Mustelid vs. primate: Yellow-throated marten pair kills rhesus macaque

Whether a harpy eagle plucking a capuchin from the treetops or a leopard ambushing a chimpanzee, predation on our primate cousins can be intense to witness – the fearful expressions of the prey hit a bit close to home, and the concept in general maybe evokes archetypal fears of the beasts that occasionally put us on the menu.

In December, a tour group in North India's Corbett National Park witnessed an unusual primate predator in bloody action: a mustelid (member of the weasel family). More exactly, a pair of yellow-throated martens, stalking and killing a legit-terrified-looking rhesus macaque.

The attack played out for at least half an hour, according to Chris Mills of Norfolk Birding, which led the tour. "Unsurpassed for me in stirring emotions," he wrote in a Twitter post on the incident.

Found from the Himalayas and Russian Far East south to Indonesia, yellow-throated martens are the heftiest of the marten genus, Martes (the fisher of North America, which can outweigh it, was long classified as a marten but now resides in its own genus), and also unusually sociable for their kind: they often scrounge in pairs (like these monkey-hunters) or larger groups.

Mustelids as a whole come well-armed and scrappy, and many tackle prey larger than themselves. (We probably should be thankful today’s weasel clans top out around wolverine- or sea-otter-size; it’s a bit chilling to think of a mustelid any bigger.) Like South America's giant otters, the yellow-throated marten combines mustelid feistiness, decent size (as weasel types go), and a lithe build with cooperative hunting habits: a formidable predatory toolkit.

That said, the marten is no dyed-in-the-wool meat-eater: fruit composes an important part of its diet in many areas. And typical yellow-throated-marten prey is on the small side: rodents, especially, and also insects, arachnids, and songbirds.

But the marten sometimes targets bigger quarry, including small and juvenile ungulates such as musk deer, goral, and muntjac. In 2014, a three-year-old giant panda succumbed to injuries suffered during an attack by a group of yellow-throated martens in China's Sichuan Province, despite being taken into captivity for medical care.

And though they’re likely fairly unusual food, monkeys are known to occasionally fall on this tenacious critter's carnivorous radar. A healthy monkey is no easy meal: it can match or exceed the marten’s arboreal agility, and big teeth, grabby hands, and communal defence make many of the primate species sharing the yellow-throated’s range downright risky targets.

The doomed rhesus in this case was apparently all by its lonesome, and fending off the darting, high-energy assault of two determined martens is a trying and tiring task for a single (and rather small) monkey. A few years ago, also in Corbett National Park, an impaired langur – much bigger than the macaque in question – had its hands full parrying the relentless strikes of a yellow-throated marten. In the video of that attack, you can see a second marten make a brief appearance when its partner gets the monkey temporarily on the ground, though it doesn’t join the attack (at least during the clip).

Mustelid predation on primates isn’t a well-documented phenomenon, though the tayra – somewhat of a Neotropical analogue to the martens, and, like the yellow-throated, often a communal forager – will also occasionally prey on monkeys. In one instance, adult female mantled howler monkeys managed to repel four tayras from their troop: the kind of strength-in-numbers boost one particular Indian macaque really could have used when up against a nimble mustelid tag-team last month.

Header image: Rushen