Well-Nigh Wordless Wednesday: Dragons and Damsels of Ireland

Long time no post, I know, but I’ve been wrapped up in a lot of different things recently and haven’t had time to even think, let alone post on my blog.  But I think things are calming down a bit and I’ll have more time to do the things I like. I’m eager to get back to blogging!

One of the things I was doing during my recent long absence was going on a really excellent vacation, a two-week trip to Ireland with my sister.  We toured almost the entire Irish coast in that time and I’m quite sure the trip is going to be one of the highlights of my life.  Ireland is unbelievably beautiful and I absolutely loved it!  It was, however, shockingly devoid of insect life.  I carefully picked out a dragonfly and damselfly field guide before I left, mapped out everywhere we were going, compared our itinerary to the range maps in my guide so I’d know what to expect where, and I hauled my book over in eager anticipation of seeing a hoard of Irish odonates.  I saw one damselflies in the 15 days I spent on the island.  One!  And I barely even got a look at it, definitely didn’t get a photo, and it flew off almost immediately after I spotted it on the banks of this pond:

Powerscourt Estate, County Wicklow, Ireland

Powerscourt Estate, County Wicklow, Ireland

At least the setting was pretty!  If you only get a glimpse of a single small damselfly on a trip, it’s nice to have that one sort of disappointing sighting occur at a place where there are other things to look at, such as grand estate houses, arboretums, and beautifully manicured gardens.  :)

I am working on getting through my massive backlog of dragonfly swarm data to get it up on Sunday this week and I should be posting on Friday.  Here’s hoping nothing else comes up to prevent that happening!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth
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Friday 5: My Favorite Dragonfly Watching Areas

Sympetrum corruptum male

Variegated skimmer

I’ve been so wrapped up in family and work related things recently that I’ve barely had any time to get into nature and experience the world outside.  But I’ve been dreaming about going oding too.  Oding, or odonate watching, has become a popular pastime for a wide variety of people  over the last few years.  Similar to birding, people who participate in oding (calling them “oders” just doesn’t sound right…) visit wild or man-made water bodies, usually toting binoculars or cameras, and see how many different types of odonates they can find.  Many people are keeping life lists of dragonfly species they’ve seen, just like birders.  If the wealth of recently published odonate field guides is any indication, more and more people are joining in on the fun and I expect that the activity will become increasingly popular over the next several years.

Because I have not been able to go oding myself, I thought I would highlight the places I would go if I had the time.  The following are my 5 favorite oding spots in or around Tucson, AZ:

Sweetwater

Sweetwater Wetlands

Sweetwater Wetlands

The Sweetwater Wetlands is a huge constructed wetland on the west side of Tucson.  Wetlands are phenomenally good at filtering nasty stuff out of water and many constructed wetlands are built with the intention of improving water quality.  The Sweetwater Wetlands are no exception and was designed to filter some of the wastewater from the nearby wastewater treatment plant.  While the water smells a little funky (as you might expect in a wetland designed to treat wastewater), the wetlands support a ton of wildlife!  As you can see in the photo, there is a lot of green stuff around the ponds.  There are also a ton of dragonflies and damselflies!  While the diversity of the odonates at Sweetwater is not as high as in some other locations in my area, the sheer number of them at this site is astounding.  I love going to Sweetwater to take photos of odonates because you are bound to get many good shots.  I rarely get to check anything off my life list when I visit, but who can resist seeing thousands upon thousands of dragonflies during a 20-30 minute visit?

Las Cienegas

Las Cienegas

Las Cienegas

Las Cienegas is one of my favorite places to visit in southern Arizona.  It’s always about 10-15 degrees cooler than it is in Tucson, it’s got a lovely spring-fed stream that has water year-round (it’s under the green stuff in the photo – that’s watercress on top!), it’s got the best ancient old cottonwood, and there is hardly ever anyone else there.  Plus, there are dragonflies!  There might not be tons of them and there might not be all that many different species on most visits, but you see some really spectacular ones there.  Besides, few things beat getting out of town and watching dragonflies in the shade of old cottonwoods while trodding on the mint growing along the banks of the creek.  Heaven!

