The uptake of organic essential fatty acids by Pogonomyrmex, and their subsequent rendering to Horned Lizards.

Pogonomyrmex harvester ants are the staple food for most species of Horned Lizard, and these lizards eat large numbers of them in the wild. Many know that these ants make use of formic acid in their sting. It was a previously held theory that the Horned Lizard required the formic acid to survive. This turns out to not so much be the case. However, it appears that there may be an untold story of how beneficial and important these ants, and their formic acid, is nonetheless. Through my on-going research of Horned Lizards, I have also begun to study entomology in order to understand more about what makes these ants tick, and why Horned Lizards prey on them to such a great degree in the wild. This has also led me down the path of chemistry, which fortunately I have some knowledge of. What follows is my hypothesis based upon certain known facts an observations.

Formic acid is a type of simple organic acid, which is important as a building block for cellular structure, for creating more complex protein chains, and for cellular repair.

Pogonomyrmex harvester ants, naturally are harvesters of plant matter, including seeds. Interestingly enough in the plant matter that these ants harvest, more complex organic acids, known as unsaturated essential fatty acids, can be found. These fatty acids are also very important to living organisms. Due to their molecular structure they can be stored very densely in the tissues and are easily metabolized, thus providing a very efficient source of energy, while taking up relatively little space ( in the form of traditional "fat" ). In other words, "lean energy", which is ideally suited to ants, no?

The highest concentrations of these essential fatty acids are often found in the seeds and other reproductive parts of the plant, also interesting, since these ants are also often referred to as "seed harvesters".

Personal observations of captive Pogonomyrmex colonies has shown that these ants do not spend a great deal of time eating, despite the fact that they are quite lean and do not appear to have traditional fat stores, as might be more observable in crickets and worms. They do spend a great deal of time working themselves to death. When harvester ants take in these essential fatty acids from the plant matter, it is logical to assume that some of it is stored for extended use, especially given the efficient molecular structure mentioned which makes it particularly suited for storage and use in these ants. In almost a "divine" way you might say, this seems to work out too perfectly to be coincidence.

Formic acid is rendered from the "oxidation" ( metabolization ) of organic unsaturated essential fatty acids. As the ant uses it's fuel stores, it produces and stores the formic acid, making use of it in it's defense in another of natures miracles of efficiency. Nothing is wasted if it can be helped. This is true also of the Horned Lizard.

When a Horned Lizard eats harvester ants, it then breaks down this formic acid during digestion, which renders salt, CO2, and water, which hydrates the normally desert dwelling lizard. I hypothesize that this may be one particular reason why the more humid and high elevation dwelling short horns do not need to rely on these ants.

The formic acid has other beneifts; such as helping to maintain proper gut flora by inhibiting the proliferation of harmful bacteria, and providing a less hospitable environment for parasites ( much the same way as your grandma used to disinfect things with a lemon or with vinegar...the acidity ). Formic acid is conveniently used for this very purpose in livestock feed. The colder climate inhabited by many short horns may be less hospitable to potential parasites and bacteria that could infest low land Phrynosoma. Possibly another reason for their reduced or lack of need for the benefit from these ants. High elevation species of Phrynosoma may benefit in other ways from a reduced risk of parasites and harmful bateria if this is true; as they give birth to live young, unlike low land species.

Harvester ants have other advantages over other insects used as feeders. When a lizard eating ants passes scat, you will notice that the ants are identifiable in the scat, and that the scat is typically very dry. They are also passed rather quickly because they aren't completely digested ( exoskeleton ). I contend that this really means the Horned Lizard does not have to. That it is very efficient the way it is. On the other hand, a Horned Lizard eating crickets and mealworms takes typically more time to digest the meal, and the scat often appears to have much more moisture content. This is because many other feeders are much higher in a different type of fat content that the lizard must work harder to digest. This uses more water stores to do the same digestive job and render use from the fatty meal. Not efficient for a desert reptile. This places undue strain on other organs such as liver, kidneys, and heart... the same as in other animals, including people.

My hypothesis based upon all this: is that the harvester ant must maintain some stores, even if small stores, of the unsaturated essential fatty acids it takes in from plant matter, and that, though the formic acid component is very benificial; the most important component derived from the ant to the lizard may in fact be the "lean energy" unsaturated essential fatty acids. Since this is a very lean source of fuel and can be put to use quickly due to it's structure, and, because the Horned Lizard does require some fat stores, I advocate the theory that this is why the Horned Lizard takes in large numbers of ants. Not because the ants are not as nutritious as other insects, per se. But because it is more efficient to have many partially digested items for only what component is needed, rather than a few large items that need to be completely broken down to provide a substandard fuel to the lizard.

In conclusion:
Until harvester ants can be examined more closely, or corroborating evidence I am unaware of surfaces, the importance of unsaturated essential fatty acids derived by Horned Lizards from the activity of harvester ants remains a theory. But a theory nontheless grounded in logical, even if layperson, scientific methodology. The Horned Lizard species which take in high numbers of these ants must derive something more to fully operate on than the simple organic formic acid component. Though very beneficial, it is quickly metabolized into water and CO2.

I maintain that Pogonomyrmex harvester ants are a superior food source for Phrynosoma, as affirmed by their own habits in nature. In much the same way that a Horned Lizard knows how to burrow, thermoregulate, rain harvest, and use camouflage and it's other defenses without being taught...it also knows what primary food is best for it. Even if we don't fully understand why.

Fireside3/Phrynosoma_Texas

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"A man that should call everything by it's right name, would hardly pass the streets without being knocked down as a common enemy." The Complete Works of George Savile, First Marquess of Halifax 1912,246

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