Why do some animals commit mass suicide? Like the 28 cows in Switzerland over the course of 3 days and dozens of squids

Question: Why do some animals commit mass suicide? Like the 28 cows in Switzerland over the course of 3 days and dozens of squids beaching themselves all at once?
- Keywords:
  cow,
  death,
  squid,
  suicide
Asked by michelletherezien to Charlotte, Jo, Kevin, Louise, Valeria on 19 Jun 2012. This question was also asked by jessc.
- Kevin Mahon answered on 19 Jun 2012:
  
  I can’t really comment on those specific two examples but I know the most common cause of animals seemingly commiting ‘mass suicide’ is actually incredibly strong biological urges to migrate quickly, often resulting in stampeding, falling off cliffs etc – the deaths are a result of this, not out of a desire to die.
- Valeria Senigaglia answered on 19 Jun 2012:
  
  Agree with Kevin.
  
  I never heard about squids beaching but dolphins are known for mass strandings, especially the species I used to study, Pilot whales. This species in particular mass strand because they all follow a leader so if this leader strand because is lost or sick, the rest of the group follow.
  Other times a great number of individuals are affected by the same problem, for example mass strandings of sperm whales may be caused by military sonar that disorientates the whales

Question: Why do some animals commit mass suicide? Like the 28 cows in Switzerland over the course of 3 days and dozens of squids beaching themselves all at once?