘kernel border.’ Densities of scent marks were calculated for each of these areas and

7 also for the whole area inside the border (i.e. the entire 85% kernel).

9 Owing to small sample sizes, we used mainly nonparametric statistical techniques

10 (Siegel & Castellan, 1988), in the programme R for Microsoft Windows, version 2.3.1 (R

11 Development Core Team, 2006). When t-tests were appropriate, we used unequal

12 variance t-tests of the ranked data (Ruxton, 2006). Results are all presented as means +

13 SE unless indicated otherwise. During the summer season we could not record all

14 activities, for individuals were usually highly active after sunset and impossible to follow

15 even with night vision goggles. In summer, adults were primarily babysitting at the

16 sleeping burrow during daylight hours and started foraging late in the afternoon, not

17 returning from foraging and, presumably, scent marking, until after dark. Out of 201

18 summer observation sessions, mainly focused on habituation, we obtained eight ad

19 libitum foraging sessions in total, for three adult males. This number of sessions was too

20 small to compare statistically with the six to 14 sessions per adult male (n = 6) obtained

21 for each of the other seasons.

9 1 Results

3 Home range sizes and scent mark locations

4 Yellow mongoose densities in the KRR population varied between four (non-breeding

5 season) and 14 (breeding season) individuals per km2. Groups consisted of 3.7 + 0.4

6 members (range: 2-7), including offspring. Dominant male territories were 0.76 + 0.21

7 km2 in size (n = 6), ranging between 0.17 and 1.53 km2, with a perimeter length of 5.49 +

8 0.96 km. These territory sizes remained constant across seasons. Each male’s territory

9 completely encompassed the home ranges of his offspring, which were far smaller at 0.18

10 + 0.20 km2 (n = 10; range: 0.11 - 0.28 km2) with a 2.34 + 0.19 km perimeter length. The

11 only dominant female that we followed had a home range size of 0.20 km2 (perimeter

12 length: 3.05 km) near the centre of her mate’s territory, which was 1.11 km2 in size.

13 Dispersing animals established new territories 2.5 + 0.4 km (n = 6) from their natal

14 territories.

16 Territorial defence

17 Only dominant males were observed to patrol territory borders, whereas their offspring

18 remained within a smaller area inside the males’ territories, marking at low rates (Table

19 1). The scent marking rates of dominant males were significantly higher than those of

20 their offspring (unequal variance t-test: anal marks: t15.9 = 6.97, P < 0.001; cheek marks:

21 t12.0 = 4.33, P < 0.001; body rubs: t10.0 = 5.60, P < 0.001).

10 1 Table 1. Average scent marking rates (marks per hour, mean + SE) for the dominant 2 males (n = 6), offspring (n = 10), and one dominant female habituated at the Kuruman 3 River Reserve. Significant differences were found between dominant males and offspring 4 in terms of glandular marking rates. 5 Identity Anal mark Cheek mark Body rub Dominant male 9.11 + 2.01 4.80 + 1.13 1.89 + 0.47 Offspring 1.08 + 0.22 0.80 + 0.56 0.28 + 0.14 Adult female 1.02 + 0.60 0.55 + 0.28 0.04 + 0.04 6

7 Some differences were evident in the density of dominant males’ scent marks

8 throughout their territories (Table 2). Anal marks in the territory core were denser than in

9 the territory border as well as in the kernel border, but denser on the territory border than

10 in the kernel border (Kruskal-Wallis Anova: χ²2 = 12.43, P = 0.002; post hoc tests: P <

11 0.05). There were no differences between these areas in cheek mark density (χ²2 = 4.53, P

12 = 0.104) or ‘body rub’ density (χ²2 = 4.10, P = 0.129).

