Weather and Odonate Behavior

Anax junius in flightI’m running a little behind this week, but it’s a new year and I think it’s time to discuss my favorite scientific topic in the world: odonate behavioral responses to weather!  I have been interested in dragonflies for a long time, almost as long as I’ve been interested in insects.  I think they’re beautiful, amazing animals and I am in complete awe of them for many reasons.  When I was an undergrad, I took an ecology class in which we were required to do a personal project, so I naturally gravitated toward dragonflies.  That project turned into a senior thesis for my biology B.A. and eventually became the basis for a scientific paper.  I’ll talk about the results of my study next week.  Today I want focus on what’s known about the behavioral responses of odonates to weather, observations by other scientists who have inspired my work in this field.

As most of you reading this will know, dragonflies are powerful fliers.  However, they still have limitations.  They have massive, broad, flat wings and though they have bulky bodies, they just don’t weigh that much.  So, imagine you’re a dragonfly.  It’s a nice sunny day, but a storm is moving in.  It starts to get cooler, darker, windy.  Are you, as a light-bodied animal with gigantic wings, going to keep flying as the weather deteriorates?

If you answered no, you’re spot on!  Dragonflies and damselflies are known to be strongly affected by changes in weather.   Changes in weather throughout the day can have a significant impact on how a population of odonates behaves.  In fact, weather plays such a huge role in odonate behavior that you see some variation on this sentence in countless scientific papers:

“Data from days exhibiting inclement weather were removed from the data set before analysis.”

There’s a reason so many people do this though.  Though very few researchers have looked specifically at the role weather plays in shaping odonate behavior, these insects are well-known to behave strangely under certain conditions.  If your study is looking at, say, patrolling behaviors in a dragonfly species and a change in weather occurs that disrupts their normal behavior, that data really doesn’t help answer the questions you’re interested in.  You therefore remove that data before you analyze your results because it is not related to your study.  And ultimately, even scientists don’t like to stay outside when it’s rainy, cold, very windy, or otherwise unpleasant.  Scientists just miss a lot of what happens during those inclement weather days.  That’s unfortunate because that’s when some of the most interesting things happen!

Snowman

Snowman from one of our aquatic entomology field trips. Dragonflies would not fly in this weather! Photo by Dennis Suhre.

So what do we know about odonate responses to weather?  Several things.  Let’s consider temperature first.  Odonates are exothermic, like all insects.  If they get too cold, they can’t warm their bodies up enough to fly.  If they get too hot, all kinds of nasty chemical reactions start taking place in their bodies that can result in death if they become severely overheated.  (Long ago, I posted about obelisking behavior in dragonflies, a behavior that helps dragonflies cool down on hot days.)  Changes in temperature are known to influence odonate behavior such as the time of day that a species normally flies, flight activity levels throughout the day, and the postures of dragonflies.

Wind and a palm tree

A palm tree on a windy day.

Wind also plays a role in odonate behavior.  On very windy days, damselflies won’t fly at all, or only in places that are protected from the wind by barriers of some sort.  Dragonflies are able to fly in stronger winds, but even these larger insects have their limits and must stop flying if the winds become too powerful.  Light intensity hasn’t been looked at in as much detail as wind, but it is known to impact fight activity as well.  Activity levels tend to go up and down with light intensity.  More odonates tend to fly on sunny days than on cloudy days.

These are the obvious weather factors.  You can easily observe an increase in wind speed, a drop in the light levels, or a drop in temperature.  What about the less obvious changes in weather like barometric pressure and relative humidity?  Relative humidity isn’t considered by most researchers, so there is very little data available on its effects.  However, one Russian scientist in the 60’s published a paper proposing a link between barometric pressure and dragonfly behavior.  I happen to disagree with him, but I’ll talk about my reasons when I discuss my own study next time.

The Catalina Mountains as a storm rolls in

The Catalina Mountains as a storm rolls in.

Finally, let’s consider rain.  Glorious rain, my favorite weather!  Damselflies almost never fly in the rain.  Some of their larger dragonfly relatives have been observed flying during rain (including my favorite magnificent flier, the wandering glider), but few reports have been made of any dragonflies flying during heavy rains.  In fact, several researchers have observed that dragonflies and damselflies essentially disappear from the water’s edge right before it starts to rain.  This behavior has been named pond abandonment behavior, and it is this behavior that I am most interested in.  Why are they leaving?  Where do they go?  Are they using cues from their environment to tell them when to leave the pond and when to return?  This behavior is fascinating!

This is the sort of information I had to go on when I started my project looking at dragonfly behavioral responses to weather as an undergrad.  The few researchers that have examined the role weather plays in odonate behavior tended to analyze each weather factor separately, sometimes using data from different days.  If you’ve ever watched a storm rolling in, you know that light intensity rarely changes without a change in temperature and the wind often increases before it starts to rain.  Weather factors are clearly linked.  And most of the time you’re not lucky enough to find studies that overtly link weather and behavior to begin with.  The information about this topic tends to be hidden in papers about completely unrelated subjects, often preceded by one of those, “Data from days exhibiting inclement weather…” statements.  I happen across most information about odonates and weather when I’m reading about territoriality or dragonflies using sunny spots in forests as hunting areas.  Lots of odonate researchers know that weather plays a role in odonate behavior (a significant role in fact!), but figuring out exactly how weather does this…  Well, that’s what I am interested in figuring out!

Next up is another Friday 5, but my post early next week will focus on the things I’ve learned in my own work with odonates and weather.  This has been my pet topic ever since that first little study I did in my first ecology class in college – I love this subject!  I hope you’ll enjoy it too!

