Ants: Slave-makers

Summary: Did you read that title right? Yes, you did. Some ants make slaves of other ants! Join Kiersten to find out how.

 

For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean

 

Show Notes: 

“Tales from the Ant World” by Edward O. Wilson

“Adventures Among Ants” by Mark W. Moffett

Music written and performed by Katherine Camp

 

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Kiersten - Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating. 

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

In the last episode we talked about communication and how pheromones allow ants to give each other important messages and instructions. This is an amazing adaptation that makes them one if the most efficient organisms on the planet, but it does have a downside. Relying on pheromones as your main source of communication can lead to loop holes that others will take advantage of and by that I mean enslavement. Yep! Some ants enslave other ants. It’s not exactly something I like, but it is incredibly interesting. So, the fourth thing I find interesting about ants is how they use and misuse pheromones to their greatest advantage.

We discussed how ants know who is allowed to come in and out of a colony in the last episode. When ants emerge from their pupal stage their body oils absorb the unique smells of their colony. This gives them the key to re-enter their colony when they venture out, and it helps protect the colony from intruders, but it can also be used to enslave them. 

Let’s find out exactly how this works. The workers of ant species specialized to be slave-makers will raid colonies of other species. Workers from Polyergus lucidus or Formica subintegra will raid the colony of a vulnerable species such as Formica subsericea. When they raid the colony they have one target, the pupae. The adults of the colony being raided certainly put up a fight and ants on both sides of the battle will lose their lives but the raiders will retrieve at least some of the pupae they were after. That pupae is taken back to the raiders colony and settled in with the nursery there. Within a few days or weeks, the raided ants will emerge and soak up the scent of their new colony. They believe this is their home. It’s where they are meant to be. They accept the raiders as their sisters and the raiders accept them as their own. So, the enslavement isn’t like what we think of from the human perspective. It is a bit more like capture and domestication of wild animals.

In the north temperate zones of North America, Europe, and Asia ant slavery is common especially in the subfamily Formicinae. Oddly, slavery is known in only temperate areas. Five species of Polyergus ants are known to be slave-makers and these ants range across North America, Europe, Russia, and Japan. All of them enslave ants in the genus Formica.  

Let’s follow a specific raid detailed by Mark W. Moffett in his book Adventures Among Ants. At Sagehen Creek Field Station in the Sierra Nevada of the United States, Moffett and his graduate student watched a raid between Polyergus breviceps, also known as Amazon ants, and Formica argentea. The Amazons were raiding the Formica colony. They watch as the Amazons forced their way inside the Formica colony and then head out the other side with the pupae of the Formica. They flipped a rock to find out what was going on inside and expected to see a war going on between the raiders and the Formica, but that is not what they saw at all. The only fight they saw was one Formica ant in a tug of war with a n Amazon over a pupa, but all the other Formica were just walking around, business as usual. These species of Formica only fight raiders by putting up blockades of dirt. Once the raiders destroy those blockades and enter the colony, the residents just give up and let the Amazons raid the nursery.

Mark and his student followed the Amazons back to their own colony and were amazed at what they saw. The Amazons were greeted by adult Formica slaves that took the pupae that they’d just raided from them and scuttled off with the stolen pupae. Other adult Formica ants exited the Amazon colony and picked-up the raiding party and carried them back into the colony where they would be waited on hand and foot. The majority of the time, the Amazons never did anything for themselves they just laid around maybe grooming one of their sisters as the Formica slaves did everything in the colony.

A quote from Moffett’s book explains everything we need to know about the fate of the stolen Formica pupae, “Assimilated into the wrong society, the ants are duped into a life of servitude, doing all the drudge work their masters won’t: building nests, foraging for prey, harvesting honeydew, slaying free-living Formica that enter their territory, and taking care of the brood. The Amazon slavers’ only job is to go on raids, replenishing the store of Formica pupae as their enslaved workers age and die.” End quote.

The other side of this raiding behavior is also quite interesting. The Amazon ants can’t actually take care of themselves. The literally can’t do anything but raid Formica nest to steal pupae. They cannot create nests, they cannot find food for themselves, the cannot take care of themselves. They must have slave ants to do it for them. 

Moffett tells his readers about an instance when he dropped a piece of his turkey sandwich near an Amazon worker. She walked right by completely ignoring it, not knowing it was a tasty bit of food. It remained where it fell until a Formica slave ant came upon it and took it to the colony. 

The Amazon raiders are so out numbered when they enter a Formica colony that, if the Formica actually fought back, the Amazons would lose, but these species have evolved in this unusual dance for years. The Amazons are now dependent on the Formica for survival. Maybe the Formica have accepted the raids as just another day in the colony.

Polyergus aren’t the only ants that make slaves. It seems to be spread through the ant kingdom. In Yosemite National Park, Edward Wilson came across a raid in progress. The raiders were Formica wheeleri and they had four different species of Formica spread throughout their colony with some of the enslaved ants participating in the raid on another nest. 

You would think that slave-making would be a dead end evolutionarily speaking for the ants that adopt this behavior, but it doesn’t seem to be causing any of them to go extinct yet. It can degenerate into social parasitism though. Strongylognathus testaceus has completely lost their raiding warrior spirit. The newly mated queen simply moves into a colony of another species and sets up shop right next to that colony’s queen. The host colony workers take care of both queens. When the parasitic queen lays eggs the host workers take care of them as well. The adult parasitic ants just kind hang out with the other workers but don’t do any work at all. Talk about the couch surfing friend that just won’t leave!

How did slave making evolve in ants? No one is sure of an answer, but the most accepted hypothesis is that the first slave-makers were competitive species that raided other colonies for whatever they needed and took the pupae as part of their booty and most likely ate them. Some of the pupa survived and became the first slaves. Evolution and survival took over from there. Nature can be so very interesting.

Thank you for joining me for the fourth episode of ants. I know it was a choice to listen to this specific episode based on the title, but I am glad you did listener’s, because my fourth favorite thing about ants is how the use of pheromones have evolved into something so surprising.

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change. 

Join me next week for another exciting episode about ants.  

    

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, my very own piano playing hero.