Dispersal patterns of Corsican mouflon ewes: importance of age and proximate influences

~,,,~ ~ APPLIED ANIMAL ~ BEHAVIOUR

~!~ ~,~L~: SCIENCE ELSEV I ER Applied Animal Behaviour Science 42 (1994) 29-40

Dispersal patterns of Corsican mouflon ewes: importance of age and proximate influences

M i c h e l D u b o i s * , R i c h a r d Bon , N a t h a l i e C r a n s a c , M a r i e - L i n e M a u b l a n c

Institut de Recherche sur les Grands Mammiferes (I.N.R.A.), CRA Toulouse, BP 27, 31326, Castanet Tolosan Cedex, France

Accepted 14 September 1994

Abstract

The dispersal patterns of radio-collared Corsican mouflon (Ovis musimon) ewes inhab- iting a low Mediterranean massif in the south of France were followed. Despite spatial instability being more marked in winter and spring, females (n = 17 ) remained on a single home range. The changes in spatial behaviour which appeared in March did not seem to be linked solely to ecological parameters. The use of the spring range was particularly no- ticeable among the different seasonal ranges since it was characterised by long-distance movements (n = 16, x = 740 + 320 m ) and the large overall area used (x= 330 + 90 ha).

The age of individuals had an important influence on space use. With increasing age, spatial patterns became more firmly fixed, which appeared to be linked to a better under- standing of the different ecological and social contexts occurring in the population. Some characteristics of spatial behaviour may create certain management difficulties in the introduction or reintroduction of the species. Age and season seem to have a strong effect on the organization of spatial patterns. Managers and hunters should therefore consider the implications of the age of individuals and thus their stage of development, and also of the season, to guide management decisions. For example, disturbance of young individuals must be strictly limited, particularly during the spring and the rut which appear to be important periods in the organization of spatial behaviour patterns.

Keywords: Dispersal patterns; Seasonal home range; Stage of development; Wild ungulate

I. Introduction

In numerous ungulate species, age and stage of deve lopment greatly influence dispersal patterns. In sheep (Ovis aries) and bighorn (Ovis canadensis), several authors have noted the impor t an t influence of early experience on the develop-

* Corresponding author.

0168-1591/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0168-1591 ( 94 )00533-8

30 M. Dubois et al. /AppliedAnimal Behaviour Science 42 (1994) 29-40

ment of spatial behaviour (Hunter and Davies, 1963; Berger, 1979a,b; Leslie and Douglas, 1979; Key and McIver, 1980; Lawrence, 1990). Evidence has been presented by Key and McIver (1980), Lawrence and Wood-Gush ( 1988 ) and Law- rence (1990) that sheep spatial habits are acquired by 'copying' the spatial behaviour (seasonal home ranges) of their mother. Nevertheless, young domestic ewes often form peer groups (Lawrence, 1990) that become independent in their movements from those of the older ewes (Lawrence and Wood-Gush, 1988 ).

Little information is available on the ontogenesis and seasonal changes of space- use in mouflon ewes (Ovis musimon). The aims of this paper are first to describe the organization of the mouflon ewes' home range, and second to examine the effect of age in its construction and utilization. In order to obtain this information, we studied the differences in spatial use between two age-categories of mouflon ewes.

Before the home range is established, and in relation to several developmental parameters such as exploratory tendencies or social and habitat experiences, the spatial behaviour of young ewes may be different from that of older females. For example, because of a lack of experience, we can make the prediction that the spatial behaviour of younger ewes, particularly in such important contexts as renewal of vegetation in spring or rutting in autumn, would be differently mani- fested than in older animals. As we observed among rams in a previous study (Dubois et al., 1993), spatial behaviour gives a good indication of the stage of development and the manner in which individuals integrate their previous experience.

