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Oren Marciano and Pablo Riba working in the field.

Just finished 3 and a half days of training in the field with Pablo Riba, an experienced Costa Rican biologist. I was introduced to Pablo through a good friend of mine, Daniela Solano, who I met while studying my master’s at the National University of Costa Rica. Working with him was a great suggestion on her part, as he not only has vast experience working with monkeys in the tropics he is also a fun guy to tromp through the woods with. And tromp we did. Each day we woke up early, trying to avoid the sun’s worst rays (we ended up baking anyway), put on our hiking boots and gathered up the various pieces of equipment we would need out in the field. Laser Rangefinder

Most of our time was dedicated to looking for the best places to lay out our line-transects, which we will use to estimate the population density of the 3 species of monkey found in this part of Costa Rica: Squirrel Monkey (Saimiri oerstedii), White-face Capuchin (Cebus capucinus) and Howler (Alouatta palliata). Mono titi, Mono Carablanca and Mono Congo in Costa Rican.

Population density is one of several estimators of the overall population for a given species in a given area. Line-transects in turn, are a relatively simple way to help us measure this estimator, and therefore the number of animals found there. Think of the line itself as just like a trail through the forest, or whichever habitat you are working in, which can even be a city street. Each time an individual animal or groups of animals is found just a few basic measurements need to be taken, hence it’s simplicity (simple = beautiful). We always start at the beginning of the line and end up at the end (points previously defined by the researcher) walking at a specific pace throughout. This data, when enough is collected and put into a well established formula allows us to estimate population density. If we can assume conditions are similar enough throughout the area, we can estimate the number of individual animals that are found there.

This type of information is useful for many reasons. Firstly, knowing the size of a population (it’s always just an estimate, it’s extremely difficult to measure the exact size) can give you information as to it’s health and stability. If these measurements are made year after year you can look for trends, such as increasing or decreasing populations, number of births and deaths, ratio of males to females, etc. As well, studying the habitat where these populations reside you can also infer a connection between what types of trees and plants are found in an area and the health and size of a population of wild animals, as well as its demographic trends. This is actually the focus of our first study here. We are examining the effects of urbanism (how built up an area is, such as roads, houses, electrical lines and people) on the populations of these three primate species.

Costa Rican Squirrel Monkey

As we start understanding this particular effect we will start examining the situation here from differing perspectives, asking and answering questions that will bring us closer to achieving the long term conservation of these valuable wild creatures and creating a sustainable future for the Manuel Antonio area.