Insects, Ants, and the Food Chain

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Zoo InternQuest is a seven-week career exploration program for San Diego County high school juniors and seniors.  Students have the unique opportunity to meet professionals working for the San Diego Zoo, Safari Park, and Institute for Conservation Research, learn about jobs, and then blog about their experience online.  Follow their adventure here!

Paige Howorth, Animal Care Manager at the San Diego Zoo, introduced us to the world of insects and invertebrates today, and helped us put into perspective how important insects really are. Insects are the foundation of our food chain and the one class of animals that we still are uncovering new members of every day. Most people would classify insects, like mosquitos, as pest because they carry diseases; however they are an important food source for other species like fish and bats. Insects are an important part of our ecosystem, so they should be valued for their contribution to our world.

One of the least understood insects is the ant. Ants are also sometimes viewed as pests because they can be destructive. Ants play many different roles in our ecosystems some of which are:  decomposers, gardeners, pollinators, and soil aerators. Ants are some of the most advanced species on earth. Despite their poor eyesight, ants have an advance communication system using smells, pheromones, and sounds. All ant colonies have class systems where each class carries out a specific job in the colony, and the ant’s size indicates their role. This specialization in size and function helps them to be very efficient at what they do.

Today, Ms. Howorth brought us to the exhibit of herbivorous leaf cutters ants (Atta cephalotes) that live in Central and South America. These ants do not eat the leaves they harvest, but instead cut leaves from plants and carry them back to the colony to be ground into a paste.  The paste is then spread with fecal matter, which becomes a growth medium and is deposited into their fungus gardens also known to be their food source.  The fungus that the ants grow is the only food source for the colony. One ant colony found in South America was roughly the size of a football field.

A threat to the leaf cutter ant colony is a parasitic mold called Escovopsis, which can be accidentally introduced into the colony when the mold “hitch hikes” on the backs of the ants. This mold can attack the fungus and wipe out a colony.  The ants also have a weapon to combat this mold, it’s a bacterium they carry on their body to kill the mold before it damages their fungus. This struggle amongst these various life forms is sometimes called an “arms race.”

As a species, leaf cutter ants are not categorized as threatened. Most farmers view them as pests; however, they are an important part of an ecosystem and should be valued for their unique contributions. In the case of the leaf cutter ants, they prune plants to stimulate new growth, are a food source for other animals, and aerators of the soil. Ms. Howorth explained that we should be concerned and educated about all parts of an ecosystem and how they interact as a whole. It is important to have healthy ecosystems for our food chain to continue to thrive.

Colton, Wildlife Conservancy Corner
Fall 2012, week five