U-M biologists grab super-scary photos of Amazon spiders preparing meals of frogs, lizards and fur-bearing mammals

ANN ARBOR – Warning to arachnophobes and the faint of heart: These are nightmares, so it is prudent to proceed with caution.

A team of biologists led by the University of Michigan documented 15 rare and disturbing interactions between predators and prey in the Amazon rainforest, including evening images as a plate-sized tarantula causing a young opossum on the ground of the forest.

The photos are part of a new journal article entitled "Ecological Interactions between Arthropods and Small Vertebrates in a Rainforest Rainforest of the Plain". the crustaceans.

The article, published online Feb. 28 in Amphibian & Reptile Conservation, describes examples of arthropod predators, mainly large spiders accompanied by a few centipedes and a huge aquatic insect, attacking vertebrates. such as frogs and tadpoles, lizards, small opossum snakes.

"This is an underestimated source of mortality among vertebrates," said Michigan University evolution biologist Daniel Rabosky. "A surprising amount of small vertebrate deaths in the Amazon is probably due to arthropods such as large spiders and centipedes."

Once or twice a year, Rabosky leads a team of UM researchers (professors, post-docs, graduate students and undergraduates) and international collaborators on a one-month expedition to the Biological Station of Los Amigos, in the remote region of Madre de Dios, in southeastern Peru.

"We were rather ecstatic and shocked, and we could not really believe what we were seeing, we knew we were attending something quite special, but we did not know it was the first observation after the fact."

Michael Grundler

The study site, located in the Amazon lowland rainforest near the foothills of the Andes, lies at the heart of one of the most diverse ecosystems on the planet. The team focuses mainly on the ecology of reptiles and amphibians. But over the years, scientists have witnessed and documented many interactions between arthropod predators and vertebrate prey.

"We continued to record these events and, at one point, we realized that we had enough observations to gather them in a document," said Rabosky, an associate professor in the department of ecology and science. evolutionary biology and conservative associated with the museum of UM. Zoology.

Spiders are among the most diverse arthropod predators in the tropics. Previous reports on spider predation in the Amazon included prey from all major taxonomic groups of vertebrates: fish, amphibians, reptiles, birds and mammals.

However, knowledge of these interactions remains limited, particularly because of the diversity of vertebrate prey and potential predators of arthropods in species-rich tropical communities. The new document includes observations from 2008, 2012, 2016 and 2017.

"These events provide insight into the many connections that shape food webs and provide information on a major source of vertebrate mortality that appears to be less common outside of the tropics," said the study's first author, Rudolf von May, postdoctoral researcher. in Rabosky's laboratory.

"We are doing this research on about 85 species of amphibians – mostly frogs and toads – and about 90 species of reptiles," von May said. "And since there are hundreds of invertebrates likely to attack vertebrates, the number of possible interactions between species is enormous, and we emphasize this in this paper." said von May.

In addition to the biological station at Los Amigos, other observations were made at the biological station of Villa Carmen, also in the region of Madre de Dios in Peru, and at the research station of Madre Selva in the region of Loreto to the north from Peru.

Almost all observations were made at night, when predatory arthropods are the most active. During their night surveys, team members slowly walk through the forest with flashlights and headlamps, in single file, walking through the forest and listening intently.

During one of these night surveys, the U-M doctoral candidate, Michael Grundler, and two other students "heard noise in leaf litter."

"We examined and saw a large tarantula on an opossum," said Grundler, co-author of the newspaper. "The possum had already been gripped by the tarantula and was still struggling weakly at that time, but after about 30 seconds, he stopped kicking."

The tarantula was the size of a plate and the young mouse opossum was about the size of a softball. Grundler's sister, Maggie, took out her mobile phone and took pictures and videos.

Later, an opossum expert from the American Museum of Natural History confirmed that they had captured the first document on a large mygalomorphic spider feeding on an opossum. The Mygalomorphae infraord is a group of mainly heavy spiders with thick bodies, including tarantulas.

"We were pretty ecstatic and shocked and we could not really believe what we were seeing," said Michael Grundler. "We knew we were attending something quite special, but we did not know it was the first observation after that."

Most predatory arthropods use specialized body parts and venom to capture and paralyze their vertebrate prey. These adaptations include modified jaws, enlarged jaws and massive fangs. Some groups have developed dozens of venom proteins that are injected during prey capture.

Other predator-prey interactions described in the Amphibian and Reptiles Conservation Document include:

• Several examples of large spiders of the family Ctenidae feeding on frogs and a lizard. Most of the predation events documented in the document involve spiders, and most of them were ctenids, commonly referred to as wandering spiders. Ctenid spiders are predators sitting and waiting who hunt at night and use special hairs on their legs to detect air vibrations and the direction of prey. Their main eyes are responsible for the discrimination of the objects, and the secondary eyes detect the movement.
• A large scolopendrid centipede eating a live snake-eating snake, and another centipede eating a dead coral snake that he had beheaded. "Coral snakes are very dangerous and can kill humans," said Joanna Larson, PhD candidate and researcher at U-M University. "To see one who was taken by an arthropod was very surprising. These centipedes are terrifying animals, actually.

In addition to predation events, the researchers also reported deadly parasitic infections in lowland Amazonian frogs and commensal relationships between spiders and frogs. A commensal relationship is a relationship in which one body benefits and the other does not suffer any harm.

"One of the most interesting aspects of working in Peru is the large number of species you encounter every day just by walking in the forest," said Larson, who studies the evolution of frog feeding. "Every day you see something new and exciting."

"One of the results of the work we have done is this collection of strange natural history events involving arthropod predators and vertebrates," she said. "I have not reached the level of rudeness yet. We will see what Peru has to offer. "

Besides Rabosky, von May, Michael Grundler and Larson, the other authors of the document are Emanuele Biggi of the International League of Conservation Photographers; Heidy Cárdenas and Roy Santa Cruz of the Natural History Museum of the National University of San Agustín, Peru; Mr. Isabel Diaz from the National University of San Antonio Abad del Cusco and Peru's Biodiversity Museum, both located in Peru; Consuelo Alarcón of the John Carroll University and the Museo de Biodiversidad del Perú; Valia Herrera of the National University Mayor of San Marcos, Peru; Francesco Tomasinelli from Milan, Italy; Erin P. Westeen and Maggie Grundler from the University of California at Berkeley; Ciara Sánchez-Paredes of Universidad Peruana Cayetano Heredia, Peru; and Pascal Title and Alison Davis Rabosky of the Museum of Zoology U-M and the Department of Ecology and Evolutionary Biology.

The field research was funded by a David and Lucile Packard Foundation Scholarship to Daniel Rabosky, as well as the Amazon Conservation Association, the Wildlife Conservation Society, the Rosemary Grant Award, the Edwin C. Hinsdale UMMZ Scholarship and the University of Michigan. .

The document is available online at the following address: Conservation of Amphibians and Reptiles