The year of the Dragon Fly?

[Tom Rankin]

I've seen TONS of dragon flies while hiking this summer, and especially at summits. I'd expect to see these guys near swamps, lakes, etc.

Vermont seems to be especially 'plagued'.

Does anyone know what's up?

 

[marty]

There have been an abnormal number of monster-sized ones both in Northeastern MA and in Rangeley, ME, too.

My guess: they've been bulking up on deer flies

 

[SAR-EMT40]

There have been an abnormal number of monster-sized ones both in Northeastern MA and in Rangeley, ME, too.

My guess: they've been bulking up on deer flies

I have noticed a large number of them also, some very large in CT also. I love dragonflies and often spend my lunch hour just watching them near the pond where I work. Only hummingbird flight fascinates me as much. You are probably correct about their food supply being at a peak.

Keith

 

[bikehikeskifish]

I noticed way more than usual while on the 4-day trip to western Maine. I also believe that last week at Lake Sunapee there were more damselflies (bluetails) than average. Many of the fish we caught had them in their mouths.

Three things jump out at me as potential explanations - a very warm July, low rain / low lake levels, and abundant deer fly / black fly as a food source. The larvae are aquatic (and remain larvae for up to 5 years), so I'm not sure if low lake levels is a pro or a con in terms of metamorphosis to adult or if they are coincidental observations.

(to be fair, I've never hiked Bigelows or Saddlebacks before, and both are co-located with large bodies of water, which is generally untrue of the Whites.)

Tim

 

[ColdRiverRun]

Absolutely, I thought being one of the "big guys" it would be directly bat related. I love'em more of them the less of all the little biters. Big Slide's summit was swarmed last weekend.

My friends who live in E-town had so many in there yard the other night (dusk) that the sky looked like something out of the movie "birds". Most I've ever seen by two fold, and that is growing up a redneck country kid.

 

[una_dogger]

Agreed! We've been seeing them on summits, too. More dragonflies than I can remember ever seeing.

 

[mirabela]

Certainly the NEK of VT has been crawling with them.

I wonder if the precipitous decline in bat population has anything to do with it. There's about 1% the normal bat pop around here these days. Something has to eat up all those bugs.

 

[Puck]

I don't think the bat population crash is a factor. Bats hunt at night and dragonflies are active by day. Tim pointed out that the nymph stage can be up to five years in some species other species it can be a few months. So what is happening in the water? Are there enough aquatic preditors to eat the nymphs or the adults like frogs. What is the current trend in the bird populations? Are conditions more favorable for the nymphs i.e. earlier ice outs, warmer tempuratures at the beds? Is this a cyclical pattern see in other predator species?

 

[bikehikeskifish]

Perhaps more on-topic, what is the attraction to the summits? Must be other insects there to eat.

Tim

 

[SAR-EMT40]

Perhaps more on-topic, what is the attraction to the summits? Must be other insects there to eat.

Tim

For the larger dragonfly's its the smaller dragonfly's. For the smaller dragonfly's maybe its a oops?

Keith

 

[Snowflea]

Lots more than usual at my folks' house in the Northeast Kingdom of Vermont...

I love them, too!

 

[RollingRock]

I live near Waterville Valley along the Mad River and when I took my trimmer startled about a dozen dragonflies hanging together in the grasses. They then started to swarm around me. Thankfully they were not hornets I've seen some dragonflies around the house this summer which in itself was strange. I don't live near any ponds. I'm just hoping this is an anomaly and not indicator of something else climate change is impacting.

 

[DougPaul]

I don't think the bat population crash is a factor. Bats hunt at night and dragonflies are active by day. Tim pointed out that the nymph stage can be up to five years in some species other species it can be a few months. So what is happening in the water? Are there enough aquatic preditors to eat the nymphs or the adults like frogs. What is the current trend in the bird populations? Are conditions more favorable for the nymphs i.e. earlier ice outs, warmer tempuratures at the beds? Is this a cyclical pattern see in other predator species?

A possible link could be:
fewer bats -> more insects
more insects = more food for dragonflies
more food -> more dragonflies

(Yes, dragonflies are also insects.)

"Everything is connected to everything."

Doug

 

[w7xman]

2010... The year of the unquantifiably qualitative comparative superlative?

But yes...and I agree with DougPaul above ...

 

[dug]

Funny, I hadn't noticed any difference in So. NH. But, last night I was cleaning my pool and there must've been 50 buzzing around. I had to think of this thread....

 

[Puck]

A possible link could be:
fewer bats -> more insects
more insects = more food for dragonflies
more food -> more dragonflies

(Yes, dragonflies are also insects.)

"Everything is connected to everything."

Doug

Assuming the increase in insects that the bats prey on are also insects that the drargon flies prey on. Someone needs to do a population analysis going back five years and then do a series of regressions and multivariant analysis. To see what corellations exist. The increase we see now are do to factors that can go back five years. At any rate it can be assumed that most predators are K species in the context of population ecology meaning they are predicatble and close to the carring capacity of the environement. The dragonfly population will correct itself without a huge crash.

Enough of that....Watching dragonfly nymphs crawl out of a pond or watching them catching other insect was one of the best hours I have ever spent.

 

[DougPaul]

Assuming the increase in insects that the bats prey on are also insects that the drargon flies prey on. Someone needs to do a population analysis going back five years and then do a series of regressions and multivariant analysis. To see what corellations exist. The increase we see now are do to factors that can go back five years. At any rate it can be assumed that most predators are K species in the context of population ecology meaning they are predicatble and close to the carring capacity of the environement. The dragonfly population will correct itself without a huge crash.

It was only a suggestion of a plausible link to counter an earlier suggestion that there would be no relation between bat populations and dragon fly populations.

The relationships can be very complex, nonlinear, and may involve many species some of which may be very unobvious.

Doug

 

[Puck]

It was only a suggestion of a plausible link to counter an earlier suggestion that there would be no relation between bat populations and dragon fly populations.

The relationships can be very complex, nonlinear, and may involve many species some of which may be very unobvious.

Doug

Only plausable if the two predators are using the same prey. Bats and dragonflies occupy two very different niches.

 

[DougPaul]

Only plausable if the two predators are using the same prey. Bats and dragonflies occupy two very different niches.

That is why I suggested a possible link through an intermediate group of species for this particular hypothesized interaction.

Cause and effect chains can involve one or more intermediate species making them very hard to predict or guess (or ferret out of data).

For instance, the introduction of wolves into Yellowstone caused an increase in aspen trees... http://www.sciencedaily.com/releases/2007/07/070726150904.htm

Doug

 

[Puck]

Doug
Seems like we are the only two left at the bar talking about this.

Yes trophic effects are hard to tease out. The species interplay is very dynamic and is loaded with confounding variables. One can spend years doing a study, might answer the orignal question but will produce ten more questions. During a masters course in ecology my prof had a hard time telling me that a regression with an R^2 value of 0.51 was significant. With my line of work anything less then .990 is a bad day. But I am not doing regressions.

I love the article you posted. That study is very important and shed new light on hunter prey and trophic modeling. The results were than expected.

I am sure you are familiar with Macarthur's work on feeding warblers. Different species will feed in different zones on the same tree in order to curtail competion. The same thing happens with diurnal and nocturnal preditors.