Dynamics of Neo-Tropical Arachnids

Today’s post is a guest post by Andrew Mularo,  an undergraduate student in the Department of Evolution, Ecology and Organismal Biology. He is currently doing his Tropical Behavior Evolution and Ecology research project under Dr. Rachelle M. M. Adams and Dr. Jonathan Shik.

You may love them or you may fear them, but no one can deny the incredible ecological importance of spiders and scorpions. As an aspiring biologist, I have chosen to study the interactions between arachnids and their environment in the tropical rainforests of Panama for the 2017 Tropical Behavioral Evolution and Ecology course. The tropics are a biodiversity hotspot for the majority of the world’s organisms, so there are plenty of creatures to look at. From the smallest spiderling to the largest tarantula, I am curious to see how these cryptic and intriguing animals interact with their ecosystem.

For my project, I am doing an observational study where I am assessing the relationship between leaf litter and arachnid diversity and abundance. I am accomplishing this by creating several 50 meter transects in the Panamanian rainforest, sampling leaf litter with 1 square meter quadrants along each transect. For each quadrant, I take a measurement of leaf litter depth, and sift through the leaves to extract any organisms out of the area. Back at the lab, I sort through the organisms, first finding any arachnids in the sample, and then any other insect or invertebrate, such as ants, beetles, millipedes, snails, mites and many others. With these data, I hope to make a correlation between leaf litter abundance and arachnid diversity and abundance, as well as a correlation between the diversity of potential prey items and arachnid predators.

Naturally, the majority of the organisms that I have been assessing have been very small, from the size of a thumbnail to not even being visible to the human eye. However, there

Wandering Spider (Photo by A. Mularo)

are several occasions where I have observed some extremely imposing arachnids in the tropical forest. One of these includes the huntsman spider, an extremely large nocturnal species that does not rely on a web to capture its prey. This family of spiders is very poorly researched, and is largely unknown how dangerous the venom is for the majority of species. However, they are quite shy, and often scurry away at the sight or sound of a human.

Another fascinating group of organisms I see occasionally are scorpions. The two pictured below are from the genus Tityus, whose venom is very potent. I found the two in the picture below, which we believe to be different species, huddled in close quarters in the water well of a bromeliad. While potentially dangerous, these are a relatively uncommon sight in the rainforest. Nevertheless, it is always good to be careful where you step.

Tityus scorpions (photo by A. Mularo)

While many of them are feared, arachnids are some of the most fascinating organisms on the planet. They come in all shapes and sizes, and have a wide array of interesting characteristics that are of great interest to scientists. Being interested in biology since I was a child, I have always dreamed of coming to the tropics so I could study the vast diversity of organisms, and I could not have picked a better group of organisms to focus on!

Field ornithology

A recent post on Cool Green Science about Margaret Morse Nice “How a Scientific Outsider Changed How We Study Birds” inspired me to think more generally about how researchers study bird behavior in the field and how acoustic recordings can help us understand bird behavior. By the way, here “field” does not refer to a type of habitat rather it encompasses any natural habitat (rivers, lakes, meadows, forests etc.) in which animals live.

Margaret Morse Nice portrait

Margaret Morse Nice looking into a nest of baby sparrows, 1956 (Wikipedia)

Margaret Morse Nice’s most important contributions to ornithological research were probably in the advancement of techniques in studying birds. She was one of the few American women ornithologists in the 1930s and the first to make detailed observations of individual birds. She followed Song Sparrows through their lives, took notes on their life history and published her observations in over 200 papers and books. Most of her publications are listed in her autobiography “Research is a passion with me“.

cover of Margaret Morse Nice's book Research is a passion with me

Book by Margaret Morse Nice “Research is a passion with me”

Interestingly, Nice who was born in Massachusetts in 1883 studied Song Sparrows in Columbus, OH where she and her family lived in 1927-1936. During these eight years she closely followed birds on their property off Patterson Ave, a floodplain on the east-side of the Olentangy river just north of Lane Ave, what is today Tuttle park. Even though the habitat has changed from the shrubs, weeds and gardens in Nice’s time you can still find open areas especially along the river which Song Sparrows to this day use to build their nests and raise their young.

To follow individual birds closely, identify them repeatedly and note their behavior and interactions with each other, it was clear to Nice that she needed to mark the birds. Over the years she trapped some 870 Song Sparrows which she marked with unique combinations of plastic color bands on their legs. We still use the same technique today.

color-banded Song Sparrow

“Red-black / yellow-metal” banded Song Sparrow (c) K. Whittaker

Bird banding actually started in Europe as an aid to follow migrating birds and still is used for this purpose: Researchers put a metal band with an engraved unique number on a bird’s leg – just like your social security number. They report this number as well as where and when the bird was caught and banded to a central lab, here in the USA the central bird banding lab in Maryland. When somebody then recaptures or finds a banded bird, they can access this information through the bird banding lab and relate it to data they collect about the bird.

Colored leg bands help researchers to follow individual birds. Sounds easy? It can be once you have the colored leg bands on the bird. First you have to catch the bird and that can prove tricky. We primarily use two established bird trapping techniques: walk-in traps and mist-nets.

