Angolan Black and White Colobus Population Densities

Every time a group of GVI volunteers heads into the forest, there is one form that always goes with them: Casual Observations. It’s our most basic survey, run every day from the moment we leave the house until the moment we step back in the door at the end of the day – every animal we see, we write down, along with the time and location of the sighting.

Over 4 years, this has given us a huge amount of data (more than 5000 documented sightings!) But as yet, not much has actually been done with it all, which makes it both a challenging and actually pretty exciting task (at least, as exciting as messing around with Excel spreadsheets can be) to go through it all and find out what this mountain of data actually says about our forest. This analysis is still in the early stages, but I’ll keep you posted as we continue digging through it. But for now, here’s a nice early result:

-Angolan Black & White Colobus sightings by transect-

This chart shows how frequently we’ve seen Colobus monkeys on each of our transects in Shimoni East forest. We have 6 transects, or straight-line paths, in Shimoni East, and all of our surveys are run on these. The “Individuals/Effort/# of sections” bit just means the number of monkeys we’ve recorded, divided by the number of times we’ve been on that transect, divided by the size of the transect – by doing this, we account for the fact that some transects are visited more often than others, and all of our transects are of slightly different sizes.
So what does it mean? Well, more detailed analysis is needed before we can say anything conclusive, but potentially something quite important: Transect 1 (where the big spike is) is located very close to the coastline – so the implication of our Casual Observation data seems to be that there is a significantly higher density of Colobus in forest near the coast than further inland. This would be a very interesting finding on its own, but when you also consider that the coastline forest is currently suffering most from degradation and land development, it makes it all the more important, highlighting how critical the situation in Shimoni forest currently is.

Angolan Black and White Colobus Population Densities