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1 Vigilance Behavior of Pyrenean Chamois (Rupicapra 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 Animal 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
15 Words: 4281
16 Figures: 2
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26 2
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 animals 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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52 3
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 bison), mule deer (Odocoileus
72 hemionus), bighorn sheep (Ovis canadensis) and pronghorn (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 Cantabrian chamois 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 horn 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.
158
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.
169
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).
197
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.
207
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 serows (Capricornis spp.), gorals (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.
270
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
279 REFERENCES
280
281 Alados CL, 1985. An analysis of vigilance in the Spanish ibex (Capra pyrenaica). Zeitschrift fur
282 Tierpsychologie 68:58-64. 12
283 Alados CL, 1986. Spatial structure in groups of Spanish ibex (Capra pyrenaica). Biology of Behaviour
284 11:176-185.
285 Altmann J, 1974. Observational study of behavior: sampling methods. Behaviour 49:227-267.
286 Beauchamp G, 2001. Should vigilance always decrease with group size? Behavioural Ecology and
287 Sociobiology 51:47-52.
288 Beauchamp G, 2008. What is the magnitude of the group-size effect on vigilance? Behavioral Ecology
289 19:1361-1368.
290 Berducou C, Bousses P, 1985. Social grouping patterns of a dense population of chamois in the western
291 pyrenees national Park, France. In: Lovari S, ed. The biology and management of mountain
292 ungulates. London: Croom Helm, 166-175.
293 Berger J, Cunningham C, 1988. Size-related effects on search times in North American grassland female
294 ungulates. Ecology 69:177-183.
295 Blumstein, DT, Daniel, JC, Evans, CS, 2001. Yellow-footed rock-wallaby group size effects reflect a
296 trade-off. Ethology 107:655-664.
297 Bowyer RT, Kie JG, 2004. Effects of foraging activity on sexual segregation in mule deer. Journal of
298 Mammalogy 85:498-504.
299 Cameron AC, Trivedi PK, 1998. Regression analysis of count data. Cambridge: Cambridge University
300 Press.
301 Dalmau A, Ferret A, Ruiz de la Torre JL, Manteca X, 2009. Habitat selection ina a Pyrenan chamois
302 population (Rupicapra pirenaica pirenaica). Journal of Mountain Ecology (in press).
303 Elgar MA, 1989. Predator vigilance and group size in mammals and birds: a critical review of the
304 empirical evidences. Biological Review 64:13-33.
305 Elsner-Shack I-Von, 1985. What is Good Chamois Habitat? In: Lovari S, ed. The biology and
306 management of mountain ungulates. London: Croom Helm, 71-76.
307 Fitzgibbon CD, 1990. Why do hunting cheetahs prefer male gazelles? Animal Behaviour 40:837-845. 13
308 Fortin D, Boyce MS, Merrill, EH, 2004. Multitasking by mammalian herbivores: overlapping processes
309 during foraging. Ecology 85:2312-2322.
310 Frid A, 1997. Vigilance by female Dall’s sheep: interactions between predation risk factors. Animal
311 Behaviour 53:799-808.
312 Gerard JF, Richard-Hansen C, 1992. Social affinities as the basis of the social organisation of a Pyrenenan
313 chamois (Rupicapra pyrenaica) population in an open mountain range. Behavioural Processes
314 28:111-122.
315 Gonzalez G, Berducou, C, 1985. Les groupes sociaux d’isards et de mouflons au massif du Carlit
316 (Pyrénées Orientales). Gibier Faune Sauvage 4:85-102.
317 Gurri F, 1997. Cadí-Moixeró Parc Nacional, Pedraforca Paratge Natural. In: Parcs naturals de Catalunya.
318 Bacelona, Editorial 92, 62-77.
319 Janis C, 1982. Evolution of horns in ungulates: ecology and palioecology. Biological Reviews 57:261-
320 318.
321 Jarman PJ, 1974. The social organisation of antelope in relation to their ecology. Behaviour 48:215-266.
322 Levet, M, Pepin, D, 1994. Sociabilité et domaine vital d’isards (Rupicapra pyrenaica) máles au printemps
323 à Orlu (Ariège). Gibier Faune Sauvage, Game Wildlife 11:51-64.
324 Lima SL, 1995. Back to the basics of anti-predatory vigilance: the group-size effect. Animal Behaviour
325 49:11-20.
326 Lima SL, Dill LM, 1990. Behavioural decisions made under the risk of predation: a review and
327 prospectus. Canadian Journal Zoology 68:619-640.
328 Locati M, Lovari S, 1991. Clues for dominance in female chamois: age, weight, or horn size. Agressive
329 Behaviour 17:11-15.
330 Lovari S, Cosentino R, 1986. Seasonal habitat selection and group size of the Abruzzo chamois
331 (Rupicapra rupicapra ornata). Bolletino di Zoologia 53:73-78.
332 Machlis LP, Dodd WD, Frentess JC, 1985. The pooling fallacy: problems arising when individuals
333 contribute more than one observation to the data set. Zt. Tierpsychol. 68:201-214. 14
334 Molvar EM, Bowyer RT, 1994. Costs and benefits of group living in a recently social ungulate: the
335 Alaskan moose. Journal of Mammalogy 75:621-630.
336 Mooring MS, Fitzpatrick TA, Benjamin JE, Fraser IC, Nishihira TT, Reisig DD, Rominger EM, 2003.
337 Sexual segregation in desert bighorn sheep (Ovis canadensis mexicana). Behaviour 140:183-207.
338 Pérez-Barbería, FJ, Nores, C, 1994. Seasonal variation in group size of Cantabrian chamois in relation to
339 escape terrain and food. Acta Theriologica 39:295-305.
340 Richard-Hansen, C, González, G, Gerard, JF, 1992. Structure sociale de l’isard (Rupicapra pyrenaica)
341 dans trios sites pyrénées. Gibier Faune Sauvage 9:137-149.
342 Richard C, Pepin D, 1990. Seasonal variation in intragroup-spacing behaviour of foraging isards
343 (Rupicapra pyrenaica). Journal of Mammalogy 71:145-150.
344 Risenhoover KL, Bailey JA, 1985. Foraging ecology of mountain sheep: implications for habitat
345 management. Journal of Wildlife Management 49:797-804.
346 Ruckstuhl KE, 1998. Foraging behaviour and sexual segregation in bighorn sheep. Animal Behaviour
347 56:99-106.
348 Ruckstuhl KE, Neuhaus P, 2000. Sexual segregation in ungulates: a new approach. Behaviour 137:361-
349 377.
350 Shank CC, 1985. Inter- and intra- sexual segregation of chamois (Rupicapra rupicapra) by altitude and
351 habitat during summer. Zeitschrife fur Säugetierkunde 50:117-125.
352 Skogland T, 1991. What are the effects of predators on large ungulate populations? Oikos 61:401-411.
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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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377 16
1a) Feeding time 600
500
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Seconds 200
100
0 Central Peripheral Central Peripheral
Females Males 378 1b) Vigilance time 200
150
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Seconds 50
0 Central Peripheral Central Peripheral -50 Females Males 379 380
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2a) Central position
200
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Vigilance behavior (seconds) Vigilance behavior 0
23 30 43 50 54 60 78 88 90 19 125 Group size
2b) Peripheral position
200
150
100
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Vigilance behavior (seconds) Vigilancebehavior 0
19 23 30 46 58 85 40 52 68 89 118 Group size
387