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1 Vigilance Behavior of Pyrenean ( pyrenaica pyrenaica): Effect of Sex and Position in

2 the Herd

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4 Antoni Dalmau1), Alfred Ferret2) & Xavier Manteca2)

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6 1Irta, Finca Camps i Armet s/n, Monells, Girona, 17121, Spain.

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8 2Universitat Autònoma de Barcelona, School of Veterinary Science, Departament de Ciència i

9 dels Aliments, Bellaterra, Barcelona, 08193, Spain.

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11 Corresponding author: Antoni Dalmau. IRTA. Finca Camps i Armet s/n, 17121, Monells, Spain. Phone:

12 +34 972 63 00 52, [email protected]

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14 Vigilance behavior of Pyrenean chamois

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27 ABSTRACT

28 The Pyrenean chamois (Rupicapra pyrenaica pyrenaica) is a mountain-dwelling ungulate with an

29 extensive presence in open areas. Optimal group size results from the trade off between advantages (a

30 reduction in the risk of predation) and disadvantages (competition between members of the herd) of group

31 living. In addition, advantages and disadvantages of group living may vary depending on the position of

32 each individual within the herd. Our objective was to study the effect of central vs. peripheral position in

33 the herd on feeding and vigilance behavior in male and female Pyrenean chamois and to ascertain if a

34 group size effect existed. We used focal animal sampling and recorded social interactions when a focal

35 animal was involved. With males, vigilance rate was higher in the central part of the group than at the

36 periphery, probably due to a higher density of in the central part of the herd and a higher

37 probability of being disturbed by conspecifics. With females, vigilance rate did not differ according to

38 position in the herd. Females spent more time feeding than males, and males showed a higher frequency of

39 the vigilance behavior than females. We did not observe a clear relationship between group size and

40 vigilance behavior. The differences in vigilance behavior might be due to social interactions.

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42 Keywords: antagonistic interactions, group size, position, Pyrenean chamois, sex, vigilance

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53 INTRODUCTION

54 The Pyrenean chamois (Rupicapra pyrenaica pyrenaica) is a mountain ungulate with an extensive

55 presence in open areas, especially in the case of females with offspring (Elsner-Shack, 1985; Lovari &

56 Cosentino, 1986). Skogland (1991) argued that when foraging in open habitats, herbivores have three

57 options: restrict themselves to habitats with a low risk of predation, form groups, or spend less time in

58 some activities to increase time available for predator detection and avoidance. Researchers have

59 associated social evolution in ungulates with the change from closed to open habitats, with the need to live

60 in groups as an antipredator strategy (Jarman, 1974; Janis, 1982). One advantage of living in large groups

61 is that an individual can be less vigilant because it is more difficult for a predator to approach a large

62 group without being detected. As a result, an individual can spend more time feeding with little or no

63 decrease in overall vigilance of the group (Lima, 1995). In ungulates living in open areas, several authors

64 have described how individuals decrease vigilance and increase bite rate with increasing group size

65 (Risenhoover & Bailey, 1985; Molvar & Bowyer, 1994). However, this relationship could also be related

66 to the distances to escape terrains, as Frid (1997) described for female Dall’s sheep, in which sheep

67 became less vigilant as group size increased. However, this relationship became weaker as they got closer

68 to cliffs.

69 The position of individuals inside the group is also a factor to be considered. According to Fitzgibbon

70 (1990), central positions in a group may be safer from predators than peripheral positions. In accordance,

71 Berger and Cuningham (1988) described how, with (Bison bison), mule (

72 hemionus), bighorn sheep ( canadensis) and (Antilocapra Americana), the individuals at

73 the periphery of a large group showed increased levels of vigilance and a higher degree of variability in

74 vigilance rates than those in central locations. Therefore, the central position in a group could have

75 advantages for individuals and competition for these spots could be the consequence of it. Chamois

76 appears as a particularly interesting species for studying aspects related to social behavior, because in

77 comparison with other ungulates, some authors have described them as a primitive species. For instance,

78 they have a less developed social behavior and frequently display overt antagonistic interactions between 4

79 females (Locati & Lovari, 1991). Pyrenean chamois have been classified in different groups. The most

80 usual are females with offspring, followed by females without offspring, mixed groups (at least one male

81 and one female) and finally groups of males or solitary males (Gonzalez & Berducou, 1985). According to

82 Richard-Hansen et al. (1992), males form few social relationships, even between themselves. Furthermore,

83 their sociability decreases with age (Levet & Pepin, 1994).

