Did you dive in the Gili Islands yet? Were you lucky enough to visit the baby sharks, or pups as they are technically called? The Gili Islands are unique for their shark nursery of whitetip reef sharks. This is one of the reasons why we started our project – to ensure the protection of the shark nursery.
Shark reproduction is something out of the ordinary. It includes nothing less than deep wounds, mermaid’s purses and potential cloning. These incredible reproduction systems don’t come as a surprise, considering that the ancestors to sharks originated 400 million years ago.
There is a big difference in shark reproduction. Some shark species lay eggs while others give birth to fully developed baby sharks. Some sharks will perform a mating dance while others will travel long distances to find a mate. Some sharks give birth to a large litter while others give birth to a single baby shark. Convinced that shark reproduction is fascinating? Let us enlighten you further.
Where Do Baby Sharks Come From?
Shark reproduction happens through internal fertilization in all species of sharks. This is different from most fish, who will send their eggs and sperm into the blue void and pray for the best. Sharks are a K-selected reproducer and produce small numbers of well-developed baby sharks. In the other spectrum are R-selected species who produce large numbers of poorly developed young.
Shark mating starts when the female releases chemicals into the water to attract male attention. Some sharks, like the hammerhead and the great white shark, have complex mating rituals; including dancing, fighting, and deep diving.
One of the benefits of internal fertilization is that the female can choose her ideal mate. There are species who will bluntly reject a male if he’s not seen fit. Some species, like the nurse shark, choose to mate with several males during mating season. Other species again, will store the seamen for up to two years.
The actual mating of sharks is where the action happens. Imagine if you had to perform a love scene while being weightless in the water and with no hands. Not the easiest, right? Neither is it for the sharks. So they use the means they have: teeth!
The male shark bites on to the female while he inserts and hooks one of his claspers into the female cloaca. The intimate moment leaves a bloody mark on the female shark. This is the reason why evolution has gifted the female shark with a skin that’s up to three times thicker than the male. Sharks also have magical healing capabilities, which allows the female to recover from her wounds in a matter of weeks.
It’s Not Easy To Become A Baby Shark
Shark’s gestation (pregnancy) periods are infamous for being incredibly long. Their gestation periods vary from five months to three years, though most sharks gestate for about 12 months. There are four different ways shark babies are being brought into this world.
1. Oviparous reproduction
This is the shark reproduction method where the female shark will lay eggs in a leathery pouch. The baby sharks will then develop on their own from the egg’s food supply. Sharks using this reproduction method spend a long time finding the right place in the shark nursery to hide their eggs. Other sharks stay behind to guard the eggs until they’re hatched. The leathery pouch is sometimes found washed ashore, which is why it’s also called a mermaid’s purse. Oviparous sharks include catsharks, zebra sharks, carpet sharks, and epaulette sharks.
2. Viviparous reproduction
Through this shark reproduction method, the female shark develops the embryos inside her uterus. Here they receive nutrients and oxygen through the umbilical cord, just like humans. Viviparous sharks include bull sharks, hammerhead sharks, and whitetip reef sharks.
3. Ovoviviparous reproduction
This shark reproduction method, the female shark develops eggs like the oviparous method. Instead of placing the eggs straight into the shark nursery, she keeps them inside her. The baby sharks are not connected to their mum through an umbilical cord. Instead, they feed on their egg’s yolk supply, other unfertilized eggs or even the embryos of their brothers and sisters. Through the latter method, only the strongest 1-3 sharks will get born, which is seen in the sand tiger shark.
4. Asexual reproduction
Even though this shark reproduction method is rare, it is so fascinating that it deserves equal attention. It’s observed with hammerheads and zebra sharks to reproduce without fertilization. Because no new genes get introduced, the baby shark is technically a clone of the mother. Asexual reproduction has only been observed with sharks in captivity. In the wild, it may be a survival method, should the female shark be incapable of locating a male shark.
A Baby Shark Is Born
As soon as the baby shark is born, they are ready to swim and hunt. The mother won’t care for it, but she will make sure to deliver it in a safe place in the shark nursery. Shark nurseries are found along coastlines, estuaries, and seamounts. In here, the water is shallow and warm and the food supply is plentiful. Baby sharks eat smaller and slower prey until they grow larger and stronger. Baby sharks are at high risk of being predated themselves by fish, birds or even other sharks.
The Gili Islands host a shark nursery for both black and whitetip reef sharks. The blacktip reef shark babies are mostly found feeding in the shallow waters, where larger predators can’t reach them. The whitetip reef sharks are a big attraction among scuba divers in the Gili Islands. Pregnant females come into the same place as they were born, to deliver their young. The baby sharks then hide from predators under rocky and coral overhangs during the daytime. They’ll stay here up until the age of four years old, only moving house when they outgrow it.
Shark Conservation For A Brighter Future
Understanding shark reproduction can make a big difference when it comes to the conservation of sharks. It is difficult for sharks to replenish themselves at the rate they are being fished. This is due to several reasons:
- Sharks don’t mature and reach their reproductive stage until the age of 7-15 years. The Greenland shark, as a jaw-dropping exception, doesn’t reach maturity until the age of 150 years old.
- Sharks have long gestation periods of up to three years.
- Sharks will often let years pass between reproducing.
- Sharks only have a few offspring at a time.
- Shark nurseries are often located by populated areas and are experiencing habitat loss.
Sharks are nature’s A-grade child, with 400 million years of evolution. Sharks survived what the dinosaurs didn’t. But nature couldn’t take human activity into account. Sharks, the mighty apex predator of the ocean, had undergone a perfect evolution up until the humans started over-fishing.
An estimated 100 million sharks get killed each year for their fins. In the past 15 years, shark populations have decreased by 60-90%. Experts estimate that most shark species will disappear within the next 10 years if strong measures are not taken.
Sharks are vital for marine ecosystems. Apex predators ensure larger biodiversity and healthier populations of fish. If there are no sharks, fish populations will go down, leaving thousands of people without a source of food or income.
Are you ready to do ourselves a favor and fight for shark rights? Get involved in shark and marine conservation and be part of our team of researchers on the paradise island of Gili Air.