Paul McCartney may have been “the walrus,” according to one Beatles song, but this week the legendary singer is working on behalf of the elephants.

In recognition of World Elephant Day this week, a Martin D-28 left-handed guitar, autographed by McCartney himself, will be auctioned by elephant-protection group, Nature Conservancy. The guitar was provided by the C.F. Martin & Co., a founding sponsor of the Conservancy’s African Elephant Initiative, and features across its top the words, “This Guitar Saves Elephants”—written by McCartney in a nod to Woody Guthrie’s famous anti-fascist guitar credo. The starting bid for the guitar was set at $10,000.

Funds raised from the August 13 auction will go to the African Elephant Initiative, which partners with agencies in Africa, China, and elsewhere to help protect elephants on the ground in Africa and to reduce demand for ivory in such regions as southeast Asia, where it is heavily trafficked.

David Banks, managing director for the African Elephant Initiative, calls working with McCartney and Martin Guitars an “honor.”

“This caliber of collaboration will make a difference to help end the worst poaching crisis in history,” said Banks.

According to a report by elephant-conservation groups MIKE and ETIS, it is estimated that there were 1.2 million elephants in Africa in 1980; now only about 430,000 remain, with an estimated 20,000 elephants killed last year alone for their tusks.