Sharks have captivated our imaginations for centuries. Their sleek, streamlined bodies and rows of serrated teeth inspire both fascination and fear. While male sharks get most of the headlines, female sharks play a critical role in the ocean ecosystem.
If you’re wondering what female sharks are called and want to learn more about their biology, you’ve come to the right place.
In short, female sharks are simply called female sharks, cows or dames. But there’s much more to learn about their anatomy, reproduction and behavior in the underwater world.
In this comprehensive guide, we’ll provide a deep dive into the unique traits of female sharks. You’ll learn about their intriguing courting rituals, key physical differences from males and special adaptations that allow them to bear live young.
We’ll also explore how female sharks support the next generation and the vital part they play in maintaining balance in the oceans.
The Role and Importance of Female Sharks
Maintaining Healthy Shark Populations
Female sharks play a vital role in maintaining healthy populations of sharks. As the child-bearing sex, females are responsible for reproducing and giving birth to new generations of sharks. Their ability to produce offspring directly impacts the size and genetic diversity of shark populations.
Females also invest significant energy and resources into gestating embryos and giving birth. The number of pups a female can successfully raise during her lifetime has a major influence on population numbers.
For example, some species like great white sharks give birth to just a handful of pups every 2-3 years. Protecting reproductive females enhances the chances of sharks producing enough offspring to maintain or grow their populations.
Passing On Genes and Traits
Female sharks pass on important genes and traits that equip the next generation to thrive. These inherited adaptations involve key functions like sensing prey, migrating across oceans, dealing with changing environmental conditions, and avoiding predators.
Losing reproductive females means losing sharks genetically suited to survival. Having a diversity of genes via different mothers also enables populations to withstand threats like disease outbreaks. For instance, some individual sharks may carry genes or immunities that provide protection against a virus sweeping through a region.
Essential for Reproduction
Quite simply, sharks cannot successfully reproduce without females. While male sharks contribute DNA in the form of sperm, females provide the eggs as well as the internal environments for embryos to gestate and hatch.
A single reproductively viable female shark is essential for giving birth to pups. But diverse reproductive females – meaning variation in age, size, genetics – help ensure ongoing propagation of the species.
According to the Lenfest Ocean Program, models show losing just a few mature female sharks can collapse regional populations.
Physical Differences Between Male and Female Sharks
Size and weight
When it comes to size and weight, female sharks tend to be larger than males on average. This difference can be quite pronounced in some species. For example, female great white sharks typically measure 15-21 feet long and weigh up to 5,000 pounds, while males only reach 11-13 feet and 3,000 pounds (Florida Museum).
Theories suggest this size difference likely evolved so females could accommodate more pups during gestation periods.
Claspers
One of the most visually obvious differences between the sexes is the presence of claspers on male sharks. Claspers are a pair of elongated reproductive organs used to transfer sperm to the female during mating. They are located on the inner side of the pelvic fins. Females do not have claspers.
Oviducal glands
While less noticeable from the outside, female sharks possess special oviducal glands that produce egg cases for embryos. These glands allow female sharks to lay fertilized eggs with tough, protective coatings around them. This eggs case keeps the growing embryos safe until they are ready to hatch.
Male sharks lack oviducal glands.
Uterus
The most significant internal organ difference between the sexes is the uterus. Female sharks of course have a uterus where embryo development occurs before birth. Some species have two uteruses. Males lack this specialized reproductive organ.
Instead, they utilize testes and other parts of their reproductive system to produce and store sperm cells.
Shark Mating and Reproduction
Courtship behaviors
Sharks have some interesting courtship rituals. Male sharks will bite, bump, or rub the female to show interest. Some species perform elaborate mating dances. The male may swim in circles around the female or make figure-eight patterns to try to attract her.
Once the female is receptive, she will allow the male to come closer.
Copulation
Most sharks mate through internal fertilization. The male inserts one of his claspers into the female’s cloaca to deliver sperm. Mating can last a few minutes to over an hour depending on the species. Some sharks like nurse sharks rest on the sea floor during mating.
Others like tiger sharks and great whites need to keep swimming to breathe and have to mate while moving.
Gestation periods
Gestation periods for sharks vary widely across species. The shortest gestation is around 5-6 months for small shark species like spiny dogfish. Larger sharks like great whites have longer gestation of 15-18 months. The longest gestation period belongs to the frilled shark at over 3 years!
Birth and litter sizes
Most sharks give birth to live young, though some species lay eggs encapsulated in egg cases. Litter sizes range from 2-12 pups on average depending on the species. The great white shark has small litters of just 2-10 pups.
Other sharks like blue sharks may have litters of 25-50 pups in a breeding cycle! After birth, baby sharks are already fully functional and ready to hunt and avoid predators.
Female Shark Behaviors and Adaptations
Migration and habitat use
Female sharks exhibit complex migratory patterns and habitat usage that are adapted for optimal breeding and raising young. Many species migrate long distances to preferred nursery grounds or mating areas (Florida Museum).
