Tuesday, 5 February 2019

Twin-spot Hunters find Canberra

It was Saturday afternoon and 40 degrees outside. I was in the relative comfort of the study, the fan blowing a cooling breeze, when a report came through on the online Canberra Nature Map (CNM) of a Unicorn Hunter – a type of dragonfly that, in the ACT, frequents sand or shingle beds along some of the lower altitude rivers. As a moderator for dragonflies on the CNM platform I logged in and had a look at the photo. An initial cursory glance showed a tell-tale yellow double band at the 7th abdominal segment, then I looked at the antehumeral stripe to ensure it was ‘attached’ to the collar – it was; but something about the spots on the side of the final abdominal segments, and the pattern of the yellow patches on the side of the thorax, just didn’t seem quite right. Then I looked at the location of the sighting. It was all wrong. It was from open woodland, though not too far from a few small ‘farm’ dams. But nothing like the sandy-edged river locations preferred by Unicorn Hunters.

The photograph submitted to Canberra Nature Map, initially suggested to be a Unicorn Hunter.
So I took a closer look at the thoracic and abdominal patterns against the various other ‘hunters’ in the Theischinger & Hawking field guide, and it became very apparent that the photo was in fact of a thing called Austroepigomphus praeruptus or Austroepigomphus melaleucae, the Twin-spot Hunter.

This species pair has a bit of a confused history. The original A. praeruptus was described by Selys, in 1858, based on a single specimen from South Australia; but the specimen was lost and has never been relocated. Meanwhile, in 1909, Tillyard described a very similar species from Queensland and called it A. melaleucae. Although the vast majority of known records are from Queensland and northern NSW, it seems that the species has now been accepted as A. praeruptus and A. melaleucae has been relegated to junior synonym status.

There are close to a hundred records of the species in the Atlas of Living Australia (ALA), generally from inland south-eastern Queensland and inland north-eastern NSW, but with some more coastal records, including as far north as Cairns and as far south as Sydney. Interestingly, there is a 1976 record from Elanora Heights in the bushland of northern Sydney, less than a kilometre from where I grew up and where I was a teenager at the time! There is also a tight cluster of three records by Reiner Richter, from January/February 2016, from a small drying creek between Shepparton and Euroa in northern Victoria.

Distibution of the 92 Atlas of Living Australia records (Jan 2019).

In a personal email, Reiner indicated to me that a record, in iNaturalist, is of, finally, a recent record of the species from South Australia. This was of an individual in a very poor state from the Adelaide hills. 

So the finding of an individual of this species in the ACT is an important and, for me personally, very exciting outcome, and fills a sizable gap in the species’ distribution. I got onto John Bundock (the naturalist photographer ‘colleague’ of mine who found the dragonfly and submitted the record) immediately by phone, quizzing him on details such as was it just the one individual, how far was it from the nearest water, did it hang about, did he have any other photos of it etc, etc. It seemed to take a while, but I eventually convinced him of the significance and excitement of his find and we agreed to go out together in the morning to try to gather further evidence.

Next day, Sunday 27 January 2019, dawned quite overcast and we were even subjected to the occasional brief shower as we searched the first dam. Not the greatest dragonfly hunting weather. It remained cloudy for several hours but eventually gave way to more extended sunny periods and reached a temperature of 30 degrees. We searched the woodland where John had seen the dragonfly, now three days prior; we searched another couple of nearby small dams, all of which had relatively low water levels. Blue Skimmers and Common Bluetails were particularly evident, and we also recorded a few Red & Blue Damsels and a single Blue Ringtail, but we found no evidence of any Twin-spot Hunters.

We decided to head deeper into the woodland reserve to a couple of other small dams that I’d been wanting to survey for a while, and as we went, photographing any other insect life that caught our attention, my mind started to formulate a possible scenario. If this species is known to inhabit “sluggish streams and rivers, including isolated riverine pools”, it may well be likely that the species has adapted to a nomadic lifestyle. This might go some way to explaining its very patchy distribution through eastern and south-eastern Australia, and the individual John had seen may well have been an itinerant or wind-blown ‘traveller’. Fine as a theory, but not great for my personal aspirations of seeing the species which I desperately wanted to do.

