Effects of howler monkey reintroduction on ecological interactions and processes

Abstract

Rewilding has been an increasingly popular tool to restore plant-animal interactions and ecological processes impaired by defaunation. However, the reestablishment of such processes has seldom been assessed. We investigated the restoration of ecological interactions following the reintroduction of the brown howler monkey (Alouatta guariba) to a defaunated Atlantic forest site. We expected the reintroduction to restore plant-animal interactions and interactions between howlers and dung beetles, which promote secondary seed dispersal. We estimated the number of interactions expected to be restored by the reintroduction to provide the baseline interaction richness that could be restored. We followed the reintroduced howler monkeys twice a week for 24 months (337 hours total) to assess their diet. We used howler monkey dung in secondary seed dispersal experiments with 2484 seed mimics to estimate the removal rates by dung beetles and collected the beetles to assess community attributes. We compared the potential future contribution of howler monkeys and other frugivores to seed dispersal based on the seed sizes they disperse in other areas where they occur. In 2 years, howler monkeys consumed 60 animal-dispersed plant species out of the 330 estimated. Twenty-one dung beetle species were attracted to experimentally provided dung; most of them were tunnelers, nocturnal, and large-sized (>10 mm). On 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, howler monkeys may consume more large-seeded fruit species than most other frugivores, highlighting their potential to affect forest regeneration. Our results show reintroductions may effectively restore ecological links and enhance ecological processes.

Co‐declining mammal–dung beetle faunas throughout the Atlantic Forest biome of South America

“…Studies on the ecological interactions between dung beetles and mammals suggest that the structure of dung beetle feeding and breeding networks did not differ significantly and showed high degree of nestedness and low levels of trophic specialization (Raine et al 2018, Raine andSlade 2019). On the other hand, the reintroduction of folivore primate (Alouatta guariba) in a previously defaunated Atlantic Forest site restored lost ecological interactions and promoted secondary seed dispersal, two years after the release of the first individuals (Genes et al 2019). This is critical as secondary seed dispersal by dung beetles increases along the ecological restoration trajectory of tropical forests (Derhé et al 2016).…”

“…Ecological networks derived from the incidence matrix of dung beetles (at genera level) according to mammal species presence across assemblages coalesced into 5, 10 and 20-km radial clusters throughout the Atlantic Forest. On the other hand, the reintroduction of folivore primate (Alouatta guariba) in a previously defaunated Atlantic Forest site restored lost ecological interactions and promoted secondary seed dispersal, two years after the release of the first individuals (Genes et al 2019). but very modest patterns of modularity.…”

Modifications of the rain forest frugivore community are associated with reduced seed removal at the community level

“…A recent study by Genes et al. () showed that the successful reintroduction of howler monkeys to a defaunated site of the Atlantic Forest of Brazil restored ecological interactions between howler monkeys and the plants that they consume, as well as secondary seed dispersal by dung beetles, a group commonly affected by hunting through the loss of mammals whose feces they rely on (Culot et al. , Feer and Boissier ).…”

“…, Beck , Genes et al. ). We thus highly encourage similar attempts to reintroduce Atelids to sites from where they have been extirpated.…”

Conserving the Diversity of Ecological Interactions: The Role of Two Threatened Macaw Species as Legitimate Dispersers of “Megafaunal” Fruits

“…Recovery projects are needed to reverse the high range contraction and population declines of both LM and HM but also to restore their ecological functions (seed dispersal and also food-wasting [65]) at larger spatial scales. There is, however, only one reintroduction project for LM [96], which could be used for assessing the recovery of ecological functions as it has been recently done after the reintroduction of a monkey species [97].…”