84 Our objective was to study the effect of central vs. peripheral position in the herd on feeding and vigilance

85 behavior in male and female Pyrenean chamois. We observed groups of varying sizes at different times of

86 day, seasons and zones (different altitudes), and in all cases with more than 100 metres of distance to an

87 escape terrain. Our initial hypothesis was that animals in the centre and at the periphery of a group show

88 different behavioral patterns in vigilance and feeding behavior, and that a group size effect could exist.

89 We tested the hypothesis with the following predictions:

90 1) Animals at the periphery of a group are more vigilant than in the centre.

91 2) When the distance to an escape terrain is fixed, the time spent being vigilant by an individual

92 decreases when the group size increases.

93 Our study area was a hunting reserve where trophy hunting was the main form of predation on Pyrenean

94 chamois. Natural predators (such as wolves (Canis lupus)) were lacking. However, observations on the

95 same population (Dalmau et al., 2009) were in accordance with other studies on Pyrenean chamois

96 (Berducou & Bosses, 1985; Gerard & Richard-Hansen, 1992) and with the presence

97 of wolves (Pérez-Barbería & Nores, 1994). This confirms the gregariousness of female Pyrenean chamois

98 and the formation of the biggest groups in summer, when apparently kids are more vulnerable to

99 predation.

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101 MATERIALS AND METHODS

102 Study area

103 We conducted this study in the Cadí-Moixeró Nature Reserve, in Northeastern Spain (42º15'N, 1º41'E).

104 Annual rainfall ranged from 1,500 mm on the eastern side of the mountains to 700 mm on the western 5

105 lower areas, which are more protected from maritime winds. Snow was present for approximately 6

106 months in the year at the highest altitudes (from November to May). The average annual temperature

107 fluctuated from 11ºC to 0ºC. Winter temperatures fell below -20ºC, while summer temperatures reached

108 35ºC. Alpine meadows, from about 2,200 m, were covered with a great variety of graminoids, Festuca

109 airoides being the most dominant. Below 2,200 m, there were Pinus uncinata forests and areas with

110 bushes such as Juniperus nana, Rhododendron ferrugineum and Arctostaphylos uva-ursi. In the middle

111 and lower zones, Pinus sylvestris forests were the main vegetation type, with an understory predominantly

112 comprised of Buxus sempervirens (Gurri, 1997). The study area was between 1,600 and 2,500 m a.s.l. and

113 had a population of 150-200 chamois, with an estimated density of 20-25 chamois/km2. Most of the

114 Nature Reserve was utilized for chamois hunting with a harvest season that ran from September to

115 January.

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117 Data collection

118 We collected data from mixed groups (at least one adult male (> 2 years old) with females and offspring)

119 or females with offspring (FKS) groups from winter 2001 to summer 2004. We considered two animals as

120 being part of the same group if they were less than 50 m apart (Berducou & Bousses, 1985). Due to the

121 fact that human presence could be perceived as a threat by the study animals, we only studied those groups

122 where animals remained undisturbed (without the presence of humans in the area at least 30 minutes

123 before the beginning of the observations). To minimize disturbance of the focal animal, the observer used

124 15 x 30 binoculars and was over 200 m from focal animals, ensuring that animals were not able to see the

125 observer. Groups were observed in each season of the year and throughout the day. The areas selected

126 were situated in all cases at more than 100 metres from an escape terrain, defined as forest or a slope of

127 more than 45º (Dalmau et al., 2009).

