Pregnant hermit crabs have an egg sac attached to their abdomen, which starts bright red, like a punnet of berries. This means that pregnancy in hermit crabs is sometimes known as “berrying.”
If a hermit crab is pregnant, she’ll be particularly docile and refuse to trade shells. The egg sac on her abdomen will grow increasingly prominent throughout the pregnancy, and its color will fade to a dull gray as the birth approaches.
It takes around 30 days for a female to conclude her pregnancy. When this month elapses, she drops her eggs into saline water so they can hatch. For this reason, pregnant hermit crabs often avoid bathing.
While a pregnant 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, so it is unlikely that a female will fall pregnant while being kept as a pet.
However, there’s a slim possibility that a female hermit crab is pregnant at the point of purchase.
How Do Hermit Crabs Get Pregnant?
Mating in hermit crabs requires a male and a female. The process of mating will follow these steps:
- 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 gently 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 – tiny holes above the third set of legs.
The encounter is over quickly, and neither hermit crab needs to leave its shell throughout 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. A female in season will cease releasing pheromones after 3-4 days and will hide in her shell until this period passes.
As a rule, larger males will approach females of equivalent size. The bigger the female hermit crab, the more eggs she’ll be able to carry. Smaller males will gravitate to smaller females to avoid confrontation with a rival.
Will My Hermit Crabs Breed?
If two hermit pet hermit crabs are going to mate, it’ll usually happen between February and August – most often in June and July. However, captive hermit crabs rarely breed for two reasons:
- Wild hermit crabs mate in the ocean while the tide is high.
- Hermit crabs lay eggs in the sea, then leave their young to complete their life cycle.
It’s challenging to trick captive hermit crabs into thinking their surroundings match a wild habitat. You may be able to achieve this if you set up a specialist breeding tank, but it takes effort and patience.
Your captive hermit crab may be pregnant upon purchase. Beachfront gift stores and other sellers source hermit crabs from their natural habitat. If a female is pregnant upon the point of capture, she may still be when you bring her home.
What Does a Pregnant Hermit Crab Look Like?
Only female hermit crabs can fall pregnant, so your first step to acknowledging pregnancy is sexing a hermit crab. Female hermit crabs will have the following physical traits:
- Smooth legs – those of a male hermit crab are covered with fine hairs.
- Legs on the left of the abdomen; males don’t have legs here.
- Gonopores above the legs, as opposed to a penis. The Royal Society explains how a hermit crab’s penis covers up to 60% of its body size.
- Slightly smaller than a male, especially when younger.
Female hermit crabs are also more explorative and adventurous than males. However, every hermit crab is unique and has its own personality, so this isn’t a given.
If a hermit crab is pregnant, a swollen egg sac will be attached to her abdomen. This will be deep, fire truck red, growing in size as the pregnancy evolves. The sac fades to gray when the female is ready to lay her eggs.
You may not immediately spot this egg sac, as your 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 pregnancy cycle of a hermit crab lasts around a month. Throughout these four weeks, 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 duller gray.
You’ll notice an aversion to saltwater in hermit crabs toward the end of pregnancy. This is because, as discussed, wild hermit crabs birth their young in the ocean. Pregnant hermit crabs avoid bathing to minimize the risk of premature egg hatching.
How Do Hermit Crabs Give Birth?
In the 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 offspring if they survive long enough to evolve into adults that join a colony.
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 begin exhibiting 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 of any size to have less than 1,000 eggs during pregnancy. The number of eggs depends on the size, age, and fertility of the parent hermit crabs.
Don’t be alarmed if your captive hermit crab is pregnant – this doesn’t mean thousands of new pets to care for. Upon hatching from an egg, the hermit crab 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 in the wild by passing fish or whales. |
| Megalopae | The handful of zoeae that survive make their way to the shore. 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 have survived to this third stage of evolution. After a month buried under the sand, a megalopa emerges as a juvenile hermit crab that must find a shell. |
Life in the wild can be tough for an adult hermit crab, who must always be aware of potential predators and sun exposure. It’s even harder for newborns, which is why hermit crabs lay so many eggs – only a handful transition into adulthood.
Even in captivity, few hermit crabs will make it past the first two life cycles. Juveniles will be safe in a tank, assuming you provide appropriate living conditions.
How Many Times Can a Hermit Crab Get Pregnant?
Hermit crabs don’t experience menopause, so a female can become pregnant throughout her life cycle. Most hermit crabs prefer to reproduce while young. The first year of a hermit crab’s life may see multiple breeding and birth cycles.
Female hermit crabs like to reproduce while young because this freezes the molting cycle. Every time a hermit crab molts, it increases in size and thus needs to identify a new shell. If the hermit crab remains the same size, less trading is required.
Older hermit crabs can and will continue to breed. After a few years, hermit crabs will have experienced multiple molts and increased mass. A larger female is more attractive to an equally mature male hermit crab, as she will be able to 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, the greater the chances of population expansion.
What to Do if Your Hermit Crab is Pregnant
If your female hermit crab is pregnant, she doesn’t need to give birth.
If you care for your hermit crab appropriately, she’ll avoid saltwater and leave the eggs to rot before discarding them. No young will be born, but the mother will be unharmed.
If you want to assist a female give birth, move her to a large, isolated tank. This habitat will need to contain a large saltwater tub – big enough to replicate the idea of giving birth in the ocean but not so oversized that your hermit crab will drown.
Once the eggs are laid and hatched, this water needs to be filled with microplankton to feed the zoeae. Those that survive – and there will not be many – will then crawl onto the substrate and bury themselves, as in the wild.
Fill the tank with small shells, so the hermit crabs that emerge as juveniles can find a vessel. Remove the mother from the tank as soon as she gives birth, and leave the juveniles to grow together. Once they’re of appropriate size, they can join your main colony.
It’s unlikely that your hermit crab will fall pregnant in captivity. There’s a slim chance that you’ll adopt a pregnant female, but it’s almost unheard of for pet hermit crabs to breed.
Ensure you understand the signs of pregnancy in hermit crabs, so you don’t mistake symptoms of another condition for impending birth.
