15 replies to this topic

[ConcordAntman]

About a month ago I found a Camponotus americanus colony nestled in my back patio. I’ve taken to feeding the colony leavings of the baked mealworms mixed with bird droppings found in my bird feeders. I thought it’d be an opportunity to watch the action and possibly capture some photos. After placing the leavings near the C. americanus nest, a group of Tetramorium sp. showed up and began what appeared to be cooperative (or at least non-competitive) foraging between the two species. In the shot below, the C. americanus nest is to the right with a worker at the entrance. The mealworm leavings are frame left. At the lower left and center of the frame you can see the proximity of the Tetramorium to the C. americanus workers and to their nest entrance. I naively imagined invisible pheromone markers separating one species’ territory from the other’s and expected carnage to ensue once the Tetramorium breached the larger C. americanus’ “land”, but no. As I watched, both species foraged, taking care to keep out of each other’s way. What about this setting fostered coexistence rather than foment conflict? It was quite interesting to watch. 
 

 

[ANTdrew]

Hard to say. In birds, mixed species flocks forage together because it means more eyes to look out for predators and more chances of finding food. Maybe something similar is going on, or maybe it's just not worth the energy expended fighting each other when there is enough for everyone. You might see a different scenario if two Tetramorium colonies came upon the resource.

Is it just me, or do the larger workers look like Formica?

[ConcordAntman]

ANTdrew, remember my species ID'ing skills suck  (I'd better go out again with my field guide). I compared them with the C. americanus I have and thought I had a match. I'll admit, I just did it on gross morphology and color. Perhaps I need new glasses too.

 

What interested me over the 25-30 minutes I watched was that while they were certainly within eyeshot or pheromone range of the other species, they seemed to take pains to avoid each other. There were no attacks. In fact, if two ants approached and a "personal space" boundary was broached, one of the offenders (usually the larger species) jumped out of the way and just kept on truckin'. I wasn't looking for conflict but given my understanding of chemical signage as a tool for pathfinding and kin/colony identification, I was surprised at this non-competitive behavior.

[Kaelwizard]

ANTdrew, remember my species ID'ing skills suck (I'd better go out again with my field guide). I compared them with the C. americanus I have and thought I had a match. I'll admit, I just did it on gross morphology and color. Perhaps I need new glasses too.

What interested me over the 25-30 minutes I watched was that while they were certainly within eyeshot or pheromone range of the other species, they seemed to take pains to avoid each other. There were no attacks. In fact, if two ants approached and a "personal space" boundary was broached, one of the offenders (usually the larger species) jumped out of the way and just kept on truckin'. I wasn't looking for conflict but given my understanding of chemical signage as a tool for pathfinding and kin/colony identification, I was surprised at this non-competitive behavior.

They’re Formica. I’m not great with ID’s either, but a quick google search of Camponotus americanus is told me that these were not them. The head shape also gives it away. Camponotus minors have rectangular heads, while the large ants in the picture do not.

Edited by Kaelwizard, August 21 2020 - 1:25 PM.

[ConcordAntman]

Yeah, I just looked more closely on buggide.net     What can I say  I’ll obviously have to add this to my list of things to work on! Still, I’m curious about the behavior. Is this just quirky behavior in some random foragers or is it a generally witnessed behavior?

Edited by ConcordAntman, August 21 2020 - 6:11 PM.

[Kaelwizard]

I think it also has something to do with size difference. For example, a tiny ant might be completely ignored by something like Camponotus. I have seen that many times before.

[OhNoNotAgain]

This is really cool. I suspect that there's a cost/benefit ratio for engaging in hostilities. Just like dominance competition has ritualized conflict to minimize great harm/damage (costly), I suspect many ants won't engage immediately in very hostile behavior until/unless conditions cue a change to more aggression. I don't know about Tetramorium sidewalk battles, but having seen a Camponotus run screaming out of the nest of a different species (my bad, mistaken identity), vs. seeing a suicidal orphan P. californicus trying to rescue her sister brood from a P. subnitidus nest (again, my bad, mistaken identity), it must be very circumstantial.

Edited by OhNoNotAgain, August 22 2020 - 8:23 AM.