At the other dams there were lots more of what we’d already seen and we added Tau Emeralds, an Inland Hunter and Wandering Percher. But still no twin-spots. So finally, defeated by lack of success and the heat, we decided to head back towards the car. We did a bit of a loop past another drying dam before rejoining the main track just above one of the dams we’d checked earlier that morning. As we approached, I noticed a Royal Tigertail perched on a small emergent branch just out from the bank. We hadn’t seen this species earlier, so I raised my camera and, even through the viewfinder, I realised fairly quickly that this was no Royal Tigertail. I mentally checked off abdominal banding and spots and thoracic markings and knew straight off this was in fact a Twin-spot Hunter. Yes! We spent about half an hour scanning the dam and taking hundreds of photos, eventually seeing three of the twin-spots together.

When we dropped down to the next dam, the one we first surveyed in dull showery conditions, we tallied no less than eight individual Twin-spot Hunters, all along one edge of the dam, perching mainly on logs and emergent submerged branches, but also occasionally on the stems of rushes or on the gravelly bank. What a difference a bit of sunshine can make.

This completely changed things. These were not blow-ins, but in all likelihood had emerged locally. The species was a ‘resident’, at least for one season, of the ACT.

Now we need to monitor over the remainder of this season, and more importantly, check other potential sites in the region, and see if they show up again next season.

Tuesday, 8 December 2015

Inland Hunter inexpectata

Last Wednesday I took a lunchtime stroll along the northern edge of West Basin, a section of Lake Burley Griffin. It is just across Parkes Way from where I work and is in the heart of Canberra. I should confess that it wasn’t really just a stroll, so much as a survey of what odonates (dragonflies and damselflies) might have been present at the time. This is part of my fairly concerted effort this summer to get a feel for what odonate species occur in the ACT and when they are present through the season.

Apart from the expected damselflies - Blue Ringtails, Red & Blue Damsels and Common Bluetails (all of which have been present there for the past month or so) - I saw four or five individuals of a smallish black and yellow dragonfly. From the shape and body markings these were clearly a type of gomphid (Family Gomphidae) and at first I thought they might have been either Stout or Southern Vicetails (Hemigomphus heteroclytus and Hemigomphus gouldii respectively) which are not uncommon in some of the ACT’s rivers. But some decent views through the binoculars at close range of one individual made me think differently. It clearly had dorsal stripes down the abdominal segments and appeared to be some sort of ‘hunter’ rather than a ‘vicetail’, possibly a Unicorn Hunter Austrogomphus cornutus, but clearly not a Yellow-striped Hunter Austrogomphus guerini that I’m relatively familiar with. As I didn’t have my camera with me I took mental notes of what would hopefully be diagnostic ID features and jotted down a few comments in my little notebook.

Stout Vicetail Hemigomphus heteroclytus; Coppins Crossing, ACT; 5 Dec 2015.

Southern Vicetail Hemigomphus gouldii; Gudgenby River, ACT; 26 Dec 2014.

Unicorn Hunter Austrogomphus cornutus; Gudgenby River, ACT; 26 Dec 2014.

Yellow-striped Hunter Austrogomphus guerini; Gudgenby River, ACT; 26 Dec 2014.

When I got back to work I looked up the field guide (Theischinger & Hawking 2006) and the only thing that looked like what I had seen was Inland Hunter Austrogomphus australis. A species I'd never seen before.

The match was good for what I had seen, and nothing else really fitted. The problem was the field guide, and later the Atlas of Living Australia (ALA) when I looked it up, indicated that this species doesn’t occur in Canberra. The nearest records in ALA are from Wodonga (220 km to the south-west), Griffith (300 km to the west) and up near Tambar Springs (415 km to the north).

Distribution of Inland Hunter according to the Theischinger & Hawking field guide.

Distribution of records of Inland Hunter in the Atlas of Living Australia (ALA) at 4 Dec 2015.

It was kind of exciting but also frustrating that I had no visual record, and I determined to go back next day, with camera, and get some evidence/proof. So you can imagine my acute frustration when Thursday lunchtime revealed absolutely no sign of any of these dragonflies, despite walking back and forth and checking closely the locations where I had seen them the day before, under similar warm, bright sunny conditions.

What had been clear on the Wednesday was that these dragonflies were always associated with sandy/gravelly patches, be they gravelled pedestrian tracks along the edge of the lake or the tiny patch of gravelly sand that purports to be Acton Beach. I thought it unlikely that there would be several individuals at this location one day, and none the next, so I returned again on Friday lunchtime and this time was successful. I spent the better part of an hour photographing one of these dragonflies as it came and went, perching on the gravel and darting out over the water if I got too close or something else disturbed it. Just before heading back to work I saw a second individual and they had a brief skirmish the way dragonflies often do.

