Abstract Figs ( Ficus spp.) are widely considered keystone resources in tropical ecosystems, yet mechanisms underlying their importance to primates are rarely assessed. We tested five hypotheses explaining the importance of figs for mantled howlers ( Alouatta palliata ) using a 10-year phenological dataset from southeastern Mexico. We monitored 57 trees representing figs and five other dietary species weekly from 2012 to 2021. The asynchrony hypothesis predicted lower intraspecific synchrony in figs, but we found no differences between figs and other species. The keystone hypothesis was strongly supported: this genus reduced weeks below critical thresholds by 59.5%, rescuing the community from scarcity in 72 weeks (14.7% of monitoring). During these events, figs contributed 20% of resources despite representing one-sixth of monitored taxa. The bet-hedging hypothesis predicted lower interannual variance in fig fruiting, but figs showed significantly higher variance than most species. The complementarity hypothesis predicted negative correlations between fig and non-fig phenology, yet we found positive correlations. The multiple cropping hypothesis predicted more fruiting cycles in figs than other species, but frequencies were equivalent (2.16 vs 2.13 cycles/year). Figs function as a keystone resource for mantled howlers not through unique phenological patterns but through reliable provisioning during critical scarcity periods, preventing resource bottlenecks that could otherwise limit the persistence of howler populations.
Dias et al. (Thu,) studied this question.