One of the most mysterious things about Pokemon is exactly how they come into this world. We know only that Pokemon come from eggs, which leaves us with so many questions. While we may not know just how they come into our lives, we do know how to care for them.
You may notice I use the term 'gravid'. While this term is used for reptiles, fish, birds and insects, the fact that Pokemon are oviparous(egg-laying) means that the term is generally more accurate than 'pregnant'.
An egg is an organic incubator, containing a developing embryo(and in later stages, a fetus). In most birds, reptiles, insects, molluscs, fish and monotremes, the egg is expelled from the body and develops outside the mother's body until the embryo is sufficiently developed.
It is not currently known how Pokemon fertilize an ovum. The exact time between fertilization of the ovum and oviposition is estimated to be extremely short, but has not been accurately measured. Pokemon lay a single egg at a time, but can lay multiple eggs in a short period of time, although this is not recommended.
An egg has thousands of tiny holes in its shell, allowing the growing embryo to breathe. The color and pattern present on an egg shell is an important part in the formation of the egg, and is influenced by the species of the Pokemon. A shiny Pokemon will have the same kind of egg as a normally-colored sibling.
Like most eggs, a Pokemon egg contains a yolk, which nourishes the growing Pokemon inside. This particular egg yolk is extremely nutritious for the embryo, containing all the nutrients needed to produce a fully-developed infant Pokemon.
A Pokemon egg initially develops in the body as a fertilized ovum. It is not known how Pokemon fertilize an ovum, as Pokemon will seek solitude when fertilizing and laying the egg. If a Pokemon is 'gravid', the egg is developing inside their body. They carry the egg briefly, before seeing a spot to undergo oviposition(the laying of the egg).
Pokemon eggs are macrolecithal, meaning that they have large yolks and hatch into fully-developed offspring. Early on, the yolk takes up most of the space in the egg, dwarfing the embryo. As the embryo grows, however, it uses up the yolk. In the wild, Pokemon often care for their own eggs, keeping them at the proper temperature to hatch and protecting them from intruders. Pokemon trainers often care for eggs laid by their own Pokemon, with varying results.
If you are planning to breed a Pokemon, you must provide both Pokemon with an ample food supply, as oviposition takes a heavy physical toll on any animal, and Pokemon are no exception. Those breeding Pokemon at Day Care centers have less to worry about, as experienced caretakers know to have a store of food to allow Pokemon to eat as they need.
Our knowledge of the mating and reproductive habits of Pokemon are very few, so at the moment it is not known if Pokemon can produce unfertilized eggs or experience problems with their pregnancy. There have been reports of 'Bad eggs', which are an anomaly in themselves. Bad Eggs seem to have strange effects on the people and Pokemon around them. Hallucinations and in some cases paralysis have been reported by people unfortunate enough to have one. It is suspected that the rotten egg produces fumes that affect the nervous system.
Pokemon eggs are far more resilient than other eggs, possessing a thin membrane that prevents brittleness. They are resistant to temperature, as cold generally does not affect the developing embryo. Unlike other eggs, heat alone does not prompt an egg to hatch.
Pokemon eggs hatch quicker when they're exposed to various stimuli. Walking with an egg, especially if one has other Pokemon in their party, can achieve this very well.
When most Pokemon hatch, they hatch as the lowest line of their evolutionary family. These 'neonates' are generally capable of caring for themselves soon after hatching.
Pichu, Cleffa, Igglybuff, Togepi, Tyrogue, Smoochum, Elekid, Magby, Azurill, Wynaut, Budew, Chingling, Bonsly, Mime Jr, Happiny, Munchlax, Riolu and Mantyke are 'baby' Pokemon, which are something entirely different. Baby Pokemon are an immature stage of evolution that some Pokemon have. They have been known to imprint on the first living being they see after hatching, believing it to be their mother. They are less capable of self-sufficiency than a normal newborn Pokemon, but they are still able to function. Many baby Pokemon evolve through happiness, suggesting that the reason they seek out a mother is to help prompt evolution.
Health and Development
Baby Pokemon require adequate feeding to help them develop. The amount of food required depends on the Pokemon species itself. Pokemon that need to undergo drastic changes during evolution tend to eat more than species that do not.
Munchlax, for example, spends a lot of time finding and eating copious amounts of food. Though it is the heaviest baby Pokemon, it is still dwarfed by its evolution.
Unlike a human infant, a baby Pokemon does not have a weak digestive system, allowing it to eat a wide variety of foods.
The Pokemon Snorlax, Wobuffet, Chansey, Blissey, Mr. Mime, Chimecho, Sudowoodo, Roselia, Roserade, Marill, Azumarill and Mantine are able to lay eggs containing baby Pokemon, but only when certain requirements are met. When these Pokemon breed, they divert extra nutrients to their offspring, which prompts it to develop past the baby stage.
Baby Pokemon only develop when environmental conditions are good for their survival, as they are less developed and weaker than their parents. The incenses(Full, Lax, Luck, Odd, Pure, Rock, Rose, Sea and Wave) prompt the development of baby Pokemon, though it is not understood how.
There is another, much rarer item that is said to affect breeding. The Oval Charm is said to increase the chances of finding an egg. As much of breeding and the processes involved are a mystery, it is unknown if or how the Oval Charm accomplishes this.
At the moment, there are two abilities that are known to affect breeding. They are exclusive to fire types and make an egg develop(and hatch) twice as fast. Slugma and Magcargo are capable of having either of these abilities, making them a popular choice for breeders.
The first, Flame Body, is the primary ability of the Magmar, Litwick and Larvesta families. Ponyta, Rapidash, Moltres and Heatran have it as a hidden ability.
Magma Armor is much rarer and only Slugma, Magcargo and Camerupt have it.
These two abilities do not 'stack', meaning that having a Camperupt and a Magmar in your party at the same time will not make eggs hatch 4x faster.
The presence of eggs and baby Pokemon offer countless more mysteries to be uncovered. Caring for an egg is one of the most rewarding and educational experiences one can have, as it demonstrates the development of life from beginning to end.