Canada's Calgary Zoo will be returning two giant pandas on loan from China because a scarcity of flights due to COVID-19 has caused problems with getting enough fresh and tasty bamboo to feed their gargantuan appetites.

Pandas Er Shun and Da Mao arrived at the zoo in 2018 after spending five years living at the Toronto Zoo and were supposed to remain in Alberta until 2023.

Er Shun and Da Mao were born at the Chongqing Zoo a year apart between 2007 and 2008. Er Shun -- the oldest -- was named for her smoothness, and the name Da Mao means "first of Mao," as he was his mother's firstborn.

TWO GIANT PANDAS MATE AT EMPTY HONG KONG ZOO FOR FIRST TIME AFTER LIVING TOGETHER FOR A DECADE

More than half a panda’s day is spent eating bamboo, which makes up 99 percent of its diet. An adult panda will consume up to 38 kilograms, or about 84 pounds, of bamboo a day.

The zoo’s president, Clement Lanthier, told The Associated Press on Thursday that the facility spent months trying to overcome transportation barriers in acquiring fresh bamboo during the global pandemic. Bamboo is rare in Canada and Er Shun and Da Mao prefer only certain kinds.

“They are picky,” Lanthier said. “There’s a reason why they are endangered. They need their bamboo. That’s all they do. They eat bamboo and they sleep.”

The nearly five-month-old female Panda bear named Chulina, left, eats bamboo at her enclosure at the Madrid Zoo in Madrid, Spain, Thursday, Jan. 12, 2017. Madrid's zoo has named its latest baby panda bear Chulina (Cutey), in homage to Chulin, the first panda born at the zoo 34 years ago. (AP Photo/Daniel Ochoa de Olza) (The Associated Press)

Transporting bamboo from California added even more frustration to the process. Some of the bamboo shipments the panda duo received were promptly turned away upon receipt and other shipments that had arrived from Los Angeles were past their expiry point. The shelf life of bamboo is only four to five days long.

“Every 10 days there is more and more problem moving bamboo to Calgary. This risk is unacceptable,” Lanthier said.

“I cannot risk not being able to provide the best care to the panda every day. For other species there are options. For the panda, it has to be freshly delivered twice a week. It’s time for the panda to go back home," he said.

Lanthier also reported that the news came as a bit of a shock to the Chinese government. In other locations where pandas are exhibited -- such as France, Spain, and different parts of Asia -- bamboo can be grown locally.

The pandas had been one of the largest draws at the Calgary Zoo.

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While there is currently no date on the calendar for when the pandas will return home, Lanthier hopes it will happen in the next couple of weeks. He expects to get an export permit next week.

“I hope they move swiftly. We need to move them to a place where bamboo is abundant,” he added.

The Associated Press contributed to this report.