Written by Jennifer Brousseau (BNF’s Primate Scientist)
In the month of April, the BNF-OuTrop Programme began surveying dragonflies and damselflies in the Sabangau forest to assess differences in species abundance and richness throughout the forest. Ari Purwanto, OuTrop Biodiversity Coordinator, explains a bit below about why survey dragonflies, how to carry out the surveys and preliminary results.
Ari: Dragonflies and damselflies possess the ability to move forwards, backwards, sideways and hover like a helicopter, enabling them to be ruthless hunters. Besides possessing incredible maneuvering skills, dragonflies and damselflies have also been around since pre-historic times. But, why are dragonflies/damselflies interesting to survey? Both function as ecological indicators, meaning they are sensitive to changes in the environment and researchers can monitor fluctuations in dragonfly/damselfly populations to assess changes in the surrounding environment.
Our Biodiversity Team is surveying dragonflies/damselflies by walking along 250 meter long transects and catching all individuals, if possible, as we go using a hand net. Once we trap the individuals, we handle them carefully to take photos to identify the species, measure the individual and then release the individual again. We are surveying six different transects in order to assess differences in species richness and abundance among different habitats within the forest (i.e. disturbed vs. non-disturbed forest type, canal vs. forest transect and inside vs. outside the forest). Originally, we thought we could survey all six transects in one day, but on our first day, we caught over 100 damselflies/dragonflies over the course of five hours walking only 250 meters!
What is the difference between a dragonfly and damselfly you may ask? I had no idea before we started. Damselflies are thinner and longer than dragonflies and rest their wings along the side of their bodies when resting. In comparison, dragonflies rest with their wings perpendicular to their body. Prior to this past month, only one other researcher carried out surveys in Central Kalimantan for a month in 2012, so there is still a large amount of information unknown about dragonfly and damselfly species in the surrounding area. From our first survey period during April, we have already observed that there were almost no dragonflies found within the forest (compared with almost all damselflies caught inside the forest), but almost solely dragonflies were found in the open area just outside the forest edge. Almost all individuals we captured were found near water, so it will be interesting to see what we find in the dry season when there is almost no water around. We aim to continue to carry out these surveys with volunteers this summer and continue for a period of six months, so stay tuned for further updates!