Soil DNA analysis from paw prints could help Sumatran tigers

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Editor’s Note: Netflix’s “Tiger King” exposed how tigers were abused and exploited. This Sunday at 10pm ET, “This Is Life with Lisa Ling” encounters some people trying to stop it.



CNN

Dr. Mrinalini Watsa, a researcher with the San Diego Zoo Wildlife Alliance in California, scoops up soil from a fresh paw print made by Rakan, a 4-year-old male Sumatran tiger living at the San Diego Zoo Safari Park, and secures it in a test jar .

Back in her lab, Watsa analyzes the sample using a small electrophoresis device connected to a smartphone. jackpot. She can detect Rakan’s DNA in the soil.

The proof of concept experiment is part of her work adapting existing genome sequencing technology so that it can be easily used to detect individual tigers in the wild using their DNA. Watsa hopes the application will make it easier to track Rakan’s wild counterparts on Sumatra, Indonesia’s largest island, and tiger populations through the rest of Asia.

“Now, instead of saying we’ve seen about 40 prints in this 3 square kilometer (1.8 square mile) area, you can actually see those 40 prints add up to four tigers and that gives us so much more power in how we count them,” she said on the latest episode of CNN Original Series “This Is Life with Lisa Ling.”

All living organisms, including humans, shed genetic material into the environment when they excrete waste, bleed, or shed skin or fur.

Conservation scientists are increasingly using this environmental DNA — whether it’s in the soil, water, snow, or even air — to gather information about particular species or ecosystems. It can alert scientists to the effects of the climate crisis or the existence of harmful pathogens, and help them track animal populations.

In her experiments so far, Watsa has been able to detect Sumatran tiger DNA in the soil and determine the sex of the animal. Watsa wants to refine her approach so she can identify individual tigers before testing them in the field.

Tiger numbers are up 40% in seven years, from 3,200 in 2015 to 4,500 in 2022, according to the latest estimates released in July by the International Union for Conservation of Nature.

This promising population growth has been hailed as a conservation success story, but Watsa and other tiger experts say the mission is not accomplished. Tigers still hold an endangered status on the IUCN Red List of Threatened Species and make up a fraction of the 100,000 inhabitants that roamed Asia in the early 20th century.

Moreover, the main figures mask a more nuanced picture.

Tiger populations are growing in some places in India and Nepal, but the big cats claw a much more fragile existence in Southeast Asia. Tigers have been extinct in Vietnam, Cambodia and Laos since 2000 and teeter on the edge of Malaysia. In Sumatra, where Watsa’s work focuses, fewer than 800 tigers are estimated to live, with only two protected areas having more than 25 breeding female tigers.

Moreover, it is not clear to what extent the detected increase in numbers is due to intensified and improved tracking techniques or to actual population growth. Tiger counts are rarely based on direct observations; instead, population numbers are inferred from tracks or pug marks, or how often tigers are detected by hidden cameras.

“It is a cautious optimism. Tiger numbers are better known than ever before. It’s more than a rebound, I’d say it’s a much more accurate estimate,” said Abishek Harihar, the deputy director of the tiger program at Panthera, the big cat conservation group.

“Many of the so-called increases have more to do with better estimation methods,” he added.

Watsa hopes that the DNA detection methods she is developing, with Rakan's help, will improve the tracking of tiger populations in the wild.

For example, Harihar said India, which accounts for about 64% of the world’s wild tiger population, conducts a survey every four years, but the area surveyed has increased over the past 12 years, making it difficult to really understand population trends. .

Population monitoring in India is mostly done using camera traps, Harihar added. He believes DNA techniques could help scientists better understand how some tigers disperse between different areas, which is hard to see with cameras.

“It’s good to understand where the different tigers come from and then we can secure these dispersal routes,” he added. “DNA techniques will also be useful where camera trapping is difficult,” he added, such as in the remote, mountainous regions of Southeast Asia.

Watsa believes the techniques she is pioneering will overcome some of the weaknesses of camera-based monitoring.

“The camera is only looking at a very small radius around it, so an animal could walk just outside of it and it would be missed completely. This means they have a huge margin of error,” she said.

In developing techniques that are more cost-effective and user-friendly, Watsa is aiming for more accurate numbers of tiger populations.

Watsa also hopes that her portable DNA analysis techniques can be used for forensic investigations. The biggest threat to tigers today is poaching and trade in their body parts, which are prized for traditional medicines in places like China.

The analysis of tiger DNA in soil samples can help forensics in the fight against illegal wildlife trade.

Tigers occupy only 45% of the 2.1 million square kilometers (1.3 million square miles) of remaining tiger habitat that still exist in South Asia and East Asia, an indication of the extent of poaching, Harihar said.

Analysis of DNA samples from seized skins, bones and animals could help identify tiger populations most at risk from poaching and track down people and organizations involved in the illegal tiger trade, Watsa said.

According to Traffic, a group that monitors the illegal wildlife trade, there were 2,205 seizures of tigers and their body parts in 50 different countries between 2000 and June 2022. Of these, a third were whole tigers, with 665 found alive and 654 found dead.

In the United States, the popular 2020 Netflix documentary “Tiger King” exposed the exploitation of tigers for entertainment. The Big Cat Public Safety Act, a piece of legislation that would set limits on private tiger ownership and help prevent big cats from entering the illegal pet trade, passed the House of Representatives in late July.

The Valley Voice
The Valley Voicehttp://thevalleyvoice.org
Christopher Brito is a social media producer and trending writer for The Valley Voice, with a focus on sports and stories related to race and culture.

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