Predictions of Seed Shadows Generated by Common Brown Lemurs (Eulemur fulvus) and Their Relationship to Seasonal Behavioral Strategies
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Frugivorous primates in the family Lemuridae, the largest seed dispersers in Madagascar, often modify their behavior dramatically to cope with seasonal fluctuations in food availability and climate. Such behavioral strategies influence seed dispersal distances and seed shadows, which determine seed fate, gene flow, and the geographical range expansion of plant populations. To examine seasonal variation in seed shadows generated by the common brown lemur (Eulemur fulvus), I combined data on movements of a wild group of lemurs in northwestern Madagascar from full-day observations made twice weekly for 1 year and full-night observations made once a fortnight during the dry season, with gut passage times for three captive individuals in a Malagasy zoo. During the rainy season, brown lemurs increased traveling effort (mean daily path lengths: 1172 ± SE 59 m), adopting a high-cost/high-yield foraging strategy to maximize harvest under periods of fruit abundance; this resulted in long seed dispersal distances (median: 170 ± MAD 77 m). During the dry season, daily path lengths (mean: 469 ± SE 30 m) were shorter owing to midday resting and consumption of water-rich succulent leaves, probably to avoid overheating and dehydration. These behaviors led to short-distance seed dispersal (median: 75 ± MAD 47 m). Although brown lemurs moved nocturnally during the dry season (mean nightly path lengths: 304 ± SE 58 m), nocturnal seed dispersal distances were short (median: 34 ± MAD 21 m). This seasonal variation in seed shadows might cause different population dynamics for rainy- and dry-season-fruiting species of large-seeded plants that depend on brown lemurs for seed dispersal. Additionally, lemur-facilitated seed dispersal distances were shorter than those of large frugivores elsewhere in the world. Therefore, lemur-mediated seed dispersal systems are likely to be vulnerable to forest fragmentation, which can isolate new recruits and prevent gene flow among plant metapopulations.
KeywordsLarge frugivores Madagascar Movement patterns Seasonality Seed dispersal distance
The author is grateful to A. Mori, H. F. Rakotomanana, F. Rakotondraparany, and all members of the Antananarivo-Kyoto University research team for their support in carrying out fieldwork; to G. Yamakoshi, A. Mori, and N. Nakagawa for their research guidance; and to all of the staff at Ankarafantsika National Park and Tsimbazaza Botanical and Zoological Park for giving permission to conduct this research. I thank O. Razafindratsima, Y. Tsuji, and L. Culot for co-organizing the special issue “Advances and Frontiers in Primate Seed Dispersal” in the International Journal of Primatology. I also thank J. M. Setchell, the editor-in-chief, and the three anonymous reviewers for their constructive comments and useful suggestions to improve my manuscript. This work was supported by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (Nos. 17405008 and 21-3399).
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