2. Animals, materials and methods

2.1. Study area and animals

The hills of Caroux-Espinouse are part of a mountain range forming the southern border of the Massif Central. They are situated between the Montagne Noire and the Causses in the north-west of the department of Htrault (South of France). This low massif, which rises to around 1150 m, shows a great diversity of vegetation, influenced by a Mediterranean climate in its southern part and an Atlantic one in its northern part. A Mediterranean-type habitat, obvious on southerly slopes, whose climax is the evergreen oak (Quercus ilex), is replaced towards the north and west by oceanic vegetation whose climax stage is characterized by the beech (Fagus sylvestris), associated with some planted coniferous forest (Bon et al., 1990). The central part of our study area is a National Wildlife Sanctuary covering an area of 1800 ha. The mouflon population was introduced there towards the end of the 1950s (Pfeffer and Genest, 1969 ).

In the present study, individuals were trapped at the end of spring or in summer. The age of the 17 females, except for the three lambs, was determined by morphological characters (i.e. teeth, size of facial spots and corpulence ) (Pfeffer, 1967), ranging at the moment of capture from less than 1 year (i.e. lamb) to

M. Dubois et al. / Applied Animal Behaviour Science 42 (1994) 29-40 31

around 8 years (including three lambs, two 1-year-olds, five 2-year-olds, two 3- year-olds, one 4-year-old, two 5-year-olds, one 7-year-old and one 8-year-old). From this, by including data on the lambs only when they had achieved the age of I year, we distinguished two categories: A, 1-3 years old (n = 12 ); B, 4-8 years old (n= 5 ). This distinction was made first on the basis ofbehaviour, since Hass (1990) observed that females of bighorn sheep do not appear to act as 'adults' until 4-5 years of age, and second on the basis of morphological development, since Blood et al. (1970) and Jorgenson and Wishart (1984) noted that female bighorn sheep do not reach full body and horn size before 2-3 years. A common birth date of 15 April was used to assign ages (Bon, 1991 ). The mating period occurs in autumn, from October to December (Bon et al., 1992), and we used these months to determine the rutting ground. In the Caroux-Espinouse massif, lambing occurs in springtime and most ewes lambed in April.

2.2. Methods

From summer 1987 to the beginning of 1992, ewes were radio-tracked on a daily basis for 4-33 months. For these animals, we used radio-tracking from the ground. The accuracy of the system employed was tested. The angular error distribution obtained by radio-tracking accuracy tests fits a Gaussian distribution (Dubois et al., 1992), and led us to estimate that the actual bearing was found within an interval of _+ 20 o around the value measured in 90% of cases. This level of inaccuracy corresponds to a polygon of 15 ha for a distance of 500 m between the receiver and the target animal. Thus the error polygon around each location corresponds roughly to nine 125 m X 125 m squares. Radio-collared mouflon were located 10-20 times a month throughout the year. Home-range data were plotted on a detailed map ( 1:25 000) of the study site overlaid with a scaled grid of 125 mX 125 m quadrats (see Dubois et al., 1994, for more details on the method). Daily location records, made at different hours of the day, were compiled by monitoring the individual from the day of capture. All the error polygons of a given individual were combined to obtain the area used for a given period. Direct visual observations were added to radio-tracking data. Movement distances served as an additional index of spatial behaviour, and were calculated as the distance between the centre of successive error polygons, or between these centres and the centre of the square where the animal was observed. We calculated mean movement distances per period for each category of ewes. To evaluate seasonal and annual faithfulness to the same area, and also to evaluate spatial stability dynamics, the centre of activity for each home range was calculated (Hayne, 1949) for a given period (i.e. a month, a season, or a year). To first demonstrate an overall seasonal and monthly effect on the various variables, we used a two-way analysis of variance (Friedman test). Only non-parametric tests (Friedman test, Mann- Whitney U-test and Wilcoxon signed ranks test) were used for inferences based on quantitative variables (Scherrer, 1984).

32 M. Dubois et al. / Applied Animal Behaviour Science 42 (1994) 29-40

3. Results

3.1. General spatial patterns

The mean annual home range was 440 ha and the mean distance of movements between locations was 610 m (Table 1 ). For the eight ewes which were followed in at least two successive years, the mean distance between the annual home- range centres of activity was 280 m (Table 1 ). For two ewes followed in three consecutive years (one between 1 and 3 years old, and one between 4 and 6 years old), the distances between the first and last annual centres of activity were 175 m and 275 m, respectively.

