Sand gobies eat offspring when risks too high

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Sand gobies will consume their own eggs if they believe that the costs of trying to raise the brood outweigh the benefits, a new study has shown.

Published in the journal Animal Behaviour, this new research suggests that, when threatened, the sand goby may decide that the pros of recouping some of their investment in the eggs through cannibalism, and subsequently trying again with a new batch, may outweigh the cons of having lost those eggs.

They've decided it's just not worth it right now and for whatever reason they want to leave, Ashley Chin-Baarstad told New Scientist.

It is the male sand gobies, Pomatoschistus minutus, that focus their energy caring for the eggs, and during a long summer they may have the opportunity to raise several broods.

By introducing no predator, visual cues from an egg predator, and both sensory and visual cues from an egg predator, the researchers were able to observe the different reactions in male sand gobies protecting eggs.

It was found that smaller males were more likely to consume their entire batch of eggs than larger males, suggesting that these males would have a greater need for the nutrients gained from the eggs if they were to try and raise another clutch than their larger counterparts.

However, males in poor condition were less likely to consume the entire batch than those in good condition. It is suggested that the eggs were worth more to these fish intact as it would aid him in attracting females over by demonstrating his potential ability to care for her eggs.

The males in good condition, on the other hand, would have less trouble attracting another female to supply him with more eggs, and consequently would benefit more from gaining the nutrients.

Chin-Baarstad, A., H. Klug and K. Lindstrm (2009). Should you eat your offspring before someone else does? Effect of an egg predator on filial cannibalism in the sand goby. Animal Behaviour 78(1). pp. 203-208.