Assertion: shark | /r/CapableOf | arch its back
Facets:
value: to signal feeding time
type: PURPOSE
Source sentences:
text: If captured, the shark can arch its back to pierce its captor with spines near the dorsal fins that secrete a mild venom into its predator.
text: For example, sharks that live in schools, like the gray reef shark, arch their backs to signal feeding time.