Army Ants' Engineering Skills

New research on South American army ants shows that raiding parties plan ahead and "resurface" the roadway for a quicker return with plunder. From Eurekalert:

"Certain army ants in the rainforests of Central and South America conduct spectacular predatory raids containing up to 200,000 foraging ants. Remarkably, some ants use their bodies to plug potholes in the trail leading back to the nest, making a flatter surface so that prey can be delivered to the developing young at maximum speed.
"The raid always remains connected to the nest by a trail of forager traffic, along which prey-laden foragers run back to run back to the nest. This trail can be extremely uneven and full of ‘pot holes’ as it passes over leaves and branches on the forest floor.
"The study, by Dr Scott Powell and Professor Nigel Franks at the University of Bristol, and reported in the June issue of Animal Behaviour, shows that these living ‘plugs’ improve the quality of the surface. This increases the overall speed of the traffic and results in an increase in the amount of prey delivered to the nest each day." ...
"Their experiments showed that individuals size-match to the hole they plug and cooperate to plug larger holes. 'We did this by getting the ants to literally "walk the plank",' said Powell. 'We inserted planks drilled with different sizes of hole into the army ants’ trails to see how well different sizes of ant matched different sizes of pot hole. Indeed, they fit beautifully', explained Franks.
"Overall, this behaviour results in an increase in the average speed of prey-laden traffic. Moreover, calculations suggest that under a range of realistic scenarios, plugging behaviour results in a clear increase in daily prey intake. In other words, the behaviour of the pothole pluggers more than compensates for them not carrying prey themselves."