(This study)

1 Study lengths vary: Morland (1991), 12 months over 18-month period; White (1991), 2 months; Rigamonti (1993), 7 months; Balko (1998), 18 months over four-year period; Vasey (1997), 13 months; Ratsimbazafy (this study), 18 months White's percentages are based on percent food patches used. Percentages for other studies are based on time point samples.

2 Flowers, buds, shoots, shelf fungus, unidentified (0.9%).

3 Mushroom.

4 Unidentified (2%).

5 Bracts, exudates, fungus.

shows that Varecia has the least structural complexity, as determined by the lack of tenaie and subsequent sacculations (Campbell et al., 2000). These authors suggest such a lack of sacculations may explain the inability of this species to subsist on a diet high in secondary compounds, such as those found in leaves. Compared with other sites, Varecia living at Manombo had the highest percentage of foliv-orous material in the diet through every season, yet they concentrated on the leaves of only two plant species, Polyalthia oligosperma (ramiavitoloha) and Cynometra cloiselii (hazomby). These two species are present in Ranomafana, but only ramiavitoloha is listed in the food species of Varecia in that site.

Even living in a harsh environment, Varecia spent an overwhelming percent of their feeding time on seasonal rather than perennial foods, as demonstrated by the high percentage of feeding time spent on fruits and young leaves, and a preference for nectar and shelf fungi. The abundance, distribution, and availability of a given food in the habitat may influence feeding behavior, but there is strong evidence in Varecia that seasonal foods are much preferred.

Comparing food species in disturbed (Manombo) and pristine (Nosy Mangabe, Ranomafana) forests, ruffed lemurs concentrated their feeding on relatively few tree species in the undisturbed forests. At these different sites, total food species utilized by ruffed lemurs were as follows: In Ranomafana, the three study groups used 27 plant species in 17 different families, 16 species in 12 families, and 14 species in 9 families; on Nosy Mangabe, 67 species in 24 families; and in Manombo, 83 species in 43 families. Preliminary data from a plant inventory study of the Nosy Mangabe rainforest indicate that this forest has very high species diversity (Gentry, 1988). In Manombo, although long-term effects of logging activities limit food choices, there is increased plant diversity due to massive invasions of various new plant species. This allows animals to diversify the number of food species ingested. Additionally, because different species fruit asynchronously, but within a species-specific 2- to 3-month period, feeding diversity is important to any animal with a small home range (Milton, 1980). The two study groups used mainly four small core areas of about 3 or 4 ha during this study, but the entire area used by each group was summed, and the home range was quite large: estimated at 70 and 30 ha for Groups I and II, respectively. Nevertheless, the food species chosen by Varecia at Manombo indicates that they were opportunistic feeders. Results of this study demonstrate that 35% of food species were used on only 1 day, and more than half of all food sources were eaten on less than 4 days of the entire study. This further underscores the opportunistic strategy used by ruffed lemurs at Manombo.

Varecia may travel less, and broaden the species they ingest as a strategy to cope with disturbed habitats (Milton, 1980; Terborgh, 1983; Dunbar, 1988). There are two possible explanations for this strategy: (1) to better guard and control food patches both from intraspecific competitors, and from other species at Manombo such as the brown collared lemur (Eulemur albocollaris) and frugivo-rous birds; and (2) to minimize use of the home range and distance traveled thereby conserving energy. It is important to note that the two study groups at

Manombo were not prevented from ranging farther and could have adopted an alternative strategy, traveling and foraging more if needed. Moreover, solitary foraging seemed to be another strategy for Varecia at Manombo, to avoid or reduce direct competition between group members, thus maximizing foraging success. Indeed, this allows a species to survive in areas where the distribution of resources would not support a cohesive group (de Thoisy and Richard-Hansen, 1997).

It is also important to note that even though the use of C. hirta tallied higher than any of the other food sources during the whole study, this does not necessarily mean that C. hirta was preferred, because when other food sources became available, its role was reduced. However, the two alien species, C. peltata and C. hirta, could be considered as "important foods," because these two species were eaten on many days during the study. Neither of these species is listed in the diet of Varecia at other sites. Overall, 38% of the total amount of feeding time was spent on those two species at Manombo. The survival of this frugivorous lemur in the highly disturbed Manombo forest seems to be related mainly to the availability of fruits of these two exotic plant species, because many of the endemic plant species did not produce fruits.

In comparing the five most important food families among the three sites (Manombo, Ranomafana, and Nosy Mangabe), no single family was present in all three (Table 3). Individually, Manombo shared one family (Clusiaceae) with Ranomafana and one family (Moraceae) with Nosy Mangabe. That Clusiaceae family at Ranomafana was consumed by the group living in selectively logged areas. Once again, this demonstrates changes in diet composition correlated with changes in the forest quality.

Some of the foraging strategies exhibited by the ruffed lemurs at Manombo forest can be explained by the high relative abundance of few plant species within the animals' territory. For instance, each time a preferred tree-food became less

Table 3. Comparison of top five plant families exploited by Varecia variegata groups at various sites in Madagascar


Table 3. Comparison of top five plant families exploited by Varecia variegata groups at various sites in Madagascar


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