These migratory behaviors are precisely timed around reproductive cycles and stages of embryonic development.
Pregnant females may prefer specific temperature ranges or access to more plentiful food sources to nourish their developing embryos. Some species are remarkably accurate in returning to the exact location where they were born decades earlier in order to give birth in the safest habitat for their offspring.
Egg cases and live births
There are two main shark reproductive strategies. Many lay egg cases, known as mermaid’s purses, that incubate the embryos until ready to hatch. Others give live birth to fully formed pups. Mother sharks that give live birth demonstrate fascinating adaptations that allow their bodies to sustain embryos throughout gestation.
Sharks have uteri with individual compartments for each pup, complex attachments to nourish the growing young, and the ability to store sperm for delayed fertilization until conditions are optimal. The length of gestation varies by species from about 5 months to 2 years.
Mothering instincts and protecting young
Mother sharks make great efforts to protect their young once born. Species that lay eggs often seek out the safest nesting sites with ample hiding places. According to Whale and Dolphin Conservation, female sharks modify their swimming to create a supremely gentle action that will not disturb the newborns until they are stronger swimmers.
Some mother sharks even pick up wayward pups delicately in their mouths to transport them to better habitat. Female sharks have been observed adopting orphans or allowing the young of other females to trail them for protection in a nursery herd.
Unique adaptations like atavism
The phenomenon of atavism demonstrates how female sharks have uniquely adapted their reproductive capabilities over millions of years. Atavism is when ancestral traits suddenly reappear in later generations after being evolutionarily lost for ages.
In 2020, scientists reported (ScienceDaily) the first observed case of a shark embryo hatching prematurely from its egg case inside the mother’s uterus. This reproductive quirk had disappeared in ancestral sharks over 300 million years ago when they transitioned to live births.
Threats Facing Female Sharks
Overfishing
Female sharks face significant threats from overfishing around the world. As apex predators, their populations are vulnerable when too many individuals are removed from the oceans. Many shark species take a long time to reach sexual maturity and have relatively few offspring, making them slow to recover from overexploitation.
Sharks are caught both as targeted catch and as bycatch in other fisheries. Globally, an estimated 100 million sharks are killed annually due to fishing activities. This excessive mortality threatens the stability of shark populations and the health of ocean ecosystems.
Habitat loss
The degradation and loss of marine habitats is another major threat to female sharks. Sharks rely on coastal wetlands, seagrass beds, coral reefs, and other habitats for shelter, nursery grounds, and hunting territories.
The destruction of these habitats through pollution, development, climate change, and other human activities removes critical resources and territory for female sharks.
Since female sharks show strong site fidelity and dependence on specific nursery areas to give birth and raise young, destruction of these habitats can have an outsized impact on reproductive success and pup survival.
The loss of these key habitats contributes to the endangerment of shark species worldwide.
Pollution and climate change
Ocean pollution and climate change pose both physiological and ecological threats to female sharks. Toxins like heavy metals, pesticides, and plastic accumulate in shark tissues, causing immune dysfunction, impaired reproduction, and abnormal offspring.
Climate change is altering ocean temperatures, chemistry, currents and food web dynamics in ways that disrupt shark habitat, prey availability, migratory patterns, and reproductive cycles.
As large predators near the top of the food chain, female sharks are vulnerable to bioaccumulation of toxins and biomagnification of environmental contaminants that can be passed from mother shark to developing pups.
Ultimately, these external stressors may reduce female shark fitness, fertility, and breeding success over time.
Trophic cascade effects
The loss of female sharks has cascading impacts that reverberate through marine food webs. As top predators, sharks help regulate prey populations and maintain balanced ocean ecosystem functioning. When shark populations decline, mesopredator release can occur in which mid-trophic level species like rays, smaller sharks, and fish experience population surges and in turn overexploit lower trophic levels.
Such trophic cascade effects can destabilize entire marine ecosystems. For example, the collapse of large shark populations along the U.S. East Coast led to explosions in the cownose ray population which then overfed on commercial scallop stocks, resulting in scallop fishery closures.
Maintaining healthy populations of female sharks is key to sustaining functional ocean food webs.
Conclusion
Female sharks are impressive creatures that play a critical role in ocean ecosystems. Their unique adaptations allow them to produce and protect the next generation of sharks. While often overshadowed by notoriously aggressive males, female sharks have captivating behaviors all their own.
Learning more about female shark biology provides a window into their importance underwater. By better understanding their reproduction, instincts and challenges, we gain perspective on how to protect these vital predators.
While their legacy includes cultural fear and myths, female sharks are intelligent creatures deserving of respect and conservation efforts.
The ocean depends on the survival of female sharks. As top predators, their existence maintains balance across the marine food web. Protecting areas where female sharks breed and raise pups supports future generations.
Reducing activities like overfishing and pollution can help safeguard female sharks and their habitat.
