Winter has arrived in the Netherlands, not yet in full force, but cold enough that lots of amphibians have retired to their hibernation sites. Still, the odd sighting can be made and yesterday we made two really nice ones. When walking near a breeding water in a forest near our home town we came across two remains of predated female frogs. Our frog species lay their eggs in (early) spring. The rest of the year is spend foraging and building up reserves. But the females also develop new egg masses for the next spring. Right after hibernation they will deposit the eggs. So the females will go into hibernation with a belly full of eggs!
But as always predators are on the prowl. Frogs are a food source for predatory species like herons, martens and shrikes. The female frogs are also on the menu. In late fall, early winter and during the spring migration female frogs are preyed upon by these species. The egg mass they carry however are not on the menu!
The jelly that encapsulates the eggs swells up after coming in to contact with moisture. Not so handy if you swallowed this and it swells up in your stomach. Most predators regurgitate this part of the frog leaving weird snot like lumps in frog habitat. Some predators avoid ingesting the eggs all together and just don’t eat them. The egg mass that is left behind also swells up. In the Netherlands these leftovers are called “Starshot”, “Witches snot” or “Witches butter”. But as you now know it is just the left over egg mass from a predated frog. In our case we probably found the remains of the Common- or Grass frog Rana temporaria.
So next time you are in a European frog habitat and find this gooey stuff you will know what it is!
By Tariq Stark