Animals have evolved complex survival strategies to suit the demands of their habitats. Through these changes, many have become excellent architects, working with their environment to meet their needs.
By Ethan Hatchett
Instead of creating or collecting objects, some animals manipulate other organisms. In a sense, that makes them farmers. These animals basically gather livestock, creating relationships that benefit them both, and grow crops.
The black carpenter ant is one of North America’s largest ant species. Found in woodlands, forest edges and suburban neighborhoods throughout Georgia, carpenter ants live in wet, dead wood, in tunnels they chew out themselves. They will leave this nest to forage up to 100 yards away. To minimize the cost and risks of foraging, these ants have adopted a very effective technique.
Like many other ant species, carpenter ants enjoy sweet foods. One of their favorites is honeydew, a sticky, sugar-rich liquid excreted by aphids. As a result, carpenter ants and aphids have developed a strong working relationship.
Aphids are vulnerable to many predators such as birds, wasps and lacewing larvae. Black carpenter ants offer protection, sometimes even herding aphids away from danger. In return, the ants milk honeydew from the aphids, lightly stroking them with their antennae to coax out the liquid they’re after.
Black carpenter ants prize aphids and will go to great lengths to protect their “flocks.” It is not uncommon for the ants to herd aphids under leaves to shield them from predators and heavy rain. In some cases, ants even bring the aphids inside their nests at night to keep them safe.
Carpenter ants can be a serious pest if they infest your home, but you can take measures to prevent problems and still be able to observe their interesting behavior. Carpenter ants are attracted to wet and dead wood. Routinely cleaning gutters and keeping outdoor wood products dry will greatly reduce your chances of an infestation.
The relationship between carpenter ants and aphids is classified as “high-level food production” because of the sophistication of the ants’ farming methods. The more recently discovered agricultural inclinations of marsh periwinkle snails is considered a lower level of food production. But it is no less fascinating.
Marsh periwinkle snails are found in marshes along the Atlantic and Gulf coasts of North America. The small, gray snails are easily overlooked because they feed on smooth cordgrass and blend into the marsh.
Yet while these snails may seem slow and uninteresting clumped together on a blade of grass (watch), they are practicing a captivating form of farming. Biologists often wondered why marsh periwinkle snails spent so much energy munching on cordgrass, which is not known for high levels of nutrition. In 2003, they discovered the answer: The snails were using the grass as a host to farm fungus.
Marsh periwinkle snails chew holes on the surface of the smooth cordgrass. The desired fungus – which the snails eat – grows more readily when the grass is rubbed with the snail’s sandpapery tongue-like organ (called the radula) and fertilized with droppings the snail leaves near the holes. The process takes time, but once grown, the fungus is highly nutritious for the snails.
Farming the fungus isn’t a conscious decision for marsh periwinkle snails. They have developed this process over millions of years. Their instinct is simply to create an ideal environment for the fungus.
Humans tend to view farming as our exclusive domain, but we share this, and many more practices, with animals. Food is a top priority for wildlife, and they have developed strategies complex and simple to ensure its abundance.
Everywhere you look in nature you can find structures created by talented animal architects. Even now, they are hard at work excavating, collecting, producing and farming. Take a moment to explore your surroundings. What you find may amaze you.
Ethan Hatchett is a communications assistant in DNR’s Wildlife Conservation Section.