128 We used continuous recording of focal individuals (Altmann, 1974). We analysed a total of 105 focal

129 animal samplings. Each animal was observed only once for 10 minutes. Chamois were not marked. To

130 minimize the potential problem of individuals contributing more than one observation to the data set 6

131 (Machlis et al., 1985), we considered our observations biologically independent only if they involved

132 individuals that we could recognize by size and position in the landscape or occurred on different

133 days. To ensure this, no more than 8 animals per group a day were observed and only one observation was

134 carried out a week. The mean SE of animals observed by group was 4.1 0.35. Furthermore, data were

135 collected from a population of 150-200 adult chamois. Given this large population size, we believe that

136 pseudoreplication occurred at an acceptably low level. We recorded observations using a portable tape

137 recorder continuously for 10 minutes and we registered feeding and vigilance activity -defined as animals

138 interrupting grazing by standing with the head raised above shoulder height (Frid, 1997). For vigilance

139 activity, two variables were considered: time spent being vigilant, and the number of times in which other

140 activities were interrupted to start being vigilant. Being vigilant was not exclusive to processing food

141 (chewing and swallowing) (Fortin et al., 2004). We ignored animals that were resting at the beginning of

142 the observation. We recorded interactions between individuals when a focal animal was involved. We

143 considered an interaction as such when the action of an individual was immediately followed by a change

144 in the behavior of another individual.

145 Further, we noted if the focal animal was located in the centre or at the periphery of the group. We defined

146 an individual to be central when it was within the area circumscribed by lines joining the outlying animals

147 in the group and as peripheral if it was on any of those lines (Alados, 1986). We rejected groups smaller

148 than 15 individuals or if group geometry was linear due to the difficulty in differentiating central and

149 peripheral individuals in these groups. We alternated central and peripheral positions during the

150 observation sessions, with a final result of 59 peripheral and 46 central individuals being observed. We

151 observed a total of 96 females (55 peripheral and 41 central) and 9 males (4 peripheral and 5 central). We

152 rejected focal animal samplings in which animals were not observed for the whole 10 minutes.

153 The 105 focal animals studied were observed in 27 different Pyrenean chamois groups. There were 125

154 individuals in the biggest group and 19 individuals in the smallest one. The mean group size was 54.9

155 2.47 with a median of 50. We observed animals from 10:00 to 18:00 and this time was divided into three 7

156 periods for their analyses, from 10:00 to 12:59, from 13:00 to 15:59 and from 16:00 to 18:00. We used the

157 4 calendar seasons in the present study.

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159 Statistical analysis

160 Data were analyzed using the GENMOD procedure (SAS; software SAS Institute Inc. 1999-2001). The

161 dependent variables were: time spent feeding, time spent vigilant, frequency of vigilance behaviour, and

162 number of interactions between individuals. The independent variables considered were: position of the

163 animal in the herd, sex, time of day, group type (FKS or mixed) and season. The duration of time showing

164 vigilant behavior was also studied independently in relation to group size by central and peripheral

165 position. We applied a negative binomial regression in all cases (Cameron and Trivedi, 1998). The

166 residual maximum likelihood was used as a method of estimation. We used the least square means of

167 fixed effects (LSMEANS) when analysis of variance indicated differences at P < 0.05. In all cases, the

168 accepted significance level was fixed at P < 0.05.

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170 RESULTS

171 Position

172 Time spent feeding and being vigilant by position, for males and females, is shown in Figure 1. No

173 differences were found between central or peripheral position for time spent feeding, but it was observed

174 that females spent more time feeding than males (χ2 = 8.09, df = 1; p = 0.0100). Animals at the periphery

175 of the group showed a lower vigilance frequency and less time spent being vigilant than animals in the

176 central position (χ2 = 8.16, df = 1; p = 0.0100 and χ2 = 8.77, df = 1; p = 0.0011, respectively). The

177 frequency of vigilance was 1.6 0.20 and 0.7 0.30 for animals in the centre and at the periphery of the

178 group, respectively. When sex was taken into account, no differences were found for females in the centre

179 or at the periphery of the group. In contrast, males at the periphery of the group showed a lower frequency

180 of vigilance than in the central position (χ2 = 9.35, df = 1; p = 0.0034). In addition, females in the centre of 8

181 the group showed a lower frequency of vigilance than males in the same position (χ2 = 9.10, df = 1; p =

182 0.0089).