Inland Hunter Austrogomphus australis; Acton Beach, Canberra, ACT; 4 Dec 2015.

Inland Hunter Austrogomphus australis; Acton Beach, Canberra, ACT; 4 Dec 2015.

Inland Hunter Austrogomphus australis; Acton Beach, Canberra, ACT; 4 Dec 2015.

So I felt vindicated. Not only had I relocated at least two of these dragonflies, but I got quite a few photos, and most gratifyingly they clearly indicated that they were indeed Inland Hunters - and my mental note taking was validated.

Later that night as I went through the photos, culling the out-of-focus and leaving the small fraction that remained acceptable, it became clear, based on details of the colour development on the final four segments of the abdomen, and to a lesser extent the shape and completeness of the humeral stripe on the synthorax, that the photos represented at least six different individuals – all males. Only twice had the same individual returned for a second sitting. My initial assumption that the same individual had been coming and going was patently wrong.

But the question remains – what was this species doing in Canberra? The field guide indicates that the species “inhabits rivers and riverine pools, common and widespread in the inland river systems of eastern Australia.” Well that description is not at odds with the Canberra situation, but it doesn’t explain the near total lack of records of the species (at least in ALA) from the Murrumbidgee and Lachlan catchments.

So what was going on? Could it be that Canberra is within the species’ normal range but for whatever reason had not been reported from here before? Seems unlikely given that one of Australia’s foremost odonatologists, J.A.L. Watson had lived and worked in Canberra for many years. And why are there no records from along the lower courses of the ‘bidgee and Lachlan?

Or might it be that the species has expanded its range or increased its population size in this region? Could climate change be a factor? Or might the species be migratory and I had just happened across a cluster of migrants, or even wind-blown individuals from further west? Starting to scrape the barrel a bit here I think, particularly as, as far as I know, Gomphids tend to be rather territorial rather than migratory.

Anyway, I got to thinking if there were at least half a dozen of these things at one small beach right near the city, there must be others about. The closest place I could think of with similar habitat features was Grevillea Park at the eastern end of Lake Burley Griffin (LBG), about 3 km away. So early on Sunday afternoon I dropped by and scanned the ‘beach’ there and did indeed find and photograph another single male Inland Hunter.

Inland Hunter Austrogomphus australis; Grevillea Park, Canberra, ACT; 6 Dec 2015.

Inland Hunter Austrogomphus australis; Grevillea Park, Canberra, ACT; 6 Dec 2015.

But the more surprising discovery was of yet another individual at Coppins Crossing on my way home. Coppins Crossing is on the Molonglo River about 12 km downstream of the lake and presents quite a different habitat to the shores of LBG. The river there is fairly muddy (probably due to the massive multi-suburban development of ‘North Weston’ not far upstream) and not particularly fast-flowing except where it percolates through some rocky sections. The male I saw (which I had initially assumed was just another of quite a few Stout Vicetails present along that stretch of the river, and only discerned as an Inland Hunter later that night as I went through the photos) was perched on the top of a small rock in the middle of an expanded pondage where the water was murky and still.

Inland Hunter Austrogomphus australis; Coppins Crossing, ACT; 6 Dec 2015.

So it has been quite a special few days in which I’ve found a species that supposedly doesn’t occur in Canberra in three different Canberra locations. And I’m left wondering what to think about it and what to do about it. As a first step, I’ve written this blog post and will make the records available on ALA and Bowerbird…

And I'll keep hunting!

Friday, 27 November 2015

Rhapsody in Blue Ringtail

Before starting to read, consider if you'd like to listen to George Gershwin’s Rhapsody in Blue while you read this post - if so you could try this link - https://www.youtube.com/watch?v=eFHdRkeEnpM

Last Summer I introduced myself to the amazing world of dragonflies and damselflies in the Canberra region. Prior to that I’d taken opportunistic photos of some fairly spectacular dragonflies (see for example earlier posts on Cape Dragonflies and Top end Dragonflies), but this was a concerted and systematic effort to try to find out what was present in the various watery habitats of the ACT.

At the end of the season I had seen and photographed 32 of a total of somewhere around 50 species that I think are likely to occur in the ACT (based on my interpretation of the Theischinger and Hawking 2006 Field Guide and occurrence records in the Atlas of Living Australia). Some of these were featured in an earlier post, Damsels - Down at the Local.

