By Blaise Jones
The reproductive habits of sharks have long been a mystery to science. Early research into sharks focused primarily on the basics of their anatomy and their predatory behaviors, with little research into their social behaviors or mating rituals. Research into all areas of shark lives greatly expanded in the 1980s, but even in the 21st century there is still very much that is unknown about sharks. As far as how many pups a shark gives birth to at a time, we can only make educated guesses.
Counting Eggs Before they Hatch
Egg laying sharks (oviparous) are some of the easiest sharks to study when it comes to offspring numbers. All a research has to do is observe where a female lays her eggs and count how many she left. Because of this we have the most data on egg-laying shark birth rates. On average an egg-laying shark will lay approximately 20 eggs at a single birthing. However, many species lay their clutch of eggs over a period of several days, adding up to as many as 50 eggs.
The number of eggs oviparous sharks lay depends greatly on the size of the animal. Bigger sharks have more space to gestate eggs and store fat, which fuels the whole process. Therefore, as sharks mature and get older, they can lay more eggs.
The vast majority of sharks are ovoviviparous (gestating eggs inside their body and then giving birth to live young), and thus we find the widest range in pup numbers across the ovoviviparous species. On one end we have species like the sand tiger shark, which only gives birth to one or two pups due to intrauterine cannibalism.
On the other end of the spectrum is the whale shark, which can gestate and give birth to as many as 300 pups. Whale sharks reproduce in large number because it takes a whale shark 30 years to reach adulthood.
The 300 pups in a whale shark’s birth is very unusual for ovoviviparous sharks, who usually average between six to eight pups.
Tons of Tiny Tiger Sharks
The types of sharks that tend to have the lowest amount of pups per birthing are the live-bearing sharks, or viviparous. Nourishing a growing fetus takes a great deal of energy from the mother, forcing the small birth rate of viviparous animals, which usually average six to eight pups per birth, but can be as few as one or as many as 20.
Tiger sharks are the one exception to the viviparous rule of smaller birth numbers, often producing birth litters with dozens of pups. Large female tiger sharks have been recorded giving birth to as many as 80 pups at one time. As with many aspects of sharks, the exact reasons why tiger sharks can produce such large litters. Scientists speculate that the large size of tiger sharks provides enough room for more pups to develop. Adult tiger sharks are also known to eat just about anything they can fit into the mouth, a habit that provides pregnant tiger sharks the added energy needed to complete such a large birth.
“Sharks: The Animal Answer Guide” by Gene Helfman and George H. Burgess
“The Encyclopedia of Sharks” by Steve Parker