PS 47-127 - Investigating the dietary composition and diversity of Varecia variegata in a fragmented landscape

Background/Question/Methods

With sustained deforestation occurring globally, large tracts of continuous forest are increasingly divided into small forest fragments. The edge effects that accompany fragmentation (e.g., increased wind speed and light intensity) result in alterations to plant communities, and ultimately food availability for primary consumers. The abundance of large, fruiting trees has been found to substantially decline in forest fragments, challenging frugivorous species such as the Critically Endangered black-and-white ruffed lemur (Varecia variegata). We investigated how forest fragmentation impacts the dietary composition and species diversity of V. variegata across three forest fragments – Sangasanga (71 ha), Vatovavy (232 ha), and Tsitola (597 ha) – in the Kianjavato region of Madagascar. We hypothesized that individuals in Sangasanga and Vatovavy would be faced with reduced fruit availability relative to Tsitola, and increase the diversity of the diet in response. Behavioural and phenological data were collected over a period of 17 months by technicians with the Madagascar Biodiversity Partnership. Fruit, flower, and leaf phenology were recorded to determine food availability over the duration of the study, while instantaneous focal animal sampling enabled the construction of V. variegata dietary profiles. Statistical analyses were conducted using a combination of generalized linear mixed models and Hutcheson's t-tests.

Results/Conclusions

We found that as fragment size decreases, there is a corresponding decline in the availability of fruit per hectare of forest. Fruit availability was significantly greater in Tsitola compared to both Sangasanga (t = 4.6, p < 0.001) and Vatovavy (t = 2.5, p < 0.03). As predicted, individuals in Sangasanga had significantly higher dietary diversity when compared to individuals in Tsitola (p < 0.01), maintaining a surprisingly high level of frugivory. Contrary to our predictions, individuals in Vatovavy had significantly lower dietary diversity when compared to individuals in Tsitola (p < 0.01). These individuals consumed nectar from the traveller’s tree (Ravenala madagascariensis) for over 40% of the diet - much higher than the 3-5% reported for other, continuous forest populations. These results suggest that, depending on the local conditions of a forest fragment, varied feeding strategies may be employed in response to reduced food availability. Furthermore, these results suggest that R. madagascariensis may be a valuable resource in supporting vulnerable populations of V. variegata in disturbed and fragmented habitats. Future research should investigate if these divergent feeding strategies result in differences in nutrient intake between forest fragment populations, and the ability to meet nutrient requirements.