A Ribbeting Discovery

All, Nature Notes
A pond frog (genus: Rana) was spotted at Glenwood Gardens earlier in 2019. A person grasps the frog in their hand. The frog isn't fully grown, but is sprouting an extra hind leg on its left side.

Park guest Lisa spotted this hopping mad frog at Glenwood Gardens earlier this fall. It’s cool to see a not-quite-grown frog still with its tail, but this guy also has an extra leg!

We asked our nature interpreters what may have caused this odd phenomenon. Though we can’t say for sure what caused this frog to develop its extra hind leg, there is a fascinating parasite that can cause frogs to grow extra legs. Farbach-Werner Nature Preserve nature interpreter, Paul Seevers, shares how this parasite affects amphibians.

The parasite, Ribeiroia ondatrae, is a flatworm that has a bit of a complicated life cycle. Ribeiroia ondatrae is transmitted from birds to snail and eventually to the leg buds of developing tadpoles.

  • Adult flatworms sexually reproduce inside birds.
  • The bird defecates Ribeiroia ondatrae larvae into freshwater such as lakes or ponds.
  • Snails pick up the larvae, which then asexually reproduce inside the snails.
  • Larvae are once again ejected into water, where they then attach to the legs of certain amphibians, like the frog seen above, and form cysts that can cause creatures to grow extra legs.

Here’s the cool part: Scientists believe that the extra leg is not a side effect, but is actually on purpose! An extra appendage makes the frogs hosting the parasite easier to spot – and thus, eat – for birds. Which, of course, puts Ribeiroia ondatrae back into the bird, benefiting this flatworm!

Such is the circle of life.

A bullfrog (Lithobates catesbeiana) enjoys the rain at Highfield Discovery Garden.
A bullfrog (Lithobates catesbeiana) enjoys the rain at Highfield Discovery Garden.

Spotted a curious wildlife find while visiting a Great Park? Share your photos with us on social media. Use the hashtag #GreatParksofHamiltonCounty.


Nikki Ferrell, Social Media Strategist & Caroline Wiita, Content Marketing Coordinator