This season, apart from wanting to find as many as possible of the expected species I didn’t pick up last year (I’ve got two so far – Slender Ringtail and Powdered Flatwing), I’ve been trying to get a better idea of the time and sequence of emergence of dragonflies and damselflies after the long Canberra winter. 

A teneral (recently emerged immature) female Slender Ringtail Austrolestes analis, 24 Oct 2015.

Male Powdered Flatwing Austroargiolestes calcaris, Orroral Valley, ACT, 8 Nov 2015.

So far it is pretty clear, and not surprising, that the first emergences occur in the shallower water bodies at lower elevations (presumably because the water warms more quickly than water bodies that are either deeper or at higher elevations). The earliest species I saw, in mid-September, were Wandering Ringtail and Tau Emerald at a small pond at the local golf course. And I’ve only just in the past week or two (i.e mid-November) started to see the occurrence of river dragonflies in the lower reaches of the mountain rivers.

One of the most spectacular emergences I’ve witnessed this season has been at the large pond at the entrance to the National Arboretum. I drive past this most days on my way to and from work, but had always considered it to be fairly uninteresting and sterile – the pond, and arboretum, are still in a fairly early stage of development. I was in for a shock!

My first visit to the pond was on 17 October, and I wasn’t expecting much – just filling in surveyable sites really. And at first there wasn’t much to be seen along the narrow muddy edges fringed with rushes. But as I approached the end of the pond where the run-off from the surrounding slopes enters, the numbers of Blue Ringtails and Red and Blue Damsels increased, and there was also a single Australian Emperor and a few Tau Emeralds.

Adult male Blue Ringtail Austrolestes annulosus, Australian National Arboretum, 9 Nov 2015. 
A tandem pair of Red & Blue Damsels Xanthagrion erythroneurum, 9 Nov 2015.

Three weeks later when I returned, on the afternoon of 9 November, the numbers of damselfies had increased greatly and I estimated a total of at least 300 Blue Ringtails and probably about 60 Red & Blue Damsels, just at that end of the pond. The large number of teneral (immature newly emerged adults) Blue Ringtails I saw in the clumps of rushes and tall grasses bordering the pond indicated the population is still on the increase. The emperor and emeralds were still there, and I also picked up a handful of fairly newly emerged Common Bluetails.

Newly emerged (teneral) male Blue Ringtail. The areas of pale orange will eventually mature to a bright sky blue. During this vulnerable stage, when they are comparatively soft and weak-flighted, they tend to stick to the safety of dense grasses and other vegetation.

A teneral female Blue Ringtail.

The following photos attempt to convey a sense of the intense activity at the pond.

Perching spots were at such a premium that the different species even tolerated each other briefly. 

Blue Ringtail and Red & Blue Damsel sharing a perch.

Pairing up was a clear priority...

The protagonists of this newly established pair were a little awkward and had some trouble knowing just how to get it on, but eventually figured it out. 

Nuh-uh - wrong!

Let's try that again...
nearly there...
Ahh - yes, that feels right!

There was a lot of competition involved, leading to some pretty debauched behaviour. This male tried his luck with a female who was already paired up...

...and this one even tried it on with a hapless female who was all but dead and was floating on the water!

There were swarms of ovipositing tandem pairs of both Blue Ringtails and Red & Blue Damsels - presumably there were suitable water plants and twigs just below the surface that provided prime egg laying sites.

Both Blue Ringtails and Red & Blue Damsels are species which will totally submerge when laying eggs, the female dragging the male below the surface as she works her way deeper and deeper down a submerged plant or twig.

Two pairs of ovipositing Blue Ringtails. The lower pair is completely submerged; the upper pair is still working its way down the substrate, while another male flies past.

But not all had a successful or happy ending!

This is the biggest massing of damselflies I’ve yet experienced. Which is interesting, because last season, the only Blue Ringtails I recorded were a couple of males at the local golf course dam in November and December. This year I’ve already seen them in reasonable numbers at Acton Beach on Lake Burley Griffin (deeper water), and the lower reaches of the Gudgenby River (admittedly at still water of the pondage created by a weir). It’ll be interesting to see if they tend to be an early season specialist. Or whether this year might be a good year for them whereas last year wasn’t – for whatever reason. I have no idea yet how much variability there might be from year to year.

Another thing that is intriguing me for the moment is the absence so far of any Blue Skimmers which are normally very common. Last year, I saw my first Blue Skimmer on 26 October and that was in the backyard so I wasn’t even looking for them. 

Like with nearly everything – the more you find out, the more questions arise to be answered. But then isn’t that the fun of it?