14 Table 2. Dominant male (n = 6) scent mark densities, presented as number of marks per 15 km2 (mean + SE). Different parts of territories are based on kernel methods (elaborated 16 on in text and Fig. 1). 17 Territory core Kernel border Territory border Type of mark 85% kernel (65% kernel) (65 - 85%) (>85% kernel) Anal mark 1391.1 + 784.4 145.2 + 22.3 640.6 + 284.4 258.8 + 37.9 Cheek mark 881.0 + 576.2 142.1 + 97.5 432.0 + 270.6 162.0 + 63.0 Body rub 213.3 + 91.1 24.1 + 15.1 103.7 + 44.3 37.5 + 12.3 18

20 Sexual advertisement: seasonal changes and overmarking

21 There was some seasonal variation in the hourly marking rate of adult males (Fig. 2), but

22 offspring’s marking rates did not vary across seasons (Fig. 3). Dominant males’ cheek-

23 marking rates were higher during ( spring (pre-breeding season) than autumn (post-

24 breeding season; Kruskal-Wallis Anova: χ²2 = 8, P = 0.018), and body-rubbing rates

11 1 differed in the same respect (χ²2 = 6.26, P = 0.044). Anal-marking rate did not differ

2 between seasons (χ²2 = 3.14, P = 0.208). None of the offspring’s marking rates (Fig. 3)

3 were affected by month of the year or age.

autumn 7 * * winter spring 6

Hourly marking rate marking Hourly 2

1 ▲ ▲ ▲ 0 ▲ anal mark cheek mark body rub Type of mark 5 6 Fig. 2. Dominant male scent marking rates as affected by season (* P < 0.05). Summer 7 marking rates (for n = 3 males) were 7.1 + 2.0 per hour for anal marks, 1.9 + 0.7 for 8 cheek marks, and 2.5 + 0.8 for body rubs. Filled triangles represent average marking rates 9 of dominant males in a high density population, calculated across nine months, which 10 excluded the summer season (after Wenhold & Rasa, 1994). 11 12 13 No overmarking was observed between adults and offspring, even though group

14 members were observed foraging together. However, the area where the dominant female

15 deposited most of her cheek marks was a location where her mate concentrated a high

16 number of cheek marks (15 marks in a 10m radius). Her anal marks were in an area

17 where the male also marked anally, but the closest male anal mark was 20m from her

18 marks.

12 1

1.6 pup 1.4 juvenile subadult 1.2

0.8

0.6

Hourly marking rate marking Hourly 0.4 ▲ ▲▲ 0.2

0 anal mark cheek mark body rub Type of mark 2 3 Fig. 3. Offspring scent marking rate as a function of age class. Scent marking rates were 4 not affected by age or season. Filled triangles are average marking rates for ‘juvenile’ (< 5 1 year old) yellow mongooses in a high density population, calculated across nine 6 months, which excluded the summer season (after Wenhold & Rasa, 1994). 7

9 When offspring dispersed (spring season), dominant-male marking rates increased

10 (Fig. 2). However, this increase was not focused specifically in the territory core, where

11 offspring used to mark. Although a high proportion of marks were made in the territory

12 core (Fig. 4), the distribution of marks did not vary across seasons for anal marks

13 (Friedman Anova: χ²2 = 0.4, P = 0.819) or body rubs (χ²2 = 0.4, P = 0.819). Cheek-mark

14 distribution varied, however (χ²2 = 7.6, P = 0.022), as winter and autumn proportions

15 were significantly higher than spring proportions (post hoc tests: P < 0.05). Relatively

16 more cheek marks were therefore located outside the territory core during spring.

13 0.9 autumn * winter 0.8 spring

0.7

0.6

0.5

0.4 Proportion of marks in core Proportion of marks 0.3

0.2 anal mark cheek mark body rub Type of mark 1

2 Fig. 4. The proportion of dominant male scent marks that were made inside territory 3 cores, according to season. The proportion of cheek marks inside the territory core was 4 significantly smaller in spring than in winter and autumn. (* P < 0.05) 5

7 Discussion

9 Territoriality

10 In the low-density KRR population, only the dominant males were observed to defend

11 and mark their territories, in contrast to the high-density BI population, where especially

12 subordinate individuals maintained the territory borders (Wenhold & Rasa, 1994). In

13 obligate social carnivores, the dominant male is usually the main scent marker, but group

14 members often contribute substantially to territory defence and scent marking, for

15 example in Ethiopian wolves Canis simensis (Sillero-Zubiri & MacDonald, 1998), and

16 meerkats (Jordan et al., 2007). Group defence appears to occur together with other

17 cooperative behaviours, such as the communal rearing of young (Sillero-Zubiri &

14 1 Gottelli, 1994; Clutton-Brock et al. 2001). Unlike the KRR population, subordinate

2 mongooses in the BI population not only share the mated pair’s territory, but contribute to

3 the rearing of their subsequent litters (Wenhold, 1990; Balmforth, 2004), which may

4 explain why their pattern of territory defence resembles that of obligate social carnivores.

