The world is full of fascinating paradoxes. For instance, does this article even exist before you’ve read it? If I traveled back in time and eliminated my grandfather, would I still be here writing this? And why is it that two socks can fit into the washing machine, yet only one emerges? Perhaps one of the grandest paradoxes is how a frog can shrink as it matures.

Meet the paradoxical frog (Pseudis Paradoxa). These frogs lay their fertile eggs in South America’s lakes and lagoons, where they hatch into tadpoles that begin to consume the eggs.

The voracious larvae feed mainly on algae and begin to grow quite rapidly. Initially, they develop like ordinary tadpoles, but…

If conditions are ideal, these tadpoles can grow remarkably large. Bigger than blueberries, larger than strawberries—think of it as if “satsuma stuffed into ankle socks.” That gives you a sense of their size, and perhaps you’ve even located your missing socks.

The tadpoles of the paradox frog, with their plump, rounded bodies and long muscular tails, can reach lengths of up to 22cm (8.6 inches). Rearrange the movie Jaws, and you’ll need a bigger jam jar!

This size is about three times more significant than the adult frogs they eventually become, with much of the necessary development already complete.

By the time they morph from tadpoles to frogs, males possess well-formed testes and can produce sperm, while females create mature eggs.

This is distinct from typical frog tadpoles, which take longer to reach sexual maturity during the male frog phase of their life cycle.

So, how does a giant tadpole transform into such a small frog? It’s remarkably simple! At least half of the paradoxical frog tadpoles are made up of tails. Once they lose their tails, they undergo a normal transformation into relatively small adults, measuring about 7cm (approximately 2.5 inches).

This “contraction” of the amphibians explains the phenomenon often referred to as frog shrinkage.

The paradox appears resolved. Yet, as one riddle is solved, another emerges: Why do the tadpoles expend such energy in growing so large in the first place?

One possible explanation lies in the timing and location of their birth. Paradoxical frogs time their spawning for the rainy season.

In Trinidad, this occurs around May.

Some eggs are laid in permanent bodies of water, while others are deposited in fleeting ponds that eventually dry up. Those born in small, temporary locations with limited food and aquatic predators do not grow much. In contrast, tadpoles born in larger, more stable ponds with abundant food and fewer predators tend to thrive.

In these circumstances, growing larger can enhance survival since larger tadpoles are less likely to be consumed by predatory fish and other animals.

If you have questions, please email us at Question @sciencefocus.com or Message Facebook, Twitter, or Instagram (please include your name and location).

Check out our ultimate Fun fact and explore more amazing science content!

Read more: