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Fish eat babies when paternity seems in doubt

Fish eat babies when paternity seems in doubt

Fishy behaviour

February 7, 2007

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By Stuart Colcleugh

A new study in the February 2007 American Naturalist, co-authored by SFU biologists Suzanne Gray and Lawrence Dill, demonstrates that male fish are more likely to eat their young when they have been cuckolded during spawning.

It also appears that the more males that are in attendance during spawning, the more likely it is that a male will try to eat the eggs, as it is less likely he fertilized them — a fact that has never been shown before.

"The most drastic decision a father can make is to cannibalize his own offspring," write researchers Gray and Dill, and University of Wisconsin-Whitewater biologist Jeffrey S. McKinnon. "These results support and extend previous findings suggesting that confidence of paternity is a key factor in determining a male's behavior toward his offspring — including whether or not to eat them."

Scientists have long theorized this brutal reaction to unfaithfulness, but it has never been documented in fish without parental care until now. The results came from studying Telmatherina sarasinorum, a small fish found in Indonesia's Lake Matano. The researchers found that females who recognize their own eggs never eat them. But increased levels of cuckoldry led to increased levels of cannibalism by the males.

"Our results clearly show that the probability of (offspring) cannibalism attempts in T. sarasinorum courting males increases in the presence of sneaker males, suggesting that they can use detection of sneakers as an indicator of lowered certainty of paternity," the study concludes.

"Since T. sarasinorum males do not invest in their offspring after egg-laying, cannibalism cannot be a tactic used to optimize the trade-off between present and future reproduction, except with respect to recouping energy lost through mating efforts.

"Instead, it seems the male may benefit from the energy contained in the eggs, and the less likely he is to have fertilized the eggs, the more likely he is to eat them."

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