In three species of monkey, the complex pattern of ridges on the feet and palms vary between individuals, similar to human fingerprints, according to a study publishing November 11, 2026, in the open access journal PLOS One by Juliana Vieira Flores Sales at Universidade de Brasília and colleagues.
The tiny ridges on the surface of our hands and feet help us to grip slippery surfaces, and the unique patterns they form on our fingertips have become an important forensic tool. These friction ridges are also present in other species of primate, and preliminary research has found evidence for variation between individuals that might be useful for identification.
To investigate this phenomenon further, researchers collected foot- and palm-prints from captive owl monkeys (Aotus infulatus) and squirrel monkeys (Saimiri collinsi) at the National Primate Center in Pará, Brazil, as well as from capuchin monkeys (Sapajus spp.) that were either permanently housed at the Universidade de Brasília Primate Center or had been admitted to the University of Brasília's Veterinary Hospital. They analysed the pattern of ridges on each palm- and foot-print, identifying arches, loops and whorls, as well as minute details.
They found that none of the 116 individual monkeys had identical foot- or palm-prints. There were also consistent differences between species, which may reflect the species' different ecologies. For example, owl monkeys, which are nocturnal, had more deltas and whorls and showed less variety in their ridge patterns compared to squirrel monkeys and capuchins, which are diurnal.
The study adds further evidence that palm- and foot-prints vary between individuals in non-human primates, as they do in humans. This variation could prove useful for conservationists, scientists and wildlife forensic investigators, the authors say. However, more research is needed to determine whether non-human primates have unique prints that could be used to reliably identify individuals.
Juliana Vieira Flores Sales adds: "Our findings show that palm and foot ridge patterns vary among non-human primates and reveal differences that may be associated with their ecological characteristics. Beyond their potential applications in individual identification, these patterns offer an opportunity to explore how dermatoglyphic traits develop and vary across primate species. Further research will help us understand their biological significance and potential applications in conservation."
Author interview: https://plos.io/4AaRfrc
In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/4jOMijb
Citation: Sales JVF, de Barros RM, de Castro PHG, Souza AR, Hirano LQL (2026) Taxon-related variation in palmar and plantar friction ridge patterns among Aotus infulatus, Saimiri collinsi and Sapajus spp.: Individual-level variation and implications for identification. PLoS One 21(11): e0360621. https://doi.org/10.1371/journal.pone.0360621
Author countries: Brazil
Funding: The author(s) received no specific funding for this work.
