Lots of things changed during the global COVID-19 pandemic – and while the effect of restrictions was felt keenly by the world's human population, the animal kingdom was also affected, with some surprising outcomes.
On a small island along the Thai Gulf in Koh Ped (KPE), eastern Thailand, a group of common long-tailed macaques (Macaca fascicularis fascicularis) were observed doing something that had never been seen in that group before: using stone tools to crack open rock oysters (Saccostrea forskali).
The macaques have been watched frequently for more than 10 years, but were first observed using stone tools during the COVID-19 pandemic in July 2022.
The researchers think these events are linked. The KPE island is a tourist hotspot, and the monkeys were frequently fed by the tourists during their visits to the islands. However, during the pandemic, no tourists were allowed onto the island – and thus the monkeys had to find new ways to make up for the loss of food from humans.
These observations mark the sixth wild nonhuman primate to use stone tools to forage foods. Only one other species of macaque– the Burmese long‐tailed macaque (Macaca fascicularis aurea) – is part of that list.
In March 2023, the team observed the macaques throwing stones, which is a known precursor to using the stones to access food and they named the technique “pound-hammering-like”. The team observed 17 adults and sub-adults using the stone tools and found that 15 of the 17 monkeys using the tools were males. They also observed that the macaques were mostly solitary when performing this behavior.
Given that travel restrictions have now eased and tourists are once again returning to KPE, the team thinks that the tool use could even disappear as more food becomes available for the macaques once more.
The paper is published in the American Journal of Primatology.