GUWAHATI, India - Poachers in northeast India have slaughtered 13 endangered one-horned rhinos in the last two months, officials said Friday as another death added to worries about a recent surge in killings. The attacks have taken place around the Kaziranga National Park in Assam state, home to more than two-thirds of the world’s one-horned rhinos where heavily-armed poachers shoot dead the giant herbivores. On Thursday, forest rangers deployed to protect the species were engaged in a gun battle for more than seven hours but failed to prevent the killing of another animal. “The poachers killed the rhino and took away its horn. In two months they have killed 13 rhinos,” Kaziranga park warden N.K. Vasu told AFP.