Have any species (with the exceptions of humans) been observed to kill themselves purposefully?

What maintain homeostasis when a persons internal body temperature is 97.5°f

Several billion years ago which gas was the least prevailant in the atmosphere

Npiranha, fish with large teeth represent the dominant trait. because the dominant trait masks the recessive trait, in a population of 1,000 piranhas, all with large teeth, we could expect about the next generation of fish to have small teeth.