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Honey, I ate the kids: When caring fish turn cannibal

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    Honey, I ate the kids: When caring fish turn cannibal * 16:28 23 June 2009 by Ewen Callaway  Some fathers show their affection by spending time with their
    Message 1 of 1 , Jun 24, 2009
       Honey, I ate the kids: When caring fish turn cannibal

          * 16:28 23 June 2009 by Ewen Callaway


      Some fathers show their affection by spending time with their children, others spoil their kids rotten. Some fish, on the other hand, value their offspring so much that they devour them before a predator gets the chance.

      Savage as it may seem, filial cannibalism makes perfect sense for animals such as sand gobies that invest time and energy in raising large numbers of offspring, says Ashley Chin-Baarstad, a biologist at Purdue University in West Lafayette, Indiana, who led the study.

      In a role reversal of sorts, male sand gobies tend the eggs from multiple females, who go off on a search for more mates. But a long summer breeding season gives the males ample time to raise multiple broods and, rather than waiting until the eggs have hatched, sometimes they simply make a snack of them.

      "They've decided it's just not worth it right now and for whatever reason they want to leave," Baarstad says. By eating their eggs, they can at least recoup some of their investment.
      Goby caviar

      To determine under what circumstances sand gobies decide to eat their offspring, Baarstad's team mated dozens of males and females in outdoor tanks that mimicked conditions in the wild. Males kept close guard on their hundreds of eggs, all buried safely in the sand.

      However, when the researchers introduced an egg predator – the brown shrimp – into the tank, male gobies generally wolfed down their offspring and headed straight for the back of the tank.

      Introducing the shrimp within plastic containers let the researchers restrict exposure to the egg eaters. They found the gobies' cannibalistic tendencies increased at the sight and smell of the shrimp. A plastic container alone did not make dads turn cannibal.

      Smaller males, who may need every calorie than can get, were more likely to eat their eggs than larger males. Yet healthy males proved more cannibalistic than fathers in worse shape. Because males with eggs are more likely to attract other females, Baarstad hypothesises that sickly males might have extra incentive to hold onto their clutch.

      Journal reference: Animal Behaviour (DOI: 10.1016/j.anbehav.2009.04.022)
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