Wednesday, May 25, 2016

Male-Male Interactions in Darners

Here's an article I've just submitted to Argia, the journal of the Dragonfly Society of the Americas.  The article details my observations of darners interacting more and more aggressively as the end of the flight season nears.


Male-Male Interactions in Darners
James S. Walker
Anacortes, Washington

Cranberry Lake in Anacortes, WA (Figure 1) is a wonderful place to observe dragonflies – especially darners.  The first species to start flying is the California Darner (Rhionaeschna californica), followed in short order by the Blue-eyed Darner (Rhionaeschna multicolor).  Later in the season, in October and November, the darner population shifts to Paddle-tailed Darners (Aeshna palmata), with a few Shadow Darners (Aeshna umbrosa) tossed in for good measure.  As a result, Cranberry Lake is an excellent place to observe darner behavior throughout the flight season. 











Figure 1 Cranberry Lake, home to many darners.

Over the years, it has become apparent that the way darners interact with one another evolves as the season progresses.  Early in the season, darners fly in mixed flocks – though comprised mostly of males – at convenient hill-topping locations, where the individuals hunt for prey peacefully with little interaction (see the online video links at the end of this article).  This is the time when the darners are feeding to attain maturity, after which they return to nearby ponds or lakes to mate.

As the season progresses, and more and more darners are present at local waters, the interactions begin in earnest.  In what follows, I describe the types of interactions, and the changes in behavior, observed at Cranberry Lake – both during the peak of the season, and extending well into the final days of flight.

Peak Season Interactions

Interactions during the peak of the season are observed to be rather benign and, one might almost say, gentlemanly.  Darners patrol the shoreline of their territory, looking for rivals, mates, and prey.  When a second darner flies into the territory of a resident darner, the resident flies toward the intruder.  Typically, what happens next is a respectful assessment of the situation, in which the intruder changes course to navigate out of the disputed territory.  Once the resident darner observes the change in trajectory of the intruder, it changes course as well, and returns to its territory.

As mentioned, these interactions are usually peaceful affairs, with no physical contact between the competing darners.  The darners approach to within a few feet of one another, veer off as they change course, and go their separate ways.  As the season progresses, the situation changes.

Late Season Non-Contact Interactions

Late in the season, when the days are growing shorter, the air is getting cooler, and the biological imperative to mate is intensifying, the interactions between darners takes a decidedly aggressive turn.  The first signs of change are apparent in the way a resident darner interacts with an intruder.  Often we see that instead of veering away from the intruder once the intruder is heading out of the territory, the resident keeps up a prolonged chase – though, again, generally without physical contact.  

In such cases, I’ve observed the resident male persist in chasing the intruder to an extent that seems, to a human observer, beyond all reason.  Even though the intruder is clearly departing the area, and seems no longer to pose a threat, the resident darner expends a great deal of energy and time in an extended chase.

Sometimes, the intruder is so pressured by the resident that its wings clip the water as it zigs and zags trying to escape.  In other occasions, the intruder intentionally plunges into the water in a splash/dunk (Walker 2011-2014, and online video), and then, as the pursuing resident continues on its course, the intruder emerges from the water and takes off in the opposite direction.  Clearly, drastic circumstances result in drastic measures.

The aggressive harassment described above still results in no physical contact.  Cases that do involve contact become more and more common as the season progresses.

Late Season Contact Interactions: The Final Days of Flight

As the end of the flight season approaches, the interactions between darners become more frequent, and more physical.  Males are seen to attempt to attach in tandem with other males, and to grapple with one another in flight for extended periods of time.  The whole tenor of their interactions changes.

The first sign of contact interactions is observed in perched darners.  Even though darners are flying dragonflies, they do perch from time to time to rest, eat large prey, or sunbathe.  They hang vertically in a bush with full exposure to the sun, as shown in Figure 2.  It’s common to find 3 or 4 darners perched at a time in the bushes near the shore of Cranberry Lake in peak season, but the number roughly doubles or triples near the end of the season, as more darners seek to warm themselves in the sun. 



Figure 2  A perched Paddle-tailed Darner at Cranberry Lake in its usual vertical orientation.

In late season, there may be a dozen darners perched in the bushes, but still with plenty of room to accommodate all of them.  Even so, they are often seen perched near one another, as in Figure 3.  What’s really odd, though, is that a darner coming in to perch often lands on an already perched darner.  Close observation reveals that the incoming darner lands on the thorax of the perched darner, and bends its abdomen downward and forward in an apparent attempt to attach in tandem.  At this point the perched darner takes off, and the two darners continue their interaction in flight.



Figure 3  Two darners, a Shadow Darner on the left and a Paddle-tailed Darner on the right, perch near one another.