Sabino

Me in Sabino Canyon. Photo by Laura Goforth.

Sabino Canyon

I’ve been going to Sabino Canyon as long as I can remember.  Even when my family lived in Colorado and we only visited Tucson once a year, we always made a trip to Sabino.  It’s a gorgeous place to visit on the northeast side of Tucson and has a cool, clear creek that tumbles down off the Santa Catalina Mountains.  It’s chock full of fabulous aquatic insects (and a whole lot of invasive, awful crayfish) and there are always a lot of dragonflies flying around.  Sabino is where I saw my first giant darner (Anax walsinghami) and my first filigree skimmer (Psuedoleon superbus).  I was blown away by the beauty of each.  It’s also home to the Sabino dancer (Argia sabino), a damselfly listed on the IUCN Red list as a vulnerable species.  Sabino is nearly always crowded, but it’s such a nostalgic place for me and so pretty that I love it anyway.

Madera

Madera Canyon

Madera Canyon

Like Sabino, I’ve been visiting Madera Canyon for as long as I can remember.  It too has a lovely, clear creek flowing down the middle of it.  It too is full of aquatic insects and attracts many odonates.  Madera is a little less crowded though and has some different odonates that you don’t see in Sabino, so it’s still really exciting to go there.  It’s nice to take a camera, a soup strainer, and a lunch.  That way, you can have a picnic by the creek, snap a few photos of any odonates you see, and collect some aquatic insects.  And, you can do this all on one perfect 3 hour trip!  What a great place!

Agua Caliente

Agua Caliente

Agua Caliente

Agua Caliente is another nostalgic place I’ve visited since I was a kid, but it is different from every other place I’ve mentioned so far.  Like Las Cienegas, it is a spring-fed system, but here it fuels a natural oasis in the desert valley east of the city.  The property used to be a cattle ranch and has been significantly modified to create more cattle ponds with a little stream that runs between them, but the whole system still depends on the spring for its water.  Now it’s a county park and is known as a great place to bird (it’s got wood ducks!), but I keep going back for the odonates.  The diversity of habitats within Aqua Caliente Park results in a high diversity of species within a small area, which makes this a great place to go with a pair of binoculars and a camera and knock off several species on your life list in only an hour or two.  It’s really gorgeous too!  I love Agua Caliente!

Man, now I’m itching to get out and do some oding!  Maybe I can cram in a quick trip to Madera this weekend…

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Unless otherwise stated, all text, images, and video are copyright TheDragonflyWoman.com

Behavioral Responses of Damselflies to Storms

Fountain Creek Park

The pond where I did my research at Fountain Creek Regional Park, CO.

Last week I talked a bit about how weather affects odonate behavior, my favorite topic in biology. Today I’ll go over the study I did to look at these weather related behaviors more closely. Like the little study I did that focused on damselflies and weather in my first college ecology class, this study was done at the wetlands in Fountain Creek Regional Park outside Colorado Springs, CO.  This research was actually part of my undergrad senior thesis!

pond at Fountain Creek Park

My study site. It extended from the cattails on the left side out to the end of the log in the water and from the dock (not visible) to just beyond the log.

I had to work the summer I collected my data, but I went to the wetland most days after work and recorded observations from 4-5PM.  I plopped down on the dock with all of my weather measuring equipment and watched the damselflies in a 5.5 square meter area along the edge of the pond for an hour.  I divided the hour into 5-minute periods and recorded weather data (wind speed and direction, temperature, light intensity, barometric pressure, relative humidity, and whether it was raining or not) for the first minute of each period.  I then spent the remaining 4 minutes counting the number of damselflies that flew within my study area.  Part of that area was filled with cattails and the rest was over open water as you can see in the photo.

