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However, differences are almost statistically significant (0.05< p <0.1), and would possibly be significant if sample size was enlarged. Hence, statistically significant differences in grooming behavior are expected, if more data were available, and would corroborate subjective impressions from observations.

Food Resources. Food resources in both species have been analyzed in detail elsewhere (Thalmann, 2001) and results are shortly summarized here. Both species fed primarily on leaves over the entire year (77% of feeding bouts in Avahi, 74% in Lepilemur). In the balanced sample (one night per individual per month), the male Avahi Aim used 25 different tree and 5 different liana species at 102 (trees 89, lianas 13) locations. The two focal Lepilemur individuals together used 25 different tree and 5 different liana species at 112 locations (trees 101 trees, lianas 11). Avahi used on average 2.5 times larger food patches in terms of TCV than Lepilemur. Neither Avahi nor Lepilemur showed a conspicuous preference for clumped plant species. Food resource overlap between the two species is very low, and virtually absent if seasonality and availability in terms of TCV is taken into account. Lepilemur select significantly more common trees and liana species than Avahi do. Avahi have a narrower food niche compared with Lepilemur and are, hence, more specialized folivores than Lepilemur.

Vocalizations. (Figure 6, Appendix A-VII). Vocalizations have not yet been described and analyzed in detail for the two species (Thalmann, unpublished data). Presented results are hence restricted to the most conspicuous vocalizations in Lepilemur. These are loud vocalizations in which most often more than one individual is involved. Here, I call them complex vocalizations. Indeed, these vocalizations seem to be duets between opposite-sex individuals sharing the same home range, such as in the case of the focal animals Lepilemur L1m and L2f. In some cases, the female Lepilemur individual L18f—living in the same range— contributed too, but it seemed that this individual did not fully participate.

The highest rates of complex vocalizations appear at the beginning and during the rainy season; virtually no complex vocalizations occur during the dry season. The positive correlation (Spearman rank correlation r = 0.85, p <0.001) between

Compex vocalizations in Lepilemur

Compex vocalizations in Lepilemur

Lepilemur male L1m Lepilemur female L2f Lepilemur (m, f)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 6. Complex vocalizations in Lepilemur over an entire year. Very high rates occur at the beginning and during the rainy season whereas there are almost no complex vocalizations during the dry season.

Lepilemur male L1m Lepilemur female L2f Lepilemur (m, f)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 6. Complex vocalizations in Lepilemur over an entire year. Very high rates occur at the beginning and during the rainy season whereas there are almost no complex vocalizations during the dry season.

Lepilemur male and female is highly significant and indicative of coordination between the individuals. Complex vocalizations correlate positively and significantly with rainfall, Nightly Path Length, range size expressed as usage of different quadrats, availability of possibly preferred food items (sBsLyL), and negatively with grooming rates and night length (Table 2).

No comparable complex vocalizations are present in Avahi. In Avahi there was only a simple loud vocalization, the typical "vou-hi." Neither the focal male Ami nor the female of the same group was observed uttering this call. It seemed that this vocalization occurred only in special situations, when the male Avahi suddenly and very quickly moved away from the group. In this situation it was always lost and out of sight but the conspicuous vocalization was heard.

Ranges (Figures 7-10, Table 3). Home ranges (convex polygons) for neighboring Avahi groups (n = 4, including the focal Avahi male Aim) and individuals of Lepilemur (n = 7, including focal Lepilemur individuals Lim, L2f) belonging to different range associations (n = 4) are shown in Figures 7-10. In general, there is little overlap between neighboring Avahi groups for which data were available for 1996 (Figure 7). The gaps between the different groups are mainly due to differences in intensity of data collection. Based on the observations of the focal Avahi male Aim the range size is approximately 1.1-1.4 ha for a group. The home range remained quite stable in size and location over 4 consecutive years as shown by the comparatively small shift of home range centers and borders for different years (Figure 8). In Lepilemur, again, overlap is not extensive between range associations (Figure 9). The focal male L1m and female L2f together with the young female L18f formed a range association. The males L22m and L29m had overlapping ranges as well, and most likely belonged to the same association; L24m and L5f were members of other associations. Because Lepilemur individuals often lost their transmitters and changed sleep trees less often than did Avahi, less spacing data are available overall. However, the gaps are most probably due to differences in observation intensity, as the different range associations seemed to be neighbors. The ranges of the focal Lepilemur male L1m and female L2f

Table 2. Selected correlations between complex vocalizations in Lepilemur and environmental and behavioral variables (n =12 for all correlations)

Variable Spearman's r p value

Table 2. Selected correlations between complex vocalizations in Lepilemur and environmental and behavioral variables (n =12 for all correlations)

Variable Spearman's r p value

Rainfall

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