6 Dominant males in the low-density population had high marking rates compared

7 to individuals in the high-density population, but group’ cumulative marking rates were

8 similar between populations (see Wenhold & Rasa, 1994). Territories in the BI

9 population were five times smaller than those at KRR, implying a five times greater

10 density of scent marks in BI territories. This probably allowed dominant males in the BI

11 population to use the border-marking strategy in territory defence (sensu Gorman &

12 Mills, 1984). The hinterland-marking strategy (Gorman & Mills, 1984) used by dominant

13 males in the large KRR territories is used by a number of carnivores such as the solitary

14 honey badgers (Begg et al., 2003), and social meerkats (Jordan et al., 2007). This strategy

15 reflects the need to protect core resources, such as sleeping burrows and feeding sites, in

16 large territories where intruders may not come across border marks while traveling

17 through an area (Gorman & Mills, 1984; Jordan et al., 2007).

19 As with other herpestids (Rasa, 1973; Baker, 1982; Baker, 1988), anal marking

20 was the predominant form of territorial marking in yellow mongooses. Anal gland

21 secretions in the yellow mongoose (Apps, Viljoen & Taylor, 1989) and other herpestids

22 function as long-lasting markers carrying information on individual identity (Rasa, 1973;

23 Hefetz, Ben-Yaacov & Yom-Tov, 1984; Decker, Ringelberg & White, 1992). Dominant

15 1 males in the KRR population increased body-rubbing rates during spring, when intruder

2 pressure increased as dispersers attempt to find new territories. Males also had high anal

3 marking and body rubbing rates after dispersal, while establishing new territories. The

4 combination of anal marking, border latrines (le Roux, 2007) and body rubbing could

5 function as a scent-matching system of territory defence (Gosling, 1982), whereby

6 intruders match the scent of territorial marks with the scent of the owner when

7 encountering this individual. The scent-matching system is found in various mammals,

8 including beavers Castor canadensis (Sun & Müller-Schwarze, 1998), and snow voles

9 Chionomys nivalis (Luque-Larena, Lou Pez & Gosaulbez, 2001). This facilitates

10 recognition of ownership, which in turn reduces the aggression of agonistic interactions,

11 to the mutual advantage of intruder and owner (Gosling & McKay, 1990).

13 Aggression between familiar neighbours appeared to be low in the KRR

14 population. During more than 100h of observing two habituated neighbours, we observed

15 only five encounters, which were brief chases and fighting (<2 min in duration) that did

16 not appear to draw blood. Adult males had almost no visible scars, and territory

17 expansion into neighbouring territories was never observed. Preliminary experiments

18 with fresh faeces from foreign (non-neighbouring) males (A. le Roux, unpublished data)

19 indicated that foreign males’ latrines always provoked an immediate countermarking

20 reaction. Latrines of familiar neighbours typically evoke only sniffing (le Roux, 2007).

21 Such a tolerance of familiar neighbours, with higher aggression against unfamiliar

22 intruders, is known as the ‘dear enemy’ effect (Fisher, 1954), and occurs in a variety of

23 territorial species (reviewed in Temeles, 1994). This contrasts with the ‘nasty neighbours’

16 1 effect found in, for example, banded mongooses, Mungos mungo (Müller & Manser,

2 2007), that treat neighbours more aggressively than transients because groups readily

3 expand into neighbouring territories. In high-density populations of yellow mongooses,

4 intergroup encounters appeared to be more violent and frequent (Wenhold & Rasa, 1994;

5 Balmforth, 2004) and scent-mark densities were much higher than the KRR population.

6 This may be ascribed to the definite risk of territory reduction in areas with high territory

7 saturation.

