Cannibalism

Parents eat their own offspring --- as a natural order in the animal world. Unthinkable, but it's true. Studies show that likely this behaviour is for the energy source. Other says this alone cannot explain the phenomenon. New studies show reproductive activity is also connected to the behaviour of cannibalism. The strange fact is that those parents who eat their own young lings also raised up selected offspring. The secret of nature, according to the new studies is that, (for the young ones to avoid the danger of cannibalism) --- is "Grow faster or Get eaten."

cited from: http://news.yahoo.com/s/livescience/20071114/sc_
livescience/whysomeanimalseattheiroffspring
the image is from www.ansc.purdue.edu/CAWB/Images/chicks.gif