CALGARY -- With bamboo becoming harder and harder to source due to direct flights between Calgary and China being cancelled for the last two months, the Calgary Zoo has decided its two resident giant pandas will be returned to Asia.

Bamboo makes up 99 per cent of the giant panda diet. Once direct flights between Calgary and China were cancelled in March, WestJet began transporting fresh bamboo to Calgary from Toronto. But when flight frequency between Toronto and China lessened, that option was no longer viable, zoo officials said in a statement.

“We believe the best and safest place for Er Shun and Da Mao to be during these challenging and unprecedented times is where bamboo is abundant and easy to access,” said Calgary Zoo president and CEO, Dr. Clément Lanthier.

“This was an incredibly difficult decision to make but the health and well-being of the animals we love and care for always comes first.”

The zoo is now working with the Canadian and Chinese governments to secure transport permits, said Alison Archambault, the zoo's communications director. They expect that to be completed and the animals to depart sometime in the next few weeks.

Each adult giant panda consumes about 40 kilograms of bamboo daily.

"The Calgary Zoo team has worked tirelessly with alternate bamboo suppliers to find a way to keep the giant pandas fed, despite misdirected shipments, slower than acceptable delivery times causing some poor quality bamboo that the giant pandas won’t eat, and concern with limited supplies," the zoo said in a statement.

"Forces beyond the zoo’s control could disrupt these remaining lines of supply at any time — and without warning."

Er Shun and Da Mao arrived in Canada in 2014 as part of a 10-year agreement between Canada and China. After spending five years at the Toronto Zoo, the two adult giant pandas arrived at the Calgary Zoo in March 2018 with cubs, Jia Panpan and Jia Yueyue.

The cubs are already back in Asia, returning last fall as part of a breeding program.

"Er Shun and Da Mao will be deeply missed by staff, volunteers, donors and visitors from around the world," read the statement.

Calgarians are invited to say a virtual goodbye to the pandas through the PandaCam.