Isotope data strengthens suspicions of ivory stockpile theft

CITES-marked tusks from a recent seizure of ivory from Uganda. Credit: John E. Brown III

In January 2019, a seizure of 3.3 tons of ivory in Uganda revealed something surprising: Markings on some of the tusks suggested they may have come from a stockpile of ivory that the government believed was kept strictly under lock and key from Burundi. .

A new study from the University of Utah distinguished Professor Thure Cerling and colleagues, published in: Proceedings of the National Academy of Sciences, uses carbon isotope science to show that the marked tusks were more than 30 years old and had somehow found their way from the guarded government stockpile into the hands of illegal ivory traders. The results suggest that governments holding ivory stocks may want to take a closer look at their inventory.

Ivory’s isotope signatures

Cerling is a pioneer in using isotopes to answer questions about physical and biological processes. Isotopes of a particular element refer to atoms of the element that vary in their number of neutrons, and thus vary slightly in mass. For example, a carbon-14 isotope has one more neutron than carbon-13.

Some isotopes are stable and some are unstable. Unstable isotopes decay into other isotopes or elements through radioactive decay. Since the rate of decay is known for unstable isotopes, we can use the amounts in a sample to determine the age. That’s how radiocarbon dating works: It uses the decay rate of unstable carbon-14 to determine the age of organic material.

About a decade ago, Cerling attended a presentation to the U by Sam Wasser of the University of Washington who studied the genetics of wildlife and used those tools to research the date and place of poaching in the wild. Cerling, realizing that his expertise in isotope science could add useful information, began an ongoing collaboration with Wasser.

In 2016, Cerling, Wasser and colleagues published an investigation that addressed an important question in the ivory trade: how old is the ivory that has been seized by governments? Some traders have claimed that their ivory is old, seized before 1976, and thus exempt from sales bans. And with an average of ivory catches of more than 2.5 tons, researchers, governments and conservationists are wondering how much of the ivory is recent and how much comes from criminal stockpiles — or has been stolen from one of the many ivory stockpiles held by governments. of some countries in Africa.

“Governments hold their stocks for several reasons,” Wasser says. “They hope to be able to sell the ivory for income, sometimes to support conservation efforts. However, they can only sell ivory from elephants that died of natural causes or were culled because they were problem animals. They can’t sell confiscated ivory because they don’t.” don’t’ I don’t know it came from the land.”

Combining Cerling’s isotope data and Wasser’s genetic data, the 2016 study found that more than 90% of the ivory seized came from elephants killed less than three years earlier. It was a sobering result, showing active and well-developed poaching and export networks. The investigation seemed to show that little ivory from government stocks had ended up on the black market.

marked tusks

But the 2019 ivory seizure in Uganda showed something troubling. Some of the tusks had markings suspiciously similar to those used by CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, to inventory stored ivory.

“Due to the markings seen on some samples of the ivory,” Cerling says, “it was thought that quite a few samples in this shipment could be related to material in a government stockpile in Burundi. We were asked to provide samples of this, and three other recent ivory catches, to see if some samples may be from older stocks.”

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To determine the age of the ivory, the researchers collected small samples of the tusks and analyzed them for the amount of carbon-14 isotopes in each sample. They were specifically looking for the amount of “bomb carbon” in the tusks. Between 1945 and 1963, nuclear weapons testing doubled the amount of carbon-14 in the atmosphere, so anything living that has consumed carbon since then, including you, has a measurable carbon-14 signature. The amount of carbon-14 in an ivory sample that hasn’t radioactively decayed can tell scientists when the ivory stopped growing or when the elephant died.

The method requires some calibration, using samples from organisms living in the same area. Some of the samples came from schoolchildren in Kenya, through a program called ‘Kids and Goats for Elephants’. Because most families in rural Kenya keep goats, the program, led by WildlifeDirect’s Cerling and Paula Kahumbu, involves children in collecting hair samples from goats for isotope analysis. The isotope data is useful for many applications, including fighting elephant poaching and, in this case, calibrating the bomb’s carbon decay rate for more accurate dating of ivory.

A consistent result

The researchers analyzed ivory from four seizures in Angola, Hong Kong, Singapore and Uganda. Genetic data kept them from sampling two tusks from the same individual. The results of the analysis of the seizures in Angola, Hong Kong and Singapore were as expected – the samples were mostly about three years after the elephant’s death, with no tusks taken more than 10 years earlier.

But the seizure of Uganda, with the inventory markings on the tusks, showed something quite different. Nine of the 11 tusks tested had been taken more than 30 years ago, with death dates between 1985 and 1988. Those dates correspond to the age of ivory in the Burundi government stockpile, which was inventoried and stored in sealed containers in 1989.

“My suspicions were confirmed,” Wasser says. “The bigger surprise was how close to 1989 the elephants were killed.” At the time Burundi built up its stockpile, a prerequisite for joining CITES, which helps governments manage its ivory reserves, was that the ivory to be preserved was ancient. The results suggest that wasn’t the case, Wasser said, which would violate Burundi’s requirements to join CITES.

“The hope is that CITES will call for inventory restocking,” said Wasser, “including aging randomly selected tusks and securing remaining stocks.”

How scientists are using DNA testing to disrupt international ivory smuggling networks

More information:
Cerling, Thure E., 14-Carbon shows that illegal ivory is extracted from government stocks, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2211550119.

Provided by the University of Utah

Quote: Isotope data bolsters suspicions of ivory stockpile theft (2022, Oct. 17) retrieved Oct. 17, 2022 from

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