Predatory fishes have a lot of guts, according to research published in a recent issue of the journal Nature.
Jonathan Armstrong and Daniel Schindler utilised mathematical models applied to 38 species of predatory fish (including species that fed on invertebrates rather than other fishes) to arrive at their conclusion.
Calculating the load:capacity ratios for the digestive systems of the fishes, the authors found that the guts of the fishes were capable of handling daily feeding rates two to three times higher than what they experience on average.
This suggests that episodes of gorging and fasting are common in fishes, and occur not only in ambush predators that pursue large prey, but also in predators that feed on insects and zooplankton.
As having a large digestive system is energetically expensive, "his much excess capacity suggests predator-prey encounters are far patchier — or random — than assumed in biology and that binge-feeding enables predators to survive despite regular periods of famine", according to senior author Armstrong.
"For predator fish, the world is a slot machine — sometimes they stumble upon small meals and other times they hit the jackpot. It's just not as predictable as some have thought," continued Armstrong.
"Unlike some other animals, fish can't just hoard their food behind a rock in the stream and eat it later. They need to binge during the good times so that they can grow and build energy reserves to survive the bad times."
For more information, see the paper: Armstrong, JB and DE Schindler (2011) Excess digestive capacity in predators reflects a life of feast and famine. Nature 476, p. 84.
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