Last Updated on: 3rd October 2023, 03:04 pm
Hermit crabs are oviparous animals, which means they carry eggs that hatch after being laid. This means that hermit crabs become gravid, not pregnant.
Gravid hermit crabs have an egg sac attached to their abdomen, which starts bright red. This means that ‘pregnancy’ (egg-carrying) in hermit crabs is sometimes known as “berrying.”
If a hermit crab is gravid, she’ll refuse to trade shells. The egg sac on her abdomen will grow prominent, and its color will fade to a dull gray as the time to release her eggs approaches.
It takes around 30 days for a female to complete the reproductive process. When the month elapses, she releases her eggs into saline water so they can hatch.
While a gravid hermit crab carries over 1,000 eggs at a time, only a tiny fraction of these eggs survive and evolve into juvenile hermit crabs.
Hermit crabs don’t reproduce asexually, and captive hermit crabs rarely breed. Consequently, it’s unlikely that a female will become gravid in captivity.
How Do Hermit Crabs Get Pregnant?
Mating in hermit crabs requires a male and a female. The process of mating is as follows:
- The female releases pheromones to announce she’s in season, attracting male attention.
- Male hermit crabs compete for the right to breed, with the victor approaching the female.
- The male invites the female to mate by rapping on the shell.
- If the female is interested, she partially emerges from her shell.
- The male faces the female so their stomachs touch before gripping the female with his large cheliped and rocking her back and forth.
- The male hermit crab’s penis releases spermatozoa into the female’s gonopores. These are tiny holes above the third set of legs.
The encounter is over quickly, and neither hermit crab needs to leave its shell during mating.
How Do Hermit Crabs Choose a Mate?
According to the Journal of Crustacean Biology, females decide whether to mate. Males will always be interested, but females enter ‘season’ regularly and won’t breed on every occasion.
If a female hermit crab isn’t interested in breeding, she’ll ignore any propositions from a male. The female will cease releasing pheromones after 3-4 days and will hide in her shell until this period passes.
Large males will approach females of equivalent size. The bigger the female hermit crab, the more eggs she can carry. Smaller males gravitate to smaller females to avoid confrontation with rivals.
Will My Hermit Crabs Breed?
If two hermit hermit crabs are going to mate, it’ll usually happen between February and August. June and July are most common. However, captive hermit crabs seldom breed for these reasons:
- Wild hermit crabs mate in the ocean while the tide is high.
- Hermit crabs lay eggs in the sea, leaving their zoea to complete their life cycle.
It’s difficult to trick captive hermit crabs into thinking their surroundings match a wild habitat. You may achieve this if you set up a specialist breeding tank, but it remains unlikely.
What Does A Pregnant Hermit Crab Look Like?
Only female hermit crabs can become gravid, so sexing a hermit crab is essential.
Female hermit crabs have the following physical traits:
- Smooth legs – The legs of a male hermit crab are covered with fine hairs.
- There are legs on the left of the abdomen because males don’t have legs in this area.
- Gonopores above the legs, as opposed to a penis. The Royal Society explains how a hermit crab’s penis accounts for up to 60% of its body size.
- Slightly smaller than a male when younger.
Female hermit crabs are also more explorative and adventurous than males.
If a hermit crab is gravid, a swollen egg sac will be attached to the abdomen. This will be deep red, growing in size as the process evolves. The sac fades to gray when she’s ready to lay her eggs.
You may not immediately see the egg sac because the hermit crab’s shell will likely shield it. Pregnant hermit crabs rarely trade shells as they’re keen to protect their unborn young.
How Long Is A Hermit Crab Pregnant?
The entire cycle lasts around a month. The egg sac on the female’s abdomen will grow increasingly prominent and fade in color. What was once a bright and vivid red will become a dull gray.
You’ll observe an aversion to salt water before the eggs are soon to be released. Wild hermit crabs release their eggs in the ocean, avoiding bathing to minimize the risk of eggs hatching prematurely.
How Do Hermit Crabs Give Birth?
Wild hermit crabs give birth by tossing their eggs into the ocean.
Some hermit crabs stand at the shore’s edge, while others climb trees and drop their eggs into the water. The eggs then explode upon exposure to saltwater.
Her maternal duties are concluded as soon as a female hermit crab has cast away her eggs. Hermit crabs don’t care for their young, nor will they recognize their offspring.
Her reproductive cycle restarts as soon as a hermit crab has given birth. The female hermit crab will enter ‘season’ and release pheromones every few days, and males will again show interest in mating.
How Many Babies Do Hermit Crabs Have?
Larger female hermit crabs can carry up to 50,000 eggs.
It’s rare for a hermit crab to have less than 1,000 eggs during pregnancy. The number of eggs depends on the hermit crab’s size, age, and fertility.
Upon hatching from an egg, the hermit crab’s life cycle begins. This unfolds as follows:
| Zoeae | Tiny larvae float toward the surface of the ocean. The zoea stage lasts up to 60 days, and most larvae are eaten. The zoeae that survive make their way to the shore. |
| Megalopae | Megalopae are microscopic hermit crabs that frequently eat each other for strength. They then burrow under sand for around 30 days. |
| Juvenile | Of the thousands of eggs that hatched, just a tiny number will survive. After a month under the sand, a megalopa emerges as a juvenile hermit crab that must find a shell. |
Life in the wild can be difficult for newborns, hence why hermit crabs lay so many eggs.
How Many Times Can a Hermit Crab Get Pregnant?
Hermit crabs don’t go through menopause, meaning a female can become gravid at any age. Most hermit crabs prefer to reproduce while young, especially in the first year.
Female hermit crabs reproduce while young because this freezes the molting cycle. Each time a hermit crab molts, it increases in size and needs a new shell.
After a few years, hermit crabs will have experienced many molts and increased mass. A larger female is more attractive to a mature male hermit crab because she can carry more eggs.
Like most animals that are low on nature’s food chain, hermit crabs are driven by an instinct to propagate their species. Few eggs survive the evolution into adult hermit crabs, so the more eggs are laid.
What to Do if Your Hermit Crab is Pregnant
If a female hermit crab is gravid, she doesn’t need to release her eggs. She’ll avoid salt water.
If you want to assist a female in giving birth, move her to a large, isolated tank. This habitat must contain a large saltwater tub to replicate the release of eggs in the ocean.
Once the eggs are hatched, microplankton are needed to feed the zoeae. Those that survive will crawl onto the substrate to bury themselves to avoid being eaten and the sun’s UV rays.
Fill the tank with small shells so the hermit crabs that emerge as juveniles can find one.
Remove the mother from the tank when she releases the eggs, leaving them to grow together. Once they’re of appropriate size, they can join the colony.
