Can Frogs Be Pollinators?
This Brazilian frog may pollinate milk fruit trees as it visits flowers to sip nectar.
By The Nature Conservancy's Nature Lab
Cool Green Science - Stories of the Nature Conservancy
X. truncata head down in a Brazilian milk fruit flower (2023-04-12) by Carlos Henrique de-Oliveira-NogueiraThe Nature Conservancy's Nature Lab
A new species of pollinator?
Nestled on a branch in the forests of Brazil lives a frog that may well be helping trees reproduce! The frog species is X. truncata, also known as Izecksohn's Brazilian Tree Frog.
It could be an inadvertent effort. The frog wants to sip nectar and covers its back with pollen in the process, but if it is helping trees reproduce, it’s the first pollinating frog ever recorded!
An intriguing observation
Brazilian herpetologist Carlos Henrique de-Oliveira-Nogueira and a team first made the connection between the Xenohyla truncata frog and pollination in the scrubby, sandy ancient dunes off Brazil’s Atlantic coast while conducting routine amphibian and reptile monitoring.
Rare Sightings
They knew an opportunity to watch a threatened species was rare, so they waited, watched, and were stunned to see them not only eating fruits but also diving headfirst into the flowers of Brazilian milk fruit tree and making “suction-like movements.”
Discovering pollen on X. truncata frogs
The team speculated the plant’s sweet nectar may be important fuel for the exhausting work of calling, arguing over territory and mating. When they looked at the pictures later, they discovered the frogs had pollen dotting their backsides and legs after emerging from the flower.
The frogs looked much like bees and other flying pollinators who dip into flowers to drink nectar and pop out covered in plant reproductive dust.
“That caught our attention because, since the species usually visits various plants throughout the night, it could carry pollen from one flower to another and possibly play the role of a pollinator,” writes Henrique de-Oliveira-Nogueira.
How X. truncata frogs affect plants
If the frogs are pollinating plants, it’s likely rare. Most frogs rarely visit the flowers of plants, and the ones that do aren’t always helping out. When X. truncata frogs visit the nonnative bearded iris flower, it eats its petals and can destroy the flower in the process.
However, when the X. truncata frog enters the native Brazilian milk fruit tree’s white, cup-shaped flowers, it sips nectar, wiggles around in the pollen, then leaves.
“Xenohyla is the only species that actively seeks out fruits, and now, flowers and nectar for feeding. It is a unique case among amphibians.”
A threatened species
The frogs and the Brazilian milk fruit tree live in Brazil’s Restinga areas along the coast of the state of Rio de Janeiro in the northeastern part of the country. The region is part of the Atlantic Forest that “is heavily influenced by the sea" - Henrique de-Oliveira-Nogueira.
Unusual behavior for amphibians
The sandy soil supports mostly shrubs where the X. truncata feeds on insects and fruits from four native plants and two flowers. They swallow the small fruits whole, then hop around leaving seeds behind in their droppings, effectively replanting the forests.
Endangered status
Brazil lists the X. truncata frog as vulnerable to extinction and its populations are fragmented and scattered. The coastal, sandy areas the creature calls home are also facing rapid habitat loss through urban growth, real estate speculation and development.
The vital role of amphibians
Frogs move nutrients around. As tadpoles, they eat decaying leaves, plants and algae that accumulate in wetlands. Then as adults, they migrate out of the water where they eventually die or become a snack.
According to JJ Apodaca, “in a lot of ecosystems, amphibians in general are the most abundant vertebrate, so they act as a bridge between invertebrates and higher vertebrates,” he says. “In most areas, there’s more frog and amphibian biomass than all the other vertebrate biomass combined.”
In other words, frogs eat smaller creatures and bigger creatures eat frogs! Frogs eat a lot of bugs, sometimes at levels high enough to qualify as pest control.
Multiple X. truncata by a fruit from the Brazilian milk fruit tree (2023-04-12) by Carlos Henrique de-Oliveira-NogueiraThe Nature Conservancy's Nature Lab
Wonders of nature
Frogs as pollinators are just another example of the myriad interactions between species we don’t yet know: “There’s still so much in the world left for us to understand and discover.”
All photos and videos are by Carlos Henrique de-Oliveira-Nogueira.
Content and quotes are adapted from the TNC Cool Green Science blog article - Frogs as Pollinators? By Christine Peterson.
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