A new study found out that there are two different groups of Indian star tortoises living in the wild. These tortoises are among the most trafficked animals in the world. One group lives in the northwest of India, and the other lives in the south.
This study found that the wild Indian star tortoises are organized in a specific way based on where they live, which is called biogeography. It also discovered that the two groups of tortoises have a good amount of genetic variety, which is different from what was thought before.
Using genetic information to help manage Indian star tortoises can be really helpful. It means we can understand more about their characteristics and the natural differences in their genes. This way, when authorities seize tortoises that have been trafficked, they can release them into environments where they’re more likely to survive.
The Indian star tortoise is often smuggled to be sold illegally as pets or for their body parts. They are only found in certain dry areas in India and parts of Pakistan in the northwest, and in southern India and parts of Sri Lanka. Since it was declared highly endangered and given the highest level of protection under international law, there have been hundreds of news reports about the tortoises being trafficked. Just between October 2021 and February 2022, government authorities in India seized over 5,000 star tortoises from smugglers.
When authorities catch trafficked animals, they usually end up in places like zoos or wildlife centers. But often, these places don’t have the right knowledge to take care of them properly. Sometimes, the animals are put back into the illegal wildlife trade. Other times, they’re released into wildlife sanctuaries nearby without proper planning or research.
To stop the wrong release of these tortoises in India, a group of scientists from the Wildlife Institute of India and Panjab University did some tests. They used genetic testing and looked at physical features to understand where these tortoises live. Their findings show that the tortoises in India have a good amount of genetic variety, even though they’ve been illegally hunted for many years.
The scientists think that the differences they found might mean that the tortoises are better suited to living in either the northwest or south of India. So, if we use genetic information to manage these tortoises better, we can make smarter decisions about how to help them and where to release them after they’ve been rescued.
The Indian star tortoise is one of the most trafficked species in the world. Photo by Ankit Rainloure/Pexels.
Could the two populations be grouped as separate subspecies?
The scientists collected samples from 82 tortoises from different places in both northwest and south India. They took bits of tissue from the tortoises and extracted DNA from them. Then, they used a technique called polymerase chain reaction (PCR) to make more copies of specific genes or sections of DNA. After that, they figured out the order of the building blocks (nucleotides or bases) in these genes, which is called sequencing.
They looked at a specific group of genes to learn about the history of the tortoises – like how their populations changed over time in terms of size, structure, and where they moved. They wanted to see if the tortoises from the northwest and south of India were part of one big group or if they were separate. They also measured different parts of the tortoises’ bodies to understand their physical features better.
The genetic studies showed that the star tortoises in the northwest and south of India are very different from each other. They’re so different that they might actually be considered as two different types, called subspecies. This difference probably happened because a long time ago, there was a period when it was really dry, followed by a time when there was a lot more rain during certain seasons. This change in climate helped grasslands to spread across India, and the star tortoises moved to where they live now in the north and south. Later on, there were other changes in the climate that caused some parts of India to have more forests and some to have fewer. This split the star tortoises into the two groups we see today, about 2,000 years ago. These groups stayed mostly the same until maybe 100 or 200 years ago, when people started trading star tortoises.
The tortoises from the north and south have shells with different patterns. The ones from the south have fewer lines on their shells and the patterns are more noticeable compared to the ones from the northwest. Also, the tortoises from the northwest are usually bigger. Even though female tortoises are bigger than males in both groups, the females from the south are about the same size as the males from the northwest.
Surprising results on genetic diversity
The scientists also looked at another type of genetic marker called microsatellites to see how healthy the wild star tortoise populations are. Before, other studies suggested that the tortoise populations weren’t doing well genetically, and their habitats were getting worse. One reason for this difference in results might be that earlier studies used genetic samples from places like zoos, captive populations, or pet stores. But this study looked at tortoises in their natural habitats in the wild.
The tortoises in the northwest have moderate genetic diversity. This could be because their habitat is pretty similar throughout. They live in places that are mostly dry, like semi-deserts and semi-arid savannas, with the Aravalli hills in the north and the Kutch and Kathiawar peninsula in the south. This kind of environment might have made them adapt to living there in a certain way.
On the other hand, the tortoises in the south have a lot of genetic diversity. People call this area a “hotspot of genetic diversity” because there are four different groups of tortoises living there. These groups are a bit different from each other but they also have some similarities. The southern population of tortoises lives in different parts of central and southern India and in Sri Lanka. They live in places with lots of different landscapes and climates, like ancient hill ranges and dry zones.
How do these results impact management strategies?
Right now, when authorities seize star tortoises in India, they often release them into wildlife sanctuaries like the Chinnar wildlife sanctuary and Sathyamangalam wildlife sanctuary. But the scientists who did this study say that doing this without knowing where the tortoises come from – whether they’re from the northwest or the south – might not be a good idea.
As per the study, the biogeogrpahy of wild Indian star tortoises is well-structured and that the two populations have moderate to high genetic diversity. Photo by Adityamadhav83/Wikimedia Commons.
The scientists said, “We should keep the natural differences between the northwest and south star tortoise populations to avoid mixing their genes because of human activities like illegal trade and releasing them. We need to make sure that when we release seized tortoises, we put them back into the area where they belong genetically, based on what we know from studying wild tortoises, and not mix up the two groups.”
Basically, putting northwest tortoises in the south or southern tortoises in the northwest could harm them or their babies because they might be better suited to where they originally came from. But most of the time, the pet trade sells young tortoises that haven’t fully developed yet, so it’s hard to tell where they’re from just by looking at them. The scientists suggest doing genetic testing before deciding where to release them.
“Our research gives a database we can use to release tortoises in a smart way for better management and protection. Using genetic information to manage these highly trafficked tortoises will help us make better decisions based on evidence, using their natural traits and genetic differences,” the study concludes.
“These findings are surprising and interesting, especially for a species like the Indian star tortoise, which has been traded as a pet for a long time, both in India and worldwide,” says Uttara Mendiratta, a scientist affiliated with the Wildlife Conservation Society (WCS) in India. “The authors’ advice to be cautious about releasing seized tortoises without knowing where they come from makes a lot of sense. Additionally, having this genetic information could help enforcement agencies figure out where these tortoises were taken from and where they’re being traded the most. These results also make us think about how these different groups of tortoises have managed to survive despite being traded so widely.”
[Caption: The picture shows an Indian star tortoise in Polonnaruwa, Sri Lanka. In India, there are two separate populations of these tortoises – one in the northwest, near Pakistan, and the other in the south, near Sri Lanka. Photo by Jon Gudorf Photography/Flickr.]