Just as the name implies, wire-mesh traps are placed on the ground, seeded with some tasty morsels and when the bird in search of food walks into the trap a door closes behind it and traps it within.

Collared Dove in a Potter Trap

Collared Dove in a Potter Trap (c) Third Wheel Ringing Supplies

For a mist-net imagine a volleyball net strapped between two poles but with finer mesh and all the way to the ground. These nets work best in foggy weather conditions when they are nearly invisible and when placed strategically in a bird’s flight path, the subject will fly into the mesh, bounce and fall into a fold at the bottom of the net and get entangled. We then “extract” the bird from the net and band it. – By the way not everybody can trap and band birds because they are highly protected under the Migratory Bird Treaty Act dating back to 1918. Through training with a master bird bander researchers can obtain a U. S. Federal Bird Banding and Marking Permit.

So what role does sound play in this? Sometimes we lure birds to the mist-net by playing calls or songs of its species. Why does this attract a bird? Most songbirds are territorial, i.e. they defend an area that they use exclusively for feeding or breeding and song keeps every other bird of the same species out of this territory. Some researchers have actually done clever experiments to prove this keep-out function of birdsong, but that is a story for another post.

Doug Nelson holding up a loudspeaker playing bird song in front of a mist net

Doug Nelson holding up a loudspeaker playing bird song in front of a mist-net in Oregon (c) Angelika Nelson

So, birds do not produce their most beautiful songs to please us, rather one function is to repel a male contender. If the opponent does not take this warning, a bird will switch to physical attack. Exactly this behavior can get them trapped in a mist-net as they search intently for the invisible opponent, aka loudspeaker, and eventually dive at in attack.

This brings me back to Nice’s contributions to field ornithology: Nice studied closely the territorial behavior of “her” birds. Once all males were banded she made close observations of where they sang, how they interacted with neighbors and whether they were able to attract a mate. She described patterns of invaders and defenders during territorial encounters and described the role that song played in these. To this day this is a prominent research topic in our lab where we have studied territorial singing behavior in the White-crowned Sparrow and other species over the last decades.

Following in the footsteps of Margaret Morse Nice, Dr. Chris Tonra, Assistant Professor in the School of Environmental and Natural Resources at Ohio State, has started a project to continue work on behavior of the Song Sparrow. He and his students regularly band today’s local Song Sparrow population at Ohio State’s Wilma H. Schiermeier Olentangy River Wetland Research Park, less than one km upstream from Nice’s former home, and follow them throughout the year. He uses some of the techniques from Nice’s days, others have advanced – read more about the project here!


About the author: Angelika Nelson is the curator of the Borror Laboratory of Bioacoustics. Her recent research has focused on song and behavioral ecology of the White-crowned Sparrow in Oregon; each spring Angelika teaches the OSU course “Ohio Birds” where students learn about the life of birds and how to identify them in the field – by sight and sound.



“Nice, Margaret Morse.” Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com. (August 17, 2016).

Christmas Tree Ornament Snails


Halotudora gruneri (Pfeiffer, 1846)

Halotudora gruneri (Pfeiffer, 1846)

As the holidays are upon us, it is comforting to know that even the lowliest creatures celebrate the season.

The Caribbean land snails in the family Annulariidae do a lot of strange things, but among the strangest is their propensity to hang upside down from a thread or threads of hardened mucus like Christmas tree ornaments. Why they do this is a mystery. But as near as we can tell, many of them do it – no matter where they are from: Cuba, Jamaica, Hispaniola, Puerto Rico, Curaçao, Guatemala – their entire zoogeographic range. This suggests that this odd behavior is quite ancient. The thread-spinning trait must have evolved very early on in the history of these snails before they dispersed throughout the Caribbean and Central America.

When do they do it? Well, they seem to do it at night and they will suspend themselves from caves, trees, walls – pretty much anything, including other snails. They secrete a mucus thread or threads from which they hang. To my knowledge no one has actually seen them do it. The previous evening they are crawling around, the next morning they are suspended. From where is the thread produced? Unknown. The snails have an operculum – a trapdoor attached to their foot that seals the shell opening when the animal is withdrawn. The operculum is clamped down on the thread suggesting that the animal does not have to expend energy holding on to the thread.

Why do they do it? No one knows. But the thread is very fragile – the slightest touch will break it, causing the snail to fall to the ground. The most plausible suggestion as to why they bother is that the behavior is an antipredator device. Any would-be predator crawling down the thread would cause the thread to break, thus losing the snail and their potential lunch. The fall apparently does not harm the snail; dented and broken shells are common in some species.

The photos below show some ornamental snails from Guatemala.

Diplopoma osberti (Tristram, 1861)

Diplopoma osberti (Tristram, 1861)

Gouldipoma coltrorum Watters, 2014

Gouldipoma coltrorum Watters, 2014

Parachondria rubicundus (Morelet, 1849)

Parachondria rubicundus (Morelet, 1849)

Diplopoma rigidulum (Morelet, 1851)

Diplopoma rigidulum (Morelet, 1851)

















About the Author: Dr. G. Thomas Watters is Curator of Molluscs at the Museum of Biological Diversity.