Yellow-bellied Toad

The unken reflex is a distinctive defensive posture in which the toad arches its back downward, lifts its limbs upward and outward, and in more extreme versions flips fully onto its back, all in order to expose the vivid black-and-yellow warning pattern on its underside that is normally hidden from view while the toad rests or moves normally. This sudden display of bright, contrasting colour is a form of aposematism, a warning signal intended to startle a predator and remind it, or teach it for the first time, that this toad's skin produces unpleasant, mildly toxic secretions, making the display an effective bluff-and-warning combination rather than any kind of physical attack.

Small, shallow, often short-lived bodies of water such as wheel ruts, flooded hoofprints, and puddles collecting in quarries or construction sites offer a significant advantage that larger, more permanent ponds typically lack, namely the absence of fish, which are voracious predators of amphibian eggs and tadpoles. By specialising in these temporary, fish-free pools, the yellow-bellied toad's offspring face considerably less predation pressure during their vulnerable aquatic larval stage, even though this strategy comes with the real risk that a chosen puddle may dry out completely before the tadpoles have finished developing, which the species compensates for partly by breeding repeatedly across the season in multiple locations.

Rather than laying all of her eggs in one single clutch during a brief breeding window, as many amphibians do, a female yellow-bellied toad typically lays several smaller clutches spread out across the breeding season, often in different temporary pools. This strategy functions as a form of risk-spreading, since relying on temporary, unpredictable puddles for breeding means any single pool could dry out and destroy an entire clutch of eggs or developing tadpoles before they mature, so by distributing reproductive effort across multiple pools and multiple points in the season, the toad improves the overall odds that at least some of her offspring will survive to complete metamorphosis even if several individual pools fail.

Yes, both belong to the same genus, Bombina, and share several core traits, including the striking black-and-yellow or black-and-red warning colouring on the belly, the defensive unken reflex display, mildly toxic skin secretions, and a general preference for shallow, often temporary pools for breeding. They differ mainly in the specific colour of the warning pattern, yellow-based in this species compared to the more red-based pattern typical of the European fire-bellied toad, and in the details of their geographic ranges across Europe, with some overlap and hybridisation reported where their ranges meet.