[Odonata-l] territoriality

[Dennis Paulson]

Dear Carlo,

My suspicion is that at least some odonates that mate away from water  
perhaps haven't even seen that particular water body before, but  
instead meet a member of the opposite sex, quickly get through the  
candy-and-flowers stage and mate, THEN fly in tandem until they find  
a suitable habitat in which to lay their eggs. I don't know how to  
gather any evidence other than anecdotal to support this hypothesis.  
I have seen tandem pairs of Sympetrum occidentale (Western  
Meadowhawk) flying over sagebrush some miles from the nearest water,  
and it's hard to imagine they would have wandered that far from a  
preferred habitat just to find a mate. More likely, I assumed the  
male was out in the dry shrub-steppe, came across a female, mated,  
and then flew until they reached an appropriate wetland.

I have also seen tandem pairs of Pantala flavescens (Wandering  
Glider) come in to a hotel where I was staying in the tropics and  
start laying their eggs in the swimming pool. I don't think it is  
likely that the male had found the swimming pool, gone away from it  
and found a female, and then brought her back to it, but of course I  
have no way of knowing this. Perhaps P. flavescens is a special case,  
as it is such a great wanderer anyway, but I have also seen many  
tandem pairs of Tramea (saddlebags), Celithemis eponina (Halloween  
Pennant), and Erythrodiplax berenice away from water and seemingly  
moving long distances overland. This has been reported for more than  
one species of Sympetrum. And of course there are reports of Anax  
junius (Common Green Darner) apparently migrating in tandem.

Tim Manolis reminded me about Anax junius, which oviposits in tandem  
(mostly) or not. It would be interesting to know the mating history  
of solo-ovipositing females. Is this a different female strategy, or  
did the pair break up for some reason and she just continued the  
ovipositing that had begun in tandem? As the latter happens in many  
other tandem ovipositors, it may be no big deal.

Your comments on the two species of libellulids are fascinating. I  
guess you are saying that the males switch from non-territorial to  
territorial as soon as they have mated. Then I assume in subsequent  
matings, that particular female oviposits in the male's territory, so  
he has no motivation to change territories. Of course, many such  
dragonflies may only mate once.

Speaking of Libellula, at least some American species of this genus  
(certainly Libellula forensis, Eight-spotted Skimmer) are not  
territorial but instead fly over ponds and lakes much like species of  
Aeshna do. I once marked large numbers of L.forensis at a long pond  
and never saw one of my marked individuals again, exactly what  
happened with several species of aeshnids flying there. I'll admit  
that I had no way to know if the occasional male that mated might  
then remain on that "territory." At the same place, territorial  
libellulids such as Plathemis lydia (Common Whitetail) that I marked  
might be back in their territory within minutes. Other Libellula  
maintain territories, and it would be interesting to understand why  
this difference within a group. The "moving territories" of aeshnids  
seem to make sense evolutionarily, as they are looking for stationary  
ovipositing females, while in L. forensis, they are unlikely to come  
across an ovipositing female that doesn't already have a male  
guarding her, so why not maintain a stationary territory?

One of the variables here that has not been much examined is  
territory quality. If a pond or lake is essentially the same all  
around its margin, then having a moving territory might be as good a  
strategy as having a stationary territory, as females should be  
equally likely anywhere.

I wish I could read Corbet's chapters on these matters once and  
commit them to memory!

Dennis

On Feb 8, 2007, at 9:52 AM, Carlo Utzeri wrote:

> Dannis wrote
> "Many odonates mate away from water, and those would be interesting  
> to look at more closely, as in those cases, there is no "territory  
> quality" entering into the picture, so one wonders if another sort  
> of female choice might be exercised."
>
> Several years ago I published a study on territoriality in  
> Libellula depressa (Advances in Odo natoogy. 4: 133-147) in which I  
> concluded that males, as soon as arrived to the water, were not  
> chosing any particular site as their territory, but they  
> established territories around the oviposition site of a female  
> with which they had mated. Successive observations (unpublished)  
> convinced me that the same occurs in Crocothemis erythraea. So in  
> this case, males "learn" the good oviposition site and enclose it  
> in their territories, since many other females will probably come  
> to the same site. I believe that this system might be valid for  
> many other libellulids. Don't you think that the same may be the  
> case with dragonflies which mate far from the water?
>
> Greetings
> carlo ùtzeri
> _______________________________________________

-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net



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