Poachers are killing 40,000 elephants a year and with a global elephant population of just 400,000, it doesn’t take a mathematician to figure out that there is an urgent need to stop the killing.

But it’s hard to catch poachers in the act. They operate over a wide area, move just a few elephant tusks at a time and once their ivory contraband reaches a major port, it can be easily hidden among other goods, said Samuel Wasser, director of the Center for Conservation Biology at the University of Washington.

In a new study published Wednesday in Science Advances, Dr. Wasser and several colleagues demonstrated an approach he hopes will help catch and convict more international ivory traffickers.

Dr. Wasser had already developed a genetic map of African elephants by analyzing scat from across the continent. Now, he can link that map with genetic analysis of confiscated tusks to determine where the animal was living when it was killed. This can help law enforcement target areas most susceptible to poaching, he said in a telephone news conference on Tuesday.