Can the captured tigers be part of efforts to save the country’s inhabitants?

Captured tigers in the United States outnumber those living in the wild. The World Wildlife Federation estimates about 5,000 big cats live in the US, most of them privately owned.

The health of this population is a genetic mystery for conservation groups and researchers who are interested in how captive tigers can help stabilize or restore wild tiger populations. Are privately owned animals similar to wild tigers, or do they reflect traits favored in the illegal trade? Are they the offspring of a wild tiger, or were they born dangerously?

New research from Stanford University, published Sept. 19 in Bulletin of the National Academy of Sciencesdelves into these questions and provides a new tool that conservationists and law enforcement can use to protect animals and prosecute those responsible for their abuse.

“We’re trying to use genomic technology to be useful for conservation purposes—there are very few tigers. We won’t get a second chance if they disappear,” said Ellie Armstrong, Ph.D. , who is the lead author. of paper.

Unknown people

The study was led by Armstrong, who conducted the research as part of his doctoral studies in biology, and his co-advisors and co-authors Elizabeth Hadly, the Paul S. and Billie Achilles Professor of Environmental Biology, Emerita; and Dmitri Petrov, the Michelle and Kevin Douglas Professor, both in the School of Humanities and Sciences.

Researchers became interested in studying the genetic diversity of privately held tigers – called “generic” because their sources are unknown – after researching the effect of genetics genetics of group isolation in the wild tiger.

“We were doing a big survey of the population of wild tigers and we used this data to solve the captive tiger problem in the United States. At first it was unbelievable that you could have a tiger living close to home that you don’t know,’” said Armstrong, now an assistant professor of evolution, ecology and biology at the University of California, Riverside.

“We got in touch with Tigers in America, and that’s when we realized that there were a large number of these cats outside of the legal enclosures that were bred to meet animals, they were kept as pets. of circuses, or sold as pets. But we didn’t know what kind of tiger it was or where it came from,” Armstrong continued.

The obstacle for the research team was the absence of official data on the common tiger. Shows like Netflix’s 2020 “Tiger King” and the 2009 documentary “The Tiger Next Door” have helped increase public awareness of the tiger problem with private individuals, but access to the animals for research purposes is it was still a challenge.

“There were a lot of rumors related to these captive populations and a lot of them are self-contradictory. People say, ‘All cats are really inbreed,’ or ‘All cats have genes, said Armstrong. “We didn’t know what to expect and we think genomic technology can help us answer some of these questions.”

Building a genetic database

By collaborating with conservation areas that had rescued common tigers, the team obtained samples and studied tigers, including areas where many animals were rescued.

The researchers collected samples from 154 wild-type tigers and used another 100 samples from the National Institute of Biotechnology Information (NCBI) database. From their previous work, the team knew there were six species of wild tigers. With this information, they created a reference base for tigers that was used to accurately identify each animal and assign their genes. Armstrong compares it to popular genetic testing for humans.

“When we do 23andMe, we don’t sequence the entire genome — we sequence the part of it that tells us about your health and your ancestry,” he said. “That’s what we want to be able to do, but for tigers. It’s difficult and expensive to sequence and analyze the entire genome, especially in terms of conservation. The process we’ve built allows you to sequencing part of the genome and finding answers in the individual and the tiger lineage.”

The benefit of law enforcement

Knowing a tiger’s lineage has benefits beyond conservation and breeding programs—criminals can use it to prosecute.

The National Big Cat Protection Act came into force on 20 December 2022, ending the private ownership of big cats as pets and placing restrictions on breeding, trade, keeping and use certain species, including tigers. (People who owned cats before the law was passed must register the animals.) However, the US Fish and Wildlife Service has warehouses full of tiger wounds, bones, teeth, etc., and cases which they cannot sue because they cannot. to accurately identify the origin and lineage of the samples. The agency has already asked to work with investigators.

“We will work with law enforcement to try to use this in a forensic setting to prosecute wildlife crimes like those seen in ‘Tiger King,’ to track US citizens, and to track illegal trade,” said Armstrong. “Materials such as teeth and pellets have very little DNA in them, and the reference system we’ve built here can allow wildlife agencies to identify where the samples were taken, even with sequencing a small part of the genome. That has been the most rewarding part of this research – we know that this work has future applications.”

Putting the rumors to rest

As for those who wonder, “What are these animals?” researchers feel they can put this question to rest. The number of tigers in captivity in the United States did not show the prevalence of different species compared to wild tiger species. Nor did they show that common tigers have a single type of lineage, as is the case with tigers kept in zoos or tigers in the wild.

These common tigers are a mixture of different types of tigers. Armstrong and colleagues show that the non-zoo tiger population in the United States is less genetically diverse than that found in the wild.

Hadly said: “This absence of unique genes in captive tigers means that there will be no ‘genetic rescue’ of wild tigers with non-human populations. and in captivity. “In other words, the genetic diversity of the wild tiger is all that evolution has to deal with going forward.”

DNA is the only way to distinguish between different species of tiger—there are no distinguishing physical differences among the six known species. If the unique evolutionary history of other tiger species remains a priority for tiger management, and we can overcome the major obstacles to releasing animals into the wild, the reference point is can be used to refer to people who do not have mixed ancestry.

Armstrong said, “This technology is often a ‘fun’ thing for people, to learn more about your genes, but we can use genomics in a profound way to help our wildlife thrive in the wild. and prevent them from being abused.”