Jester, a California sea lion at the Buffalo Zoo, died over the weekend.

The 12-year-old male came to the zoo in January of this year from the Aquarium of Niagara, where it spent the previous eight years. Jester was born at Sea World in Orlando.

Preliminary necropsy reports found no clear cause of death, said Rachel Gottlieb, the zoo’s spokeswoman. Tissue samples have been sent to a pathology lab for further analysis.

Jester’s death leaves Dallas, a 15-year-old male, as the zoo’s lone remaining sea lion. He came to the zoo in 2005.