- Food: Crabs are opportunistic feeders and will eat a wide variety of food items, including algae, plants, small invertebrates, fish, and even other crabs. Some crabs are also known to scavenge on dead or dying animals.
- Shelter: Crabs need shelter to protect themselves from predators and the elements. They may use burrows, rocks, caves, or other structures for shelter. Some crabs may even live in the shells of other animals, such as snails or mussels.
- Water: Crabs need access to water to breathe and to regulate their body temperature. Most crabs live in saltwater environments, but some species can also be found in freshwater habitats.
- Social interaction: Some crabs are social creatures and may live in groups or colonies. They may interact with each other through touch, sound, and chemical signals.
- Reproduction: Crabs reproduce sexually, and most species have complex mating rituals. Male crabs may use their claws or other body parts to attract females and to defend their territory.