Surviving on a risky diet: monitoring the effects of a devastating tropical cyclone on the diet of frugivorous black-and-white ruffed lemurs in southeastern Madagascar

Background/Question/Methods

: The decline of frugivores worldwide underscores the urgent need to prevent their further decline. Climate change is a potent threat to frugivores, as increasing evidence suggests that there has been a considerable increase in the destructiveness intensity and frequency of extreme climatic events such as tropical cyclones, which alter the availability of fruits. Madagascar is prone to cyclones which have been suggested to play a major role on the ecology and evolution of the island’s biota. Yet, cyclone occurrence and intensity are highly unpredictable, so investigating the effect of these climatic events on the diet of frugivores remain opportunistic. Here we exploit a unique situation where we investigate the immediate effects of cyclones on the diet of Varecia variegata, a highly frugivorous lemur, after our study site experienced two severe cyclones. We characterize the nutritional landscape post-cyclone in terms of quality (nutrient availability) and quantity (fruit abundance) along botanical transects. Further, the diet of V. variegata was monitored daily through full-day continuous sampling of feeding bouts. We then determine how each lemur species selects their food plants post-cyclone using a network analysis, to identify variation in feeding patterns relative to the quantity and quality of food plants.

Results/Conclusions

: Peak fruiting in our study site is typically in April followed by a season of fruit scarcity. However, our preliminary results suggest that the availability of fruiting plants is altered in the immediate aftermath of the two cyclones. This is characterized by lower availability of fruiting events during a period where fruiting intensity is expected to be the highest throughout the year. We suggest that the cyclone has altered the nutritional landscape by altering the temporal availability of lemur foodplants, resulting in an earlier switch to the fruit scarce season, relative to previous years. An immediate consequence of the earlier modification of the nutritional landscape is the alteration of the feeding ecology of V. variegata. Results suggest that there is an earlier reliance on fallback foods (foods with decreased energy returns), because of the earlier shortage of preferred fruits. Further, preliminary results from the network analysis suggest that the dietary selectivity of the study species is both driven by abundance of fruits (quantity) in the landscape and their nutritional content (quality). Our study is unique in that in that it provides an insight on how frugivores cope with altered nutritional landscapes in the face of climate change.