Invading army ants

At the Catalina sector wetland, a group from Clemson and I discovered a stream of army ants (Eciton burchellii; I think) that had fanned out into a raiding swarm at one end.  There were hundreds of hidden cockroaches, crickets, hemipterans and other insects fleeing the area that was being scavenged by the ants.  A few insects appeared not to be bothered by the biting, stinging formacids, and soon became prey.  We watched the wasp pictured here go from freely sitting on a leaf to being completely dismantled with little or no reaction by the wasp.  The other picture is one of the soldier ants that was provoked by myself and others.  At first I laughed at her futile attempt to protect her sisters, until I realized that she was merely distracting me with a pose while several others climbed up my camera strap…army-ant-invasion-at-catalina-wetland-05212009-165117army-ant-invasion-at-catalina-wetland-05212009-165703

Limpkin feeding sites

Last updated:
23 May 2009

Figure 1 - Potentia limpkin feeding site
Figure 1 - Potential limpkin feeding site
Figure 2 - Potential limpkin feeding site
Figure 2 - Potential limpkin feeding site

Figures 1 and 2 show a potential limpkin feeding site. I discovered 3 sites, one of which I had observed a limpkin fly away from. Before flying off, the limpkin was within 10 m of me, so I’m fairly confident that it had been standing at that location, but I was unable to observe a limpkin actually feeding at one of these locations. The shells are from a very thin-shelled aquatic snail that appear to be extremely abundant in a variety of vegetation types. I have encountered the snail in Pistia (Figure 3), an unknown emergent plant (see Massive herbivory; Figure 4), and Eichhornia.

The snail has no operculum and, when handled, doesn’t usually escape into its shell. I’m unsure whether or not the snail is a scraper, consuming epiphytic biofilm, or consumes macrophytes proper. If they snails are scrapers and are limpkin prey, there may be an interesting interaction occurring; Apple snails tend to consume macrophytic tissue and scraping snails have been shown to increase macrophyte growth. It may be far fetched, but could apple snail predation effectively farm these snails?

Reduced apple snail density = greater macrophyte biomass = more surface area for biofilm formation = great thinned-shelled snail densities

Thin-shelled aquatic snail
Figure 3 - Thin-shelled aquatic snail

Figure 4 - Thin-shelled aquatic snail
Figure 4 - Thin-shelled aquatic snail

Other than apple snails at snail kite perches, there was one other species of snail present. Figure 5 shows a snail shell found along with apple snail shells at a snail kite perch. Although this snail may also have been prey, several individuals were found lodged within apple snail shells, so these snails may have died while consuming left over apple snail tissue or attempting to escape drought. The shell is much thicker than the shells found at the limpkin sites discussed in this post, and is not likely the same species.

Figure 5 - Non-apple snail species found at snail kite perch.

Macrophyte Herbivory

In CSW, there is an abundant emergent macrophyte that I am unable to identify. It hasn’t flowered yet and the key in Crow’s Aquatic Plants of Palo Verde National Park and the Tempisque River Valley hasn’t been much help. If someone knows right away what this plant is, please let me know.

I’ve identified it to Thalia geniculata. Only the leaves are present currently.

Figure 1 - A common emergent macrophyte in CSW
Figure 1 - A common emergent macrophyte in CSW

Figure 2 - Minor herbivory on the macrophyte

Today (23 May), while wading though the wetland, I noticed that this plant has been hammered by herbivory (Figure 2 and 3). The nearly complete consumption of the leaves of this plant throughout the entire wetland appears to have been a result of a caterpillar (Figure 4 and 5).

  • What effects does this level of herbivory have on Thalia? Is it able to regrow leaves? Will it flower?
  • What is the herbivore? Is a a moth? Is a multivoltine and will it knock back the Thalia when it grows back? Why does it appear to specifically feed on Thalia and how to the adult find it?
  • Where are the pupa?
  • Where were the caterpillar predators to mediate the herbivory? The caterpillar seems rather conspicuous, so does it employ some sort of other prey escape mechanism, like tasting bad?

Figure 3 - Massive herbivory on the macrophyte from Figure 1.
Figure 3 - Massive herbivory on the macrophyte from Figure 1. Notice that there are limited reminents of the leaves on each stem or petiole.

Figure 3 - An active herbivorous caterpillar on the macrophyte from Figure 1
Figure 4 - An active herbivorous caterpillar on the macrophyte from Figure 1

Figure 4 - An active herbivorous caterpillar on the macrophyte from Figure 1
Figure 5 - An active herbivorous caterpillar on the macrophyte from Figure 1

Jacana Eggs

I’ve found and have GPS coordinates of 4 Northern Jacana nests, three with four eggs and one with three eggs. I don’t know if they are from the same female, nor have I actually observe a Jacana incubating the eggs. The nests are fairly deep in the Catalina Sector Wetland (CSW) and are not observable from the road through the wetland, but I could observe them within the wetland itself. How is this usually done? The cattail is tall and basically impossible to see through or over.

Figure 1 - Jacana nest with 4 eggs
Figure 1 - Jacana nest with 4 eggs

Figure 2 - Jacana nest with 3 eggs
Figure 2 - Jacana nest with 3 eggs

Is it possible to weigh or gently handle the eggs? I wonder if I can find more nest that are obviously from different females and monitor some measure of fitness for each: number of eggs, weight per egg, hatchling success, hatchling growth rate, etc. These could all vary by habitat perhaps. The two locations pictured in Figures 1 and 2 are dominated by Pistia and are open areas surrounded by cattail. One location is pure cattail, but is open and the nest rests on a bed of decomposing cattail.

Three bloody attempts

It took three bloody attempts to capture a single Thamnophis (Garter or ribbon snake) the other day.  Of course, I didn’t take a photo of the actual snake, just three hands, one of which is mine, that it had bitten before we were able to tame it.  The other two hands belong to Rafael, the assistant director of the station, and Jessica, a professor of a tropical diversity course from Clemson.thamnophis-proximos-bite-three-hands-three-bites-05202009-083931

A Typha fire

Last Thursday, the sky appeared to glow orange on the eastern side of the wetland from the OET station.  When Boa, Daniela, and I went to investigate, we discovered that there was a gigantic ‘natural’ fire sweeping through the decomposing, dry Typha (cattail). I took some poor photographs of the blaze, and then one the next day from the top of a nearby hill.

Although there was lightning striking that night, Mahmood believes that local hunters had illegally started the fire so that when regrowth occurs, they can shoot the deer that come to consume the seedlings and other young plants.  MINAE appears to agree with his hypothesis, since they bulldozed a road to allow fast access to the area with a car, presumably to catch potential poachers.burned-spot-in-the-cattail-05162009-164004cattail-typha-fire-05152009-192617