Depending on the season, the area used was different (Z2--11.03, dr=3, P< 0.01, Friedman test). For all females, an increase was observed in the area used in spring compared with that used in winter (Table 1, z= -2.36, P< 0.01, where z is given by Wilcoxon's signed rank test, unless otherwise specified), and a significant decrease was observed in summer (Table 1, z = - 2 . 8 2 , P<0.01 ). The area occupied was lowest during summer and highest in spring. The mean movement distance did not vary very much, but was significant (•2 = 7.05, df= 3, P < 0.05, Friedman test). A significant difference was observed between winter and spring ( z = - 2 . 4 3 , P<0.01 ) and between spring and summer ( z = - 5 . 3 0 , P< 0.01 ). It was apparent that the mean movement distance was lowest during autumn and maximal in spring (Table 1 ). The mean distance between successive seasonal centres of activity was 450 m (n = 45, range 0-1305 m; Z 2 = 7.50, dr= 3, P< 0.05, Friedman test). This difference was significantly higher between winter and spring than between spring and summer (z= - 3.36, P< 0.05 ). Although there were no significant differences, it was noted that for females followed in at least two successive years, the mean distance was minimal between winter centres of activity, and maximal between summer centres (Table 1 ).

The area used was small between December and March, and maximal during the three spring months (Z2= 25.03, df= 11, P< 0.01, Friedman test). Compared with March (Fig. 1 ), there was a significant increase in the area used in April ( z = - 1.82, P<0.001, mean 119_+ 12 ha and 170_+34 ha for March and April, respectively) and a significant decrease in the area used in July ( z = - 3 . 6 8 , P<0.001, mean 170+6.5 ha and 120_+6.5 ha for June and July, respectively). The significant increase in September (Fig. 1, z= - 2.82, P< 0.01, mean 95 _+ 6 ha and 145 _+ 7.5 ha for August and September, respectively) was followed by a decrease in the area used. The increase in November was followed by a trend for a decrease in December (Fig. 1, z = - 1.78, P< 0.1, mean 140 _+ 8 ha and 100 _+ 12.5 ha for November and December, respectively).

The mean movement distance showed some variability (X2=21, df--11, P< 0.01, Friedman test). Compared with February, it was significantly higher in March (z = - 3.82, P< 0.001 ). The difference between inter-location movements was maximal in April (850 m; n = 12 ) and decreased progressively until August. It was minimal in December (485 m; n= 12).

Tab

le 1

A

rea

(ha)

of

the

annu

al h

ome

rang

e an

d se

ason

al r

ange

pat

tern

s in

the

ew

es s

tudi

ed

Surf

ace

area

M

ovem

ent

dist

ance

(h

a)

(m)

Dis

tanc

e be

twee

n se

ason

al

cent

res

of a

ctiv

ity

(m)

iQ

n R

ange

A

4 n

Ran

ge

JQ

n R

ange

Ann

ual

dist

ance

be

twee

n se

ason

al

cent

res

of a

ctiv

ity

(m)

.Q

n R

ange

Ann

ual

hom

e ra

nge

440

13

319-

604

610

13

185-

1605

Win

ter

**

250

] 12

20

0-36

0 **

6

20

] 1

24

50

-90

0

Spri

ng

..330

1

16

220-

410

..7

40

] 1

64

20

-10

70

Sum

mer

22

0 21

11

5-31

5 55

0 21

34

0-10

60

Aut

umn

230

14

155-

320

510

14

270-

730

780

q 8

375-

1305

] 22

0 13

0-

375

400

14

0-80

0

580

10

375-

1305

280

8 12

5-63

0

195

5 12

5-35

0

395

6 17

5-63

0

440

8 12

5-60

0

410

7 35

0-50

0

e~

2~

3 4~

Ix

a

x~

~Q=

mea

n va

lue;

n=

nu

mb

er o

f set

s of

dat

a ta

ken

into

acc

ount

. F

or a

nnua

l ra

nge,

onl

y th

e re

sult

s fr

om e

wes

wit

h a

num

ber

of lo

cati

ons

grea

ter

than

90

arc

pres

ente

d.

** p

< 0

.01

; *p

< 0.

05 (

Wil

coxo

n si

gned

ran

k te

st ).

