Poison arrow?

[Steve Lawrence]

Reading suggests that in the 1840s, and even beyond, single shot rifles prevailed. Native Americans were able to shoot perhaps a dozen arrows in the time it took to reload rifles. Often enough Comanches especially triumphed due to skill in horsemanship and knowledge of terrain. But why did Comanches not use poison arrows, as are used for example by San people of Africa when hunting game? Was usable poison available on the Western plains?