Dragonflies & the Dry Final Report 2017

Dragonflies & the Dry

Citizen Science Project

Final Report 2017

Image of common gliders at East Point, May 2017 Photo credit: Marleen van Maastricht

Professor Jenny Davis School of Environment & RIEL Charles Darwin University

Summary • Charles Darwin University, Territory NRM and Identifly collaborated to run ‘Dragonflies and the Dry’, a citizen science project, from April to July 2017. • The Top End community submitted photographs of dragonflies and damselflies to the project using a web-based portal: https://identiflyapp.com/competition.html. • A monthly prize was awarded for the best photo ($500) and a random draw ($250). Participants could submit as many photos as they wished. Additional information included the date and location of the image. • A free app, Identifly - a guide to the dragonflies and damselflies of the Top End, was available to help participants identify the specimens photographed (although identification was not a condition of entry). • A total of 222 people participated in the project, with the submission of 2,265 images over the four months. • A total of 1,202 dragonflies representing 33 species and 268 damselflies representing 12 species (Table 3) were recorded across the Top End during the competition. • The largest number of participants and the largest number of images were recorded in April. Lower numbers were recorded in the following months, with the number of participants and images being highly correlated (R2 = 0.94). • Analysis of relative abundances revealed that high numbers of the common glider, Tramea loewii, the slender skimmer, Orthetrum sabina, the graphic flutterer, Rhyothemis graphiphtera, the coastal glider, Macrodiplax cora, and the common bluetail, Ischnura heterostica, did herald the end of the Wet season. In contrast, the painted grasshawk, Neurothemis stigmatizans, and the redtail, Ceriagrion aeruginosum, steadily increased in relative abundance from April to July. • The reason for the large number of gliders present at the end of the Dry season is not known. One possible explanation is the prevailing Top End winds, that switch from the northwest to the southeast in April, bring large numbers of emerging dragonflies from the extensive wetlands of the Adelaide, Mary and Alligator Rivers floodplains. These large dragonflies are highly visible whilst gliding on the thermal updrafts of the Darwin coastline. • The photographic quality of many of the images submitted to the project was exceptionally high. Images will be added (with permission) to the Identifly app. The images not only provide species records, they demonstrate the variability in colour that can exist between males and females of the same species and a range of behaviours and habitat use. • Conclusion: Do large numbers of dragonflies herald the arrival of the Dry season in the Top End? YES….... but only certain species, mainly the large- winged gliders, flutterers and emperors. Some species are always present, regardless of the season. 2

Acknowledgements

This project could not have been undertaken without the following support.

Territory NRM providing essential funding, with logistical support from Tida Nou.

The Identifly app team, James Friend and Dora Kojevnikov, administered the project and provided ongoing voluntary support.

Caroline Camilleri (Darwin Photographic Professionals) donated valuable expertise to the photographic competition and judging panel.

Danielle Choveaux, Charles Darwin University, mapped the location data.

The citizen scientists of the Top End of the Northern Territory (and beyond) who provided the outstanding images, across a wide variety of times, dates and locations, and who made this project possible.

The project received some great feedback:

I have only just realised the beautiful variety of dragonflies and damselflies we have in the Top End - quite amazing and the Identify App certainly helps us amateurs on the path to identifying the species we manage to capture through the lens.

….and some truly spectacular images!

Photo credits L-R: Gerald Enhrenbrandtner, David Webb, Deb Jovanovich

Introduction

Dragonflies, with their variety of colours, behaviours and incredible flying skills are eminently watchable. They are also a distinctive part of the tropical biodiversity that distinguishes Darwin from all other Australian capital cities. Top Enders will tell you that the appearance of large numbers of dragonflies heralds the end of the Wet season. However, we have little scientific data to support this theory. The aim of this citizen project was to collect information on dragonflies and damselflies with the help of Top End residents and tourists through a photo competition that anyone with a camera or smart device could participate in. This information would help us understand how dragonfly and damselfly numbers change from the Wet to the Dry. It would also provide information on the location of dragonfly and damselfly ‘hotspots’.

Methods

The Top End community was asked to photograph dragonflies and damselflies through the months of April, May, June and July and submit the images to the competition using a form available on the Identifly – Dragonflies and Damselflies of the Top End website https://identiflyapp.com/competition.html.

