Checking the traps

Traps should be left in place overnight and checked in the morning of the next day. If at all possible, traps should be checked before 10:00 A.M., as the number of invertebrate prey items under the traps drops very sharply around this time, based on our testing in New York. Try to check the traps in the same order in which they were placed to equalize the amount of time that the traps are out. If you are doing the regular BFL protocol on the same day at that point, check the traps first before doing BFL.

To check each trap, first note and count any individuals of any prey species on its top surface. Then carefully lift the side of the cardboard farthest away from you and flip the cardboard over towards you so that it is bottom up. (In areas where small snakes are common, you may want to turn over the cardboard with a stick.) Then quickly get a count of the faster prey species (centipedes, millipedes, and isopods; see mini-field guide) before they can run away; slugs and snails aren't so good at escaping. You should count all the animals on the cardboard (both top and bottom) as well as any animals on the surface of the leaf litter that was under the trap. (Don't actually search through the litter itself.) Sometimes animals hide along the edge of the cardboard, so check there, too.

Then use the "size class ruler" on the field form to assign each of the animals found to the proper size class; hold the line under the "Start here" arrow next to one end of the animal, and note the box in which the opposite end of the animal is located. This is the size class to which it should be assigned (see diagram below). Note this size class, and measure the next animal until all have been measured. For snails, measure the width of the shell at its widest point. For slugs, first touch the animal to be measured with a twig, to cause it to contract (wait a second or two), then measure the slug in its contracted state. Some participants found it easier to make "size-class rulers" out of popsicle sticks, etc.

You may brush the animals from the surface of the cardboard with a twig after you are done. (Note: Because snails and slugs may serve as intermediate hosts for a number of parasites that can cause disease in humans, we recommend that you do not handle them with your bare hands, and that you wash your hands after any contact.) Remember to check all traps before 10:00 A.M., if possible. Note the time and the temperature (if you have a thermometer use it; otherwise estimate the temperature, or use the NOAA website for your region.) After you are done, you may retrieve the cardboard for proper disposal away from the study site.