When Smithsonian researchers set out to discover why black rhinos in human care were experiencing a range of metabolic problems, they didn’t expect to uncover the stark difference in microbes between black rhinos in human care and those in the wild.
The study involving the animals’ diet has made way for new data showing black rhinos in human care are eating too many starches, said Budhan Pukazhenthi, a research physiologist with the Smithsonian Conservation Biology Institute in Front Royal.
“Although we anticipated some changes in gut microbiome between wild rhinos and those in human care, the stark difference in microbiome — indicating more starch-metabolizing microbes in rhinos in human care — was a surprise,” Pukazhenthi explained in a news release posted at the SCBI’s website, https://nationalzoo.si.edu/conservation/news.
The study was funded in large part by the International Rhino Foundation, which has its program office in Strasburg.
Black rhinos are critically endangered, declining by more than 90% since the 1960s when there were more than 100,000 in the wild. On average, more than 1,000 rhinos are still poached each year in countries such as South Africa, Namibia, Kenya and Zimbabwe.
The SCBI is part of a global effort to help stabilize black rhinos in human care to eventually help revive their populations in the wild.
“With fewer than 100 black rhinos in zoos in North America,” Pukazhenthi stated in the release, “we need to do everything we can to improve the health of this population, which acts as a reservoir against potential extinction. This study is a great step toward being able to do so successfully.”
By comparing bacterial communities in the stool of wild rhinos to those of captive rhinos, scientists were able to identify the high level of starch in the animals’ diets. This resulted in a recommendation for a health-boosting rhino diet.
“We want animals that are breeding well and also healthy,” Pukazhenthi said in a recent phone call. “Switching the diet is relatively easy.”
The science behind the switch takes more consideration, though. Once linking the imbalance of microbes in their guts to the commercial diets that rhinos in human care are likely to have, he said scientists needed to consider that the way they manage the animals’ diets would affect their reproductive output.
He said the plan is to switch rhinos in human care to a diet of vegetation more like what rhinos in the wild eat.
“Zoo-animal nutrition is a science and an art,” Pukazhenthi explained in the news release.
“Nutritionists are constantly trying to develop the best nutrition plans for animals in human care. Systematic studies like this will better inform managers, nutritionists and researchers about what may be causing some unexplained health issues, as well as help them to evaluate the diets we provide our collection animals. It’s a win-win for all.”
As part of its efforts to fill out black rhino populations, the SCBI is also studying their reproduction through its Global Health Program.
Leading a study on wild eastern black rhinos in Kenya, One Health veterinary research fellow Dr. Maureen Wanjiku Kamau wrote about her experience at the SCBI website, calling Kenya a “stronghold for this iconic yet critically endangered African land mammal.”
Kenya hosts 84% of the world’s remaining wild population, she wrote.
Kenya is also home to the last two northern white rhinos and a healthy population of southern white rhino, the SCBI reports at its website.
“As such, Kenya represents an important stronghold for rhino conservation,” it says.
Though poaching presents a significant threat to rhino populations, the SCBI identifies changing environmental conditions and emerging infectious diseases as also imperiling wildlife.
Global Health Project staff are collaborating with Kenya Wildlife Service and Mpala Research Centre to identify and characterize these effects on short-term health and long-term survival of infected rhinos and develop treatment plans.
“Great strides in conservation have resulted in the gradual recovery of Kenya’s black rhinos from less than 400 individuals in the late 1980s to 696 at the end of 2016,” Wanjiku Kamau wrote. “Intensive anti-poaching efforts have also reduced the number of poached black rhinos to less than 1% each year. But there’s still more to learn about saving this species."
Researchers are looking to the animals’ dung for clues to their reproductive health, by measuring hormone levels to better understand why some female rhinos in the wild give birth to many more babies than others do.
Focusing on female black rhinos at Ol Jogi Wildlife Conservancy in Kenya, Wanjiku Kamau’s team collects and analyzes samples of the rhinos’ dung to monitor reproductive hormones without disturbing the rhinos.
“Looking at these hormones over time gives us a picture of a normal reproductive cycle. We can also look for any abnormalities or variations, which could help us better manage and optimize rhino reproduction,” she wrote.
The team is studying 17 breeding females over the course of a year, collecting fecal samples from each rhino at least twice a week.
The study serves as a pilot that can be duplicated across other Kenyan reserves. Information uncovered will be assessed in tandem with other studies geared toward securing suitable rhino habitat for population expansion, with the ultimate goal of strengthening wild rhino populations.
Core support for the Global Health Program’s training program is provided by the Morris Animal Foundation and Dennis and Connie Keller, Illinois residents who donate to a number of causes.