At the same time, many in-flight interactions can be seen along the shoreline.  Competing darners no longer veer off in different directions, or engage in extended pursuits, but aggressively grab one another in flight.  In some cases I’ve captured in slow-motion videos (see online videos), the two darners hang on to one another and spin round and round in flight – much as two eagles locked together with their talons.  In one particular case, they grapple with one another for 1.9 seconds as they fall toward the water, only releasing their grip just before splashdown.  They gain altitude for 0.75 seconds, and then go back at one another, clenching for another 2.3 seconds, before taking off for more interactions.

In another case, the two darners actually landed in the water as they struggled.  While floating there, the top male repeated banged the tip of its abdomen against the head of the darner below it for over 4.5 seconds, as it tried mightily to attach in tandem.  It finally gave up, flew upward to gain altitude, and 0.9 seconds later the other darner managed to escape the water as well.  Interactions like this were common at this time of year.

These observations are only anecdotal, and may not present an accurate picture of darner behavior throughout a season.  Additional observations will form a more complete picture, but so far it seems that darner interactions are much more aggressive and physical late in the season, when the darners only have days left to fly.

Conclusion

Darners interact with one another frequently all year long, but their interactions become more intense and physical in the waning days of their flight season.  Males land on one another, or grab one another in flight, and appear to attempt attachment in tandem.  Late season interactions lead to explosive events at Cranberry Lake in October and November, and likely the same type of behavior can be observed at any location with a healthy darner population.

Acknowledgements

I would like to thank Betsy Walker for her support and help with these observations.

Literature Cited

Walker, J. S. 2011.  Spin-Dry Dragonflies.  ARGIA 23(3): 29-31.

Walker, J. S. 2011.  Splash-Dunk Analysis.  ARGIA 23(4): 29-30.

Walker, J. S. 2014.  Splash-dunk Analysis for 2011-2013, Including Temporal Distribution.  Argia 26(1): 33-34.

Walker, J. S. 2014.  Splash-Dunk Analysis for 2011-2014.  Argia 26(4): 32-33.

Online Video Links

A number of slow-motion videos showing various aspects of dragonfly behavior can be found on the Dragonfly Whisperer channel on YouTube.  Here are a few that are pertinent to this article:

Non-interacting darners in a feeding group.
Soaring Darners with Mount Baker

Gentle, non-contact interaction with zig-zag flight.
Darners interact, by The Dragonfly Whisperer

Non-contact chasing.  The pursued darner escapes with a splash-dunk.
Darners interact with splash-dunk escape, by The Dragonfly Whisperer

Contact interaction.  Darners hold on to one another until they hit the water.
Darners grab one another and fall in the water, by The Dragonfly Whisperer

Extended contact interaction.
Male darners interact big time, by The Dragonfly Whisperer

Males struggling in the water as one attempts to attach to the other.
Male darners struggle in water, by The Dragonfly Whisperer

Tuesday, April 26, 2016

Dragonflying at Tortilla Creek

One of the places we like to dragonfly in Arizona is Tortilla Creek, in the little tourist town of Tortilla Flat.  The town consists of a few small "cowboy"-type businesses along the road.  Here's a picture of the town:



Most of the visitors to Tortilla Flat are probably not even aware of the small creek, Tortilla Creek, just across the street from the town.  Here's a view of the creek:



Everywhere you look when you visit Tortilla Creek you see incredible desert vistas, like the one below.



Dragonflies are out and flying at Tortilla Creek, though not nearly in the numbers that will be seen in about a month.  Even so, we had some good views of Common Green Darners, Flame Skimmers, Roseate Skimmers, Blue Dashers, and a Mexican Forktail.

The Flame Skimmers seemed particularly vibrant.  Here's one that landed right in front of us:



Notice the intense red colors in the wings, including the dark rectangular concentrations (opacities) near the wing bases – an important way to distinguish the Flame Skimmer from the similar Neon Skimmer.  I also like the yellow cross veins near the leading edges of the wings, and the contrast they make with the red colors elsewhere.

A Blue Dasher landed near us, and offered an unusual rear view:



Later, it turned around to give us some more common perspectives:





One other dragonfly gave us some nice close views – a male Roseate Skimmer.  It looked quite young and fresh, with lovely colors, and fairly clean wings.  Here are a few looks at it:





What a treat!

Tortilla Creek may not be well known, and it may be overlooked because of the tourist attractions across the road, but it's a nice place to view birds and dragonflies.

Saturday, April 23, 2016

Plateau Spreadwing at Bosque del Apache

One of the fun things about our recent visit to Bosque del Apache was seeing a new "life ode."

We were driving along the north loop road when we noticed a nice pond with lots of emergent vegetation.  It looked like a good spot to see some damselflies, so we stopped to check it out.  I saw some forktails there, and almost immediately saw some spreadwings as well.  Looking at them through my binoculars I could tell they were a species I wasn't familiar with, so I took some pics for later research.  It turns out they were Plateau Spreadwings, a new odonate for us.

