Protecting the world’s endangered wildlife is a major law enforcement challenge. Poachers, often paid by organized criminal networks, have vast wilderness areas in which to operate. Rangers and police are frequently overstretched and sometimes outgunned. Even when arrests occur, cases can be difficult to prove and successful prosecutions are rare. But new tools, ranging from drones to game theory, are starting to make progress. Now the techniques of forensic genetics used in human crime scene analysis are entering the fray.
One such technique involves something long used in the prosecution of human crimes, the Short Tandem Repeat (STR). DNA is made of pairs of small molecules called nucleotides, but there are only four nucleotides that make up a strand of DNA. Statistically, there is a lot of overlap between the DNA sequence of different individuals, even different species. Enter STRs. STRs are short sequences made up of only a few nucleotide pairs, that occur in exactly the same sequence throughout the genomes. The STRs themselves might be the same, but the number of times these sequences repeat themselves varies between species, populations, and, most significantly for crime solving, between individuals.
The human genome contains millions of pairs of nucleotides, but unique STR sequences appear in a variety of short segments. That means a unique STR sequence can be determined in a very small amount of DNA (blood, hair, etc.). The DNA trace can be amplified using a technique called PCR which allows investigators to make concrete determinations from even a tiny amount of DNA. The resulting analysis can be used to determine the likelihood that a particular sample belongs to a particular person.
For animal crimes, DNA was initially used to identify populations or geographic areas rather than individual animals. A classic example comes from Michigan, where poachers could harvest bobcats in the Lower Peninsula and claim they were from the Upper Peninsula where regulations were looser. Population models allowed biologists to predict the genetic makeup of each population, and pelts could be accurately matched to their region of harvest. In Africa, investigators matched seized ivory shipments to particular areas as way to target enforcement resources more precisely.
As more cases have occurred, animal genetic testing is being accepted as evidence in more court systems along with human DNA evidence. Now authorities treat a poached carcass as they would a murder scene, with rigorous evidence collection and chain of custody procedures. If a smuggler is caught with material or evidence that matches a given carcass, they may actually face jail time.