9 Sexual advertisement?

10 In the low-density population there was no support for Wenhold & Rasa’s (1994)

11 hypothesis that scent marking is used as sexual advertisement by subordinate individuals.

12 Whereas mongooses in the BI population found mating opportunities in neighbouring

13 groups (Wenhold & Rasa, 1994), sexually mature offspring in the KRR population

14 dispersed to new territories beyond neighbouring groups. The marks of offspring in the

15 low-density population may, however, have functioned in intra-group communication.

16 Allo-marking, displayed by high-density yellow mongoose populations (Earlé, 1981) and

17 social mongooses such as the dwarf mongoose Helogale undulata (Rasa, 1973), was

18 extremely rare in the KRR population. In the absence of such a ‘group odour’ (sensu

19 Sheppard & Yoshida, 1971) familiarity could be established through scent marks they

20 encountered on the substrate. In other group-living mammals, such as the collared

21 lemming Dicrostonyx groenlandicus (Huck & Banks, 1979), the familiarity of an

22 individual’s scent has been shown to reduce aggression from the dominant male. The

23 scent marks of KRR offspring may therefore have facilitated tolerance by the dominant

17 1 male during the time they shared a home range. In addition, offspring scent marks could

2 have augmented dominant male marks around key resource areas, thereby contributing to

3 territorial defence (Revilla & Palomares, 2002). However, dominant males did not

4 ‘compensate’ for the absence of these marks once offspring dispersed.

6 Dominant males’ cheek marking rates increased when offspring dispersed, but

7 this increase was primarily outside the territory core, and could have been related to

8 higher intruder pressure during this season, rather than the decrease in number of group

9 members. In water mongooses, Atilax paludinosus (Baker, 1988), and dwarf mongooses

10 (Rasa, 1973), cheek marks appear to carry a short-lived threatening message. During

11 fights between males, scent from cheek glands is probably exchanged, as yellow

12 mongooses attack the face and neck of their rivals (ALR, personal observation). Yellow

13 mongoose cheek marks were concentrated around bolt-holes, which are noticeable

14 landmarks regularly inspected by other yellow mongooses, especially adult males.

15 Limited data suggested that a dominant male over-marked the area that his mate cheek

16 marked. It is therefore probable that cheek marks had a function in mate guarding

17 (Roberts & Dunbar, 2000; Lewis, 2005), although the possibility of male sexual

18 advertisement could not be excluded.

20 Conclusion

21 The scent-marking patterns of yellow mongooses were affected by the long-term group

22 composition. In temporary groups where the mated pair constituted the only long term

23 residents in a territory, marking behaviour resembled that of solitary territorial mammals,

18 1 with only the dominant male appearing to defend and mark his territory. Natal philopatry

2 in high-density populations may have implications for increased facultative cooperation

3 that includes cooperation in scent marking and inter-group contests. Larger groups in

4 high-density populations interact with neighbours more frequently, causing more conflict

5 but also opportunities for mating and sexual advertisement between neighbours. Although

6 none of these results are unexpected, considering the characteristics of the different

7 populations, this may be the first mammalian study to show how individuals’ scent

8 marking patterns can be affected by intra-specific fluctuations in social structure rather

9 than just group/ territory size.

12 Acknowledgements

13 We thank Tim Clutton-Brock, University of Cambridge, for allowing us to use facilities

14 at the KRR. Thanks are also due to Helen Eaton and Samuel Guiton for their help in data

15 collection and Gilberto Passinelli for advice concerning spatial analyses. We are grateful

16 for the comments of anonymous reviewers, which improved earlier drafts of this

17 manuscript. This study was partially funded by grants to A.L.R. from the Roche Research

18 Foundation (Switzerland) and the Harry Crossley Foundation, a grant to M.I.C. from the

19 National Research Foundation (South Africa), and the Swiss National Foundation to

20 M.B.M. (SNF Förderprofessur).

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