Humans are not the only primates that consume fungi. Our knowledge about mycophagy in primates is pretty scant, but there have been scientists over the past few decades who have looked more closely at these interactions. Out of the diverse array of primates around the world, (488 species) only 22 have been observed munching on our fungal friends. In one study, one species in particular was observed spending more time foraging fungi than any other food item. Everybody, I’d like you to meet the elusive Goeldi’s monkey (Callimico goeldii). 

Callimico goeldii is a small, New World monkey indigenous to the upper Amazon region. Although it was described in 1904, very little was known about this small discrete monkey. For one, it is rare. So rare, it’s currently classified as a vulnerable species, just one category above endangered. Besides its rarity, Callimico goeldii is notoriously difficult to observe in the wild because of its habitat preference. Goeldi’s monkey is confined to extremely dense scrubby understory of tropical rainforests. Researchers find it difficult observe these monkeys through the dense vegetation, let alone get close enough without disrupting their behavior. But in the early 2000s a handful of researchers successfully observed these monkeys and learned about how they functioned in their ecosystems. 

In 2003, Amy Hanson and her team published a review on the feeding ecology of Callimico goeldii. It was here that I learned that one population of Callimico goeldii spent 63% of its feeding time on foraging for certain fungal species. These monkeys didn’t consume every species of fungus they found either, eating just a handful of species including Auricularia auricula, Auricularia mesenterica, Ascopolyporus polyporoides and Ascopolyporus polychrous. This eye opening review paper revealed that these small monkeys weighing less than half a kilogram, consume nearly 3 times the amount of fungi compared to an average human, weighing over 60 kilograms!

A more recent 2010 study by Leila Porter and Paul Garber, provide us with even more valuable information regarding this mycophagous interaction. In this long-term, 10-year study, these two scientists studied the feeding ecology of five groups of Callimico goeldii. “The annual diet was composed of fungi (31.1–34.9%), fruits (34.0– 40.6%), prey (17.4–30.1%), and exudates (1.0–10.9%).” Now these are averages of all of the groups studied, and compared to the first review I mentioned, the fungi consumed by the monkeys in the 2010 study is less. This is because some groups of Callimico goeldii depend more on fungi to supplement their diet, while other groups focus on other food items. The interesting part here is that groups that foraged for fungi had a significantly larger home range compared to groups with diets focused on other food items. 

Monkeys that are more dependent on fungi to supplement their diet must have larger home ranges, because the fruiting bodies of Auricularia auricula, Auricularia mesenterica, Ascopolyporus polyporoides and Ascopolyporus polychrous are patchy, ephemeral and occur in low density. By partitioning different food items, organisms of the same species compete less with each other overall, thereby allowing more individuals to exist in the same location; a reality of ecology we’ll see more and more as humans continue to reduce the area of suitable habitats for a diverse array of wildlife. 

Besides just a handful of studies, not much else is known about primates and their mycophagous interactions. I still have some unanswered questions that I can only begin to hypothesize about. Do these monkeys successfully disperse fungal spores to suitable habitats? Do groups specializing in mycophagy have a higher, lower, or equal fitness compared to other groups that focus on other food items? With the accelerated rate of Amazon deforestation, and destruction, there simply may not be enough time to address these questions. 

[Link 1] [Link 2]