How Long Can Crabs Live Out of Water? Understanding Crab Respiration

Crabs are amazing creatures that have adapted to survive both in and out of water Their unique respiratory system allows some species to spend extended periods on dry land But just how long can crabs stay alive when removed from water?

The amount of time a crab can survive out of water depends on a few key factors

• The type of crab species
• Environmental conditions like temperature and humidity
• Whether the crab’s gills are kept moist

By understanding how crabs breathe and what they need to survive, you can learn to keep them alive longer in transit or captivity.

An Overview of Crab Respiration

Crabs respire through gills, just like fish. But unlike fish, crabs have adapted to be able to use gills to extract oxygen from air as well as water.

Their gills are located inside a branchial chamber protected under the carapace (top shell). As long as the gills stay moist, they can absorb oxygen from the air by diffusion.

Crabs also have an organ called a branchiostegal lung. This acts as a small supplementary lung to aid breathing. It’s especially useful for terrestrial species like coconut crabs that spend more time on land.

So while crabs can survive on land, they still need to keep their gills damp to fully oxygenate. Direct exposure to air will dry out the gills, eventually asphyxiating the crab.

How Long Can Different Crab Species Stay Alive Out of Water?

Not all crabs are equally equipped to handle life on land. Some species are fully aquatic and drown in just a few hours without water. Meanwhile, semi-terrestrial and land crabs can last days or weeks, as long as humidity is high.

Here are some estimates for how long common crabs can survive out of water:

• Fiddler crabs – 1-2 days
• Blue crabs – 1 day
• Stone crabs – 7 days
• Coconut crabs – over 1 month

Fiddler crabs spend most of their time on land but need to frequently return to water to keep gills moist. Blue crabs only exit the water to molt or mate. More terrestrial species like stone and coconut crabs have adaptations that help retain moisture for long dry spells.

The numbers above are general estimates. Actual survival times depend on temperature, humidity, and efforts to keep the crabs healthy.

Why Temperature and Humidity Are Key

Crab gills dry out faster in warmer, drier conditions. Cooler temperatures and high humidity drastically slow moisture loss.

Research on coconut crabs found they survived over 9 times longer at cool temperatures compared to hot:

• At 59°F (15°C), crabs lived over 60 days.
• But at 86°F (30°C), they survived less than 7 days.

High humidity also preserved gill function. Crabs in 100% humidity had healthy gills after 33 days. But at 75% humidity, their gills were damaged after just 9 days.

So if you want a crab to live longer on land, keep it cool and mist its gills frequently. Just a light spray of fresh or salt water is enough to replenish moisture.

Keeping Gills Moist in Transit

When transporting crabs like blue crabs or Dungeness crabs, it’s important to keep their gills from drying out.

Here are some tips for maintaining moisture:

• Place crabs in a cooler lined with a wet towel over ice packs. The ice regulates temperature but doesn’t allow standing water.
• Cover buckets with a damp burlap sack. Burlap retains moisture while allowing airflow.
• Use moist seaweed or newspaper instead of just ice to line holding containers.
• Lightly mist crabs every few hours with fresh or salt water.
• Limit transport time to 6 hours or less if possible.

Avoid using fresh water ice cubes directly on the crabs, as the melting water may drown them. Refrigeration also isn’t recommended, as the cold temperatures can put crabs into shock.

How to Keep Captive Crabs Alive Out of Water

You can temporarily keep aquatic crabs alive in captivity for a few days, as long as you meet their moisture and oxygen needs.

Here are some tips:

• House crabs in a shallow dish filled with a few inches of dechlorinated water, and change it daily.
• Create humid conditions by covering most of the tank with damp cloths.
• Provide hiding places like shells and fake plants to reduce stress.
• Lightly mist the crabs 1-2 times per day with fresh or salt water.
• Drop in foods like algae, calcium supplements and meat-based pellets.
• Use aquarium bubblers to maintain oxygen levels.
• Limit handling, as it removes protective slime coatings.

Monitor crabs closely for signs of distress like low activity levels or loss of appetite. Return them to a proper aquatic habitat within 2-3 days to ensure long-term survival.

The Takeaway

Crabs can survive out of water from just hours to over a month, depending on species and gill moisture. Transport them in cool, humid containers, and mist periodically to replenish moisture loss. With a little care, you can keep crabs alive long enough to cook, study or return to the wild. Just remember – they shouldn’t stay landlubbers forever!