Other than humans, do any primates ever strike with a closed fist?
Either punching as a form of attack, or striking with a closed fist in a functional way for, say, breaking open a piece of fruit or something?
Lacking opposable thumbs makes a closed fist impossible.
The OP did specify “primates”, which would make opposable thumbs de rigueur.
You could amputate my thumb, and I’m pretty sure I could curl my remaining digits to form a fist with pretty much the same functionality it had prior to the amputation.
But what sound would that make?
chimp video here. Caption mentions the chimp striking the police car’s window with its fist, although this is not shown on camera.
Why? You don’t need an opposable thumb to be able to curl up your fingers tightly, do you?
Considering I specifically limited the scope of the question to animals who have opposable thumbs can we get past the discussion of whether opposable thumbs are needed to form a fist?
Thanks, Machine Elf for the video. Indeed, though a fist is mentioned in the description of the video it is not visible. We do see the chimp’s right hand hit the windshield (I think that’s what we’re seeing) and that hand seems to be open. He may also have been striking with his left hand- which may have been closed in a fist- but you are correct that, other than the written description of the video- there is no evidence of this.
Primates knuckle walk:
Orangitangs use their fists to walk: “Gorillas and chimpanzees are habitual knuckle-walkers, whereas orangutans usually move quadrupedally with the hand made into a fist.”
http://uts.cc.utexas.edu/~bramblet/ant301/seven.html
According to this unsubstantiated claim at ehow:
"Hitting
A chimpanzee will use a balled-up fist at the end of the very muscular arm to punch its enemy. This isn’t often the chimpanzee’s first choice in defense, but if the enemy is within range the chimpanzee will have no problem letting one fly.
Read more: How a Chimpanzee Defends Itself | eHow.com http://www.ehow.com/about_6536427_chimpanzee-defends-itself.html#ixzz1apRzTFxV
Chimpanzees will shake their fists on occasion: 5 Amazing Ways Chimps Are Just Like Us - Jane Goodall : Jane Goodall
All that said, when I read about primate fights, they generally involve biting.