There are over 440 different species of sharks on the planet and they each have unique style of mating habits. Some species of sharks lay eggs, while some give live birth. Some have complex mating dances, while others travel long distances to meet their mates. Some give birth to large litters, while others give birth to just a single pup.
Though there is a wide variety of mating habits among sharks, all sharks reproduce as a result of internal fertilization and some sharks are capable of asexual reproduction. With 100 million sharks killed every year, it is important we understand the mating habits of different species of sharks in order to promote effective conservation.
Shark Mating Habits
Little is known about the mating rituals of sharks, as they are difficult to observe. Most sharks have long gestation (pregnancy) periods, some species like Basking Sharks and Frilled sharks have a gestation period of three years. So frequency of mating varies among species. Since most sharks are solitary hunters, they travel great distances to mate. Species like Great White Sharks and Whale Sharks will travel thousands of miles to find an ideal mate. Most shark breeding grounds are found around coastlines, estuaries, and seamounts because these areas have shallow, warm waters and plentiful food sources, so they are more ideal to give shark pups a good start to life.
Shark Mating Rituals
Shark mating begins when the female shark releases chemicals into the water to stimulate the interest of a male. Some sharks like Hammerheads and Great White Sharks have complex mating rituals that include shows of strength and possibly dancing.
All sharks tend to practice biting as a way to get the attention of the female. Female sharks tend to have bite marks across their bodies after mating, though these bites are not as ferocious as feeding bites.
Some species like the Whitetip Reef Sharks will bite the fins of the prospective female. Once the male has gotten the attention of the female, the female may practice rejection behavior.
Nurse Sharks, in particular, have been observed refusing, avoiding, and blocking males they are not interested in. If a female shark does decide a male is an adequate mating partner, they will flare and cup their pelvic fins. Some species of shark like Nurse Sharks and Lemon Sharks will choose more than one mate.
Once a mate has been selected, sharks begin copulation. All sharks practice internal fertilization. Male sharks have paired reproductive organs called a claspers, and female sharks have an opening called a cloaca. Fertilization occurs when a clasper is inserted into the cloaca and sperm is injected into the female.
When mating begins, a male shark will mount a female shark, either swimming beside or underneath. Often the male will bite onto the female to hold themselves during mating. This can be a difficult process with both sharks often ending up with wounds.
Once mounted, the male inserts the clasper which hold inside the cloaca with a hook until the sperm is released. Most species of shark only use one clasper, species like Hammerhead Sharks and Requiem Sharks tend to only use the right clasper. Only the Spiny Catshark has ever been observed using both claspers. Once the sperm is injected, the sharks part ways. Usually fertilization happens immediately, though some species like the Small Spotted Catshark can hold the sperm for two years.
Types Of Reproduction
Once the embryo is fertilized, sharks have four forms of reproduction:
- Viviparity: Viviparity is when the fertilized eggs are hatched inside the female’s uterus and the pups are fed by a placenta through an umbilical cord. Lemon sharks, Blue Sharks, Porbeagles, Salon Sharks, Silvertip sharks, Hammerhead Sharks, Bull Sharks, Whale Sharks, and Whitetip Reef Sharks all use viviparous reproduction.
- Oviparity: Sharks that are oviparous will deposit fertilized eggs in the ocean which will hatch outside the mother’s body. These egg sacs are called “mermaid’s purses” and usually contain a thick, leathery membrane. Oviparous sharks will often just deposit the eggs along the reef bed and move on, while others will stay and guard them against predators. Oviparous sharks include Catsharks, Swellsharks, Zebras Sharks, Hornsharks, Carpet Sharks,, Port Jackson Sharks, and Epaulette Sharks.
- Ovoviviparous: Ovoviviparous shark eggs hatch inside of the uterus. However, the pups are not feed a placenta and will eat unfertilized eggs and other pup fetuses to survive. Great White Sharks, Thresher Sharks, Sawsharks, Mako Sharks, Tiger Sharks, Nurse Sharks, Greenland Sharks, Gummy Sharks, and Cookiecutter Sharks are all ovoviviparous.
- Asexual: Though a very rare form of breeding that has only been observed in captivity with a Hammerhead shark, female sharks are able to reproduce without a mate.
Pup litters vary in size depending on species and type of reproduction. Sharks are a K selected species which means that they reproduce for quality and not quantity. They tend to have smaller litters, but with genetically stronger offspring. This is one of the biggest challenges for conservation.
Shark Mating And Challenges To Conservation
This wide diversity of mating habits creates a challenge to conservation. Since sharks all have different mating patterns, rituals, and locations, there is not a one size fits all solution to protecting shark species. Furthermore, in shark species that have long periods of gestation or only give birth to a single pup at a time, the species cannot replenish themselves at the rate they are being slaughtered. Another issues is that most sharks don’t reach reproductive age until they are at least 7 years old, and in some species they won’t reach sexual maturity until they are 15 years of age. So many sharks are killed before they even have a chance to produce offspring. Also since sharks tend to mate along heavily populated areas, like the shallow waters around land masses, many sharks are experiencing nursery habitat loss. With all of these factors impacting mating, shark conservation efforts are incredibly difficult.
With so many different species of sharks, shark mating habits are extremely diverse. Though all sharks practice internal fertilization; mating rituals, the length of gestation, and type of reproduction vary greatly from species to species. It is important to understand the different ways sharks reproduce in order to understand how the mass killing of sharks truly threatens the species. Sharks cannot replenish the population at the rate they are being killed, so conservation efforts are a big challenge. Fortunately, the more we are able to learn about shark mating, the more likely it is we can make a difference.