Brenda, A quick Google search will bring up a lot of studies of animals being dying quickly after eating chokecherry stems, leaves, and seeds. All cherries and other species of Prunus have poisonous pits. They contain amygdalin, which the body converts into cyanide. Bears would have to eat a lot to be affected. Plus they tend to swallow the berries whole instead of crushing them.

Margaret, Yes, Pomona’s Pectin is activated by calcium. Some fruit contain calcium naturally, but adding it assures that it will gel: http://www.pomonapectin.com/faq/do-i-have-to-add-calcium-water-to-my-jam-or-jelly/