Where are all the Dragonflies?

Tristan Leong

Over the course of our expedition we observed very little dragonfly activity. For the 100 or so miles we rafted, it did not seem unlikely that we would see more than 1-3 observed adult dragonfly sightings a day. Unfortunately, I was a bit disappointed in the lack of dragonfly activity as I had expected to see more for a river of this size and character. While narrow-winged damselflies could be found nearly everywhere in the system, sample after sample produced little in terms of dragonfly abundance or diversity. Only two families of dragonflies were observed during our trip, Gomphidae and Aeshnidae.

This puzzling lack of dragonfly activity may be purely coincidental, but it seems unlikely that we would observe so few dragonflies for such a geologically diverse river. Possible reasons why we saw so few dragonflies may lie in the fact that we sampled primarily in the Canyon of Lodore, and took limited samples in the slower moving water of Brown’s Park, Echo Park, or Island Park. Still, adult sightings in even these areas were rare, even when sufficient backwater and slow-water habitat was available. In addition to improper sampling methods, many dragonflies burrow in the sand and our D-Nets were inefficient for sampling this particular type of substrate. Aside from sampling error, perhaps the damselflies of this region are able to out- compete dragonflies as the top predators in the back-water. Lastly, in the 100 or so miles we rafted, only Island Park exhibited large sections of backwater habitat surrounded by emergent vegetation that would be suitable habitat for larval dragonflies as ambush cover. While puzzling, the lack of emergent vegetation or backwater, competition among damselflies, or sampling error does not fully explain why we observed so little dragonflies on our trip. Perhaps the timing of our trip may have corresponded to a seasonally slow activity level for these insects, and thus hindered our ability to observe them. Maybe the simplest explanation is that the Green River characteristically does not have a very abundant or diverse dragonfly population. Either way it would be interesting to investigate this apparent observation further.




A rare sighting on our trip to the Green River.