Famished Frugivores or Choosy Consumers: A Generalist Frugivore (Wild Bornean Orangutans, Pongo pygmaeus wurmbii) Leaves Available Fruit for Nonfruit Foods

Research in primate nutritional ecology uses concepts of quality, preference, and energy content to explain food choice: a primate consumes high-quality, preferred, and/or high-energy foods when available, and moves to other foods when they are not. Many frugivorous primates are thought to maximize energy, suggesting that high-energy fruit is a quality/preferred resource. However, recent research suggests a more complicated picture, including nutrient balancing and state-dependent foraging decisions. This brings into question whether a food is inherently high-or low-quality or whether this depends on previous feeding choices of the consumer. We tested whether a frugivorous primate, Pongo pygmaeus wurmbii, selects non fruit foods when fruit is available. To test selectivity, we looked for three behaviors: (1) orangutans leaving available fruit for nonfruit foods, (2) evidence of orangutans navigating to nonfruit foods, and (3) orangutans selecting nonfruit when fruit was available and nearby. We use data from 51 focal follows (611 feeding bouts, 15 animals) in Gunung Palung National Park, Indonesia. We found when orangutans leave available fruit, it often is for nonfruit foods. We found evidence of orangutans navigating for nonfruit foods. GPS data show that orangutans leave or pass by fruit to consume other foods. When orangutans consumed nonfruit resources, 26% of the time, there was at least one available fruit resource within a 50-m radius. These data suggest that orangutans select nonfruit foods, strengthening the argument that feeding choice is consumer state-dependent, and leading us to argue for a revision of the use of quality as a descriptor of primate foods.

Automated summary

Research in primate nutritional ecology explores the concepts of quality, preference, and energy content in food choice. Recent research suggests a more nuanced understanding, including nutrient balancing and state-dependent foraging decisions. This study on frugivorous primates found that the choice of high or low-quality food may depend on their previous feeding choices.