New Delhi, Nov. 26 -- Authorities worldwide have seized an average of nine tigers each month over the past five years, highlighting a worsening trafficking crisis that threatens the survival of one of the planet's most iconic species, according to research released Tuesday.

A new report by wildlife trade monitoring network TRAFFIC warned that criminal networks are evolving faster than conservation efforts can respond. The global wild tiger population, once around 100,000 a century ago, has now plummeted to an estimated 3,700-5,500, it said.

Despite half a century of international protection, TRAFFIC's findings showed that tiger trafficking is accelerating and increasingly targeting whole animals, living or dead. Experts say the shift ap...