6,a i 4~

34 M. Dubois et al. I Applied Animal Behaviour Science 42 (1994) 29-40

225

I

175 * * * * *

125

10~)

75

50 t 25 ,

MofIIhs

Fig. 1. Surface area (ha) of the monthly ranges. ***P< 0.001 ; **P< 0.01 (Wilcoxon signed rank test between the box-plots marked and the previous one). Box-plots represent 80% of the distribution and the horizontal line is the median.

:::::::;..::.:.- !i!i!!!i::"

Fig. 2. Spatial dynamics determined by successive centres of activity. Examples for 1 year's movements are given for (a) a young female, and (b) a female 8 years old. The arrow marks the beginning of the first month of tracking, labelled by its number, i.e. 6 is June. In order to maintain clarity in the figure, we do not note all the reference numbers. The solid circles mark the centres of activity. The distance between the centres of activity in November and December for the female in (a) was so small that it could not be clearly represented.

The mean distance between successive monthly centres of activity was 400 m (n= 163, range 0-2180 m; zz= 17.57, d f= 11, P < 0.05, Friedman test). In Fig. 2, two examples are presented which show that animals are most unstable in their movement patterns during the winter months and in April. In addition to this general instability, we noted that the distance between centres of activity in Feb- ruary and April was very similar to the distance between centres in March and April. For all females, the distance between centres of activity in the latter 2


months was significantly higher than the distance between centres in April and May (z = -3 .92, P< 0.01 ). Similarly, the distance between centres of activity in June and July was significantly lower than the distance observed between centres in May and June (z= - 5.11, P < 0.01 ).

3.2. Age influence

In spite of a tendency for the younger animals to occupy a larger annual home range (470 ha, n=7 , and 405 ha, n=6, for classes A and B, respectively) and to move greater distances (630 m, n= 7, and 600 m, n = 6), these differences were not significant. Faithfulness to a particular home range was similar for the two age-classes but was slightly more accentuated among older animals (i.e. the distance between annual centres of activity was 320 m for class A (n = 5 ) and 260 m for class B (n = 3 ) ).

The mean area of seasonal home ranges was significantly greater for class A in summer (215 ha, n = 13 for class A, and 165 ha, n = 7 for class B, Mann-Whitney U-test, z = - 2 . 0 9 , P<0.05) and was similar in autumn and winter when compared with class B. We did not observe any significant differences between seasons for class A. For class B, however, a significant increase in spring did occur when compared with the surface area occupied in winter ( 310 ha, n = 6 in spring, and 230 ha, n = 4 in winter, z= -2 .66, P<0.01 ), and a significant decrease oc- curred in summer when compared with spring (165 ha, n = 7 in summer, z= -3.06, P< 0.001 ). The movement distances were similar in each season between the two age-classes. Nevertheless, intra-class differences were observed between the seasons. The movement distances were greater in spring than in winter (750 m, n = 11 in spring, and 620 m, n = 7 in winter, z = - 3.82, P< 0.001 for class A; 730 m, n = 6 in spring, and 630 m, n = 4 in winter, z= -2.66, P<0.01 for class B), and lower in summer than in spring (570 m, n= 13 in summer, z= -4.37, P< 0.001 for class A; 500 m, n=7 , z= -3.05, P<0.001 for class B). The distance between seasonal centres of activity did not show any significant inter-class differences. It was 450 m for class A (n=27) and 470 m for class B (n= 18). In a general manner, faithfulness to the same seasonal home range was similar. It was more accentuated for the winter home range and weaker for the summer home range.

Concerning the monthly area used, the profile was relatively similar for the two age-classes, with larger areas being used during the spring months than the others (Fig. 3 ). We noted that the area used in April was significantly greater for class B ( z = - 1.40, P<0.01; mean 142+ 13 ha and 190+ 13.5 ha for classes A and B, respectively; Fig. 3). Moreover, the patterns of space use were generally more accentuated for class B. For this age-class, the larger surface area used in April, May and June was particularly evident, while it was less pronounced in the other months. For class A, the spring increase in the area used was less apparent and the monthly area less consistent, particularly in summer and autumn.

