Animals That Grow Gardens
Ant farmers: Humans first began cultivating crops about 10,000 years ago, but ants got into the program long before that: Using genetic studies, scientists determined a few years ago that a pioneering ant species began growing its own food about 50 million years past. The most highly developed insect agriculturalist today is the leaf-cutter ant, which dates back about 10 million years and includes nearly 50 species native to South and Central America and to the southern United States. Here’s how these insects, which live in underground nests that can cover 6,500 square feet and house 8 million residents, go about gardening: Specialized workers called mediae forage around their nest for plant material, cutting off pieces of leaf—they can strip clean a citrus tree in a single day. They lug the plant material to the nest and hand it off to minims, specialized workers that fragment the leaf pieces into a sort of mulch and feed it to fungi being cultivated in the nest. The queen, which is the only member of the ant colony that lays eggs, lives in the fungus garden. There her eggs hatch, and the larvae feed on the convenient food source (adults feed on leaf sap). These ants and their relatives represent the world’s first known farmers.
Termites: Some termite species, which live in colonial nests like those of ants, also grow fungus gardens. The insects build spongy “combs,” which may include nutritious termite feces as an ingredient, and grow fungi on the combs. The termites feed on the fungi, which benefit from the protection of the insects and the habitat they provide.
Ambrosia beetles: These weevil relatives bore into and carve tunnels in dead or dying trees. They carry certain fungi in special receptacles on their bodies and deposit fungus spores in the tunnels, where the fungi grow, drawing nutrients from the wood. Rather than eat wood themselves, the beetles and their larvae feed on parts of the fungi. When larval beetles become adults, they collect fungus spores and fly off to bore into new trees and restart the process. About 3,000 beetle species use this strategy.
Bowerbirds: Lest you think that wildlife gardeners are all about fungus and insects, let’s take a look at the spotted bowerbird, a species studied in Queensland, Australia, where recent research discovered that the birds engage in gardening, of a sort. Male spotted bowerbirds build elaborate nests, or bowers, from twigs and decorate them with various objects to attract females. One decorative object much loved by females, and hence much sought by males, is the yellow-green, often purple-tinged berry of the potato bush—in fact, more berries on the bower means better mating success for the male. Males don’t generally build bowers in areas where the berries grow in abundance, but by the time a bower is a year old, it usually has a few dozen potato bushes growing nearby, giving the male more opportunity to decorate with more berries. The males throw shriveled berries outside the bower, affecting the distribution of the potato bush. Not precisely agriculture as ants and humans may know it, but still a form of opportunistic gardening. It also is the first known example of the cultivation of a nonfood plant by a nonhuman species.