Protesters have frustrated an attempt to transport eight elephants from Thailand to Australian zoos.
The elephants were forced to remain in cages during protests
Activists staged a blockade for almost 24 hours at a quarantine centre in Kanchanaburi in western Thailand, where the animals are being kept.
The protesters say the Asian elephants, which are an endangered species, will suffer if kept in captivity.
But an Australian zoo official said the transfer was part of a joint deal with Thailand to help conserve wildlife.
"I am perplexed and surprised that this would happen, given that we had complete agreement between our governments and have been so fully committed to our long-term relationship to contribute to vital wildlife conservation projects in Thailand," said Guy Cooper, head of the Consortium of Australasian Zoos.
But activists in both countries say the elephants will suffer and should not be moved.
"Keeping elephants in zoos is simply cruel," said Hugh Wirth, president of Australia's Royal Society for the Prevention of Cruelty to Animals.
Soraida Salwala, founder of the Thai group Friends of the Asian Elephant, said the animals would suffer in the confines of the zoos and that the programme would not help to conserve the species.
There have been protests in both Thailand and Australia
The transfer had already been held up for more than a year as animal rights groups fought against the move.
However, an Australian tribunal approved the transfer in February as long as certain conditions were met, such as appropriate flooring.
Mr Cooper said the zoos in Sydney and Melbourne had been renovated accordingly.
Taronga Zoo in Sydney had spent A$40m ($30m) on a new enclosure with hot and cold bathing areas, an elephant exercise area, waterfalls and ponds and specially designed "sleeping mounds".
Australian Environment Minister Ian Campbell has said the breeding program would help to ensure the survival of the species.
Mr Campbell said that with fewer than 50,000 Asian elephants remaining in the wild, "every attempt must be made to ensure the survival of the species, including through captive breeding programs," AP news agency reported.