Hermit crabs are most commonly understood to be detritivores, a type of animal that scavenges dead and decaying matter. This animal is also sometimes called a decomposer, an organism that breaks down dead matter. The difference between these two is that decomposers will also eat matter that another animal has processed.
Hermit crabs mainly eat dead animals, tiny molluscs and clams, plant matter, and algae. That means that they are an omnivorous scavenger, also called a detritivore. Such a diet means that hermit crabs play an important role in their ecosystems as a clean-up crew. By eating decaying matter, hermit crabs recycle nutrients to enrich the soil and feed plants. Removing carcasses from the environment also keeps the area healthy.
Hermit crabs help control dead matter in their local environment, so they play a critical role in the ecosystem. Aside from breaking down rotting matter, hermit crabs eat algae and prevent it from running wild by out-competing other plants. These crustaceans have an important place in the ecosystem, and we simply can’t do without them.
Are Hermit Crabs Scavengers?
As stated, hermit crabs are omnivorous scavengers that eat a wide variety of organisms. These organisms include both live and dead matter, depending on what’s available. Hermit crabs will eat algae, decaying plant and animal matter, and microscopic organisms, like tiny clams and mussels.
In the wild, a hermit crab will spend a large part of its day foraging for food. Marine hermit crabs will quickly discover and swarm carrion, as noted in Marine Biology. A dozen or more hermit crabs will find their way to a carcass within half an hour of scent dispersal.
Hermit crabs, by nature of being scavengers, will eat whatever they can find. Rich sources of protein are preferred by any omnivorous animal. If you set a piece of fruit and a piece of meat in front of a hermit crab, it will almost always pick the meat first. With that said, if there isn’t much to choose from, hermit crabs are not overly fussy. The crustaceans have been observed to eat:
- Fallen fruit
- Decaying leaf litter and wood
- Even the feces of other animals
Depending on where a hermit crab lives in the world, it will have access to whatever foods are local to the region. Generally, living close to the water will mean that the animal can access algae and debris from the sea. Any dead animals that wash ashore are also a meal. Hermit crabs are excellent climbers and will scale trees or jump piles in search of food.
Any type of decaying organic matter will draw hermit crabs, be it plant or animal. This makes them a crucial part of the food chain.
Are Hermit Crabs Also Decomposers?
Hermit crabs are considered decomposers as well as scavengers. That’s because they will eat other animals’ leftovers, decaying matter, and forage for food. Ecology describes the difference between these two as:
- Decomposers consume small particles produced by scavengers
- Scavengers consume dead matter that another organism has not yet processed
With that in mind, decomposers can be hermit crabs. However, the more common decomposers are fungi, bacteria, and worms. Classing hermit crabs as a decomposer or scavenger depends on the researcher’s personal stance or the species of hermit crab.
How Can Hermit Crabs Eat Rotten Meat?
Rotting matter is full of bacteria and other decomposers, which makes many animals sick. So, how do hermit crabs get around this?
There is little scientific research on how hermit crabs can eat decaying matter. However, studies have been done on vultures, one of the most well-known scavengers in the world. These birds have a special mix of enzymes and strong stomach acids that kill any bacteria in the food.
With that in mind, we know that hermit crabs regularly consume decaying matter and seem to thrive on it. That makes it logical to assume that they, too, have evolved stomach acids capable of killing bacteria.
Are Hermit Crabs Producers or Consumers?
“Producers” are organisms that produce their own food, such as with plants and photosynthesis. “Consumers” are organisms that get their food from external sources, such as by eating plants or other animals. There are multiple types of consumers.
Hermit crabs are secondary consumers. This means they will scavenge the carcasses of other dead animals, as well as:
As far as we know, there are no completely herbivorous hermit crabs. Only herbivores are primary consumers, which is why hermit crabs are classified as secondary consumers.
Why Are Decomposers Important?
Every animal plays an important part in the ecosystem it belongs to, from microscopic systems to macroscopic systems. Hermit crabs may be perceived as being at the lower end of the food chain, but this does not mean they are unimportant.
Hermit crabs, like other scavengers, are nutrient recyclers. By eating decaying matter, hermit crabs process these nutrients and recycle them into a type of fertilizer. The waste of hermits will go into the soil to be absorbed by plants, which other animals will eat.
Decomposers do more than provide plants with fertile soil, though. They control waste, preventing bacterial outbreaks and surrounding water from becoming contaminated. In enriching soil, they also ensure that plants can grow in abundance. Plants provide food for many animals and are critical in:
- Cycling oxygen into the water
- Removing harmful chemicals and carbon dioxide
Hermit crabs also readily devour algae, like cyanobacteria and hair algae. They even consume the food sources of these organisms. Together, this prevents the family of organisms from growing out of control. Certain types of algae, such as cyanobacteria, have been noted by Harmful Algae to impact water quality and food web resilience negatively. In controlling algae populations, hermit crabs help preserve a balance in their ecosystem.
What Would Happen If Hermit Crabs Disappeared?
Since hermit crabs play such an important role in their ecosystem, you may wonder: what if they disappeared? This isn’t an uncommon question. We often wonder about the purpose of some animals, like flies or cockroaches, and why they exist at all. The truth is, every organism has a purpose in its environment.
Decomposers and detritivores like hermit crabs play a critical role in the ecosystem. Sure, they are not the only ones that can recycle dead matter. Even still, hermit crabs share a responsibility that would otherwise overwhelm other creatures. They prevent an explosion in the population of vermin and bacteria, which would upset the balance in their environment.
Other scavengers would fill their roles in places where hermit crabs live, but perhaps not as effectively. In the meantime, dead matter would pile up and taint the environment. The lack of organisms recycling those nutrients into the earth would lead to inferior soil quality. This impacts the plants and any animals that eat the plants.
When there isn’t enough food for the herbivores, they will either move on or starve. This can lead to carnivores doing the same.
The collapse of an ecosystem can begin with one creature being removed from it. In the long term, it may recover, but there are parts of the ecosystem that may never return. The above scenario may appear exaggerated, but it is a reality in many places in the world right now. Hermit crabs, as a detritivore, recycle dead matter and help keep their environment healthy.