CALGARY, Alberta — The 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 bamboo to feed them.

 Er Shun and Da Mao arrived in Calgary in 2018 after spending five years at the Toronto Zoo and were to remain in the Alberta city until 2023.

 The zoo's president, Clement Lanthier, said this week the facility spent months trying to overcome transportation barriers in acquiring fresh bamboo and decided it's best for the animals to be in China, where their main food source is abundant.

 "It's about the animals. At the end of the day, we cannot pretend that we care for animals if we don't take those tough decisions," Lanthier said. "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."

 Lanthier said the zoo had contingency plans for a steady supply of fresh bamboo, but limits on flights from China was the first problem. Transporting more from California added even more frustrations. 

 "Every week, every 10 days there is more and more problem moving bamboo to Calgary. This risk is unacceptable. We don't feel comfortable at all that we can impose that risk on the health and the welfare of the pandas."

 Lanthier said the animals didn't like some kinds of bamboo and other supplies that arrived were past their expiry point.

 Giant pandas have unique nutritional requirements and 99 percent of their diet is made up of fresh bamboo. Each adult consumes about 40 kilograms daily. Lanthier said 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 parts of Asia — bamboo can be grown locally.

 He said the pandas had been one of the biggest draws at the Calgary Zoo, but the decision wasn't one about business.

 "It's based on animal welfare. I cannot imagine if one day, two days, three days in a row I am unable to provide the bamboo. That would be catastrophic."

 There's no date for when the pandas will return home. Lanthier doesn't want the Canadian and Chinese governments to delay things.

 "We need the federal government and the Chinese government to expedite the permit process, so we can move them back to where this risk of not getting their next meal will be managed differently," he said.