by Matt Walker
Editor, Earth News
A creature of taste
The European woodmouse has a unique taste for ferns, a food once eaten by long-extinct dinosaurs, say scientists.
The mouse regularly devours the spores of the endemic European fern Culcita macrocarpa, the only small mammal known to do so.
It is rare for modern vertebrates to eat ferns, due to the toxic chemical defences often contained within them.
But these ancient plants were a favourite of huge sauropod dinosaurs that used to eat them in bulk.
The discovery is published in the journal Mammalian Biology.
In the past, ferns are thought to have played an important role in the diet of dinosaurs, particularly huge sauropods such as Diplodocus, the longest dinosaur known from a complete skeleton.
Nowadays, invertebrates such as insects and gastropods consume ferns to some extent, but few vertebrate species are known to consume ferns regularly.
However, an international team of researchers led by Ms Marisa Arosa of the University of Coimbra in Portugal became suspicious when they noticed bite marks on fertile leaves of the rare fern C. macrocarpa, the only endemic member of a family of ferns called Dicksoniaceae in Europe.
They set out to find out which culprit was consuming the ferns, growing in Galicia, northwest Spain.
Ms Arosa had previously studied how the Azores bullfinch feeds on the spores of four fern species.
The bullfinch (Pyrrhula murina) and short-tailed bat (Mystaina tuberculata) are the only two vertebrates previously known to feed on fern spores.
The researchers studied a set of fern plants, noting how their leaves and spores were removed, and then placed cotton under the plants to collect the droppings of any animal feeding on them.
Analysis of the droppings revealed them to have been left by the European woodmouse (Apodemus sylvaticus), and that they contained the fern spores.
Foraging by the mice was greatest where most ferns grew.
Most spores has been digested, but it may be that the mouse helps disperse them, aiding the plant's reproduction.
The mice were picky about which parts of the fern they consumed, eating only the fertile parts of the plant. And they only ate the plant's spores between December and February.
But fern spores are rich in calories, lipids and proteins, providing a vital source of energy to woodmice in winter, the researchers say.
Animals are rarely thought to eat ferns because of the phytochemical defences they use, which make them difficult to digest.
However, little is known about whether there are toxins throughout the whole plant.
If they are not in the spores, it may explain why the tiny mice can eat them.
Huge dinosaurs enjoyed ferns, which dominated much of the plant-life during the Triassic and Jurassic eras.
Sauropods couldn't chew, having no back teeth to grind with, so many species are thought to have used small peg or spatula-shaped teeth to rake and slice fern leaves.
Their huge size and digestive systems may have allowed them to process any toxins in the plants.