Mycophagy in primates of the Issa valley, Tanzania

Mycophagy (fungi consumption) is an important animal-ecosystem interaction
and provides nutrients for numerous mammalian taxa, such as primates.
Although mushroom consumption is a widespread behaviour in about a quarter
of all known primate species, surprisingly little is known about their use
of mushrooms as either a staple or fallback food, and the relationship
between mushroom availability and consumption. We used direct
observational data on mushroom consumption in the diet of three sympatric
primate species: Chimpanzees (Pan troglodytes schweinfurthii) and
Red-tailed monkeys (Cercopithecus ascanius) from 2019-2022, and yellow
baboons (Papio cynocephalus) from 2015-2022 in a mosaic woodland habitat
in the Issa valley, western Tanzania, to address these gaps. We analysed
mushroom consumption patterns and assessed mushroom availability from line
transects for a period of 15 months (Oct 2022 – Dec 2023). Our findings
show that mushrooms were a consistent dietary component for all three
species during the wet season (October-April; chimpanzees – 4 %, baboons –
17 %, and red-tailed monkeys – 4 %), while baboons also continued to
consume mushrooms (> 10 % of their annual diet) even when
availability was low outside the wet season. This is also the first report
of mushroom consumption by a red-tailed monkey. We conclude that mushrooms
serve as a fallback resource for Issa chimpanzees and red-tailed monkeys,
while they represent a preferred food for Issa baboons. We contextualise
mushroom consumption as a potential strategy of niche partitioning to
reduce interspecific feeding competition as well as underscore the
importance of mycophagy and its role in primate dietary ecology and human
evolution.