Oh the Places You'll Go: Nests, Ants, and Acacias

So as I mentioned in my previous post, one of the days in Santa Rosa was spent doing a small group research project. We were split into four groups and given an advisor - either Moncho (who I had), Johel, Raquel, or Richard. We were all given a different project and were expected to collect data in the morning, analyze and prepare a presentation for later that afternoon. It was basically an introduction to presenting research projects for when we have to do it ourselves later in the semester.

So as an overview, my group was looking at relationships between Vachellia colinsii (acacia tree), three ant species (Pseudomyrmex spinicola, Pseudomyrmex nitrocinta, and Pseudomyrmex flavicornis), and two different birds (wrens and flycatchers). These ants live in the acacia trees and have formed a symbiotic relationship with the tree. One species will live in any given acacia tree, and will provide protection from herbivory for the plant and in return gets food and a place to live from the tree. Also, each of these species of ant was tested to have differing levels of aggressiveness. This was measured by how fast they swarmed out of the nest when we tapped the tree. The P. spinicola are red ants that tuck their abdomen under their thorax. These ones we found to be the most aggressive, as they very quickly swarmed out of the nest when we tapped on it. P. nigrocinta is also a red ant, but this one does not tuck its abdomen. This ant was slightly less aggressive than the P. spinicola, as they came out of the tree more slowly and there were less of them compared to the first species. The last ant, P. flavicornis, is a black ant, which was pretty easy to tell apart from the others. This ant was the least aggressive of the three species, as it took them a very long time to come out of their nest when we tapped on the tree.

Along with the ants and the acacia tree, we were more specifically looking at the wrens and the flycatcher birds. These birds each use the acacia trees to build their nests. The wrens build a nest that is used all year - round, whereas the flycatchers use the nest only during the breeding season.

Wren nest

Flycatcher nest

Our task was to determine whether or not there was a preference of wrens and flycatchers to build their nest on an acacia tree that is inhabited by a particular species of ant. To do so, we searched through the woods around our campsite for acacia trees with the nests of both of the birds, the wrens and the flycatchers. When we encountered an acacia with one of these nests, we tapped on the tree in order to determine the ant species. We did this for maybe 3.5 hours in the morning and were able to gather enough data among the 5 of us to begin doing the data analyzation in the afternoon. So basically we performed a Chi-Squared analysis to see whether the numbers we expected correlated with those we observed. In the end, we found that for flycatchers, there was no statistical significance in ant species preference for the nest building. There was a trend, however, for favoring P. flavicornis. For the wrens we found that there was statistically significant evidence that they were choosing a tree to build their nest. Wrens tended to build their nests on acacia trees with the P. spinicola.

We had some hypotheses as to why this would be the case. For one, we thought that maybe since the wrens live in their nests year-round, they would want to nest in a tree with more aggressive ants to help protect their nest, as well. This would have to be looked into further, but it made sense to us. In terms of the flycatcher, there was a trend in favoring the least aggressive ant, which could be because they only live in their nest for the breeding season, so they wouldn't necessarily need the protection of a more aggressive ant.

Here are some pictures from the experiment: