Trail of the Seahawks [The Macaque Cycle, Book Two], by Ardath Mayhar and Ron Fortier (Paperback)

Years after a plague has decimated the world, altering the remaining animals beyond recognition, the few remnants of humanity inhabit the coast of old New England. A small group of warriors, including sentient Macaque monkeys, must fight rogue outlaws and the feared Seahawks to save civilization from the barbarians.