Every one of the millions of animal species that inhabit the planet has evolved a reproduction strategy that is specific to its surroundings. Which animal, however, has the record for having the most children at once? A seemingly straightforward query soon becomes considerably more intricate.
To begin with, how you define “offspring” will determine which animal has the most offspring.” “Fish easily take the lead,” Cole said, referring to gametes, which are unfertilized eggs or sperm generated in a single step. Species that spawn—releasing their eggs and sperm freely into the water—generally generate significantly more eggs than those that carry their offspring internally or lay them as eggs later because it requires less energy to release unfertilized eggs into the water than it does to nurture fertilized ones.
Take, for example, the ocean sunfish (Mola mola), which can hold as many as 300 million eggs in its ovaries at once. Even with these startling figures, just a small percentage of those eggs might develop into children. It is difficult for scientists to anticipate how many eggs will become fertilized, much less how many will become baby sunfish, because the fertilization process takes place externally, in the vast and unpredictable ocean. Once freed, their journey cannot be practically traced. Furthermore, the IUCN Red List lists ocean sunfish as an endangered species, primarily due to bycatch in fisheries, despite their amazing capacity for reproduction. This implies that only a very small percentage of those millions of eggs ever help to maintain their population.
But social insects are the true winners when it comes to fertile eggs. In a single month, some ant species, such as the African driving ant (Dorylus wilverthi), can lay anywhere from three to four million eggs. In order to decide whether to create male or female progeny depending on the demands of the colony at any particular time, the queen, the only reproductive female, selectively fertilizes some of these eggs.
Turning our attention to birds, species such as the gray partridge (Perdix perdix) deposit a lot of eggs; their clutches can occasionally contain up to 22 eggs. The situation takes an unexpected turn for live-bearing creatures, such as seahorses, whose males, because of their special pouches, can give birth to up to 2,000 live babies at once, raising them inside their pouch, which resembles a placenta.
The record for live-bearing species on land is held by the venomous puff adder (Bitis arietans). An incredible 156 completely grown young snakes were born to a mother puff adder in one instance. Alex Pyron, a George Washington University evolutionary biologist, described them as “looking like bloated sausages.” “These mothers can carry an immense number of offspring.”
This begs the question: why do certain creatures, like whales and elephants, only have one child at a time, while others have so many? One important issue is lifespan. Because they might not live long enough to watch their young grow up, short-lived species typically have a lot of offspring. “They can’t afford to wait around to reproduce slowly,” said Cole. “They have to make their impact quickly.”
Animals like bats, on the other hand, usually only have one child at a time since they must stay light for flight and carry their young with them. Similar to this, because each one needs a lot of energy and resources, species that give their young a lot of care after birth—like the majority of mammals—generally have fewer offspring.
Another important factor is the difference between egg-laying and live birth. Compared to species that lay eggs, live-bearers often have fewer young because live-born offspring require significantly more energy to develop inside the parent. Another element is social structure: because to the protective benefits of group living, animals that dwell in colonies or groups, such as the prolific African driving ants, may afford to have more offspring.
Naturally, there are always exceptions in nature. For example, even though they give birth to live offspring, rabbits and mice are known for having big litters, whereas dung beetles may lay as few as three eggs at a time.
After graduating from Macalester College, where she experimented with screenplay writing, dinosaur excavation, and wolf vaccination, Katherine Irving is a freelance science journalist who has a strong interest in wildlife and geosciences. She now contributes to the Science Magazine podcast and loves learning about the complex beauty of the ecosystems on our world.
