Mystery over death of 137 sea lions washed up on beach in Mexico

Animals are a protected species in Mexico but not considered in danger of extinction

Mexico is investigating after 137 sea lions washed up on a beach (SEMARNAT)

Mexico is investigating the mysterious death of 137 sea lions that washed up on a beach with no obvious sign of how they died.

The country’s office for environmental protection said the animals showed no signs of injuries from getting caught in fishing nets, nor were there any visible marks on their bodies from being struck by a boat.

Both are common causes for sea lion deaths or injuries.

The dead animals were first reported to authorities on 2 September and were found along an 80-mile stretch of Pacific coast in the area of Comondu in the state of Baja California Sur. 

Authorities said tissue samples have been collected from some of the bodies to determine cause of death.

California sea lions are a protected species in Mexico but are not considered in danger of extinction there.

The animals generally live between 15 and 20 years in the wild, or longer if in human care, according to the Smithsonian’s National Zoo and Biology Institute.

Adult males grow up to be up to eight feet long (2.4 metres) and weigh up to 600 pounds (454 kilograms), while females are about six feet long (1.8 metres) and weigh an average of 220 pounds (100 kilograms).

Known for their intelligence and playfulness, the animals are highly social and travel in packs in waters between Canada and Mexico’s southern tip. 

The Marine Mammal Centre said they are among the most commonly cared for sea animals after being found malnourished, suffering cancer or pneumonia, or becoming entangled in fishing nets.

In another significant beaching event, more than 500 starving sea lion pups washed up on the Californian coastline in 2015.

The animals were less than half their normal size.