Rosalie Little Thunder, September 19, 1949 - August 9, 2014. Photo from Native Sun News

Rosalie Little Thunder, a Lakota activist who worked to stop the slaughter of bison in Yellowstone National Park, died on August 9. She was 64.

Little Thunder was a member of the Rosebud Sioux Tribe. She founded Buffalo Nations, which later became the Buffalo Field Campaign, after seeing the slaughter of the bison first-hand in 1997.

Her efforts led to international attention to the slaughter, which occurs when the bison leave park boundaries and cross into Montana. Outcry prompted the federal government to develop new policies for dealing with the last wild, free-ranging herd of bison in the U.S..

"Traditional people must guide our tribal leadership in a manner that reflects the integrity of our historical and cultural relationship with our relative, the buffalo," Little Thunder said in April 2014. "Montana politics has made a mockery of a keystone species."

Despite Little Thunder's advocacy, officials in Montana still allow bison to be killed out of fear they will transmit a deadly disease to cattle. Tribes that tried to secure some of the animals were temporary stopped by a lawsuit until the state's highest court sanctioned the transfers last year.

"While we knew her as a visionary activist, artist, and organizer who dedicated a great part of her life to protecting wild buffalo, Rosalie was so much more," Buffalo Field Campaign director Daniel Brister wrote in a tribute. "She was a counselor, a professor, a guardian of the Lakota language and culture, and a well-respected elder who fought tirelessly for the rights of Native (and all) people. As a mother and grandmother she was devoted to her extended family and their well-being."

Wake services for Little Thunder take place tomorrow at 7pm at the Mother Butler Center in Rapid City, South Dakota, and at 7pm on Friday at the He Dog School Gym in Parmalee, on the Rosebud Sioux Reservation, according to Osheim & Schmidt Funeral Home.

Funeral services take place at 2pm on Saturday at the He Dog School Gym. Burial will follow at the White Horse Cemetery.