How Crabs Use Behavior to Blend Into Their Surroundings

Jenn Hoskins
10th August, 2024

How Crabs Use Behavior to Blend Into Their Surroundings

Image Source: Natural Science News, 2024

Key Findings

  • The study, conducted at the University of Exeter, found that furrowed crabs choose backgrounds that match their brightness to enhance camouflage
  • Older crabs are better at selecting appropriate backgrounds for camouflage, suggesting improved skills with age
  • Crabs showed a slight preference for more complex environments, which might aid in better camouflage
Camouflage is a well-known adaptation that allows animals to conceal themselves from predators and prey. While much research has focused on the types of camouflage and their mechanisms, the role of behavior in facilitating camouflage is less explored and often limited to specific taxa like moths and birds. A recent study by researchers at the University of Exeter[1] delved into this topic by examining the behavioral choices of furrowed crabs (Xantho hydrophilus) in selecting backgrounds that enhance their camouflage. The study aimed to determine if furrowed crabs use behavioral choices to improve their camouflage by selecting backgrounds that match their appearance. Researchers conducted behavioral choice experiments, presenting crabs with backgrounds differing in brightness, substrate grain size, and complexity. They found that crabs preferentially chose backgrounds that closely matched their own brightness, indicating a behavioral mechanism to enhance camouflage. Interestingly, the crabs did not show a preference for substrate size, but there was some tentative support for a preference for complex, high-contrast environments. The findings suggest that environmental complexity might play a role in facilitating improved camouflage, aligning with theories on the importance of such environments. This is somewhat supported by earlier studies on other animals. For instance, cuttlefish (Sepia officinalis) also use environmental cues like contrast to decide whether to blend into a 3D object or the surrounding substrate[2]. Similarly, Japanese tree frogs (Hyla japonica) adapt their dorsal patterns based on the brightness of their backgrounds, showing that brightness is a significant factor in their camouflage strategy[3]. One notable observation in the crab study was the reduced intraspecific variation in carapace color with age. This reduction likely reflects ontogenetic changes in coloration common in crabs or could be due to higher predation rates on less well-camouflaged individuals. The propensity to choose appropriate backgrounds also appeared to increase with age, suggesting that older individuals might be better at selecting environments that enhance their camouflage. The study's findings contribute to our understanding of camouflage behavior and its ecological implications. By showing that furrowed crabs can improve their camouflage through substrate choice, the research highlights the importance of behavioral adaptations in addition to physical ones. This aligns with earlier research on frequency-dependent predation, where more common prey variants are disproportionately attacked, leading to evolutionary changes in prey appearance[4]. In summary, the University of Exeter study provides valuable insights into the behavioral aspects of camouflage in furrowed crabs. It shows that these crabs can enhance their concealment by selecting backgrounds that match their brightness, with older crabs being more adept at this. These findings, together with earlier studies on other species, underscore the complex interplay between behavior and physical traits in the evolution of effective camouflage strategies.

Animal ScienceMarine BiologyEvolution

References

Main Study

1) Behaviourally mediated camouflage in the furrowed crab (Xantho Hydrophilus)

Published 9th August, 2024

https://doi.org/10.1007/s10682-024-10308-1

Related Studies

2) The use of background matching vs. masquerade for camouflage in cuttlefish Sepia officinalis.

https://doi.org/10.1016/j.visres.2011.09.009

3) Colour and pattern change against visually heterogeneous backgrounds in the tree frog Hyla japonica.

https://doi.org/10.1038/srep22601

4) Visual predators select for crypticity and polymorphism in virtual prey.

Journal: Nature, Issue: Vol 415, Issue 6872, Feb 2002


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