In addition to the image, which provided a visual record of the dragonfly or damselfly, participants were asked to provide the location where the photo was taken and the date. Participants were advised that they could use the recently released Identifly app to name their dragonfly or damselfly, but it was not essential. The request for information was kept to a minimum to ensure that the submission process did not become a barrier to participation. A monthly prize for the best photo ($500) and one for an entry drawn at random from the submitted photos ($250) was provided to act as an incentive to participation. Participants could provide as many photos as they wished.

A free app, 'Identifly - a guide to the dragonflies and damselflies of the Top End', was available to help participants identify the specimens photographed (although identification was not a condition of entry). The app was produced by James Friend and Dora Kojevnikov and based on an unpublished guide produced by Jenny Davis, John Hawking and others.

The competition and project was launched with a community event at the George Brown Botanic Gardens on Saturday, March 25, from 9-11am. The flyer advertising the event is provided in the Appendix. The competition was advertised through local media. Channel 9 provided video coverage of the event on the nightly news on March 25. ABC radio broadcast an interview with Jenny Davis on the morning of the event. The project and competition was advertised on Facebook on the Territory NRM page, https://www.facebook.com/TerritoryNRM and the Identifly app page, facebook.com/IdentiflyApp/. Regular updates and winners were announced on the FB pages. Jenny Davis used her Twitter account (@waterpenny10) to advertise the project and provide updates.

A panel was assembled, comprising Tida Nou (Territory NRM), Caroline Camilleri (Darwin Photographic Professionals) and Jenny Davis (CDU) to judge the winning image for each month. Dora Kojevnikov, from Identifly, selected the random draw each month (using a random number generator) and administered the prize notifications and payments.

Results

Citizen Science Participation

A total of 222 people participated in the project, with the submission of 2,265 images over the four months. The number of participants and number of images submitted in each month are given in Table 1.

Table 1 The number of people who submitted images in each month of the competition, the number of images submitted in each month and the number of unique images used in the analyses

Month Participants Images Unique Images April 131 700 615 May 74 549 449 June 43 412 245 July 35 604 152

Often multiple images of the same specimen were submitted to the photo competition. These were useful because, in addition to providing occurrence records they provided information on the behaviour and habitat use of selected species. However, for the purpose of analysing the change in numbers over time only unique images were used. Removal of multiple images resulted in a working set of 1,461 images.

The largest numbers of dragonflies and damselflies were recorded in April but the number of citizen scientists submitting images in this month was also the highest. The number of participants and the number of dragonflies declined each month from April to July (Fig. 1). The number of images was highly correlated with the number of citizen scientists (R² = 0.94).

700 April y = 4.6197x + 38.407 R² = 0.93877 600

May 500

400

June 300

July 200 No. of images submitted

100

0 140 120 100 80 60 40 20 0

No. of participants in each month

Fig. 1 Change in the number of participants and images submitted from April to July, 2017

Change in Dragonfly and Damselfly Numbers over Time

A total of 33 dragonflies (Table 2) and12 damselflies (Table 3) were recorded across the Top End during the competition. At the start of the competition the aptly named common glider, Tramea loewii, dominated the dragonfly images. The equally aptly named common bluetail, Ischnura heterosticta, dominated the damselfly images. Given that we could not ascertain whether more citizen scientists recorded images in April than July because more dragonflies were present, or because there had been greater publicity for the project in this month, we analysed the change in numbers over time by considering relative abundances (Figs 2 & 3). The common glider, Tramea loewii occurred in the highest relative abundance (30%) in April but had declined to only 5% of the records by July (Fig. 2). The slender skimmer, Orthetrum sabina, was relatively highly abundant in the first three months but was not recorded at all in July. The graphic flutterer, Rhyothemis graphiphtera, was more abundant in April and May than June and July. The coastal glider, Macrodiplax cora, also declined over the four months. In contrast to these species, the painted grasshawk, Neurothemis stigmatizans, steadily increased in relative abundance from April to July.

The relative abundance of the common bluetail, Ischnura heterosticta, declined markedly by July whilst the redtail, Ceriagrion aeruginosum, increased markedly.

