DOUBLE HELPING

Passing through the digestive tract of a bird or mammal can give a seed a useful head-start in life – wider dispersal and improved germination, plus fertiliser to grow in. And according to new research, passing through the guts of two animals might be even better.

Ecologists at Canada’s University of Alberta have found that so-called diploendozoochory is not as unlikely as it sounds. They have assembled numerous records of seeds being eaten by birds or small mammals, which have then been eaten themselves by a carnivore.

There is evidence that predators disperse seeds further than seed-eaters and that two guts may better prepare seeds for germination.

“It’s even possible that some plants have evolved specifically to take advantage of these predatorspecific behaviours,” says Anni Hämäläinen of the Alberta team.

A thick seed coat may prolong digestion to facilitate long-range dispersal by migrating raptors, for example.

Large carnivores such as the red fox can disperse seeds further.