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Avahi occidentalis

About: Avahi occidentalis is a research topic. Over the lifetime, 16 publications have been published within this topic receiving 535 citations.

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Journal ArticleDOI
TL;DR: Results from a comparative field study on the feeding behavior of the gregarious Avahi occidentalis and the solitary-but-social Lepilemur edwardsi are presented to evaluate hypotheses relating to social organization and food resources.
Abstract: I present results from a comparative field study on the feeding behavior of the gregarious Avahi occidentalis and the solitary-but-social Lepilemur edwardsi to evaluate hypotheses relating to social organization and food resources. While Avahi and Lepilemur are both nocturnal, have comparable body weights and positional behaviors, and are both folivorous, they differ in their social organization. Therefore, they present an ideal model for assessing food resource characteristics through comparisons of food selection in both species with regard to forest composition. The monogamous Avahi tend to select under-represented resources. They are repeatedly exploited, which suggests that their location must be known. It is worthwhile and probably imperative to defend those resources. Such defense imposes ranging limitations on male Avahi. Females may prefer familiar mates that will share their knowledge of resource location and defend the resources. A stable monogamous pattern could be the optimal strategy. In contrast, food selection by Lepilemur is based on common resources to a higher degree, but they show a lower degree of exploitation. Lepilemur males would be less restricted and could potentially opt for a different strategy, e.g., a dispersed harem. It is unclear whether this strategy is realized or not. I discuss other possible correlates of monogamy—infanticide protection, predation avoidance—but the gregarious pattern in Avahi may best be seen as a retention, and its nocturnal activity as a secondary adaptation.

121 citations

Journal ArticleDOI
TL;DR: In this article, the energetic costs of locomotion in five nocturnal, saltatory prosimians were investigated using data on nightly travel distance, locomotor frequencies, distance and height change in each locomotor mode.
Abstract: We report the energetic costs of locomotion in five nocturnal, saltatory prosimians. Using data on nightly travel distance, locomotor frequencies, distance and height change in each locomotor mode, we

82 citations

Journal ArticleDOI
TL;DR: Lepilemur edwardsi and Avahi occidentalis are both small, nocturnal folivores, but live sympatrically over a large part of their range, suggesting that niche differentiation has occurred.
Abstract: Lepilemur edwardsi and Avahi occidentalis are both small, nocturnal folivores, but live sympatrically over a large part of their range, suggesting that niche differentiation has occurred. In order to establish whether ranging behaviour and activity patterns have contributed to niche differentiation, a field-study was carried out at Ampijoroa, Madagascar, within the area of range overlap. Four individuals of each species were fitted with radiocollars and tracked, dusk to dawn, over 18 months. Data were collected on home-range size, travel distances, activity and social behaviour. Neither showed the markedly biphasic activity patterns which have often been described for nocturnal prosimians; this might be explained by the combination of folivory and small body size. L. edwardsi spent long periods inactive, but engaged in considerable social interaction during the night, including extensive long-range calling. The mean home range was 1.09 ha, and ranges were rather evenly used. Home ranges of females overlapped extensively, and the range of the single adult male which could be caught overlapped with the ranges of several females, as is common in nocturnal prosimians. The mean nightly travel distance was very low, only 343 metres. On the other hand, social interactions in A. occidentalis were primarily within a stable monogamous family unit, and long-range calling was very limited. Home ranges were rather larger than in L. edwardsi, but less evenly used, and mean nightly travel distances were much greater, 1175 m. Differences in range-use patterns may be explained by the contrast between Avahi's, selective feeding on relatively high-quality young leaves and flowers, versus Lepilemur edwardsi's, unselective feeding on relatively low-quality, but ubiquitous and evenly-distributed, mature and old leaves. Similarly, while overlapping female ranges may be adequate when food resources are evenly distributed, monogamy in Avahi may be a response to selective feeding on a patchy food resource.

60 citations

Journal ArticleDOI
TL;DR: Avahi occidentalis and Lepilemur edwardsi are two saltatory, nocturnal folivorous lemurs of similar body size which live sympatrically over much of their range and may often be seen feeding in the same trees as mentioned in this paper.
Abstract: A well-known principle holds that where food supply is limited, two sympatric species with the same diet, morphology, and behavior will compete, leading to exclusion of one species or differentiation of their ecological niches. Avahi occidentalis and Lepilemur edwardsi are two saltatory, nocturnal folivorous lemurs of similar body size which live sympatrically over much of their range and may often be seen feeding in the same trees. We report a study of their locomotor behavior, carried out in order to determine to what extent locomotion might contribute to niche separation. Avahi lives at a higher level in the forest and is the more committed leaper, with a much larger home range and nightly travel distance, while Lepilemur climbs more and has a very small nightly travel distance. Avahi uses small, low-angled supports more often, while Lepilemur makes more use of large, high-angled supports (however, neither species uses vertical supports at a frequency greater than the availability of such supports in the forest stratum in which they live). Both species tend to land on larger-diameter supports on longer leaps, but Avahi also takes off from larger-diameter supports in longer leaps, reducing loss of energy to the substrate during takeoff. We suggest that the differences in locomotion and ranging behavior between them are consistent with niche differentiation on the basis of food quality, Avahi investing more energy in harvesting better quality but more patchy food, Lepilemur minimizing expenditure in harvesting a less selective, quantitatively poorer diet.

58 citations

Journal ArticleDOI
TL;DR: While both species showed a preference for small oblique and horizontal branches, they selected them at different heights in the forest and with varying degrees of preference and avoidance for the other available supports.
Abstract: Lepilemur edwardsi and Avahi occidentalis are two species of nocturnal, folivorous ‘vertical clingers and leapers’ (VCL). They have a similar body mass and share the same morphological adaptation for leaping. In a field study under sympatric conditions at Ampijoroa, Madagascar, comparison of support use with support availability using Jacobs' D preference values (Jacobs, 1974) showed that both species actively chose or avoided branches with certain qualities. However, while both species showed a preference for small oblique and horizontal branches, they selected them at different heights in the forest and with varying degrees of preference and avoidance for the other available supports. Despite their traditional locomotor assignation, both species showed a surprisingly strong preference for horizontal supports. These striking variations in detail of support preference may aid the maintenance of species segregation and niche difference.

32 citations

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20182
20171
20121
20112
20051
20031