Wednesday, March 12, 2008

Army Ants

On a recent jungle trek into Guatemalan jungles, the cry went up: "Army Ants!!!". And this was met with glee, as for birders, stumbling across massive columns of these voracious but Lilliputian warriors can mean only good things. The ants have been over-dramatized and probably vilified to some degree, with tales of them devouring people and anything else in their path.

While I certainly wouldn't want to get caught sleeping in their path, they pose little threat to us. Anything else that isn't alert and somewhat mobile, all bets are off. Numbering in the millions, these armies of Eciton burchellii (the most used Army Ant by birds) swarm everything in their path, and everything from spiders, crickets, mammals, and lizards trip over themselves in a mad rush to get the heck out of the way.

Enter the "ant birds", and the source of birders' glee.

A column of army ants crosses a jungle road in Guatemala. Like well-disciplined soldiers, they condensed into a tight column when crossing the foodless roadway. Upon entering the jungle on the other side, they quickly fanned out on a wide track, and the action started. Bugs galore were scrambling madly out of the path in all directions. We watched one large spider who was slow on the draw. First one ant, then within seconds many, attacked and quickly brought it down. In no time, zero out one spider - nothing is left. Imagine the swath millions of these tiny predators cut through the jungle.

Jeff Gordon (right) and I provide some scale to the column. We didn't stay there especially long. The ants have no problems attempting assaults on large mammals if the chance permits.

A gorgeous Ruddy Woodcreeper works the ant column. There were a number of this species, as well as some Northern Barred Woodcreepers and a few other birds here, going crazy over the insects fleeing the column. They would sit low in the vegetation, and quickly drop down to the ground to snare some fleeing critter. It was interesting to watch the birds periodically shake themselves briskly, to toss off the ants that had gotten on them.

Central and South American avifauna is filled with species with names like antbird, antpitta, antshrike, antvireo, etc. These names don't originate because these species eat ants - in most cases, they don't, at least typically. It is because they are army ant followers, specializing to varying degrees in following ant columns and feeding on fleeing animals.

"Ant birds" come in three general categories. There are the opportunistic ant birds; these are species that take full advantage of the havoc wrought by an army ant column as it passes through their territory, but they don't follow the ants any further.

Then there are the "semi-pros"; species that do follow ant columns for some distance, but don't depend on them entirely as a way of finding food.

Then there are the professional ant followers. These are birds that seem to depend completely on the ants to flush food for them, and nomadically follow the marching columns. The woodcreeper pictured above is probably more of an opportunist, taking advantage of the wonderfully easy feeding opportunities created as the ants passed through its turf, but probably not following along very far.

So, next time you are in the tropics looking for birds, hope for the good fortune of bumbling into a couple million war-like ants.

1 comment:

Jim Dolan said...

Cool stuff Jim. How can I get a job like yours?