Apex Predators and the Natural Order

    THE APEX PREDATOR AND THE NATURAL ORDER

Resource Intern, Dana

What is an Apex Predator?

An Apex (or Keystone) predator is the predator at the top of the food chain that is not preyed upon by any other and has a relative low abundance population size compared to those below them in the food chain.

The job of the Apex predator is to control the population sizes of those beneath it on the food chain. Scientists call this order in the food chain the Trophic Structure. Top Down control specifically refers to the job of the apex predator in terms of keeping order in the trophic structure.

What happens when the Apex Predator is lost?

Loss of an Apex predator leads to the increase of mesopredators (predators controlled by the Apex). Due to this increase in population size, smaller game population sizes decline resulting in the collapsing of an ecosystem. The biological term for this effect is Trophic Cascading - when top predators abundance changes, the next predators abundance increases from the removal of predation.

The mesopredators do not become the next Apex predators and their effect on the environment is also economically devastating to humans as well.

Image 1: Ghost crab feeding on Turtle

One example of a trophic cascade was the removal of raccoons. Raccoons feed on ghost crabs as well as turtle eggs. To protect the turtle eggs human intervention removed the raccoons. In turn, the ghost crab population which fed mainly on turtle eggs increased due to this loss of the apex predator and there were even less turtle eggs.

Another side effect with the loss of Apex control is the increase in disease among the ecosystems and unfavorable genetics in the gene pools of previously controlled populations.

Are humans able to replace them?

No. Not only is is economically expensive, but it would be as effective as mowing the lawn in Florida's wet season. In natural ecosystems the appearance of the apex predator affects the physiology of mesopredators. This results in them being smaller and causing them to stay in their natural ranges.

Re-established Apex Predators

Image 2: Yellowstone Wolf

The most well known and successful reintroduced Apex predator was the Wolf at Yellowstone park. Diversity has returned to Yellowstone due to the return of the Apex predator.

Bear populations decreased which allowed cougars to be able to recolonize. Elk populations also decreased, allowing Bison to return to the park. With decreased Elk populations saplings were able to grow into new trees because fewer of them were eaten. The new growth of trees enabled beavers, important ecosystem engineers, to return to the park since their disappearance long ago shortly after the last wolf was poached.

Poaching Impacts on Apex Predators

Image 3: Tiger at Rehabilitation

 center

One example is the near extinction of the Amur Tiger. The Amur Tiger population in Russia was nearly exterminated in 1940 due to intensive poaching for "Medicinal" tiger parts. This was despite large tracts of it's natural habitat and a large enough density of prey.

Unfortunately, even if poachers target adults, high survival rates of the kittens and juveniles do not compensate for this mortality because tigers reproduce at an older age.

The Field of Conservation

A widespread view of conservation is to consider a species to be more important if its disappearance will have a larger effect on the abundance of others in the community - large enough that the disappearance could lead to secondary extinctions or other such disappearances.

In other words, important species can be defined as those being major interactors with many links to other species. These links can be direct or indirect interactions.

If our goal of conservationists is to conserve ecosystem structure and maintain a reliable supply of ecosystem services, then identifying Keystone Predators as an important species will be a very good long-term solution for managing diversity.

The Apex Predator of Corkscrew Swamp

Right here in our swamp we have the ultimate Keystone predator! The Apex predator of the Southeast wetlands is the American Alligator (Alligator mississippiensis). The American Alligator controls the populations of both the land and the wetland area itself.

So next time you see an Alligator, let them know how awesome they are!

Image 4: American Alligators sunning themselves and 

smiling for the camera