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Reproductive woes spell need for more viable females in Sumatran rhino program

Mongabay | April 10, 2020

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JAKARTA: More fertile female Sumatran rhinos should be captured from the wild for breeding programs to save the species, scientists say, citing the prevalence of reproductive problems.

Working specifically to capture healthy, reproductively viable rhinos would be a marked shift from the current conservation policy, which has focused on capturing and trying to breed “doomed” rhinos — those defined as living alone or in groups too small to sustain natural breeding in the wild.

In a recently published paper, researchers analyzed reproductive diseases found in 22 of 32 female Sumatran rhinos (Dicerorhinus sumatrensis) captured or poached from various sites in Indonesia and Malaysia between 1984 and 2018.

“Fertility problems have been pervasive in these ‘rescued’ females,” said lead author Nan Schaffer, the founder of SOS Rhino and a veterinary expert on Sumatran rhinos.


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The researchers found that uterine cysts and tumors were the most frequently documented reproductive problems. They also identified other reproductive failures such as early embryo deaths and an enlarged uterus. While some of the observed rhinos had symptoms of a single reproductive problem, others were found to show a mix of related diseases. None of the captive animals showed signs of infections in their reproductive organs.

The authors noted that reproductive problems prevalent in small, isolated, inbred populations of captive rhinos were also evident in animals in the wild. They cited findings of reproductive problems observed immediately in female rhinos that were captured from the wild, notably rhinos captured from doomed populations from 2001 onward.

“A high rate of infertility is inherent in small inbred populations with isolated females, and it continues to interfere with the growth of captive and wild populations,” Schaffer wrote.

Indonesia is the last refuge for the Sumatran rhino. Seven captive individuals live in a sanctuary in Sumatra’s Way Kambas National Park, and a lone female is kept at the Kelian sanctuary in Indonesian Borneo. The wild population is estimated to be no more than 80 individuals living in small, fragmented habitats in Sumatra and Borneo.

The researchers suggest that, among the wild population, “only a small number of reproductively viable animals may be left.”

“In light of these facts, building a new productive captive population by starting immediately with capturing viable, productive animals from the onset and optimizing their production is essential,” the paper says.

The researchers said that, based on analysis of camera-trap photos, the rhino populations with known breeding females are located in Way Kambas, in southern Sumatra, and in the Leuser ecosystem in northern Sumatra.

“They are the first focus areas for capturing viable females, before they, too, are lost,” the researchers wrote.

The wild rhino population in Way Kambas is estimated at 30 individuals.

Conservation experts and officials are already planning to capture some of them to add to the seven rhinos held in the park’s captive-breeding sanctuary. The Indonesian government is also working to build another sanctuary for the species in the Leuser ecosystem.

However, Indonesian officials have taken a cautious approach to the program, citing the potential risks from removing fertile animals from the wild — namely, compromising the viability of the few populations that are still breeding naturally, and the hazards of trapping and translocating the captured animals.

“For the capture effort in Way Kambas, [we] must be sure about the population number and sex ratio of the remaining wild rhinos so that the sex ratio in the wild won’t be disrupted,” Indra Exploitasia, the environment ministry’s director for biodiversity conservation director, told Mongabay.

While many rhino experts support capturing fertile female rhinos for the managed breeding program in captivity, some have called for a more nuanced approach to the strategy.

“My reason for not being ‘all in’ on the idea of capturing all the Sumatran rhinos is that even with the detailed knowledge we now have on the reproductive physiology of this species and the science-based template we have for breeding them that has proven successful repeatedly, the species remains extremely difficult to breed in managed programs because individual rhino behavior is complex and difficult for humans to understand,” said Terri Roth, the head of CREW, a research facility at Cincinnati Zoo and the scientist who pioneered the process of breeding the species in captivity.

The Indonesian experts at the Way Kambas sanctuary have experience in the process, having overseen the successful births of two calves there, but also say it is a particularly challenging task and that much about the animal remains a mystery.

“A team with less experience will find the task even more daunting,” Roth said.

“However, I certainly support the plan to capture one or two females that have been seen with calves within the past five years, but only if we are sure they will go to a team that knows how to breed this species,” she added.

“We can’t capture another fertile animal and then fail to breed her for ten years as we have done in the past. If that is going to happen, her odds of contributing to her species are better if left in the forests,” Roth said.

The Indonesian government’s capture program has long targeted so-called doomed animals in populations too small to survive in the long term. Such populations are found in Sumatra’s Aceh province and Bukit Barisan Selatan National Park, and in East Kalimantan province in Borneo.

“All of the doomed rhinos will be rescued and placed in the sanctuaries in the three regions,” Indra said.

Roth agreed that there was a need to rescue these rhinos, given that there are fewer than 80 Sumatran rhinos left in the world.

“The isolated rhinos that are slated for capture may not be fertile, but if the decline of these populations was rapid and calves were still being born 5-8 years ago, then there is a chance a female rhino captured from such populations will still be fertile,” she said.

“You just hate to give up on any of them when there are so few in the world.”