Today we focused on some of the many ant species that habitate the Chiquibul forest. The cecropia tree has a symbiosis with azteca ants, which protect the tree from predators in exchange for shelter and food. We spent the morning testing a few hypothesis about how the cecropia trees avoid herbivores before they are colonized by the protector ants.
This afternoon we excavated three leaf cutter ant colonies of different maturities. Once a queen colonizes a nest after a nuptial flight she can live for 20 years reproducing, expanding the colony until there are millions of ants at any given time. There are tunnels underground leading to chambers full of the ant’s fungus garden and pupae. The youngest ones are fairly small, but once they are 10 years old they get huge, with tunnels the width of your arm full of soldier ants ready to come out and attack you when you disturb them. They have quite a pinch and we were all thankful for our rubber boots today.
We had an unexpected amphibian sighting once we got back to our housing; one of the bedrooms had a large frog on a bedpost. I caught it and took it outside to get a closer look and try to identify it. It hiccuped in my hand, puffing out its chest, in protest to its capture. The frog was dark green and brown, with some stripy markings around the forelegs. I couldn’t examine its back without it jumping from my hands so I didn’t get a clear look. It was about 2.5 inches long with horizontal pupils, bronze irises and toe pads. The toe pads indicate that its a treefrog and since there aren’t many in the area I would have to guess that it was another common Mexican treefrog, based on size and color. I released it into the trees after a minute or two to not cause it too much distressed and it leapt from my hands with a defiant squeak.
Today we started off by summarizing the results from our experiments yesterday about Cecropia and ant interactions. My group ended up with negative results. We didn’t find any evidence of young Cecropia mimicking other plants. We did notice some differences between juvenile and adult trees, such as red petioles (the stems of leaves) and slightly longer trichomes (the tiny hairs on plants). However, we weren’t able to conclusively determine that those differences had an adaptive role. One group tested the toughness of juvenile and adult leaves and found that juvenile leaves were tougher. This could be adaptive because it would make it more difficult for herbivores to eat the leaves. If the project was continued, it would be beneficial to see if herbivores preferred younger or older leaves.
We also were able to visit the cave at Las Cuevas. The cave was a part of Mayan ceremonies, and there is still evidence of their presence. There are pottery shards throughout the cave system and the cave is built up in some areas. Platforms were built near the entrance and some spaces between chambers were made to be narrower. The whole history behind the cave is extremely interesting. The caves also had some wildlife. We saw at least two species of bats, millipedes, and a species of scorpion with long legs and no tail. One of the best aspects about the cave was how undeveloped it was. I’m not used to visiting preserved caves that haven’t been commercialized. It was cool to feel like I was one of the first to visit the cave, even though many, many people have visited it before me.
My favorite trees today were the big trees that we commonly see around the Chiquibul. The cedar (Cedrela odorata) can be 20-30m tall. Right now it doesn’t have leaves, but it has some wooden seed pods that are still attached to the branches. The seed pods look like 5-petaled flowers – they’re very pretty. Another big tree is the ceiba (Ceiba pentandra). When it is mature, its bark is very smooth and it can reach 60-70m. It has been difficult for me to identify ceiba from their leaves because the trunks reach so high into the canopy.
We only have two more full days at LCRS, so we’ll have to make them count!
We began our first real experiments bright and early this morning on the cecropia, or trumpet tree, which is known for its mutualistic relationship with Azteca ants. The hollow tree tunk provides shelter for the ants, and, in exchange, the ants defend against herbivores vying for the cecropia’s lobe-shaped leaves. Though cecropia’s mutalism with ants is incredibly effective, young cecropia trees are not yet colonized. How, then, do these juvenile trees protect themselves from herbivory?
We hypothesized that young cecropia use chemical defenses (like toxins or pheromones) to deter herbivores. Our pilot experiment involved collecting generalist herbivores, such as grasshoppers, and offering them both adult and juvenile cecropia leaves. We may not have the technology for chemical analysis here, but we do have sophisticated pieces of equipment like Tupperware and a butterfly net. We’ll see tomorrow if the insects opt to consume one leaf over the other, or even die after ingesting a toxic leaf.
The day’s ant theme continued with an afternoon dedicated to the fascinating life history of leaf-cutter ants. We looked at three leaf-cutter ant nests ranging from 1 to 10+ years old, observing their intricate tunnel systems and foraging trails. I was most amazed by the anthropomorphic qualities of leaf-cutter ants; they essentially act as farmers by cultivating fungus for food. The afternoon’s primary goal was uncovering these fungus gardens, which can sustain colonies of millions of ants.
Our focus today made reptile sightings difficult, as snakes and lizards are unlikely to be found in the vicinity of a large ant’s nest. Though we walked many of the same trails as yesterday, I wasn’t able to spot any of the Sumichrast’s skinks found yesterday in the leaf litter. I actually found better luck indoors today, spotting another common house gecko (Hemidactylus frenatus) running along the walls of our classroom.
Today we looked at two species of ants, Azteca ants and leafcutter ants. Azteca ants are a genus of ants that have a symbiosis with Cecropia trees. The ants provide protection from herbivores and competitors for the trees, and the trees provide shelter and nutrition for the ants. We wanted to look at how the trees are able to thrive when they are juveniles and before an ant queen has colonized the tree. To do this, we split into groups and designed hypotheses for how the trees adapted. My group looked into whether juvenile Cecropia trees mimicked other plant species or characteristics through physical adaptations. Tomorrow each of the groups will summarize their data and come up with a conclusion. It will be interesting to see which of the groups has the most convincing argument.
During the second half of the day we examined the life cycle of a leafcutter ant nest. Queens can live more than 20 years, although workers usually do not live longer than a year. Some colonies can have around 5 million individuals. Additionally, a mature colony can be about equal to a cow, in both weight and volume of plant material processed in a year. While we’ve been at Las Cuevas, we’ve noticed a lot of leafcutter ant trails around the area. Today we learned that those trails are only made by colonies that have been established for around 10 years. Smaller nests aren’t able to create or maintain the trails.
The most interesting tree that I observed today was a papaya tree. Originally we thought that the papaya tree was a Cecropia juvenile, but the details didn’t match. The tree had large palmate leaves, a very tall and skinny trunk, and smooth bark, which are characteristics similar to Cecropia. However, the leaves were more lobed than Cecropia leaves and the reproductive structure of the papaya was different. It would be interesting to know how related Cecropia and papaya are; the books that we have access to here didn’t have information on their relatedness. I also was able to identify a tree species that we saw at Caracol with green flowers. The tree was a Mosannona garwoodii. The flowers were very camouflaged and appeared slightly waxy. I haven’t seen the same tree yet here, but it could be around.
Tomorrow we have the opportunity to explore a cave in the region. I’m excited to see what life we’re able to find in the cave.