They, well, eat... and breathe... you know, things that it needs to do to survive...
Pinsir seems to be based on a stag beetle, possibly Prosopocoilus inclinatus, a species commonly used in insect fighting. Its thorn-like mandibles most closely resemble that of Lucanus maculifemoratus hopei, whereas its Mega Evolved form's diagonal spikes resemble Calcodes versicolor.
So it's also part of Pinsir's origin.
Hope this helps! :)