EARTHWATCH PROJECT

Costa Rica's Dry Forest

Guanacaste, Costa Rica

August 13 to August 28, 1999

OUR FRASS EXPERIMENTS

Dr. Olson was conducting many simultaneous experiments dealing with various aspects of the unique tropical biology of the dry forest region. We helped him collect data for several of these experiments. The major activity in which we were involved was the frass (arthropod droppings) collection. Dr. Olson believes that the data quantifying the "frass rain" is the most reliable gauge of the activity of herbivores and their predators. We carried out procedures designed to collect and examine this frass rain in several different forest locations. Here, Dr. Olson is demonstrating the proper setup of the frass trap.

FRASS COLLECTION IN THE FIELD:

There were 8 locations in the park where frass collection stations had been plotted and marked. Our job was to set and clean the plastic traps, and then return to scrape off the frass fall. The longer the period of time of the frass collection, the better the data. Of course, rain would ruin the collection, so we would try to balance two competing objectives: to collect the frass for the longest possible time, and to avoid having rain ruin the frass. We kept detailed records of the collection sites and the exact dates and times of the data collections. We were lucky enough that in the two weeks we were there, we were able to collect at least one 24-hour frass sample from every one of the 8 sites.

	Here, Christine is setting the frass trap. The plastic had to be wiped clean and dry, and the rock was used to create a symmetrical bowl shape. The side supports were positioned to keep the shape concave, to collect the most frass rain.
We had to return to the site with small petri dishes later to scrape off the frass. Here, Dale was showing us the correct techniques. The entire plastic sheet had to be scraped carefully, and the frass had to be reasonably dry. The obvious trash (petals, flowers, dead arthropods, etc.) was picked out and discarded. We had to be very careful not to discard any tiny pieces of frass.
	Each dish was labelled with its location and the dates and times of its collection. The dish was sealed, with the label inside, and taken to the lab.

FRASS PROCESSSING IN THE LAB:

The next phase of the frass processing took place in the lab buildings near the dorms. Dr. Olson had a small building which we called the "chicken coop" (because it was an open structure surrounded by chicken wire) where we processed and sorted the frass.

First, the jars of frass had to be opened and placed in the drier, so that all the humidity was driven off. Here, Clare is preparing the dishes for the drier.
	Cleaning the frass was a delicate process which took much time and concentration. Every tiny piece of non-frass debris had to be lifted out and discarded, although we did save these pieces for some future use. We needed microscope headbands in order to differentiate between true frass, dust, insect body parts, or other airborne detritus. Here, Rachel, Wout, Doris and Ian are cleaning one frass collection.
We used microscopes, forceps, and small brushes to move the tiny particles around. After this step, the frass had to be dried again since it absorbed so much moisture from the air during the sorting. Peter was a real expert at this cleaning!
	After Dale did one final quality-control check, the re-dried frass was weighed. All the pertinent data was recorded, and the frass was transferred to plastic bags, labelled, and prepared to shipment to the USA. Later, Dr. Olson will be examining the frass, identifying its origin, and using the data in his dry forest ecology research. Here, Clare is using the balance to weigh the dried frass.

Contact: Kathy Griffin

POLYTECH HIGH SCHOOL

phone (302)697-3255, extension 317

THANK YOU to for funding my participation in this Earthwatch project!!

MANY THANKS to Jimmy Lettieri for all his help and instructions in web page design.