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Susi the elephant just hasn't been the same since her best friend Alicia died last year.
Signs of loneliness include eating her own feces and obsessively shaking her head and trunk back in forth, according to the group.
"Her life is in serious danger," Libera reportedly told a Spanish newspaper. "Susi won't last."
Libera is campaigning to move the giant beast to a park with lots of open space and other elephants.
No final word on if the zoo will comply with the group's demand.