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Fire Transforms Landscape Color, Affecting Camouflaging Animals
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by Regina Fairbanks, edited by Swapna Subramanian
“Differential survival and background selection in cryptic trunk-dwelling arthropods in fire-prone environments”
João Vitor de Alcantara Viana, Rafael Campos Duarte, Carolina Lambertini, Felipe Capoccia, Anna Luiza Oliveira Martins, Camila Vieira, and Gustavo Quevedo Romero: Read the article
Fire events impair animal camouflage. Animals adapt by choosing suitable backgrounds or being polymorphic, reducing predation risks. Our study shows how spiders find the best spots and how grasshoppers and mantises thrive on burned and unburned trunks in a neotropical savanna
Figure 1. A brown (A) and a melanic (B) morph of the praying mantis Eumiopteryx laticollis (Thespidae) rests on a unburned and burned trunk of Qualea grandiflora, respectively, one year after a severe fire event in a neotropical Cerrado savanna area. When the praying mantis avoids predators on these trunks, they also hunt for prey – camouflage helps in both situations. João Vitor de Alcantara Viana, Rafael Campos Duarte, Carolina Lambertini, Felipe Capoccia Coelho, Anna Luiza Oliveira Martins, Camila Vieira, and Gustavo Quevedo RomeroOn the left panel, a brown praying mantis on a brown tree. On the right panel, a black praying mantis on a black tree that has been burned.
Many animals evolved to escape predators by blending into their surroundings – but what happens when their surroundings change? A new study published in 2024 by de Alcantara Viana et al. explores this question in the Cerrado savanna of Brazil, where frequent fires transform the landscape. As fires sweep through the savanna, they produce patches of burned and unburned areas, potentially affecting the ability of local arthropods (a group including insects, spiders, and other relatives) to blend into the background. Their study highlights how camouflaging animals interact with their environment, allowing them to survive even in the face of rapid change.
In their Cerrado savanna system, the authors concentrated on a few arthropod species, including a grasshopper and praying mantis that both produce two color morphs (brown and dark) and a spider that produces a single color morph (dark). Brown arthropods resting on newly burnt, blackened trunks may stand out to predators, increasing mortality. But in varied, patchy environments, even dark arthropods may struggle if they cannot find the appropriate matching background. In the face of such heterogeneous environments, some species evolve multiple color types, or “morphs”.
First, the authors took a bird’s-eye view to test how well the different species and their morphs match both burned and unburned tree trunks from the savanna: They compared the color matching not with human visual systems, but with those of potential bird predators. They found that the dark arthropods blend in better with burned trunks, while brown arthropods blend in better with unburned trunks, with subtle differences depending on species and bird visual systems.
Figure 2. Fieldwork activities. Panels A, B, C, D, and E depict general fieldwork activities, showcasing the team and their engagement in the field at the Cerrado savanna. Panels F and G represent activities related to the human predation experiment.An assortment of photos of the scientists in the savanna where they conducted their studies.
The authors then conducted behavioral tests to determine whether arthropods of different colors could effectively select their matching background by providing brown and dark arthropods the choice of either burned or unburned trunks to rest upon in the lab. Interestingly, they found that only the monomorphic dark spider – the study species most specialized on trees – effectively selected the appropriate background.
To see how the camouflaging plays out in nature, the authors conducted simulated “predation” experiments using human “predators” and artificial arthropod models mimicking the coloration of the actual arthropods. Indeed, they confirmed that brown arthropods evade predation when resting on unburned trunks, while dark arthropods better evade predation when resting on burned trunks.
Overall, the authors found evidence that having different color strategies might help arthropods survive in places with patchy, ever-changing environments. As climate change, pollution, and other human activities continue to transform the planet, animals increasingly face variable, unpredictable habitats. Some species adapt and survive, like the famous peppered moth, which evolved a dark morph in the face of coal-covered trees in industrialized England. But only time will tell whether other arthropod species can evolve polymorphic strategies in time.
Regina A. Fairbanks is a Ph.D. candidate in the Population Biology graduate group at the University of California, Davis. Regina’s research aims to integrate evolutionary genomics with archaeological science to better understand crop domestication and plant-people relationships. For their dissertation, Regina uses population genomic data to study the evolutionary history of maize. In addition to their research, Regina participates in a wide range of science communication and mentorship programs, including Letters to a Pre-Scientist and the UC Davis Evolution & Ecology Graduate School Preview Program. When not staring at a computer screen, Regina can be found in museums, botanical gardens, and farmers markets.
