University of Saskatchewan (U of S) ecotoxicologist John Giesy is part of a team led by former U of S research associate Professor Xiaowei Zhang of Nanjing University in China that used genetic sequencing to study the microbiomes of wild cranes and those raised in captivity.
"I think the microbiome does a lot more than we thought," Giesy said. "It needs to be part of the understanding of what wild birds might face in a changing environment or when we have them in culture or hold them in the lab for any period of time."
Microbiome refers to the populations of bacteria and other microbes that live within all animals. While it's known that these microbes do everything from producing essential nutrients to crowding out harmful pathogens, their full role is largely unknown. The research team reported there is little information comparing the gut microbiome of captive and wild cranes.
The team, including one of Giesy's former post docs, exotoxicologist and avian ecologist Miguel Mora of Texas A&M University, collected samples from the droppings of 108 cranes, including 22 wild birds. Using genetic sequencing techniques, they identified which microbes were present and in what proportions. They found that the microbiomes of captive and wild birds were significantly different, likely due to the captive birds' diet, being housed in enclosures, and being provided veterinary care, including antibiotics.
While the care keeps the birds healthy while in captivity, their compromised microbiomes might put the captive birds at risk of infection when released into the wild. This may provide one clue as to why efforts to reintroduce red-crowned cranes from captive breeding programs have been largely unsuccessful.
"Compared with wild cranes, relatively great rearing density, formula diet and frequent contact with human keepers of artificially bred cranes might increase risk of infection from the time they were neonates," the team reported in their paper, which appears in Nature Scientific Reports.
The paper goes on to suggest one possible way to manage this would be to attempt to create the desired version of the microbiome with probiotics or microbe transplants from wild birds.
Long revered as symbols of good luck and longevity, red-crowned cranes are depicted on Chinese, Japanese and Korean art both contemporary and going back thousands of years. Standing about 1.6 metres tall and with a wingspan of up to 2.5 metres, they are one of the largest cranes in the world -- and one of the rarest, with only about 2,700 individuals left in the wild, chiefly in China, Korea, and Japan.
"They are regal birds; they're worth saving," Giesy said. "The world would be a poorer place without them."