Many species of sharks are considered apex predators in the marine ecosystems they inhabit. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic, or feeding levels. Terrestrial examples include lions, tigers and wolves.
Apex predators are typically at the very top of their food web and have few, if any, natural predators. Many species of sharks do play a critical role in maintaining the balance of marine ecosystems by controlling the populations of other species, helping to regulate the health and diversity of ocean life. In the ocean, sharks are often referred to as the apex predator- but are all sharks apex predators?
Most species of sharks are not apex predators. While many large shark species are indeed apex predators in their ecosystems, many smaller species are not at the top of the food chain at all. These smaller shark species may play different ecological roles, and their position in the food chain can vary. Let’s look at some examples below.
Apex Predator Sharks:
These are large, powerful shark species that sit at the top of the food chain in their respective ecosystems:
- Great White Shark (Carcharodon carcharias): An apex predator that feeds on marine mammals, large fish, and smaller sharks.
- Tiger Shark (Galeocerdo cuvier): An opportunistic feeder with a wide diet, including fish, sea turtles, and even birds.
- Bull Shark (Carcharhinus leucas): Known for being an apex predator in both freshwater and saltwater environments.
- Mako Shark (Isurus oxyrinchus): A fast, powerful predator that preys on fish and squid.
- Hammerhead Shark (Sphyrnidae): Large species like the great hammerhead are apex predators, particularly in reef ecosystems.
Non-Apex Shark Species:
Smaller sharks, or those with more specialized diets, are not considered apex predators. These sharks may be preyed upon by larger marine animals or do not have the same broad influence on the food web:
- Reef Sharks (e.g., Caribbean Reef Shark, Nassau Shark): While they are important predators in coral reef ecosystems, they are not apex predators because they are sometimes preyed upon by larger sharks, like the great white or tiger shark.
- Cookiecutter Shark (Isistius brasiliensis): This small shark feeds on a variety of marine creatures, including larger fish and whales, but it is not an apex predator since it is preyed upon by larger sharks.
- Spiny Dogfish (Squalus acanthias): A small, bottom-dwelling shark that feeds mainly on smaller fish and invertebrates. It is not an apex predator and is sometimes preyed upon by larger sharks or marine mammals.
- Smooth Dogfish (Mustelus spp.): Another small species that feeds on fish and invertebrates, and is not an apex predator in its environment.
Why Some Sharks Aren’t Apex Predators:
- Size and Behavior: Smaller sharks may have limited ranges and food sources, making them less dominant in their ecosystems.
- Ecological Niche: Some species have evolved to occupy specific niches that don’t involve top-predator status. For instance, some may feed on smaller fish or invertebrates, which means they’re more likely to be part of a larger food web rather than sitting at the top.
- Vulnerable to Larger Predators: While many sharks are formidable hunters, some are still vulnerable to attacks by larger sharks or marine mammals. For example, small sharks like the blacktip reef shark or whitetip reef shark can be preyed upon by larger sharks or orcas.
The term “apex predator” generally applies to those sharks that have few or no natural enemies and control the populations of other species in their environment. In ecosystems with orcas, even white sharks become prey. In summary, while several species of sharks are apex predators, many others play different, but also important, roles in marine ecosystems.