October 9, 2021 · Uncategorized

As with all of my images posted here, they are for your enjoyment and are not public domain, all are copyrighted.  Please do not copy, download, post online, or reuse in any fashion the photographs that I have posted without express written permission to do so.  Any use of my images must be approved in writing.  To access the images I have posted, you must click on the subject heading link above. By doing so, your action serves as legal recognition of my stated copyright restrictions; it signifies your willingness to use the images only after written permission is provided, and it acknowledges that failure to follow the rules is a violation of international copyright law. Thank you for your cooperation.

The complexity of a forest floor, in a rainforest (tropical and temperate), is often lost on people. The decomposition rate of leaves, sticks, and other organic materials is unbelievably rapid; however, these items are raining down on the forest floor at a nearly constant rate. The circumstances provide a microhabitat type that is humid, offers ample hiding places, and is constantly in flux. Conversely, the forest floor can be a dangerous place for small animals considering the ants, spiders, centipedes, snakes and other small predators living there. The evolution of leaf mimicry might be best exemplified by leaf litter fauna – some extraordinary examples exist. One hypothesis has it that the deception of a search image is the likely evolutionary driver of these mimicry adapted life forms. Search images are mental depictions of what something should look like as an animal scans its environment. Without consciously thinking about it, the brain constantly compares the mental image of what is being sought with what is being observed – this is a much studied phenomenon and something that primates, including humans, employ. In fact, I believe I’ve seen it in action. For example, when people first visit a tropical forest, they are often slow to find wildlife because they haven’t developed their search image yet. Over time and with effort, search images can be developed and refined, rendering an improved ability to detect something resting on a complex background – like in leaf litter. Sure enough, people visiting the tropics with me improve through time in their ability to detect wildlife in the complex environment around them and search image development can happen in a relatively short amount of time within a given person. You can imagine that as small, visually oriented predators — like birds and snakes — develop a search image, the mimicry of their prey items — like frogs, toads, and small lizards – responds over time and generations (evolutionarily) by becoming more and more cryptic, to deceive the search image. In theory, the most cryptic and deceptive mimicry survives long enough to pass those genes to the next generation and so on. It is an arms race that continues between the search image and things intended to deceive it. It is also interesting to consider the perspective from which a cryptic appearance is observed. For example, some leaf mimics don’t much look like leaves from a side angle; however, looking down on the animal, from above, (as if from the vantage point of a bird or a snake in the lower canopy) the cryptic appearance is immediate and obvious.

Thick leaf litter on an Amazonian forest floor.

There are structures on these leaf mimics that help to disrupt the recognizable outline in form of a lizard or a frog. Fleshy extensions of eyelids or of the nose help to break up an easily discernible body shape. Flanges extending off of a leg or an arm work toward that same goal. Dorsal patterns and colors add to the cryptic effect and can disrupt the outline of an animal. The sum of all of these things can be nearly unbelievable. It is also important to remember that the cryptic appearance is intended to deceive the search image of primary predators, not humans. So there may be circumstances where we are not necessarily deceived; however, a small bird, a snake, or even an invertebrate predator would be deceived. A predator may or may not see in color – yet another consideration to how a cryptic animal appears to its potential predator. This cryptic look is often accompanied by behavior. For example, many leaf litter frogs have an “escape behavior” where, if startled, they will take one giant leap and then remain absolutely motionless, sometime spread out in unnatural positions, on the forest floor. The “cryptic behavior” can significantly add to the cryptic appearance. More than once I have had a frog or a small lizard vanish into the leaf litter, right in front of me, never to be seen again. Conversely, a few leaf litter inhabiting amphibians have brightly colored patched on their sides and undersides. These colors are concealed in a normal resting position; however, when the animal leaps, the bright colors are suddenly flashed at a potential predator. One hypotheses argues that bright colors are a warning characteristic of defensive toxins or a venom (the aposematic coloration hypothesis). The hypothesis here is that these nontoxic species are using that system in a “dishonest” way. They are flashing colors to try and get a predator to hesitate. If the deception gives the potential predator a second of extra pause, the difference between life and death might very well be measured, in these cases, by milliseconds of hesitation in a potential predator. I bring all of these things up because folks are often confused by colors on leaf mimicking animals – but they can make sense for a secondary escape plan if the cryptic look didn’t do its job. It also needs to be considered that many of the cryptic animals we are discussing are also predators of smaller things themselves. Looking like something that you are not might be valuable in hiding an animal from both its predators and its prey items.

