Real Sandpiper Point
Hermit crab shells
Why a hermit crab needs a new shell, and what happens next.
Tully's shell is too small, then too tight, then too big, then just right. Real hermit crabs know the feeling.
Shells
A hermit crab moves into larger shells as it grows.
Source: Monterey Bay Aquarium
Hermit crabs outgrow their shells, "like a growing child needs new clothes," and need an upgrade.
A common California tide-pool hermit crab, Pagurus samuelis, prefers the shell of the black turban snail.
Source: Monterey Bay Aquarium
The blueband hermit crab lives in the middle to high tide zones and in tide pools, from British Columbia to Mexico.
Source: UC San Diego (Under Morro Bay)
Swapping
When a new empty shell becomes available, hermit crabs gather around it and queue up in a line from largest to smallest.
The shell swap in Tully's story is our own telling. In real life, crabs queue up when a new shell appears.
Where they live
The blueband hermit crab lives in the middle to high tide zones and in tide pools, from British Columbia to Mexico. The tide-pool hermit crab Pagurus samuelis is common in California.
In the stories
Tully and the New Baby uses the shell swap for a big change: too small, too tight, too big, just right.
If you go looking, look gently, put things back where you found them, and give wildlife room.
Sources
- Monterey Bay Aquarium, www.montereybayaquarium.org/animals-the-ocean/animals-a-to-z/hermit-crab
- National Park Service (Gulf Islands), home.nps.gov/guis/learn/nature/hermitcrab.htm
- UC San Diego (Under Morro Bay), under-morro-bay.ucsd.edu/invertebrates/blueband-hermit-crab
- ScienceDaily (University of Exeter study), www.sciencedaily.com/releases/2010/04/100426141458.htm
Each fact was read on its source page on November 1, 2026. Last updated November 1, 2026.