Why do whales beach themselves?

Several hypotheses have been put forth to explain these strandings which likely have multiple causes.   The whales may be sick or hurt; illness or parasites may affect their sense of direction.   It is believed that whales use magnetic fields and underwater topography to orient themselves.   For this reason, a magnetic field deviation or an odd coastline formation could cause confusion.

It is not an uncommon occurrence for beached whales that have been returned to deeper water to later strand on the same beach from which they were freed.

Their reference points may wrongly lead them to believe that deeper water lies in the direction of the beach.  Live strandings often repeatedly occur in the same area, in zones with specific characteristics.

Pelagic species of whales that are more at home in deep, mid-ocean waters may get caught off guard by the falling tide in shallow estuaries.   In the case of mass stranding, whales may simply be following a confused leader, or they may be swimming to the aid of an already stranded whale that is sending off a distress call.

Essentially, these strandings remain somewhat mysterious.

A live beached whale may die of disease or injury.   In these cases, the disease or injury may also be the cause of the whale's stranding.

If the whale is neither sick nor hurt, but is not able to get back into deep enough water, with the rising tide for example, it will generally die of complications related to being out of water.

At sea, water supports the whale's body.  On land, air does not offer this support.  The whale's body weighs it down and it may "suffocate" under its own weight;   its respiratory muscles are incapable of sufficiently dilating its rib cage to ensure adequate pulmonary ventilation.  Also, on the portion of the animal's body that is in contact with the ground, blood circulation is blocked by the animal's weight, causing tissues to die.   Even if the animal is returned to the water, these dead tissues will produce toxins leading to generalized infection.