Natures wonders: ant colony work arrangements (Introduction)

by David Turell , Saturday, September 09, 2017, 01:21 (2631 days ago) @ David Turell

The colonies have inactive ants who act as replacement for lost workers:

https://phys.org/news/2017-09-lazy-ants-unexpected-ways.html

"If the first thing that comes to mind when you think about ants is "industrious," you might be in for a surprise. In 2015, biologists at the University of Arizona reported that a sizable chunk of the "workers" that make up an ant colony spent the vast majority of their day engaging in one task: doing absolutely nothing.

"'They really just sit there," says Daniel Charbonneau, who dedicated his Ph.D. thesis to studying the behavior (or lack thereof) of these lazy ants. "And whenever they're doing anything other than doing nothing, they do chores around the nest, like a bit of brood care here or grooming another worker there."

"In a new paper, published in the open-access journal PLOS ONE, authors Charbonneau, Takao Sasaki of the University of Oxford and Dornhaus show for the first time that inactive ants can act as a reserve labor force. When they removed the top 20 percent of most active workers, they found that within a week, they were replaced mostly by individuals belonging to the "lazy" demographic, which stepped up and increased their activity levels to match those of the lost workers.

"'This suggests that the colony responds to the loss of highly active workers by replacing them with inactive ones," Charbonneau says.

***

"Analyzing the video recordings revealed that a colony breaks down into four main demographics, according to Charbonneau: inactive, lazy ants; so-called walkers that spend most of their time just wandering around the nest; foragers that take care of outside tasks such as foraging and building protective walls from tiny rocks; and nurses in charge of rearing the brood.

"Charbonneau observed that the lazy ants tend to have more distended abdomens, hinting at the possibility that they could serve as "living pantries." Published in another recent paper, this observation awaits further testing to determine whether their larger circumference is a cause or a consequence of the lazier workers' lifestyle.

"To see what would happen if the colony lost sizable amounts of inactive members, Charbonneau and Dornhaus did a separate experiment in which they removed the least active 20 percent. They found that those ants, unlike their top-performing peers, were not replaced.

"'This suggests that workers are not switching from other task groups to replace the removed 'inactive' workers," the authors conclude, noting that the problem of adjusting supply to demand is not unique to social insects.

***

"'My speculation is this: Since young workers start out as the most vulnerable members of the colony, it makes sense for them to lay low and be inactive," Charbonneau says. "And because their ovaries are the most active, they produce eggs, and while they're doing that, they might as well store food. When the colony loses workers, it makes sense to replace them with those ants that are not already busy pursuing other tasks.'"

Comment: Makes good organizational sense. Certainly doing it by instinct at this point. Originally guided by God?