Having spent 14 years of my life in Colorado Springs, I can tell you one thing with certainty: in the summer it rains nearly every day between 4 and 5PM.  This meant that I was out watching damselflies during the exact time the storms were blasting over Pike’s Peak and ripping across the plains.  I would sit there watching these phenomenal storm clouds rolling straight toward me with fantastic speed.  Guess who got rained on A LOT that summer?  Me!  I also got hailed on, was sandblasted in high winds, and was once driven running the half mile back to my car when the lightning got a little too close.  However, the clouds moved so quickly (they have to build up a ton of momentum to make it over Pike’s Peak’s 14,115 feet!), the storms didn’t last long, usually 30 minutes at most.  During that time, the weather would transform from hot, sunny, and still to cold, windy, and rainy in the span of a few minutes.  It would usually rain, sometimes very hard, for 10 minutes or so.  Then the storm would suddenly be over and it would become sunny, warm, and still again.  This whole series of events would take place during my hour at the pond.

Now most sane people go inside during storms.  Rain in Colorado is incredibly cold and the storms can be quite powerful with a lot of lightning.  Call me crazy, but I loved curling my whole body into my enormous rain jacket and getting rained on.  I was rewarded for my insanity too because I got to see some things that very few odonate people get to see.

First, I learned that there was a rather distinct pattern of behaviors that was associated with the weather patterns I observed.  The damselflies were most active in sunny, warm, still conditions, the typical weather central Colorado experiences during the summer.  They flew readily into and out of my study area, hunting, looking for mates, mating, and laying eggs.  As soon as a storm approached, you’d see some pretty interesting things.  As the clouds moved in and it became darker and cooler, the number of flights the damselflies made decreased so that fewer individuals flew during a counting period.  As the wind picked up, the activity decreased even further.  Flight activity ceased altogether if it started to rain.  Of all the many hours I spent at the pond, I saw only a single damselfly flying while it was raining, and it was during a very light rain when the sun was still shining.  Most interestingly to me, the damselflies would start to leave the pond when the weather deteriorated sufficiently.  They were displaying pond abandonment behavior.  However, as soon as the storm was over and the sun came back out, the damselflies would return to the pond and resume their normal activity as if nothing had happened at all.  It was fascinating and I am so happy I got to see this behavior!

pond at Fountain Creek Park

My pond at Fountain Creek Park during a light storm.

The flight activity of the damselflies at Fountain Creek Regional Park was clearly affected by the weather, but I was interested in knowing which of the seven weather parameters I measured were contributing to the flight activity I observed.  I used a statistical procedure (multiple regression for those interested) to determine that light intensity, temperature, wind speed (but not direction), and whether it was raining or not were the weather parameters most closely associated with the flight activity that I recorded.  Of these, light intensity showed the greatest association, followed closely by temperature.  Essentially, the brighter and warmer it was, the more damselfly flights you see.

(Brief aside: Remember how I said last time that I didn’t agree with that Russian scientist who thought that barometric pressure was a major player in shaping odonate behavior?  My results didn’t indicate that barometric pressure had any effect.  This coupled with the fact that the Russian didn’t even measure barometric pressure in his study makes me skeptical of his results.)

So four weather parameters were important.  The statistical test confirmed what I’d observed visually, that damselflies flew more readily in good weather than in poor weather.  “Good” conditions were warm and sunny with little or no wind while “bad” conditions were cold, rainy, windy, and dark.  I definitely observed pond abandonment behavior.

The most important question is this: what does all this mean?  I think my data suggest two things:

pond at Fountain Creek Park

My pond at Fountain Creek Park, right after a storm.

1) The damselflies might be able to pick up on cues in the changing weather that alert them that a storm is approaching.  Think about a damselfly, those big wings on a scrawny little body.  If you’re a damselfly, it could be physically dangerous for you to be out in a storm.  Being blown into the vegetation or the water could be deadly, heavy raindrops could impart a significant blow, and evaporative cooling could cause your body to cool down so fast that you can’t escape if the weather gets worse.  Better to leave the pond before a storm than risk getting caught exposed in one.  I think storms are dangerous to odonates, so the pond abandonment behavior that has been so often reported might be a means of protecting them from harm during bad weather.

