Aren't you glad you're human?

Just in time for Mother's Day, the New York Times has an article describing unmaternal behavior in different animal species.

• Pandas give birth to twins frequently. Apparently they treat one as a 'spare' and when the favored offspring seems to be sure to survive, the spare is left to fend for itself (and often perishes as a result).
  
• Egret, pelican and crane parents completely ignore bigger and stronger siblings repeatedly attacking the weaker ones. In the absence of parental intervention, the weaker bird babies rarely survive for long.
  
• A mother nurse shark may incubate as many as 20 eggs at a time. As the eggs hatch, the sharklets start feeding on each other. At the end of the gestatory period, only one sharklet survives.
  
• Magellanic penguins will lay two eggs and hatch them both. Then the Magellan mommy will feed most of the food she gets to the larger chick eventually starving out the smaller one.

Gives a whole new meaning to survival of the fittest, doesn't it?