Table 2 Numbers of dragonflies recorded from April to July 2017

Common Name Scientific Name April May June July Total Common glider Tramea loewii 171 81 15 6 273 Wandering percher Diplacodes bipunctata 35 49 28 10 122 Slender skimmer Orthetrum sabina 56 37 19 0 112 Graphic flutterer Rhyothemis graphiptera 52 34 7 6 99 Painted grasshawk F Neurothemis stigmatizans 18 36 25 15 94 Chalky percher Diplacodes trivialis 35 22 15 7 79 Painted grasshawk M Neurothemis stigmatizans 22 25 16 14 77 Coastal glider Macrodiplax cora 40 17 10 1 68 Australasian slimwing Lathrecista asiatica festa 12 8 26 21 67 Palemouth Brachydiplax denticauda 14 16 7 2 39 Australian tiger Ictinogomphus australis 26 4 1 1 32 Green emperor Anax gibbosulus 7 8 5 0 20 Scarlet percher Diplacodes haematodes 1 7 2 4 14 Red swampdragon Agrionptera insignis allogenes 8 4 1 0 13 Rosy skimmer Orthetrum migratum 3 6 1 0 10 Fiery skimmer Orthetrum villosottatum 4 3 3 0 10 Archtail Nannophlebia risi 5 2 2 0 9 Black-headed skimmer Crocothemis nigrifrons 5 4 0 0 9 Blue skimmer Orthetrum caledonicum 1 4 1 2 8 Lesser duskhawker Gynacantha dobsoni 3 0 1 3 7 Global wanderer Pantala flavescens 5 0 0 1 6 Pygmy percher Nannodiplax rubra 2 4 0 0 6 L-spot basker Aethriamanta nymphaeae 2 2 0 1 5 Yellow-barred flutter Rhyothemis phyllis 2 1 0 1 4 Coral tailed cloudwing Tholymis tillargia 1 1 2 0 4 Green skimmer Orthetrum serapia 1 3 0 0 4 Water prince Hydrobasileus brevistylus 2 1 0 0 3 Australian emperor Hemianax papuensis 1 1 0 0 2 Tau emerald Hemicordulia tau 1 0 1 0 2 Black-tipped percher Diplacodes nebulosa 1 0 0 1 Short -tailed dusk darter Zyxomma elgneri 1 0 0 1 Australian duskhawker Austrogynacantha heterogena 1 0 0 0 1 Forestwatcher Huonia melvillensis 1 0 0 1 Total 536 383 188 95 1202

Change in Relative Abundance

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% % April % May %June %July

Tramea loewii Orthetrum sabina Rhyothemis graphiptera

Macrodiplax cora Neurothemis stigmatizans F+M Other

Diplacodes bipunctata Diplacodes trivialis Ictinogomphus australis

Brachydiplax denticauda Lathrecista asiatica festa Agrionptera insignis allogenes

Anax gibbosulus Diplacodes haematodes

Fig. 2 Change in the relative abundance of dragonflies (Anisoptera) from April to July, 2017. Note that Other includes the sum of all species with an abundance of <1%.

Table 3 Numbers of damselflies recorded from April to July 2017

Common Name Species Name April May June July Total Common bluetail Ischnura heterosticta 74 45 42 5 166 Redtail Ceriagrion aeruginosum 2 13 14 51 80 Northern billabongfly Austroagrion exclamationis 1 7 0 1 9 Dusky river damsel Pseudagrion jedda 0 1 2 0 3 Eastern billabongfly Austragrion watsoni 1 0 1 0 2 Red-tipped shadefly Argiocnemisrubescens 0 0 2 0 2 Aurora bluetail Ischnura aurora 0 1 0 0 1 Black-winged threadtail Nososticta baroalba 1 0 0 0 1 Citrine threadtail Nososticta koongara 0 0 0 1 1 Pigmy wisp Agriocnemis pygmaea 0 1 0 0 1 Northern threadtail Nosoticta fraterna 0 1 0 0 1 Citrine-headed river damsel Pseudagrion lucifer 0 0 1 0 1 Total 79 69 62 58 268

Change in Relative Abundance

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% % April %May %June %July

Ischnura heterosticta Ischnura aurora Ceriagrion aeruginosum

Austroagrion exclamationis Austragrion watsoni Nososticta baroalba

Nososticta koongara Agriocnemis pygmaea Nosoticta fraterna

Pseudagrion jedda Pseudagrion lucifer Argiocnemisrubescens

Fig. 3 Change in the relative abundance of damselflies (Zygoptera) from April to July, 2017

