Adventures Among Ants - Mark W. Moffett [43]
5 group transport
It was late in 1983. For the final leg of my doctoral fieldwork, after traveling without a break for twenty-nine months, I had ended up in the Philippines. I had just arrived at the base of Mt. Apo, on the southern island of Mindanao, at almost 3,000 meters the highest mountain in the Philippines and cloaked with forests. On exiting the bus, I found José, a self-proclaimed guide who, an hour into our walk, broke his silence to speak of the need for revolution while patting what he claimed to be a gun in his waistband.
On my way to Mindanao, I had faced riots against the government outside the Manila airport. I now recalled a U.S. government advisory that Mindanao was the center of the Communist movement and unsafe for travelers. It occurred to me for the first time since I had left Massachusetts nearly two and a half years before that it might be pleasant to experience Christmas at home again—or even be reminded of what the holiday celebrated.
Mist and tree ferns gave each vista of the flanks of Mt. Apo a Jurassic Park flavor. While José talked, I located my old friend the marauder ant. Among their legions, fifteen minor workers—the chief food-delivery caste—carried a centimeter-long blue sphere through dense brush. When I picked it up, more ants poured from a crack in the sphere to expose the remains of a bird embryo.
Whether it’s political rebels or ants fetching home a bird egg, a successful social operation requires the coordination of individuals. The orchestration of a marauder ant raid is an obvious example of how organization emerges from collective masses within a superorganism. By moving in closer to watch the individuals as if they were tissues within organs, I could document equally compelling examples of social integration, involving smaller ant groups within a swarm.
Marauder ants are successful at “marauding” in part because workers can work together to haul provisions along their superhighways—or expel a rejected queen from the nest. Group transport is the carrying, dragging, lifting, rolling, or burying of a burden by multiple individuals.1 We’ve all seen group transport, if only when a few ants pilfer crumbs at our picnics. But the average interloper at a picnic represents only a crude example of the sophisticated group transport accomplished by the marauder.
GROUP TRANSPORT AMONG ANIMALS
From watching the marauder ants for months while in Asia, I had become fascinated with group transport and began to investigate which other creatures could accomplish this basic task. I discovered that group transport is as scarce in the animal kingdom as using tools or hunting in a group. Such task-oriented cooperation is particularly rare in nonhuman primates, in part due to the overwhelming drive of each individual to keep food for himself and in part because they seldom deal with large objects in nature, although captive chimpanzees will reach food by carrying a branch together to use as a ladder or by group-dragging a box.
Even for species that cooperate to kill prey, jointly moving a cumbersome meal requires a delay in gratification that few can tolerate. Litter mates of rodents such as rats will sometimes jointly convey food they had initially fought over. Lions and also hyenas, wolves, jackals, African wild dogs, and other dog-family members typically feed in a free-for-all or along dominance-hierarchy lines, but occasionally they may jointly move meat to a shady spot or protected den. Even then, they tend to act like competitors who just happen to be pulling their dinner in the same direction.2
Nonhuman mammal societies usually contain one or two dozen individuals, with a few dozen at most. It’s often simpler for such a small group, for example a pack of wolves, to travel to the kill site than to take a large carcass to a more desirable setting. Similarly, in the few ants with small colonies that eat big prey—such as New Guinea’s Myopopone castanea, which feeds on blubbery insect larvae—the entire society may up