Who walked on land as the first among all animals? Did they care for their offspring?
The answer is: not the king of the jungle or any species of bird; not even us! It was those slime-coated frogs, toads and their cousins. They are the pioneers in bending all the known laws of evolution.
They envisaged the land invasion from water, exemplifying tenacity when it came to child care. In short, they have showcased the art of adaptation to the world.
In science, we call them amphibians. And, amphibians rank higher among the most kind-hearted and attentive parents in nature.
A biological wonder
You do not need to have a vast scientific knowledge to know of a frog's residence. Decomposing leaf-litter, forest undergrowth, tiny puddles, bottom of a swamp and so on. There is no standard norm for what we might call their home-sweet-home.
Wet, damp, full of microbes, and predators lurking around – all of these make an amphibian's lair. Yet, they are successful in raising babies.
This phenomenon naturally oozes enigma for scientists. After studying for years with patience, parental care among amphibians has been decoded to a satisfactory level.
Caring parents of rainforests
Caring frog parents are mostly found in areas buzzing with life. Moist, broadleaf rainforests of the tropics are crammed with diverse species.
Thus, amphibian parents have to be extra-tending and vigorous. Therefore, amphibian reproductive expressions have resorted to extensive modifications.
Six primary modes
Biologists have grouped parental behaviours of the amphibians. From laying of eggs to transformation of larvae (tadpoles), one may see six main strategies.
These primary types are, in turn, categorised under three broad perspectives: egg caring, tadpole caring and feeding of tadpoles. These functions can be expressed in a myriad of ways, generally species-specific.
Frogs guard their eggs, carry them on their back, glue them to the body, transport them through water and what not.
Mending a safe home
Building a nest is not a postmodern act. It has been in practice since the bygone era; not uncommon among the amphibians either. They are known to build and modify dedicated places for raising their offspring. It can be a mud nest or a puddle thawed with mud or underground litter.
The extreme definition of parental care is likely the vigorous protection of the eggs and young tadpoles. Several frogs, including the infamous poison dart frogs and large salamanders, defend the clutch from any potential threat.
Frogs are generally small and quite torpid. They are not armed to the teeth and claws. So, how do they defend when encountering a larger predator? They have some tricks up their sleeves, such as distracting the predator, irritating them or leading them to a false nest and last but not the least, offering themselves to the predator so that the eggs can safely hatch.
Becoming a porteur
After mating, fertilised eggs can be glued to the back or encased in chambers inside the skin pouch.
The Surinam toad, in some sense, can give you trypophobia. The skin of the male develops a cleft as he carries the eggs on back. The egg sinks in separate rooms, a tiny portion poking out - which altogether mimic a section of a bee hive!
There is no free-living tadpole stage in certain cases, for example, the horned marsupial frog. Their tadpoles transform within fully closed chambers and when maturation is complete, tiny froglets just make their way out!
Why parental care?
After reading all the strategies, you are now pondering – why do they do this?
The care of the parents always comes from a single intention – survival of the newborn, and thus, existence of the species. It is the main pro of parental care, as investigated through various studies. This is why the primitive amphibians seem so intelligent in baby-sitting.
However, enhanced parental care often leads to a reduced life span of the parent owing to less feeding, exposure to predators and the bulk energy spent in child care.
But, by then, the upper hand is ensured and a successful progeny is left behind!