Another endangered Hawaiian monk seal has been found dead on Oahu, the fifth this year, and the cause is still unknown — bad news for a species with very few animals left.

• NOAA Fisheries confirmed the death but has not determined what killed the seal.
• Tests on samples taken from the animal are still being run.
• Hawaiian monk seals are endangered, so each loss matters for the population.
• People who find a seal that is hurt, tangled, or dead are asked to call NOAA's marine wildlife hotline at 888-256-9840.

Outlook: Test results should show whether these deaths share a common cause, which would tell officials if something bigger is going on around Oahu.