There are undoubtedly many forces influencing the evolution of an organism’s cryptic appearance. Some of those forces might be at odds with one another and there might be “character compromises,” over evolutionary time, between them. So much remains to be studied and understood. This brief explanation of a few of the hypotheses at play is not intended to be exhaustive or thorough. I just wanted to give the reader a little behind what might be happening. I have spent an enormous amount of time investigating the leaf litter community in the upper Amazon Basin and South American temperate rainforests. The herpetofauna and other small life forms living there are diverse. Sometimes they mimic things other than leaves, such as moldy and decomposing twigs. Remember, too, that this habitat type extends to the bottoms of pools and streams in these habitats and that there are as many interesting animals adapted for leaf litter in aquatic circumstances as in terrestrial ones. This post is a celebration of the diverse leaf litter community that I have been able to observe and photograph

True Toad: Bufonidae

The silouette of a Crested Toad, Rhinella margaritifera

The dominant leaf litter inhabiting toads in the upper Amazon Basin of Peru are known as the “South American Common Toad” or “Crested Toad” Rhinella margaritifera. I wanted to share images of these guys. There is no doubt that this group is comprised of a complex of similar species… someone needs to wade in a straighten out a lot of little toads (we think there are at least 7 species in the Iquitos region alone). It will be a lot of hard work. These amphibians can attain a size somewhere between a tennis ball and a soft ball – females are typically a little bigger than males and develop the extravagant crests that the species is known for – as with the adult female individuals here. But there are other species present and I think several are represented below.

Crested Toad, Rhinella margaritifera, adult female, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, adult female, ACTS, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, adult female, ACTS, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2019
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2019
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2019
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2019
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2018
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2018
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, November 2018
Crested Toad, Rhinella margaritifera, adult female, ACTS, Rio Sucusari, Loreto, Peru, 2015
Crested Toad, Rhinella margaritifera, adult female, ACTS, Rio Sucusari, Loreto, Peru, 2013
Crested Toad, Rhinella margaritifera, adult female, ACTS, Rio Sucusari, Loreto, Peru, 2010
Crested Toad, Rhinella margaritifera, adult female, ACTS, Rio Sucusari, Loreto, Peru, 2011
Crested Toad, Rhinella margaritifera, adult female, Santa Cruz Biological Station, Rio Mazan, Loreto, Peru, 2018
Crested Toad, Rhinella margaritifera, adult female, Río Sucusari, Loreto, Peru, 2018.
Crested Toad, Rhinella margaritifera, adult female, Río Sucusari, Loreto, Peru, 2018.
Crested Toad, Rhinella margaritifera, adult female, Río Sucusari, Loreto, Peru, 2018.
Crested Toad, Rhinella margaritifera, small adult female, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, young female, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, young female, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, young female, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2018
Crested Toad, Rhinella margaritifera, juvenile, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, juvenile, Sucusari Lodge, Rio Sucusari, Loreto, Peru, January 2019
Crested Toad, Rhinella margaritifera, juvenile, Ceiba Tops, Loreto, Peru
Crested Toad, Rhinella margaritifera, juvenile, Ceiba Tops, Loreto, Peru
Crested Toad, Rhinella margaritifera, juvenile, Ceiba Tops, Loreto, Peru
Crested Toad, Rhinella margaritifera, juvenile, ACTS, Rio Sucusari, Loreto, Peru, October 2019
Crested Toad, Rhinella margaritifera, juvenile, Rio Orosa, Loreto, Peru, Jan 2013
Crested Toad, Rhinella margaritifera, metamorph, ACTS, Rio Sucusari, Loreto, Peru, 2010
Crested Toad, Rhinella margaritifera, metamorph, Santa Cruz Reserve, Rio Mazan, Loreto, Peru, September 2018
Rhinella sp, male, ACTS, Rio Sucusari, Loreto, Peru, 2013
Rhinella sp., male, ACTS, Rio Sucusari, Loreto, Peru, 2013
Rhinella sp, ACTS, Rio Sucusari, Loreto, Peru
Rhinella sp, ACTS, Rio Sucusari, Loreto, Peru
Rhinella sp, Río Mazan, Loreto, Peru, 2018.
Rhinella sp, Río Mazan, Loreto, Peru, 2018.
Rhinella dapsilis complex, Explorama Lodge, Rio Amazonas, Loreto, Peru, October 2018
Rhinella dapsilis complex, Explorama Lodge, Rio Amazonas, Loreto, Peru, October 2018
The Leaf Toad, Rhinella ceratophrys, Loreto, Peru.
Ecuador Giant Forest Toad, Rhaebo ecuadorensis, Loreto, Peru, October 2016
Ecuador Giant Forest Toad, Rhaebo ecuadorensis, Loreto, Peru, October 2016
Amazophrynella minuta, Rio Sucusari, Loreto, Peru, October 2016
Amazophrynella minuta, Rio Sucusari, Loreto, Peru, October 2016
Amazophrynella minuta, Rio Sucusari, Loreto, Peru, October 2019

