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Social Structure: Size and Age-Sex Composition of the Study Community

The study population did not live in a spatially cohesive social group, but rather in a dispersed social network made up of animals that interacted with one another, but whose members were never seen all together in the same place at the same time. Such social networks are commonly referred to as "communities" rather than "groups" (Richard, 1985; Goodall, 1986). The red ruffed lemur community at Andranobe included 18 individuals after the first birth season and 31 after the second birth season (Table 2). These figures represent minimum estimates of community size based upon animals that could be positively identified, aged, and sexed. There were several additional animals that affiliated with members of the community. However, because of infrequent sightings they could not be positively identified. Nor could their core group affiliation be determined. Individuals who shared the same core area (see next section) were considered members of the same core group.

Table 2 shows the size and age/sex composition of the Andranobe study community divided by core groups. There were five core groups, the majority consisting of one adult male, one or two adult females, and immatures. Four of these core groups contained two reproductive females during part or all of the study. Core group 1 had two females that mated, but only one that gave birth. Core group 2 initially had two reproductive females, but one of these females disappeared several months after the study began. Core group 3 was composed of two juveniles or subadults. There were two reproductive females in both core groups

4 and 5, and in each core group the females would stash their infants together (Vasey, in press). There were three reproductive males in the community, and none shared the same core group. In summary, there were multiple reproductive males and females in the community, and as many as two females within a single core group. Therefore, the social structure of V. rubra at Andranobe is multife-male/multimale.

Ranging Patterns and Social Organization Communal Home Range, Core Areas, and Home Range Defense

The communal home range area of V. rubra at Andranobe, containing all five core groups, covered 57.7 ha (Figure 1). Members of each core group shared a common core area which they used preferentially throughout the year more often than any other core area. Three of the five core groups contained focal animals and their respective core areas were precisely mapped (Figure 1). To calculate core area sizes, I enclosed the annual ranges for each core group male and the Jun-Oct ranges for core group females within minimum convex polygons. I focused on Jun-Oct because usage of core areas changed seasonally and in relation to reproduction. Core areas were clearly distinguishable geographic entities during these

5 consecutive months which contained the cold rainy season, mating, and gestation (Table 1). Underlying this geographic pattern, during these 5 months animals from different core groups did not socialize. Defined as such, there was little overlap between core areas within the community, but there were no fixed or defended boundaries either (Figure 1). Between communities, on the other hand, ritualized agonistic encounters occurred at the boundaries of communal home ranges (Figure 2). Of 11 intercommunity encounters observed over the 13-month study period, all but one involved agonism: community members allowed a group of strangers to enter the communal home range with little contest during the mating season (Vasey, in press). Of the remaining 10, 6 occurred during hot months, when females, in particular, are ranging widely (see below); and the other

Figure 1. Communal home range and core areas in one community of Varecia rubra. The communal home range (57.7 ha) is contained within the most inclusive polygon. Core areas for core groups 1 (17.15 ha), 2 (10.85 ha), and 4 (17.86 ha) are enclosed by three numbered polygons. These polygons enclose male ranges over an entire annual cycle and female Jun-Oct ranges (shading). Core areas for core groups 3 and 5 were not determined.

Figure 1. Communal home range and core areas in one community of Varecia rubra. The communal home range (57.7 ha) is contained within the most inclusive polygon. Core areas for core groups 1 (17.15 ha), 2 (10.85 ha), and 4 (17.86 ha) are enclosed by three numbered polygons. These polygons enclose male ranges over an entire annual cycle and female Jun-Oct ranges (shading). Core areas for core groups 3 and 5 were not determined.

4 occurred during the transitional cold season. During these encounters, which lasted between 10 and 80 minutes, members of different communities chased each other, scent marked, and performed loud calls. Red ruffed lemurs at Andranobe can therefore be described as territorial in that they have exclusive home ranges that are communally defended from other conspecific communities.

Individual Travel Patterns and Intracommunity Spacing

Though core group members were frequent affiliates, they did not routinely travel through their core areas in a cohesive fashion (see also Morland, 1991a,b). Figures 1 and 3-6 map the spatial patterns created by community members as they moved through their home range and the extent of overlap between individual home ranges at different times of year. Males resided largely within their respective core areas year round. There was slight overlap between the home ranges of two males in June, 1 month before mating took place (Figure 1). Complementing these ranging data, which are based on focal animal sampling, community males were rarely sighted outside of their respective core areas at other times, e.g., while other Varecia focals or E. f. albifrons were under observation or during random sightings that occurred while collecting botanical samples

Figure 2. The locations of 10 intercommunity territorial battles, denoted by black dots (•), shown in relation to the trail system installed to track Varecia rubra at Andranobe. Dots denoting battles that occurred in hot months show stippling (■) behind them; dots denoting battles that occurred in the transitional cold season (Apr-May), show forest cover behind them.

