Female mantled howler monkeys (Alouatta palliata mexicana) alter their diet in terms of tannin consumption according to their reproductive stage

Abstract

Tannins (TN) are polyphenolic compounds primarily known to be involved in the defense mechanism of vascular plants against herbivory. Their excessive consumption can cause damage to an animal's digestive tract; yet, with moderate consumption, tannins have several beneficial health effects that have been well studied. However, little attention has been paid to the specific benefits of tannins for female health in different species. In this study, we investigated the role of TN content in the diet of female howler monkeys (Alouatta palliata mexicana) at different reproductive stages. From September 2021 to August 2023, we monitored a group of free-ranging mantled howler monkeys on Agaltepec island, Catemaco, Mexico. We recorded the feeding behavior of 20 adult females during different reproductive stages (cycling, gestating, and lactating stage). In 670 contact hours, a total of 1474 feeding sessions were recorded along with the collection of 31 different plant parts from 13 different vegetative species for subsequent tannin evaluation. Results showed that tannin intake significantly increased during lactation in comparison to the cycling stage. However, the increase in tannin intake was primarily due to high flower consumption. Fruit consumption did not affect dietary tannin levels. There were no significant changes in overall food consumption between reproductive stages. Our findings indicate that increased tannin consumption may play an important role for female howler monkeys during reproduction. However, the nature of the role is yet to be identified.