Lemurs and the regeneration of dry deciduous forest in Madagascar

We sought to assess the role of lemurs for seed dispersal in the dry deciduous forest of western Madagascar and the possible consequences of the demise of lemurs for forest regeneration. Forest regeneration was studied in eight plots in two large blocks of primary forest and in seven fragments of primary forest (1 plot per fragment). In 4 of the 15 study plots, the abundance of saplings was negatively and significantly correlated (p < 0.05) with the abundance of mature individuals of the same tree species. In another 10 study plots there were negative correlations, although these were not significant on the community level. Second-order statistics were significant with p < 0.001 and indicated that seed dispersal away from the parent trees was important for successful establishment of saplings. Apart from possibly the bush pig (Potamochoerus larvatus), only one vertebrate species of the dry forest, the brown lemur (Eulemur fulvus), ingested seeds > 11 mm long and passed them through its digestive tract unharmed. These results for lemurs were based on direct observations and fecal analyses. To evaluate the role of E. fulvus, we compared regeneration in forest plots with and without E. fulvus. In forest fragments without E. fulvus, fewer lemur-dispersed tree species regenerated than would be expected based on the presence of mature tree species that are lemur-dispersed (p < 0.05). No such effect was seen in primary forests with E. fulvus or for trees whose seeds can also be dispersed by other vertebrates. Thus, regeneration of the dry deciduous forest of western Madagascar with the complete set of primary forest tree species seems to depend upon the presence of E. fulvus.