As of 1990, up to 16 subspecies are recognized, which are divided into four regional groupings based on skull height and lacrimal bone length. The species lives in matriarchal societies consisting of interrelated females and their young (both male and female). Fully grown males are usually solitary outside the breeding season. The grey wolf is the wild boar’s main predator throughout most of its range, except in the Far East and the Lesser Sunda Islands, where it is replaced by the tiger and Komodo dragon, respectively. It has a long history of association with humans, having been the ancestor of most domestic pig breeds and a big-game animal for millennia. Boars have also re-hybridized in recent decades with feral pigs; these boar–pig hybrids have become a serious pest animal in Australia, Canada, United States, and Latin America.