Here's one of the first pics I got of this species.  This individual was some distance away, but my point-and-shoot camera did a pretty good job of getting a shot.



I like the iridescence in the wings.

Here's a closer shot, showing the distinctive thorax stripes – a light-colored stripe on the "shoulder", and a broad brown stripe below it.



As seen in this picture, spreadwings do sometimes perch with their wings held together, though the usual pose is with the wings spread, as in the first picture.

Tuesday, April 19, 2016

Capitol Building in Santa Fe

On a recent trip to New Mexico, we stopped at the state's capitol building in Santa Fe.  It's a very nice building, very inviting.  Here's the senate chamber:



The lobbies are full of beautiful art work, including the following painting that caught my eye:



I love the various Native America motifs in the painting, and especially the three symbolic dragonflies.  The lower one is reminiscent of a Flame Skimmer, the middle one makes me think of a Red Rock Skimmer, and the top one could be a Western Pondhawk.  In any case, it was cool to see these dragonfly representations in the halls of power in Santa Fe.

The bluish dragonfly at the top is near a spiral symbol:



I've looked for the meaning of these spirals, which are quite common in Native American art, but no one really knows what they mean.  Some say they stand for water, others say they signify life, but no one knows for sure.

My thought – a bit biased I must admit – has always been that the spirals could represent the water spraying off a dragonfly as it performs a spin-dry after a series of splash-dunks.  What is particularly interesting in this painting is the association between the dragonfly symbol and the spiral symbol – there might be something to my spin-dry interpretation after all.

Monday, April 18, 2016

Variegated Meadowhawks at Bosque Del Apache

Last week, my wife and I visited Bosque del Apache for the first time.  It's quite a delightful place, especially for birdwatchers.  There were a few dragonflies there, as well, including Common Green Darners and Blue-eyed Darners.

We also saw a number of Variegated Meadowhawks, which are wonderfully photogenic.  Here are a few pictures from April 5 this year.



This was the first Variegated Meadowhawk we saw at Bosque.  It perched nicely for us on its favorite perch over the water.

After a while it moved to a closer perch.  Here it is coming in for a landing:



The next shot shows it after its pinpoint landing:



Later we saw another individual, this one much younger:



Notice that the side of the thorax has white stripes, ending in yellow dots at the bottom.  As the meadowhawk matures, the white stripes fade away, leaving just the yellow dots.  This is the case with the first individual, show above, where we see just a faint remnant of the white stripes.

Saturday, April 2, 2016

The Unexpected Pleasures of Dragonflying

You never know what you're going to find when you're out in the field looking for dragonflies.  I went out yesterday to check on the local odes, but didn't find any.  What I did find was well worth the effort, however, and I'm glad I went.

First, I noticed that our saguaro cactus is doing quite well in our front yard.  Here's a look at it:



It has interesting needles, with one spike much larger than the rest:



Also present in the garden were roses and a type of daisy:







As I admired the flowers, I heard a pigeon cooing and strutting to woo its mate:



The really big surprise, however, awaited me when I got down to the pond.  Standing there on the shore was a Black-bellied Whistling-Duck, a species we've never seen at this location before.



That was quite a treat – just one of those unexpected pleasures!  It's especially unexpected when you consider the range of the Black-bellied Whistling-Duck:

Wednesday, March 30, 2016

First Damselfly of the Year, 2016

We saw our first damselfly of the year, Rambur's Forktail, the same day we saw the first dragonfly.  It flew on by us, however – surprisingly quickly for such a small insect – never to be seen again.

It was immediately recognizable by its green thorax and blue-tipped abdomen.  There's another forktail that's similar, the Desert Forktail, but it has yellow on the sides of the abdomen that extends up onto the top of the abdomen.  In Rambur's Forktail the yellow on the abdomen terminates in a nice, clean straight line about halfway up.  We haven't seen a Desert Forktail at our backyard pond, so we were pretty sure we were seeing a Rambur's Forktail.

A week or so later we went to Wild Horse Pass, and there we saw several Rambur's Forktails that were perching for us.  Here's a view of a male Rambur's Forktail at Wild Horse Pass:



Notice the green on the head and thorax, the blue tip to the abdomen, and the lack of yellow on the top of the abdomen.

Here's another male seen later the same day:



Heteromorphic females (those that don't look like males) start off bright orange when young, but with age turn more brownish and greenish.  Here's an immature heteromorphic female seen the same day at Wild Horse Pass:



Notice the nice straight line between the light color on the bottom of the abdomen, and the black on top – similar to the line of demarcation in the male.  We saw the female interact with a male, but she fended it off and they went their separate ways without mating.