We noted that the area used in September and November was significantly greater for class A (z= -2 .43, P<0.01, mean 128+7.5 ha and 89+ 10.5 ha for


2 0 0 -

1 8 0 -

~ 16o-

140 -

120 -

100 -

8O 710oo =

900- =

8 0 0 -

E 7 0 0 -

6()0"

500"

4O0

"~" 12O0 -

.~" 1 0 0 0 -

,-~ 8oo.

~ 6 o o . g

400-

.B 21)0.

~5 o

(a) ] ~ 7

7 4 13 10

4 11 7 6

( b )

i i i i i i

J F M A M J Ju A S f) N D

J-'F v-h M~A A-'M M'-J G, Ju:A A'-S s-b O;N N)I:, dJ

Fig. 3. Monthly dynamics of the mean area in (a), mean movement distance in (b) and mean distance between successive centres of activity in (c) for the two classes of ewes studied. Each sample size is given in (a). **P<0.01; *P<0.05 (Mann-Whitney U-test). Solid squares, class A ( 1-3 years old); open diamonds, class B (4-8 years old).

classes A and B, respectively, in September; z = - 1.60, P < 0.05, mean 133 ___ 7 ha and 97 _+ 9.5 ha for classes A and B, respectively, in November). The previously noted increase and decrease of the areas used in September and December, respectively, (Fig. 1 ) were more pronounced for class A. The September increase was associated with an increase in the inter-location movement distances even though, paradoxically, individuals are spatially stable, this being indicated by the short distance between centres of activity. Like the area used, the dynamics of movement distances were greater for class B (Fig. 3 ) although no statistical differences were observed. March, May, April and June could be distinguished from the other months for class B. After the maximum in April, a steady decrease in movement distances (over 3 months) was observed. For ewes of class A, the increase appears to occur earlier and the movement distances were maximal in March. When compared with the older age-class, the younger one showed a slower


decrease of movement distances between locations (over 5 months) and a stronger spatial instability at the end of summer and in autumn. The distance between successive monthly centres of activity was less changeable for ewes in class B than for those in class A. After a period of stability between September and November, it tended to be greater for class B between December and March. From the summer until March, this coincided with the small area used, and until February it coincided with small movement distances. However, it was with a time-lag of 2 months, and solely between February and April, that class A showed a progressively increasing spatial instability. Generally, it was during March, when spatial instability was associated with increased movement activity, that the monthly home range change was the greatest. Nevertheless, the distance existing between March and April was significantly higher for class B (z= - 1.76, P < 0.05, mean 621 ___ 100 m and 1175 + 320 m for classes A and B, respectively). It can be seen that the area used strongly increased only in April.

4. Discussion

The area of the annual home ranges of the mouflon ewes studied was smaller than that for the rams we studied previously (Dubois et al., 1993). This difference could be directly linked to the fact that rams generally have two different home ranges (i.e. a rut home range and a non-rut home range) which are used with fidelity. We did not observe such differentiation in ewes.

Ewes tended to be more faithful to their global annual home range than to their seasonal home ranges, except for the winter home range. Winter months were marked by a low variability in the area used between the two age-categories of ewes. The restriction of food availability and meteorological conditions, which can be severe in this mountain massif, could favour this global characteristic. The spatial instability (i.e. significant distances between centres of activity) occurring during this season could indicate the influence of these parameters, and also have the indirect consequence of preparing the ewes for the great seasonal movement which occurs at springtime (Dubois et al., 1992). Nevertheless, the instability period is longer and more marked in older individuals. Therefore, it seems that ecological parameters cannot entirely explain the instability, or the fact that females (depending on their age and experience ) respond differently to them. In winter, the ranging behaviour of younger ewes could be an effect of age-class seg- regation related to the stage of social development, as in the sheep studied by Lawrence and Wood-Gush ( 1988 ). From this perspective, sociality would be more influential on spatial behaviour than strictly ecological parameters.