Figure 2. The locations of 10 intercommunity territorial battles, denoted by black dots (•), shown in relation to the trail system installed to track Varecia rubra at Andranobe. Dots denoting battles that occurred in hot months show stippling (■) behind them; dots denoting battles that occurred in the transitional cold season (Apr-May), show forest cover behind them.

or mapping. Of 38 such sightings (which included every calendar month but March), in only 2 cases (5%) was a male seen outside of his respective core area, and in only 2 cases (5%) were community males sighted in proximity to another male; Yellow was sighted once with Collier Pied (in their overlap zone) and once with Petit Blanc. The latter cases all occurred during hot dry/female gestation months (Nov-Dec), and no agonistic behavior occurred.

In contrast to males, female ranging patterns changed during the course of the year. During the hot rainy season (Jan-Mar), female ranges overlapped extensively (Figure 3). Females ranged widely through the communal home range entering other core areas and affiliating with members of other core groups in temporary aggregations (hereafter "subgroups") that varied daily in membership, size, sex

Figure 3. Individual travel patterns and spatial association of Varecia rubra females in the hot rainy season (Jan-Mar). Female ranges overlap extensively during this season. Fine-lined polygons enclose female ranges in core groups 1:Pale and 2:Red. Thick-lined polygons enclose female ranges in core group 4: 4W = White, 4B = Blue.

Figure 3. Individual travel patterns and spatial association of Varecia rubra females in the hot rainy season (Jan-Mar). Female ranges overlap extensively during this season. Fine-lined polygons enclose female ranges in core groups 1:Pale and 2:Red. Thick-lined polygons enclose female ranges in core group 4: 4W = White, 4B = Blue.

composition, and duration. These subgroups comprise the daily component of their fission-fusion social organization. Affiliative behaviors that occurred in subgroups included female greeting displays, feeding, calling, resting, grooming, and traveling together. The greeting behavior of V. rubra females is spectacular, involving anogenital scent marking of each other's backs, jumping over one another in a leapfrog-type fashion, writhing together, and emitting soft squealing sounds. In the subsequent cold rainy season (Jun-Aug), the ranges of females from different core groups did not overlap whatsoever (Figure 4). Females confined themselves to small patches of their respective core areas and affiliation between them ceased; subgroups were formed only by animals from the same core

Figure 4. Individual travel patterns and spatial association of Varecia rubra females in the cold rainy season (Jun-Aug). Ranges for females in different core groups do not overlap at all during this season. 1 = Pale; 2 = Red; 4W = White, 4B = Blue.

area (except while mating, Vasey, in press). This dispersion of core groups comprises a higher-level component of their fission-fusion social organization.

During gestation (Jul-Oct), V. rubra females continued the confined ranging pattern observed during the cold rainy season, traveling only within their respective core areas (Figures 1 and 4). Female gestation coincides with part of the cold rainy season, the transitional month of September, and the first month of the hot dry season (Table 1). After giving birth and commencing lactation (Nov), females began to travel longer distances (see below). However, they remained principally within their own core areas near their nests (Figure 5). Similarly, in the second month of lactation, when infants were starting to travel short distances alongside adults and were stashed for longer periods of time (Vasey, in press), females trav-

Figure 5. November ranges for Varecia rubra females in core groups 1, 2, and 4 are illustrated, including the location of their infant nests, denoted by black dots (•). White's nest was not located. 1 = Pale; 2 = Red; 4W = White, 4B = Blue.

Figure 5. November ranges for Varecia rubra females in core groups 1, 2, and 4 are illustrated, including the location of their infant nests, denoted by black dots (•). White's nest was not located. 1 = Pale; 2 = Red; 4W = White, 4B = Blue.

eled farther, yet remained principally within their own core areas near infant stashing depots (Figure 6).

Individual Home Range Areas

Because V. rubra lives in dispersed social networks, the communal home range area of 57.7 ha, presented above, does not convey the complexity observed in home range use. Thus, I here compare individual home range areas within and between the sexes annually and according to season and reproductive stage. Mean annual forest area used per female was almost twice as large as that used per male (30.9 ha versus 16.2 ha, t = 3.05*, df = 3, Table 3). However, female home ranges were not uniform throughout the year (Figure 7). Home range areas of females were larger in the hot rainy season than in the transitional cold (t = 2.87*, df = 5), cold rainy (t = 4.01*, df = 4), and hot dry seasons (t = 3.32*, df = 4). Large fluctuations are also evident when home ranges are compared according to reproductive stage;

Figure 6. December ranges for Varecia rubra females in core groups 1, 2, and 4 including routes followed and the location of infant stashing trees, denoted by black dots (•).

Figure 6. December ranges for Varecia rubra females in core groups 1, 2, and 4 including routes followed and the location of infant stashing trees, denoted by black dots (•).

Table 3. Seasonal and annual home ranges (ha) of individuals in one fission-fusion com munity of red ruffed lemur ( Varecia rubra)"

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