Other than humans, tigers appear to be the only serious predators of wolves.[9][17][18][19][157] Wolf and tiger interactions are well documented in Sikhote-Alin, where tigers depress wolf numbers, either to the point of localized extinction or to such low numbers as to make them a functionally insignificant component of the ecosystem. Wolves appear capable of escaping competitive exclusion from tigers only when human persecution decreases tiger numbers. Proven cases of tigers killing wolves are rare and attacks appear to be competitive rather than predatory in nature, with at least four proven records of tigers killing wolves without consuming them.[162]