Concerning spatial behaviour characteristics, it was the younger ewes which in March exhibited the greatest change. The seasonal change which is expressed by the two age-classes was associated with a strong increase in the area used 1 month later (i.e. in April), at the beginning of the renewal of the vegetation (Bon et al., 1990). The fact that the change from winter range to spring range often starts abruptly with a movement of unusual amplitude (Dubois et al., 1992) may be


linked to phylogenetic inertia (Wilson, 1975; Berger, 1988 ), and imitates the seasonal migrations occurring in high-elevation mountain populations of bighorn, mouflon and Blackface sheep. Effectively, this behaviour does not, at first sight, seem to be determined by ecological constraints (Dubois et al., 1992), and ewes do not change habitat type but go back to a particular area which is used with fidelity each year (unpublished results). Moreover, ewes return more or less rap- idly, sometimes after only a few days, to their previous range.

Concerning spring, we have already noted (Dubois et al., 1992 ) that after these unusual large movements, mouflon ewes extend their range. The large area used is probably related, as in sheep and bighorn (Hunter and Milner, 1963; Grubb and Jewell, 1966; Woolf et al., 1970; Lawrence and Wood-Gush, 1988 ), to forage phenology and the seasonal grazing preferences of the ewes. The renewal of dispersed vegetation may influence this particular spatial activity. Nevertheless, April, when most births occur (Bon et al., 1992 ), is marked by an increase in the area used and a general spatial and movement instability, which primarily underlines the fact that ewes do not reduce their general activity for lambing, and sec- ondly confirms that lambs are precocious followers (Lent, 1974 ). Except for this season, the area used by older ewes is smaller than that of younger females, and could be related to a better knowledge of dispersed zones of good forage.

The decrease in instability and in the area used in summer, especially in July and August, may be considered with respect to the Mediterranean climatic characteristics (Santosa et al., 1990), which might induce a reduction of activity and the utilization of forested areas (Auvray, 1983). It seems that this constraint homogenises the spatial behaviour of ewe age-classes during that season. Never- theless, the significantly higher area used by class A underlines the fact that younger ewes continue to explore their environment.

As in the sheep studied by Lawrence and Wood-Gush (1988), the area of the autumn home range was reduced. This pattern is certainly related to the rut and its associated physiological consequences and behavioural contexts. As in the sheep studied by Lawrence and Wood-Gush ( 1988 ), and similarly to movement distances, the spatial behaviour of the age-classes tends to be homogeneous, except in December. Class B ewes became unstable when the rams left their rutting ground in December (Dubois et al., 1993 ). These spatial modalities could indicate a greater adaptation of the spatial behaviour of the two sexes when mature.

In sheep and bighorn, whatever their age, individuals appear to be consistent in their home-range behaviour, and this pattern strengthens with age (Geist, 1971; Festa Bianchet, 1986; Lawrence and Wood-Gush, 1988 ). The present study found a stronger organization of ranging behaviour in the older age-class; i.e. the profile of the curves for class B is less clear-cut than for class A. Moreover, significant differences existed in the area of the seasonal range of younger individuals, even if the area they used and movement distances between locations were generally greater than for class B. As in rams (Dubois et al., 1993), this organization may be related to the progressive setting up of their own home range among young ewes. Finally, it seems that, as in sheep (Key and Mclver, 1980), different parameters such as experience, exploratory tendencies, and assimilation of social,


ecological and physiological contexts combine simultaneously to influence the general spatial patterns and seasonal variability of space-use among mouflon ewes.

In spite of the fact that no published data are available on the yearly dispersion of individual mouflon ewes of different ages, we believe that seasonal changes in ranging represent a notable characteristic of the species. Nevertheless, age and local conditions may modulate its expression. The implication is that management of mouflon must take into account the characteristics of spatial behaviour, especially when releasing individuals in a new environment. Furthermore, age must also be taken into account and, for example, disturbance of young individuals must be strictly limited, particularly during the spring and the rut, which appear to be important periods in the organization of spatial behaviour patterns.

Acknowledgements

We would like to thank Mae Keskidy and James Content for their valuable comments on the paper, and also Peter Winterton and Mark Hewison of the Uni- versity of Toulouse III and INRA, respectively, who checked the English lan- guage. Technical support was provided by the Office National des For&s (Na- tional Forest Agency) and the Office National de la Chasse (National Game Agency), which also manages Caroux-Espinouse National Reserve.

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Documents

Dispersal patterns of Corsican mouflon ewes: importance of age and proximate influences