Discussion

This project has provided the first quantitative dataset on the change in dragonfly and damselfly numbers from the transition of the Top End wet season to dry season. The information provided by citizen scientists across the Top End, from Wadeye to Elcho Island, indicated that the visible presence of large numbers of dragonflies do herald the end of the Wet season. However, not all species of dragonflies are equal in this respect. It is the large gliding species, the common glider, Tramea loewii and the coastal glider, Macrodiplax cora, and the graphic flutterer, Rhyothemis graphiptera, that formed large and very visible flocks, particularly near the coast. These species often conveniently rested on a wide variety of perches (spear grass, pandanus, fishing rods, barbed wire fences), which facilitated close up photography. In contrast, some species, such as the large and fast flying green emperor, Anax gibbosulus, also appeared to occur in large numbers (personal observation) at this time but were very difficult to photograph because they rarely stopped flying.

In contrast to the gliders, flutterers and green emperors, other species, such as the painted grasshawk, Neurothemis stigmatizans, which usually stay close to vegetation, became more dominant as the months progressed. The numbers of some species, such as the palemouth, Brachydiplax denticauda, wandering percher, Diplacodes bipunctata and the chalky percher, Diplacodes trivialis, (all small but relatively easy to photograph because of their perching habit) appeared to remain relatively constant over the four months.

It is likely that our competition underestimated the numbers of damselflies present over the same timeperiod because they are so much smaller and harder to photograph. However, the records submitted clearly indicated a change in dominance, from common bluetails, Ischnura heterosticta, to redtails, Ceriagrion aeruginosum.

We do not understand the actual mechanism by which the large flocks of gliders and flutterers appear towards the end of the Wet season. All species spend up to a year or more as aquatic larvae in the freshwater wetlands and rivers of the Top End. It is possible that as these larvae emerge from these waterbodies they are swept towards Darwin and the Top End coastlines by the prevailing winds. A compilation of wind direction data (wind roses) compiled by the Bureau of Meteorology over the period Jan 1942 to 30 Sep 2010 (Fig. 4) reveals that a change in prevailing winds from the northwest to the south east that starts in April. It is possible that these winds bring large numbers of emerging dragonflies from the extensive wetlands, including the Adelaide, Mary and Alligator River floodplains, located to the east of Darwin. The large-winged species, in particular, appear to glide on the thermal updrafts of the Darwin coastline. However, this is one possible hypothesis. We will not know the true mechanism until it is possible to track individual dragonflies from their sites of larval emergence to adult habitats.

Fig. 4 Monthly roses indicating average wind direction vs wind speed (km/hr) in Darwin over the 12 month period, January to December. The data was compiled from weather observations over 68 years (01 Jan 1942 to 30 Sep 2010).

The photographic quality of images submitted to the project was exceptionally high. The monthly winners are illustrated in the following pages. High quality images will be added (with permission) to the Identifly app. The images not only provide species records, they demonstrate the variability in colour that can exist between males and females of the same species and a range of behaviours and habitat use.

April winner: Sid Mitchell Australasian slimwing, Lathrecista asiatica festa.

April Best Damsefly: Janis Otto Common Bluetail Male, Ischnura heterosticta 12

May Winner: David Webb Slender skimmer, Orthetrum sabina. Location: Groote Eylandt. A great image of metamorphosis - the beautiful dragonfly emerging from the dull brown larva.

June Winner: Gerald Ehrenbrandtner Graphic flutterer, Rhyothemis graphiptera 13

July Winner: Janis Otto Redtail, Ceriagrion aeruginosum

Lessons Learnt

This is the first time that a citizen science project of this type has been undertaken in the Northern Territory. Although the project started with a public event and good media coverage we had little publicity in the following months. It seems likely that the decrease in the number of participants after the first month (April) could be attributed to lack of awareness of the ongoing nature of the project. More publicity sessions held at regular intervals would have been helpful. There also be appeared to be more scope for involving scout groups, schools and community groups in various ways. It would also be helpful to develop greater engagement with Indigenous communities. Remote communities could contribute very valuable records from understudied locations.

Conclusions

Do large numbers of dragonflies herald the arrival of the Dry season in the Top End?

YES… but only certain species, mainly the large-winged gliders, flutterers and emperors. Some species are always present, regardless of the season.

Coastal gliders at Fannie Bay, May 2017 Photo credit: Krystle Keller