Narrow-mouthed Frogs: Microhylids

Carvalho’s Silent Frog, Chiasmocleis carvalhoi. These amphibians typically inhabit deep leaf litter and can be difficult to find. This individual is less than 1 cm in total length (SVL). You can see a small mite crawling on its leg. It was observed along the Río Sucusari, Loreto, Peru, 2015.
A microhylid, Ctenophryne geayi, is often found in small clearings beneath fallen debris. It likely feeds on termites and is strictly nocturnal. Breeding aggregations occur in small streams and isolated pools.
A microhylid, Ctenophryne geayi, is often found in small clearings beneath fallen debris. It likely feeds on termites and is strictly nocturnal. Breeding aggregations occur in small streams and isolated pools.
A microhylid, Ctenophryne geayi, is often found in small clearings beneath fallen debris. It likely feeds on termites and is strictly nocturnal. Breeding aggregations occur in small streams and isolated pools.
“Bassler’s Humming Frog,” Chiasmocleis {Syncope} bassleri. The species has a large distribution which includes Amazonian Colombia, Ecuador, Peru, northern Amazonian Bolivia, as well as adjacent Brasil. I’ve found this species to be patchy in distribution – we have several trails where we find them on wet rainy nights but I don’t see them that often. They feed on small invertebrates in the leaf litter.
The Dotted Humming Frog, Chiasmocleis ventrimaculata, inhabits the wet tropical forests of the upper Amazon Basin. These frogs live in leaf litter and below the ground. This specimen was photographed in Amazonian Peru in 2017.
The Dotted Humming Frog, Chiasmocleis ventrimaculata, inhabits the wet tropical forests of the upper Amazon Basin. These frogs live in leaf litter and below the ground. This specimen was photographed in Amazonian Peru in 2017.
Bolivian Humming Frog, Hamtophryne boliviana, Explorama Lodge at Yanamono, Loreto, Peru, November 2019

Leptodactylidae

Eyelashed Forest Frog, Edalorhina perezi, Rio Sucusari, Loreto, Peru
Eyelashed Forest Frog, Edalorhina perezi, Rio Sucusari, Loreto, Peru
Eyelashed Forest Frog, Edalorhina perezi, Rio Sucusari, Loreto, Peru
Eyelashed Forest Frog, Edalorhina perezi, Rio Sucusari, Loreto, Peru

Craugastoridae

The Loreto Leaf Frog, Noblella myrmecoides, inhabits deep leaf litter within the wet forests of the upper Amazon Basin. Adults are less than a centimeter in total length. This specimen was photographed in Amazonian Peru in 2017.
Loreto Leaf Frog, Noblella myrmecoides, Explorama, Rio Amazonas, October 2018
Loreto Leaf Frog, Noblella myrmecoides, Explorama, Rio Amazonas, October 2018
a developing clutch of “rain frog” eggs, Pristimantis sp., from the leaf litter of an Amazonian forest floor. These frogs do all of their development directly within the egg (a process called direct development): there is no free living tadpole stage. I shot this off of the Río Mazán, a tributary of the Napo River (a tributary itself of the Amazon) on the Peruvian side of the border with Ecuador.
Red-bellied Rainfrog, Pristimantis lythrodes, is a rare and distinctively colored amphibian with no clear affinities to other species. Known from only a few localities in northeastern Peru and adjacent Colombia, its life history and ecology remain a mystery. We have found this frog in the region of Oran on the Amazon as well as along the lower Río Sucusari near the Río Napo in Peru.
Ockenden’s Rain Frog, Pristimantis ockendeni
Rainfrog, Strabomantis sulcata, Explorama, Rio Amazonas, October 2018
Rainfrog, Strabomantis sulcata, Explorama, Rio Amazonas, October 2018
Rainfrog, Strabomantis sp., ACTS, Rio Sucusari, Loreto, Peru, October 2019

Ceratophryidae

One of the great leaf litter inhabiting predators of the Peruvian Amazon (and all the way east to the Guina shield) is the Surinam Horned Frog, Ceratophrys cornuta. At least in the Peruvian Amazon, these aren’t as easy to find as one might think. They hunker down in the leaf litter and literally vanish before your eyes. With a wide mouth and strong jaws, they make quick work of both small vertebrates and invertebrates that they can fit into their mouths. The pointed “eyelashes” above each eye are disruptive in that they help break up the recognizable outline of a frog, contributing to the cryptic nature of this species. The mix of tans, browns, and even greens on the dorsal surface of these frogs further blend them in with the leaf litter. This view is the last one many small animals have while moving along the rainforest floor. Peruvian Amazon, Loreto – September 2017.
Surinam Horned Frog, Ceratophrys cornuta
Surinam Horned Frog, Ceratophrys cornuta, in-situ
Surinam Horned Frog, Ceratophrys cornuta
Surinam Horned Frog, Ceratophrys cornuta
Surinam Horned Frog, Ceratophrys cornuta, in-situ

Hemiphractidae

The Sumaco Casque-headed Treefrog, Hemiphractus proboscideus
The Sumaco Casque-headed Treefrog, Hemiphractus proboscideus
Hélio’s Casquehead, Hemiphractus helioi
Written by


Post a comment