BANGKOK, Thailand (AFP) — Thailand has given a contraceptive vaccine to wild elephants for the first time in an effort to control their ballooning population, a conservation official said on Wednesday.

Wildlife authorities and a veterinary team administered the shots to three female elephants in southeastern Trat province on Monday, said Sukhee Boonsang, a director of the Wildlife Conservation Office.

The aim was to manage the wild elephant population, he told Agence France-Presse, adding that the mammal’s birth rate in five provinces of eastern Thailand rises about eight percent yearly compared to three percent in other regions.

This “will cause more conflict between humans and elephants in the long term if we let it continue,” he said.

Veterinarians and officials administered the vaccines this week using a dart gun without anaesthesia, the conservation office said in a statement.

Wild elephant numbers in Thailand rose from 334 in 2015 to almost 800 last year, with thousands more in captivity.

Human-elephant conflict has caused almost 200 human fatalities and more than 100 elephant deaths since 2012, the conservation office statement said.

Asian elephants, Thailand’s national animal, are classified as endangered globally by the International Union for the Conservation of Nature.

Sukhee said the three elephants had been checked for signs of infection, were well and “living their normal life,” adding that his team will follow up with blood checks every six months.

The vaccine was tested on seven captive elephants in northern Chiang Mai two years ago, he said.

Another 15 doses will be used on elephants in other herds in Thailand before this year’s rainy season starts from May, Sukhee said.