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184 Interactions and group size

185 We recorded a total of 106 antagonistic interactions between individuals (1.01 0.156) for each focal

186 sampling. The number of antagonistic interactions for each focal sampling at the periphery (0.6 0.17)

187 differed (χ2 = 8.36, df = 1; p = 0.0013) from sampling periods in the central part of groups (1.3 0.26). In

188 fact, we observed that 32% of the individuals at the periphery of the group were involved in an interaction,

189 with a mean of 2.0 0.36 interactions per individual that interacted, while this figure increased to 51%

190 with the animals in the centre of the group, with a mean of 2.5 0.35 interactions per individual that

191 interacted. There were also more males involved in interactions when they were in the central positions

192 than when they were at the periphery of the group (χ2 = 9.33, df = 1; p < 0.0001). In fact, none of the

193 males observed in the periphery of the group showed any interaction with other individuals, while 80% of

194 the males observed in the centre interacted with other individuals, with a mean frequency of 2.6 0.85

195 antagonistic interactions per 10 minutes. No relationship was found between time spent being vigilant or

196 frequency of vigilance behavior for individuals in central or peripheral position and group size (Figure 2).

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198 DISCUSSION

199 Position and behavior

200 Several authors have used the head-up posture as a measure of vigilance (Alados, 1985; Frid, 1997).

201 Therefore, in accordance with our results, we can conclude that the Pyrenean chamois population studied

202 showed a lower rate of vigilance in the peripheral part of the group than in the central part (in case of

203 males) or a similar rate of vigilance in both positions (in the case of females). This is in contrast to the

204 assumption that, due to a difference in the risk of predation, animals at the periphery of a group would 9

205 have greater levels of vigilance than in the central part, as observed by Berger and Cunningham (1988) in

206 bison, mule deer, bighorn sheep and pronghorn.

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208 Males spent less time feeding than females, and in the centre of the group males showed a higher

209 frequency of vigilance behavior than females. Ruckstuhl (1998) and Ruckstuhl & Neuhaus (2000) found

210 differences between the sexes in several activities in bighorn sheep such as grazing and standing,

211 suggesting that differences in activity budgets between the sexes caused sexual segregation in this species.

212 Researchers have described a clear sexual segregation for Pyrenean chamois (Dalmau et al., 2009; Gerard

213 & Richard-Hansen, 1992), and Shank (1985) proposed that male chamois segregate from females and are

214 often solitary in order to avoid energy-consuming social interactions. Our results could be in accordance

215 with this hypothesis. However, we made no observations on male groups to compare activities, and

216 females did not show differences in time budget when they were in FKS or in mixed groups. In addition,

217 the activity budget hypothesis was rejected in desert bighorn sheep (Ovis canadensis mexicana; Mooring

218 et al., 2003) and mule deer (Bowyer & Kie, 2004), as the activity of mixed-sex and single-sex groups was

219 not different. Therefore, although in our study the differences in time budget between sexes seemed clear,

220 further investigation in mixed and single male groups is needed to study the influence of sex differences

221 on time budgets and sexual segregation in Pyrenean chamois.

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223 Interactions

224 Researchers have defined social behavior of chamois as “primitive”, as they use overt aggressive

225 interactions more frequently than other ungulates (such as an attack in which the subject attempts to harm)

226 rather than ritualised forms of aggression (such as the use of combat rules that allows animals to reduce

227 the contact of horns with soft tissues) (Locati & Lovari, 1991). If this is the case, potentially aggressive

228 conspecifics and not predators could be responsible for the vigilance behavior of chamois, with females

229 showing similar rates of vigilance in the centre as at the periphery of the group and males with higher rates

230 in the centre. We observed that animals in the centre of the group interacted with a higher frequency than 10

231 those at the periphery, especially in the case of males, where a predominance of animals to interact with

232 other individuals in the centre was observed. This difference between males located in the centre or at the

