The Green Crab, or European Green Crab, is listed on the Global Invasive Species Database as one of the world’s 100 worst invasive alien species. Nature Conservancy Canada refers to Green Crabs as, “aggressively invasive alien species in most of the regions it inhabits.” This kind of language is so condemning and it reflects the dominant understanding of so-called invasive species as malicious invaders who don’t belong and who need to be eradicated. I strongly believe that Green Crabs deserve more respectful attention, and so I want to highlight Green Crabs specifically, and crabs more generally.
Crabs are incredible creatures who have protective exoskeletons, segmented bodies, ten legs, claws, and stalked eyes. It is common for crabs to move in a memorable sideways scuttle which is, in my opinion, one of their most charming features! Notably, a species of sandy beach ghost crab is the world record holder among crabs for being able to run sideways at 4 meters per second! Crabs grow through a process called molting. This is a process where, as adults, they absorb much of their exoskeleton’s calcium into their soft tissues, until it weakens and cracks; then they crawl out of the old exoskeleton and rest while a new one forms. This is a really vulnerable but crucial transition for crabs.
Another important trait among crabs is their ability to feel pain. Contrary to popular belief, which allows for horrifying practices like boiling crabs alive, biologists are continually gathering evidence that crabs feel pain.
As with many of the other animals who I discuss in these highlights, crabs are astoundingly diverse. There are more than 7, 000 crab species worldwide. There are also lots of species who are crab-like, and commonly referred to as crabs, but who aren’t true crabs. Horseshoe crabs, for example, fall into this category.
Crabs thrive in an astounding range of environments.
The marine taxonomist and ecologist Peter Davie describes crabs who can live 4, 000 m deep on the near-freezing and pitch-black ocean floor, crabs who thrive in mountain forests that are 2, 000 m above sea level, crabs who can live on hot, sulfuric hydrothermal vents, and crabs who spend their whole life cycle in the small pools of water collected in tree holes. There are even crabs who hibernate in deep clay burrows in the dessert, waiting six years or more rainfall that will enable them to leave hibernation.
Physically and behaviorally, crabs exhibit a remarkable array of differences.
The Japanese spider crab is the largest of all crabs. They have shockingly long legs, they can weigh as much as 42 pounds, and they can live a century long. In the wonderful book, Crab, the author Cynthis Chris offers an account of decorator crabs, who are a group of crab species who use materials in their environment likely for the purpose of camouflaging from predators. These crabs maintain gardens of live plants and animals on their shells such as algae or sea sponges.
Chris also describes the unique boxer or pom-pom crabs, who carry tiny anemones in their small claws at all times. The anemones get to reach new food sources that they couldn’t reach on their own. Meanwhile, the boxer crabs, eat a portion (often a large portion) of the food that the anemones collect for themselves. They also brandish the stinging anemones as defensive weapons in the presence predators. They have fascinating relationships with other species and their environments.
Crabs also have fascinating relationships with each other.
Crabs are quite communicative and have a lot to say! Fiddler crabs can communicate through rapping their large claw on the ground or moving their legs up and down. One species of ghost crab can make rasping sounds from their stomach! Some species of crabs migrate and congregate in massive communities so that they can communally moult, breed, or spawn. The Christmas Island Red Crabs famously shut down roadways as they migrate and gather to breed and spawn in the millions. I really wonder what the experience of these large social gatherings must be like for these crabs. Does it feel like travelling to a music festival or like attending a giant family reunion?
Green crabs, who I began this highlight with, have exceptionally good memories and are quick learners when finding food in new locations. Green crabs also have a high tolerance, relative to other crabs, for changes in salinity, temperature, and diet. These characteristics help them to be successful in so many environments which they aren’t native to.
Here is to the beauty, complexity, and adaptability of crabs!
Amanda (Mandy) Bunten-Walberg was a PhD Candidate at Queen's University's School of Environmental Studies where her research explored more-than-human ethics in contagious contexts through the case study of bats and COVID-19. In particular, Mandy is interested in how more-than-human ethics, critical race theory, queer theory, and biopolitical theory might guide humans towards developing more ethical relationships with bats and other (human and more-than-human) persons who are dominantly understood as diseased. Learn more about our team here.
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