Ants As Geochemists

Ants have been known to have a positive impact on soils by mixing different layers and by adding nutrients, etc. Now a researcher from Arizona State University, Dr. Ronald Dorn, has found that ants are enhancing the breakdown of certain minerals and the movement of carbon dioxide into calcium carbonate (limestone). The bottom line:  ants might be helping to remove greenhouse gases from the atmosphere.

Dr. Dorn did not start out to study ants. He actually began the study 25 years ago to look at weathering of olivine and plagioclase minerals from Hawaiian basalt. He placed samples in various sites in Arizona and Texas, and then went back every five years to see what was happening to them.

Other researchers have shown that weathering of calcium and magnesium silicates by living things is important in removing atmospheric carbon dioxide gases. A simplified reaction is shown here:


Over the 25 year period of this study, Dorn found the ant colonies of eight different ant species (Pogonomyrmex rugosus, Pogonomyrmex barbatus, Dorymyrmex bicolor, Forelius pruinosus, Liometopum luctuosum, Tapinoma sessile, Formica neogagates, and Camponotus vicinus), enhanced the weathering of the minerals some 50x-300x over that of the bare ground control. At the same time he found the percent carbonate increased substantially in the nests of all the different species.


Pogonomyrmex worker ant moving soil from its nest.

Of all the factors he studied, Dorn found that ants were by far the most important weathering agents. Given the amount of material a given ant colony moves around, that is not surprising.

What was a bit more surprising was that all the ant nests accumulated calcium carbonate over time, at levels well above what was happening in bare soil nearby. Perhaps it is time to investigate what exactly ants are doing in those underground galleries.

What do you think? Are ants an answer to removing excessive carbon dioxide from the atmosphere?

Dorn, R.I. (July 14, 2014) Ants as a powerful biotic agent of olivine and plagioclase dissolution. Geology.

Interested in learning more about the impact of ants on soils? Try this excerpt from the Encyclopedia of Soil Science Vol. 1

Stick Insects

It is not often you catch a glimpse of a stick insect out and about like this one I found basking on a wall a couple of years ago.

Members of the order Phasmatodea, these insects are also commonly called walkingsticks.

Why would I be featuring walkingsticks in a blog about ants?

Actually walkingsticks and ants have a very cool relationship, and it is one of my favorite stories to share.

Female walkingsticks are not particularly good mothers. When they lay their eggs, they simply drop them from the trees as they are feeding. This doesn’t seem like a safe strategy for making sure the eggs hatch, but female walkingsticks are relying on the services of a nanny on the ground to take care of their eggs.

Walkingstick eggs resemble seeds. In fact, the eggs have a knob on one end, called a capitulum, which looks and functions like an elasiosome of a seed. Ants find the eggs and drag them back to the safety of their underground nest. The ants remove and eat the capitulum, but generally leave the rest of the egg intact. After the walkingstick eggs develop in the nest, sometimes even overwintering there, the young walkingsticks emerge and crawl away from their protected nursery.

David Attenborough has a wonderful discussion of this in his BBC video, Life in the Undergrowth:

Just think, we might not have some types of walkingsticks if it weren’t for the services of ants. And you wonder why I’m “wild about ants.” 🙂

Woodpeckers That Specialize on Ants

This week we’ve been watching The Life of Birds DVD set narrated by Sir David Attenborough.  Have you ever seen the series? If you love nature you should, because it is so well done.

In one scene a rufous woodpecker from India is shown breaking open an ant nest and then busily eating ants. It piqued my curiosity, so I decided to see what else I could find out. Although I didn’t find the exact scene online to show you, I did find videos of rufous woodpeckers eating ants.

This first video is rather dark, but shows two young birds feeding on ants.

It appears that these woodpeckers from the Kerala region of India specialize on ants. Vishnudas (2008) cites an earlier worker from 1912 who found 2,600 ants in the stomach of a rufous woodpecker.

Although this video is shaky, it shows another woodpecker going after ants. (Makes you appreciate the quality of the footage from the Attenborough DVD.) It cuts away as the ants come rushing out of their nest.

It turns out that Rufous Woodpeckers, Micropternus brachyurus, not only use ants as their main food source, but also depend on Crematogaster ants for nesting sites. The birds work together to open up the carton nests of Crematogaster ants, and then build their own nests inside.

In his paper, Vishnudas also reports that several other species of birds follow the rufous woodpeckers and feed on the escaping ants when the rufous woodpeckers tear ant nests open.

In North America, there are woodpeckers specialize on ants, as well.

Northern flickers probably eat the most ants. They spend much of their time feeding on the ground around anthills. One flicker was found to have 5,000 ants in its stomach.

Doesn’t it look like the flicker is trying to dig out larvae and pupae rather than workers?

Pileated woodpeckers often cut slots into tree trunks or logs to get at carpenter ant nests inside. The woodpeckers will continue to return to the same opening over time, picking off ants that peer through the opening or that rush out to protect the nest.

It is fascinating to find out about these birds that are so dependent on ants for survival.

Have you seen any of the Attenborough series?

Vishnudas, C. K. 2008. Crematogaster ants in shaded coffee plantations: a critical food source for Rufous Woodpecker Micropternus brachyurus and other forest birds. Indian Birds. 4:9-11. (Available from Google Docs as a free .pdf)

The The Life of Birds  DVD set:

The Life of Birds  book by David Attenborough

(Affiliate links to Amazon)

New World Army Ants: Horror or Hype?

Are New World army ants the dangerous killers that movies and other media suggest?

After all, look at the jaws (mandibles) on the Eciton burchelli soldier. (Photograph by April Nobile / © / CC-BY-SA-3.0, downloaded at Wikimedia) Appears fairly fierce.

So, are they really horrors?

When reading the recent review of the Antsbirds & Ovenbirds book, Ossein asked for more information about Skutch’s descriptions of the army ants. Alexander Skutch spent years in the tropical rainforests where he commonly encountered army ants. Did Skutch worry?

On page 21 of the book (link will take you directly to the page), Skutch writes of Ecition burchelli:

“These ants are not nearly as formidable as sensational accounts depict them. They specialize on invertebrate prey. Active vertebrates of all kinds readily avoid them, perhaps not without a few stings.”

He goes on to add that

Often I have continued to sit at my table and write, while army ants scurried over the floor around me and the ceiling above me.”

On page 24, Skutch makes the point that New World army ants don’t even eat dead vertebrates. He recalls a time when a dead bird fell in the path of the raiding army ants and another time a dead snake was left in the path of the ants. Both times the army ants did not consume the remains, even though they were actively foraging.

The antbirds that follow the army ants are in no danger. In this video, you can see an elusive bare-eyed antbird standing while ants run nearby. It seems more concerned about the camera than the ants.

Bottom line, when it comes to New World army ants, the fervor has been mostly hype.

Have you ever heard that villages in some areas welcome army ants into their homes for pest control? Does anyone have a primary source for to back this up?