Secret Lives of Ants

4. Ant Ranchers: Masters of Dairy Farming Second Only to Mankind

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 masters of dairy farming second only to mankind Ant Ranchers 4 No one knows exactly when humans first started raising livestock —cows, pigs, and other now-domesticated animals. Human beings breed animals in order either to directly consume the bodily tissues, as in the case of beef, pork, and chicken, or to snatch the eggs, milk, and other materials that animals produce for their own reproduction. In order to satisfy our enormous appetites, human beings have vast pastures, cattle ranches, and poultry and fish farms that we use to raise and breed all kinds of creatures. In order to overcome the scarcity of food in Latin America, people have even resorted to farming iguanas and large rodents such as agoutis and capybaras. Ants and Aphids After human beings, ants may well raise more livestock than any other creature in the animal kingdom. Ants and aphids are frequently cited as a good example of a symbiotic relationship —different species living together and providing benefits to each other. Ants protect aphids from their natural enemies such as ladybugs and green lacewings and the aphids in return provide their ant protectors with some of the nutrients that they suck out of plants in the form of the honeydew. If we observe the behavior of ants and aphids carefully, we see that the relationship between ants and aphids is not always so mutually beneficial. British researchers have observed that aphids spend 14% of their day under the protection of the ants, but they produce 84% of their honeydew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a n t r a n c h e r s 29 during this time. In other words, the honeydew that aphids produce is almost entirely for ant consumption. One aphid does not provide enough honeydew to feed one ant. Looking at the colony as a whole, however, we see that the honeydew from the aphids that the worker ants raise individually as well as those they herd together provides as much as 75% of the nutritional needs of the colonies that raise aphids. These ants are indeed masters of dairy farming. When we analyze the contents of aphid honeydew, we can see how much they appreciate the ants’ protection. Aphids do not just suck the juice out of plants and give it directly to ants. The honeydew that aphids provide to ants contains water, carbohydrates, many different amino acids, and other nutrients in just the right amounts, making it a balanced diet for ants. Ants do more than simply protect aphids. Just as shepherds herd their flocks to places with plenty of grass, ants have been known to herd their aphids from leaf to leaf. They find the best spots on the plant for the aphids to suck the juices and transport the aphids there. Ant milking an aphid for honeydew. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t h e e c o n o m i c s o f a n t s o c i e t y 30 Some ants do not just let their aphids roam the pastures but actually build stables to raise them in. These ants build dugouts at the roots or stems of plants to house their aphids. While I was studying for my master’s degree at Penn State University I would sometimes drive in the entomology department’s old truck with Peter Adler, now a professor at Clemson University, to do field observation in the neighboring woods. At the base of a meterhigh poplar tree we discovered a mud dugout surrounded by a mud wall inside which ants were tending a herd of aphids. The next four days we returned to observe the ants and aphids. Then suddenly both ants and aphids disappeared without a trace. All the dugouts had been removed in a single morning. This happened A Paraponera worker ant returning to the nest, mouth filled with honeydew. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a n t r a n c h e r s 31 during the last week of June, and even more amazingly the ants built similar dugouts there at the almost the exact same time the next year. The year after that I transferred to Harvard so unfortunately was not able to continue our research on that project. To this day I sometimes wish we could have found out whether or not this phenomenon occurred again. Many Different Species of Livestock Humans milk not only cows but also goats, sheep, and camels; and ants, too, raise many different...