2) Pond abandonment behavior might be related to roosting behaviors.  Consider these ideas: Damselflies roost in sheltered areas away from the water at night.  Storms usually result in a drop in the light level and temperature, which are the same things that happen as it gets dark at night.  Damselflies disappear from the water before it starts to rain.  It is therefore quite possible that pond abandonment behavior and simple roosting behaviors might be the same thing: odonates returning to their overnight roosts when it gets dark and cools down.  It is likely also advantageous for damselflies to seek shelter during storms, but this could be a secondary benefit, something they gain by completing a behavior that has nothing to do with protecting them from storms.

Are odonates using weather cues to abandon ponds before storms?  Or are they simply returning to their roosts because it’s getting dark?  Are storms dangerous to odonates?  These are some of the endless new questions I had after I finished this project and would like to answer.  I had intended to study this behavior in more depth in grad school, but then I decided to attend grad school in Arizona.  Colorado’s clockwork storms are perfect for studying these behaviors.  Arizona’s wildly unpredictable storms are not.  So, I changed my focus to the water bugs and have studied them ever since.  I will go back to my beloved odonates someday though!  I also decided a while back that my damselfly study was actually pretty unique and could make a real contribution to the scientific literature on odonates.  Ten years after I wrote my undergraduate senior thesis, my data was published.  If you’d like to read more about my study, look at some pretty graphs and whatnot, the citation is listed below.

I am dealing with some heavy things in my personal life at the moment, so I have no idea what I’ll do for the next few posts.  I’m going to let myself be driven by whims for a week or two.  I hope you’ll all check back to see where my whims take me!

Paper citation:

Goforth, C. L.  2010.  Behavioural responses of Enallagma to changes in weather (Zygoptera: Coenagrionidae).  Odonatologica 39: 225-234.

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

Dragonfly Territoriality (The Dragonfly Trilogy, Part Two)

Welcome to part two of my odonate trilogy!  Last time I discussed the reasons why I think dragonflies are the best insects.  However, I didn’t talk about the final reason I think dragonflies are amazing and that is the subject of today’s post: dragonflies are territorial!

Even if you aren’t a biologist, you probably know a bit about territoriality already.  Ever see a dog lift his leg on a fence or a tree?  That is a territorial behavior, a way for the dog to say, “This is MY space, so I’m going to mark it as mine!”  In canines, males mark territories with urine and other odorous compounds so that they can chemically signal to outside dogs that the space they are marking is part of their territory (the space in which they hunt and find mates) and that outside males should stay away if they want to avoid a confrontation.  They’re trying to convince other dogs that they are bigger and badder and that they can take on anyone that wants to challenge them for their space.  Naturally, your dog peeing on a tree doesn’t have quite the same meaning as it might if it were a coyote or a wolf doing the peeing.  After all, it’s hard to defend a territory on a leash!  Still, the behavior hasn’t entirely disappeared from our domestic pets and so our male dogs continue to pee on trees.  (And yes, I am resisting the urge to post a picture of my dog peeing on my fence!)

Male dragonflies are also territorial, but their system is very different from canines and is more behaviorally complex in many ways.  Let’s go over the process!

dragonfly habitat

A typical dragonfly habitat

First of all, males are territorial because females choose mates based on who provides the best real estate for her eggs.  For a female dragonfly, this might be a nice mat of algae, open water, or a stand of cattails – different species will look for different things.  A female dragonfly will go to an appropriate body of water (flowing or still, depending on the species), find the best place to lay her eggs, and mate with whatever male happens to be in the area.  The females of some species require courting rituals, but others will just mate with the male in the area.  The pair mates as described in my last post and the female will lay eggs in the area she has chosen.  Then she’ll fly off, perhaps waiting a few more days to return to the water to lay some more eggs or simply moving to another spot.

Because females choose mates based on the quality of oviposition sites (the word oviposition means to lay eggs, so an oviposition site is the location where eggs are laid), males who remain in the best areas will be able to mate with more females than those who are in lesser quality areas.  It’s even better if you’re THE ONLY male in that really great spot so you get all of the females.  Hence, territoriality began!  Male dragonflies will protect an area from other male dragonflies of their species so that they will have the best chance at mating with as many females as possible.  The best male (generally considered the most “fit” male by evolutionary biologists) is able to protect the best spots from his competitors.  The less fit males, the ones who are unable to chase the best males out of their areas, will take the less fabulous oviposition sites.  The males who are not able to hold any spot will sometimes hang out around the body of water and wait for a space to open up or try to sneak matings while the residents are preoccupied.  These comparatively unfit males will also sometimes leave the area entirely in search of another body of water.

