An international team of researchers has created a tool that uses an interactive database of geographic and genetic information to identify where confiscated African elephant tusks came from.
More elephants die at the hands of poachers than natural causes every year. From 2006 to 2016, the number of African elephants in Africa dropped by 110,000. The rate of poaching has been increasing since 2008. Today there are only 415,000 living African elephants. There are 73 elephant population locations across various African countries that are believed to carry half of the world’s population of African elephants. The population numbers in these areas are less than 25% of what it could be if poaching didn’t occur.
Researchers around the world are using science to stop elephant poaching, by analyzing genetic markers in elephant nuclear DNA to pinpoint where the ivory is from. But there is little to no difference in the nuclear genes of elephants across central Africa. Nuclear DNA comes from both parents and can identify individual elephants, but it does not show the geographical location. Teams can find a general location, but it is difficult and requires a lot of genetic data and statistical modeling. When developing the new tool, the team turned to mitochondrial DNA.
The new tool, called Loxodonta Localizer, matches genetic sequences from poached ivory to sequences stored in its database. The tool relies on genetic information from a small and highly variable region of the mitochondrial DNA in elephants. Mitochondrial DNA is passed to offspring from the mother. The variable region of mitochondrial DNA holds more recent mutations in DNA than other parts of the genome. This is perfect for distinguishing between elephant populations. Elephant herds tend to stay in certain locations for many generations. So if a team can find the mitochondrial DNA and determine which population the elephant belonged to, they can figure out where the tusk is from.
The team used Sanger sequencing to sequence mitochondrial DNA. This method is inexpensive, easy to use and can be generated pretty much anywhere. Once sequenced, Loxodonta Localizer holds the sequences in its database. When a new sample of ivory is sequenced, it is compared to the other sequences in the database and the location is revealed. Right now, the tool holds the mitochondrial DNA sequences from over 1,900 African forest and savannah elephants.
The team tested Loxodonta Localizer with mitochondrial DNA from ivory seized in Malaysia in 2012. This ivory had already been independently analyzed and assigned geographic origin based on nuclear DNA. The nuclear DNA and the mitochondrial DNA assessments agreed on the ivory’s location, but the Localizer was faster and cheaper. The Localizer also offered a more precise geographic picture of the tusk's origin.
The tool can tell investigators which tusks in a sample will be the most helpful to complete sequencing. For example, the Localizer can determine if two tusks from different shipments are from the same elephant.
Identifying the source of poached ivory within days of intercepting it is very important for finding smugglers. The faster the smugglers are identified, the quicker law enforcement can stop them and potentially link the smugglers to larger smuggling networks.
Scientists hope that more scientists will sequence tusks using this tool and add the DNA to the database. Right now, sequences from one out of every 200 elephants in Africa are in the database. The database needs more samples so it can hold as many geographically informative sequences as possible. The more sequences the database holds, the easier it will be to identify tusk location.
A paper on this study was published in the Journal of Heredity.