Friday, June 6, 2008

THEORY: Humidity & Appetite

I have been wondering and theorizing for some time whether hermit crabs have better appetites in higher humidity. When I have humid conditions, my crabs tend to find a new item in the food dish within moments and head there instinctively.

Well, last night I was watching a program on PBS that explained how dogs track scents with their noses. One particular thought drew my notice: the moisture expelled through the dog’s nose as he sniffs the ground reconstitutes the molecules of bruised vegetation, intensifying the scent. This seemed to have more to do with the effect of moisture on scent molecules, than on the dog’s magnificent nose.

One source ( says,
"Many factors affect scent and how it travels. Most important are wind, temperature and moisture. A warm, moist, still atmosphere enhances a deer's ability to pick up scent molecules.
Both rain and falling snow carry the molecules of scent to the earth and dilutes them. Light mist and heavy fog block scent from carrying great distances. High humidity, between 50-70%, is ideal for scenting purposes and will make deer very nervous. Because more scent is carried to them, they become double alert.
Low humidity, between 10-20%, works against deer because the nasal passages have a tendency to dry out and it hampers their ability to pick up the scent molecules.
High temperatures cause air convection, and the rising thermals carry the scent molecules upward before they can reach a deer.
Extremely low temperatures also handicap a deer because the scent molecules are pushed downward.
Air movements play a big role in the deer's ability to use its sense of smell. Ideal scenting conditions mean a humidity of 20-80%, with temperatures of 40-60°F, coupled with breezes up to 10 MPH. Under these conditions, a deer will detect danger a half a mile or more away."

Hermit crabs use their antennae to identify and locate scents and I theorize that higher humidity (such as one would find in a well-maintained crabitat) aids the crab in this process of foraging for food and that a scent made stronger by moisture might stimulate the appetite.

How does this theory fit with what you’ve experienced? I welcome your comments!


NaRnAR said...

Hi there!
I have to agree that my crabs are not only more active with increased humidity but also find food quicker than when the tank is "dryer". Ill have to play with humidity and see what happens when I clean their tank..since the humidity drops so quickly out here!!

Liz said...

That would make a lot of sense. Whenever I rewet the sponges in the terrarium, the humidity is pretty high for hours afterwards and I have activity right away, checking out all of the new goodies I've added. When the humidity falls (when the day lights are off), there's far less activity going on.