Anax junius patrolling

A green darner (Anax junius) male patrolling his territory

So how does this territorial behavior work?  Let’s envision a hypothetical pond where no dragonflies have ever set up territories.  The first dragonfly arrives and takes the best oviposition site.  Depending on the species he belongs to, he will find a good place to rest while he watches his area or he will fly around his area continuously in a behavior called patrolling.  When another dragonfly comes along, unless there is another spot of nearly the same quality he can claim, he probably wants the same spot as the first male to arrive.  In this case, the new male will challenge the resident male for the position.  To do so, he will fly into the territory and the resident male will fly out to greet him.  The two will engage in a ritualistic fight where they chase each other, flying around one another in circles very rapidly and zipping across the pond, to demonstrate their strength (effectively their fitness) to one another.  Minimal physical contact occurs between the combatants (this is important when you have rather fragile wings that you depend on for everything you do!), but the male who would lose if they actually came to blows will likely give up his claim on the spot and take the next best spot.  More males arrive and fight for the spots that they want, shifting the territories between individuals.  Eventually, a sort of equilibrium is reached where the best males have the best spots, the lesser males have the lesser spots, and the weakest males have no spots.

Protecting a good territory is hard work and even the best dragonflies can’t protect them forever.  A male protecting the most popular oviposition site will be constantly challenged by neighbors and the males who are unable to claim territories, not to mention he’s getting more matings than any other dragonfly at the pond!  Male dragonflies also expend a lot of energy guarding their mates while they lay their eggs.  An unprotected female is likely to be grabbed by another male and taken to another location at the pond to mate again before she finishes laying the eggs the resident male just fertilized, and males put a lot of effort into guarding their mates.  So, territories often shift during the day as more energetic males overthrow tired resident males.  Younger males can usurp territories from older males as well.  And there are always those males who weren’t quite strong enough to claim a territory waiting for resident dragonflies to weaken to the point that they can finally overcome them and take over their positions.

Anax junius males in combat

Green darner (Anax junius) males in combat

Competition for territories can be fierce.  There are usually far fewer territories at a body of water than there are male dragonflies who want them, so they are constantly trying to claim better territories and mate with as many females as they can.  It’s effectively a war zone!  The competition doesn’t ease once all of the territories are taken either as more dragonflies may arrive at the pond and many of the less fit males stay nearby in hopes of eventually gaining a territory.

In general, males who hold territories mate many more times than males that do not have territories, but even the homeless males will secure some mates.  While a male is chasing another male from his territory, a weaker male might be able to slip in and grab a quick mating.  Males who are guarding females are less likely to chase intruders from their territories until the female is finished laying her eggs, so weaker males can sometimes take advantage of their lapse in attention to sneak in a mating.  It is also typical for males with lower quality territories to mate more often than males without territories.  You might thinks that males holding lower quality territories would never get mates and waste their energy protecting their sites because females choose mates based on who holds the best oviposition site.  However, females are in such short supply and such high demand that they are sometimes mobbed when they arrive at the best spots because so many males are competing for the same space.  A female who is harassed enough or has her egg laying interrupted enough times will seek a mate in a quieter area where she may lay her eggs in peace.

So, male dragonflies form territories so that they can mate with as many females as they can.  The more females they mate with, the more offspring they will produce and the more their genes are passed on.  Pretty simple really!  And it’s one major reason many other animal species set up territories too.

Next time, I’ll finish up my dragonfly trilogy by cheating a bit and using the British definition of dragonfly (they use dragonfly for both dragonflies and damselflies) so I can talk about a recent paper about territoriality in a damselfly species.  Damselflies are much less likely to protect territories than dragonflies, but the system works the same way.  I hope you’ll stay tuned!

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Text and images copyright © 2010 DragonflyWoman.wordpress.com