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Unless otherwise stated, all text, images, and video are copyright © 2011 DragonflyWoman.wordpress.com

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17 thoughts on “Weather and Odonate Behavior

  1. What an interesting study! It is always interesting to hear th background stories behind a scientist’s motivation, as oppose to just reading the paper about the results and discussions. Look forward to more posts about this topic.

  2. I’ve noticed dragonflies dipping down and touching the surface of cars. I thought it was because they thought the shiny cars were water. Thanks for proving me right.

  3. Thank you for posting this, I’m also interested in finding out about weather and (dragonflies) relation to it. I came across your article whilst trying to find answers to the reason behind a large number of dragonflies which arrived about 2 weeks ago and are flying constantly around our back garden. I live in Western Australia and we have had no rain at all since October last year (6 months) and have had mean temperatures of 35 degrees C for endless weeks. We have no water, ponds or rivers on our property, and live 65km’s from the nearest city. I was hoping this influx of dragonflies could mean rain is coming our way but I can’t find any information to suggest this. I’m sure our indigenous Australians would know, but unfortunately I can find little information on it.

    • Actually, sounds like you’ve got a swarm going in your backyard! I have a whole bunch of information about dragonfly swarms on my blog because I’m doing research studying this behavior. If you’d like to read more about dragonfly swarms, please check out https://dragonflywoman.wordpress.com/2010/09/22/staticswarms/. Your swarm sounds like a feeding swarm, and it’s not uncommon for them to form in areas even without rain, especially if you’ve been seeing them in your yard for a few weeks. However, the activity often increases before rains as pressure systems change and whatnot. It could mean that rain is headed your way! But it might not too. Hard to tell without a more detailed description of the behavior you’re seeing.

      I’ve got links to other dragonfly swarm information at the bottom of this page: https://dragonflywoman.wordpress.com/the-dragonfly-swarm-project/. You can read about other swarm types and some of the things I’ve learned through my research there if you wish. And if you’d like to contribute to my research on dragonfly swarms, I would appreciate your taking a few minutes to fill out a swarm report form describing your swarm! It’s located here: https://dragonflywoman.wordpress.com/the-dragonfly-swarm-project/report-a-dragonfly-swarm/. I have very few reports from countries outside of North America, so I would love to be able to add your sighting to my database!

  4. Thanks very much for your info and I’m happy to oblige in adding a report from Western Australia. I’ll fill in the swarm report when I see them back here again as I wasn’t paying a lot of attention to detail in their behaviour. I read your information on swarms and it sounds as you said, it would probably be a static swarm as there weren’t thousands of them. They tend to come and go mornings and evenings when it isn’t so windy. I will observe their behaviour more closely and keep you informed. We tend to have a variety of bugs both outside (and inside!) our house, which we relocate. Your info has inspired me to now watch their behaviour :)

  5. Thanks for your info and apologies for my late reply – hard drive failure..we received rain! the day after I posted my question. The d/flies are back but only 1 to 2 at a time, I haven’t seen the same numbers as a few weeks ago. The mozzies were prolific in some areas of Perth, but not up here? (100km North) but there must be something they’re feeding on. Our only small patch of green grass seems to be very attractive to them and they are either fighting or mating or a combination of both at the moment. Unfortunately no sight of a swarm or any further rain….but I’ll continue to watch them. Thanks for posting your info! it’s really interesting :)

  6. G’Day. I did my honours research on Orthetrum caledonicum on ponds in Canberra Australia looking at maturity and environmental affects on territoriality. You are right. Lots of researchers note that they fly on sunny days. I noted that they flew on 40degreeC days but the clouds came over and they sat down even though it was still 40deg. I looked at humidity with null result. I tried to find a way to determin why they sat down with clouds. Jon Trueman (pers comm) suggested there was polarised light at play but it never occured that clouds meant a storm as usually it was just cloudy. Rain… I went to the pond and sat alone and friendless with only kangaroos for company. My Orthetra stayed home. Barometric pressure is interesting. If you are ever in Canberra in summer drop by.

    • I’m so happy to hear that there are other people who are interested in this sort of thing too! I think weather plays a huge role in odonate behaviors of all sorts, but it’s so rarely examined in detail. I’m really hoping to get back to this subject eventually. Maybe head back to Colorado for a few summers to do research in a place that has more predictable weather than where I live now. :)

      If you happen to be interested, I can send you a copy of my pub covering the research I did on damselflies and weather.

  7. Hi. I’m based in Singapore and into insect macro photography. Found your article while doing a general search on how weather affects insect behavior. We live in a tropical climate and it’s now our rainy season. Was out last Saturday taking photos and later in the day storm clouds rolled in and there was a distinct change in insect behavior. Many were much easier to approach and photograph. The smaller the insect the more static they became which I guess makes sense cause a single raindrop could easily down a 2mm insect. By the way we have a good selection of dragonflies and damselflies here. Some allow you to get closer than others.

  8. Thanks for the video. That’s incredible. I was watching some bees yesterday feeding during heavy rain. They were been knocked by rain drops and would fall out of control for about a foot then recover themselves and go back to feeding on the flowers.

    I only took up macro photography a few months ago and still learning but truly bitten by the bug – excuse the pun. It’s a steep learning curve. I put a few from the past few weeks at this link:
    http://www.fluidr.com/photos/61587929@N06

    • Thanks for the link to your photos! I look forward to perusing them. It’s always fun to see the work other photographers do. And I’m glad you enjoyed the mosquito video. I wonder how many species of insects use a similar process to avoid being damaged in the rain, though it sounds like your bees might have been doing something similar. Fun!

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