[ConcordAntman]

I'm going to try to find some peer reviewed articles on this (while brushing up on my species ID'ing skills).I'll post what I find.

[RushmoreAnts]

I'm really surprised the Tetramorium didn't attack. Around here, Lasius and Formica like to eat each other. 

[ConcordAntman]

I think I found something that supports the concept of cooperative (or at least non-competitive) foraging between species! the article is by Riitta Savolainen and Kari Vepsäläinen in Oikos Vol. 51, No. 2 (Feb., 1988), pp. 135-155: A Competition Hierarchy among Boreal Ants: Impact on Resource Partitioning and Community Structure. I've just made it through the abstract and it seems to shed some light on the behavior I've witnessed. For those that are interested, the article is available at https://www.jstor.org/ It's behind a paywall but if you register, you're allowed access to 100 articles for free. I'll report back once I've finished the article.

 

[ConcordAntman]

So, here's the Cliff's Notes on Riitta Savolainen and Kari Vepsäläinen, A Competition Hierarchy among Boreal Ants: Impact on Resource Partitioning and Community Structure. I think it suggests the behavior I witnessed is, in fact, naturally occurring formicine behavior. Globally, colonies compete for resources among themselves. That competition is modified by physical issues (terrain, distance between competitors and resources, temperature, etc.) and biological issues specific to the competing species (colony maturity, species size, species dietary preferences) with a significant biological attribute being forager density (i.e. the number of foragers deployed by each colony per unit area). Based on other's work that had preceded theirs, Savolainen and Vepsäläinen postulated that the above factors are modified to a greater extent by a colony's position in a "competition hierarchy". This hierarchy is determined by differences in each colony's social development and behavior. There are three broad hierarchical groups; territorials (who protect their nest, food resources, and territory), encounterers (who protect their nest and food resources), and submissives (who protect only their nest). The alpha group of territorials is termed superior competitors, who fiercely protect their nest, food resources, and territory. Two colonies of territorials would not co-inhabit an area. A colony of territorials and a colony of encounterers could co-inhabit an area though the density of encounterer colonies would be diminished and pushed to the periphery of the territorials foraging area. The encounterers might also forage at a time when the territorial foragers were least likely to be present in large numbers. Encounterer-encounterer co-inhabitation is fraught but possible and encounterer-submissive co-habitation can more easily occur. Finally, territorials and submissives could co-inhabit an area with their colonies interspersed in the territorials area at a greater density than encounterers. When faced with the presence of territorial foragers, the submissives might alter their food intake (i.e., substitute a carbohydrate for protein) and/or alter foraging time to avoid contact. Through observation in the field and statistical analysis Savolainen and Vepsäläinen were able to corroborate their findings and actually predict colony behavior. It seems that the non-competitive behavior I witnessed between Formica sp. and Tetramorium sp. is a known behavior and to my eye, the Formica seemed to be the submissives!     

[ANTdrew]

Fascinating!

[Kaelwizard]

Of course the Tetramorium are dominant...

[OhNoNotAgain]

Speaking of competition/cooperation, I'm reminded of this little tidbit:

 

"One example of this is the competition for access to seed resources between the Novomessor cockerelli and Pogonomyrmex barbatus species of harvester ants. Novomessor cockerelli ants engage in interference competition against Pogonomyrmex barbatus colonies by "plugging" entrances to the nest with sand and small rocks. This delays activity of P. barbatus for one to three hours, shifting the onset of foraging until later in the day when the temperature is substantially higher."

 

 

https://pubmed.ncbi....h.gov/28311843/

Edited by OhNoNotAgain, August 23 2020 - 1:45 PM.

[ConcordAntman]

OhNoNotAgain, I think that link is bad. I got an oops not found page. Try this https://pubmed.ncbi....h.gov/28311843/

 

Whoa, I just checked out the abstract. Deborah Gordon is (or was) local when she wrote this!

Edited by ConcordAntman, August 23 2020 - 10:49 AM.

[ConcordAntman]

Fascinating!

Ain't it though! How amazing are these tiny buggers?!? One hundred twenty million years of evolution to fine tune this little socially complex species. Wow!

 

Of course the Tetramorium are dominant...

Don't mess with the little ones, if they can make it on the streets of New York City, they can make it anywhere!