Rewilding has been an increasingly popular tool to restore plant-animal interactions and ecological processes impaired by defaunation. However, the re-establishment of such processes has seldom been assessed. Here, we investigate the rewiring of ecological interactions following the reintroduction of the brown howler monkey (Alouatta guariba) to a defaunated Atlantic forest site. We expected that the reintroduction would restore plant-animal interactions and interactions between howlers and dung beetles, which promote secondary seed dispersal. We estimated the credit of ecological interactions to provide the baseline interaction richness that could be restored by the reintroduction. We followed the reintroduced howlers twice a week to quantify their rewiring with the plant community. We used howler monkey dung in secondary seed dispersal experiments using 2484 seed mimics to estimate the removal rates by dung beetles and collected the beetles to assess community attributes. We also compared the potential contribution of howlers and other frugivores to regeneration through the seed sizes they disperse.
Results/Conclusions
In two years, howlers consumed 60 animal-dispersed plant species out of the 330 estimated. They interacted with 21 dung beetle species, most of them tunnelers, nocturnal and large-sized (> 10 mm). Secondary seed dispersal was highly variable, but in average 30% (range 0-100%) of the large seed mimics (14 mm) were moved by dung beetles. About 91% of the species consumed by howlers (size range 0.3-34.3 mm) overlapped in seed size with those removed by dung beetles. In our study area, howlers can consume more large-seeded fruits than most other frugivores, highlighting their importance for forest regeneration. This study demonstrated how the rewiring of ecological interactions through reintroductions can be effective in restoring ecological links and enhancing ecological processes. Therefore, reintroductions should be encouraged as a sound conservation strategy to reverse defaunation effects.