Today marked the exciting transition between the preparation phase and the hermit crab data gathering phase of our CrabSense project.

When I got to our station on the floor, I checked the sensors that Melissa set up and attached them to the inside of the tank on the upper left side.  I checked the SD card in the DataLogger of the Arduino, and confirmed that we were getting CSV files containing reliable data from the sensors, along with date and time information.
CrabSense sensor and tank set-up
A big part of our data gathering is video and audio, which we decided not to do through the Arduino.  I checked out an AXIS 207W network camera and configured it to send me an email with an MPEG-4 video file whenever the camera detects any motion.  The sensitivity is set pretty high, to hopefully detect subtle movements.  The camera doesn’t really have a wide angle so it doesn’t capture as much of the tank as I’d hoped.  I attached it to a mic stand and set it up on the left edge of the tank, so that the Arduino could also rest on it.

Melissa wired up two small condenser microphones and attached them to quarter-inch plugs.  We checked out the Zoom audio recorder and after inserting a 16GB SD card, I configured it to record MP3 files at a variable bit rate (VBR) so that it doesn’t eat up space.  I  positioned the two mics on either side of the tank and connected them to the recorder on inputs 1 and 2.  I tested the recording and it is indeed producing a good sound file.  We’ll be importing it into a program like Audacity to look for peaks and changes in relation to time.

After getting the tech part out of the way, I then prepared the dirt substrate by soaking one of the dirt “bricks” that we got from PetCo in water, according to the instructions.  I went to PetCo and bought the remaining supplies, including sand substrate, and 3 hermit crabs with changes of shells (I chose crabs with natural shells, versus the painted shells — painted shells aren’t good for them because the paint can crack off and be ingested).  I felt and heard them moving around in their little box as I walked as quickly and steadily as I could back to ITP.  I kept telling them to “hang in there” — silly, I know, but I felt bad for them knowing it must have been so jarring to be exposed to so much movement and noise.

Once back at the station, I poured the bag of sand substrate into the left half of the tank and the moist dirt into the right side of the tank.  I took them out of the box — they were each hiding in their shells — and put them on the sand side, thinking they would like that better.  But within a few seconds of feeling the sand, they decided to move to the dirt side.  I captured their migration in a couple photos and video clips (see embedded video below).

CrabSense Project: hermit crab setup from Nisma Z on Vimeo.

After they huddled, they split up.  The one with the smooth round shell went to the right, front corner of the tank and stayed there.  The one with the cone shell positioned itself by the edge of the coconut house and the tank.  The adventurer with the spiral patterned shell wanted to be on top of the coconut house.  It peered behind the coconut fiber climbing wall and I was worried that it might go behind it, but it didn’t.  It tried to climb up the side of the tank but realized it couldn’t do that.  It eventually climbed down and onto the cone shell crab, who didn’t seem to mind.  Right before I left, I peered back in and didn’t see the adventurer – it must have burrowed into the dirt.

I was surprised that they seemed to prefer the edge by the window, which is colder.  I thought they would prefer heat and sand but apparently it’s the opposite.  I was worried about the heat though. When I was at PetCo, I purchased a 75 Watt bulb for nighttime viewing that also generates some heat and I set that up on top of the mic/tripod stand, so they should be okay for tonight.

I should have taken a photo of the whole tank set up with everything…I was in a rush to catch my train home…I’ll plan to take a photo first thing in the morning.  Aside from the sensors, two mics, and humidity and temperature monitors, the tank is now set up with the sand and dirt, a backdrop for climbing, a large natural climbing structure, a coconut house, four medium growth shells, one clam shell with eight pellets of food, one clam shell with regular water, and one bathing rock with salt water.  We intended to add plants, but we’ll either have to get a bigger tank or swap out the climbing structure with a smaller one to make room.

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