Coral reefs are often described as the rainforests of the sea.
They house an incredible diversity of life, something we try to recreate in our reef tanks.
Another common hobby I think a lot of us are involved in is the keeping of poison
dart frogs. They’re small, incredibly colorful, not too hard to keep and breed, and their tanks,
like our reef tanks, can be incredibly beautiful living works of art packed to the brim
with all manner of mosses, orchids, and pretty much every variety of plant.
Hi guys and girls, I’m ReefMan, or, for today only, Uncle Ribbit as my nephew calls me. Now,
think about frogs, and their lifecycles.
Egg, tadpole, frog - right? Seems simple enough. Most amphibians need water in order to reproduce,
and poison frogs in the rainforest are no exception.
But now, let’s think about that. Yea, rainforests are wet - they’re not called dryforests. But these
frogs live in trees and in the small shrubby plants of the understory - they don’t live on
the shores of lakes and rivers. How do they find the water they’ll need to reproduce?
Not just any pool will work - it has to be one that will stick around for a couple months,
long enough for their tadpoles to turn into small frogs.
I found a really interesting paper about this question,
titled “Tadpole-transporting frogs use stagnant water odor to find pools in the rainforest”.
There’s a link down in the description if you’d like to check it out, it’s open access.
So, a moment ago I mentioned that these frogs live in the small trees, heliconia,
and other plants of the understory. That presents a problem though, as they also lay their eggs in
protected nooks and crannies on and around the same plants. In order to do this successfully,
the frogs need to then transport their newly hatched tadpoles to a pool of water.
To do this, they back down into the newly hatched tadpoles - and then the
tadpoles riggle up onto their parent’s backs, sometimes with the help of the parent frog.
From there, it’s just a matter of where to deposit the tadpoles.
Not just any pool of water will work - some tadpoles are cannibalistic and will eat other
tadpoles. Other pools of water might contain predatory fish. Still others might not last
the couple months their tadpole will need. So, how do parent frogs find one that fits the bill?
It turns out, poison frogs are great at detecting scents. The species with cannibalistic tadpoles
can detect the scent of another tadpole already in the water. They seem to be able to sniff out the
scent of decaying leaves, an indication that water is stagnant and therefore unlikely to dry up. Now,
decaying leaves are everywhere in the rainforest, and we’re not exactly sure the
compound the frogs are smelling, but it’s clear that they CAN detect leaves decaying in water.
This great sense of smell combined with a great spatial memory allows these tiny frogs - many only
the size of your thumbnail - to have comparatively huge ranges upwards of a few hundred meters.
This is even more impressive when you consider that some poison frogs feed
their tadpoles unfertilized eggs and must remember
where all their tadpoles are so that they can return to feed them regularly.
You might be wondering, how do we know all this? Well, the team from the paper
took several plastic dishes into the rainforests of French Guiana. They filled them all with well
water, but surrounded some with leaves they had left in water for a few weeks.
Control dishes got no decaying leaves around them, and then they had trial dishes with tadpoles but
no decaying leaves, and dishes without tadpoles but with decaying leaves surrounding them.
The theory was that perhaps the frogs are just seeing other tadpoles in the water,
and depositing their tadpoles alongside. That wasn’t the case though. In the experiment,
of 253 tadpoles that were deposited, 212 were in the water surrounded by decaying leaves.
23 were deposited into water that already had tadpoles,
and only 18 in the control water that did not have any decaying leaves nearby.
There’s still a lot left to learn though - what exactly is attracting the frogs? As I mentioned,
it can’t JUST be decaying leaves as they’re everywhere in the rainforest,
it’s got to be something about leaves decaying in water.
I hope you don’t mind this brief trip into another hobby. We’ll be back to reef tanks next time!
Till then, stay safe, be kind to each other, and have a fantastic day!
Bye!