233 periphery of the group could be caused by a higher density of individuals in the central part of the group

234 (pers. observation). Although Locatti & Lovari (1991) described a clear social hierarchy in female

235 chamois, it is possible that the social hierarchy may be more pronounced in males. As a consequence, as

236 male animals in the centre have a greater likelihood of being in proximity to subordinate or dominant

237 individuals, the probability of being directly or indirectly disturbed by different activities of conspecifics

238 increases. Therefore, the lower frequency of vigilance at the peripheral position observed in males could

239 also be caused by a lower probability of being directly or indirectly disturbed by the presence of other

240 individuals (Beauchamp, 2001; Blumstein et al., 2001).

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242 Group size

243 Several authors have reported a decrease in vigilance rate when the group size increases (reviewed in

244 Elgar, 1989; Lima & Dill, 1990; Beauchamp, 2008). Nevertheless, we observed no clear differences

245 between focal animals in groups from 19 to 125 individuals. According to Frid (1997), female Dall’s

246 sheep (Ovis dalli dalli) became less vigilant as the group size increased, but the magnitude of this

247 relationship became weaker as sheep got closer to cliffs. Therefore, different predation risk factors could

248 also have an interactive effect on vigilance. In the present study, due to the areas where we carried out the

249 study having similar distances to escape terrain (more than 100 m to cliffs or forest), we thought we would

250 be able to see the effect of group size on vigilance clearly. However, other factors, such as social behavior,

251 could have an interactive effect on vigilance in species such as Pyrenean chamois. Richard & Pepin (1990)

252 observed that distance between females of Pyrenean chamois decreased as group size increased. In this

253 case, the probability of being indirectly affected by an interaction would increase with group size, showing

254 the difficulty in observing clear differences in vigilance behavior. Although no distances were measured in

255 the present study, the visual mean distance between individuals ranged from 2 to 7 meters. On the other

256 hand, most relationships between vigilance and group size taper off in groups larger than 5-10 individuals 11

257 (Beauchamp, 2008). Risenhoover and Baley (1985) stated that mountain goats (Oreamnos americanus) in

258 groups of over 10-12 individuals had no influence on individual vigilance time. In our study, the smallest

259 group observed consisted of 19 individuals. Therefore, a threshold for detecting measurable changes of

260 vigilance in relation to group size may occur, but in groups smaller than we recorded. Future

261 investigations should examine smaller sizes of Pyrenean chamois groups in addition to the different time

262 budgets in males and females in mixed or single sex groups and distances between animals when they are

263 in the centre or at the periphery of the group. Further studies are also needed on species close to chamois,

264 such as (Capricornis spp.), (Naemorhedus spp.) and mountain goats.

265 In conclusion, we observed that individuals at the periphery of Pyrenean chamois groups showed a lower

266 frequency of vigilance than those in the centre, and this could be due to a higher probability of interactions

267 between conspecifics in the centre of the group in comparison to the periphery. In addition, we observed

268 differences in time budget between sexes, although we failed to find a clear effect of group size on

269 vigilance behavior.

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271

272 ACKNOWLEDGEMENTS

273

274 This study is part of a “Comisión Interministerial de Ciencia y Tecnología” project (AGF99-0763-C02-02)

275 and was funded by a grant (2001FI-00449) to A. Dalmau from the “Departament d'Universitats, Recerca i

276 Societat de la Informació, Generalitat de Catalunya”. We thank the staff of the Cadí-Moixeró Nature

277 Reserve and the Cadí Hunting Reserve for their help and collaboration.

278

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360 Figure 1. Time spent (seconds) by male (9) and female (96) Pyrenean chamois feeding and being vigilant

361 (mean SE) in relation to the position in the group.

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363 Figure 2. Time spent (seconds) in vigilance behavior (mean SE) by Pyrenean chamois in relation to

364 group size when they are in central and peripheral position.

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1a) Feeding time 600

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0 Central Peripheral Central Peripheral -50 Females Males 379 380

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2a) Central position

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19 23 30 46 58 85 40 52 68 89 118 Group size

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