Biodiversity Expedition across Croatia

This is a write-up by James Dunne from his biodiversity expedition across Croatia with Operation Wallacea. 

Between Thursday, 22nd July and Wednesday, 4th August 2021, I participated in a terrestrial and marine biodiversity expedition across Croatia with Operation Wallacea (Opwall).

Thursday, 22nd July 2021, 07:00 am. An early start as far as summer holiday sleep schedules go. Having packed the evening before, I managed to get myself out of the flat surprisingly quickly before slumping onto the tube to Heathrow terminal 5. The flight itself only lasted around two hours, and before I knew it, we were landing in the beautiful city of Split. The airport was small but cosy, with only one baggage conveyor painfully squeaking, a sound that echoed throughout the relatively empty hall. Immediately after collecting my suitcase, I was met by the terrestrial site operations manager, who pointed me towards a group of several other students waiting just outside. The wall of heat hit me as the automatic doors parted. I glanced at my phone. 36*C! Thankfully, I was whisked out of the direct sunlight and onto a small minibus filled with students. 

The city was quickly behind us as the bus began to snake deep into the Dinaric Alps. The Croatian countryside was desolate, sprinkled with abandoned houses, acting as a sobering reminder of the damaging conflicts of the 1990s. An abandoned railway track meandered alongside the perilous road, darting in and out of sight as it slowly tapered off into the distance. The lack of urbanisation made for some remarkable scenery, and I was almost disappointed when the journey ended several hours later. I say ‘almost’ as I previously neglected to mention the claustrophobic conditions of a minibus packed with students and their luggage (not to mention the erratic air-conditioning).

Upon arrival, we were given an introductory lecture and safety briefing before being shown to our rooms. The bedroom was compacted, with precarious bunk beds planted against each of the three available walls. The students in my room instantly noticed the curtain situation (or lack of) as the daylight poured into the room, leaving me fearing for some very early wakeups over the coming weeks. I clambered awkwardly up the metal frame of my bunk, stooping my head to avoid the ceiling. Upon reaching the summit, I found that the mattress had been substituted for a thin foam mat (which offered little mercy to the metal bars that it rested upon). Aside from the network of beds and our luggage (which had already begun to spew across the floor) the room was relatively empty. We decided to venture out in the hope of locating a fan, and to our delight, we managed to secure one of the few dotted around the building.

The evening meal arrived in two large boxes (divided into vegetarian and carnivorous options), and to say the food quality was basic would be an understatement. I hadn’t been expecting much given our whereabouts, but this was an eye-opening experience that we really must not take quality food for granted. It was also our only option, as the nearest village with a shop was located about a 20-minute drive away and there was no leaving the site without a vehicle unless travelling in a group with supervision due to the nature of the mountain landscape. 

I was heading to bed when the disastrous news came in. My heart sank as I read the notice. “Group 1 – Bird survey – 04:30 am”…

Friday, 23rd July 2021 – 03:52 am. After a sweltering night, I rolled out of bed to prepare for our 4:30 am departure. The project’s main concern was “standardised monitoring locations for bird mist-netting in a range of habitats”. Fortunately, we were surveying on transect two that morning (just a 15-minute walk from the house) so for the researchers, this was considered a lay-in. As you can probably tell by now, I am not a morning person. But as soon as we left the building, the refreshing night breeze woke me up considerably. The faint orange brilliance of dawn slowly emerging behind the mountains was a sight I was thankful to be awake for. Our group throughout the trip consisted of around six students and two researchers (who were gathering data for their PhDs). The mist-netting survey lasted for six hours, and disappointingly, we only managed to catch one bird not found in the UK – the Western Subalpine Warbler (Curruca iberiae). Alongside this, we captured and documented one Blackbird (Turdus merula), one Blue Tit (Cyanistes caeruleus), and six Great Tits (Parus major), which proved to be the highest yield from transect two since the researcher’s arrival some four weeks prior. It was mesmerising to watch the researchers delicately handle the birds while measuring, weighing, and tagging them before releasing them back into the wild. Probably the greatest part about the entire trip was this ‘hands-on’ approach that we experienced, as we assisted with handling and documenting organisms throughout the expedition. During my first morning, I also had my first encounters with many European insects, including Rose Chafer Beetles (Cetonia aurata), Stag Beetles (Lucanus cervus), Praying Mantis’ (Mantis religiosa), and Longhorn Beetles (Cerambycidae). Returning to the house at around 11:30 am, I immediately collapsed into bed (ignoring the daylight) to take advantage of the designated siesta period during the midday heat. The days were well-structured, with lunch lasting from 13:00-13:30 and followed by an hour of lectures commencing at 14:00. The lecture on the first day was regarding the “Geography and History of Krka”, which went into significant detail about the geographical complexity of the region since the days of the Ottoman Empire. In the afternoon, my group was tasked to assist in a “Habitat Survey” on transect six. This involved mapping out plots of 10 m^2 and measuring the flora height, variety, and density across the area. The data collected is then used to supplement the research of fauna in the region and provide accurate updates of any potential habitat change or loss over time.

Saturday, 24th July 2021 – 09:30 am. On the second morning, I was treated to the only ‘lie-in’ of the trip as we began our day with Lepidoptera surveying and netting. The butterflies were identified and counted by species (with any unidentifiable organisms being ‘pinned’ for later examination). There was a lack of diversity among the butterflies in the area we were surveying, with the ironically named Scarce Swallowtail (Iphiclides podalirius) being extremely abundant. We also managed to survey Commas (Polygonia c-album), Large Whites (Pieris brassicae), and Small Whites (Pieris rapae). The 2 pm lectures on Saturday discussed the birds of Europe, specifically, species found in the Krka National Park and the great variety of species not seen in the UK. From 16:00-18:00, I took part in a Chiroptera workshop, which consisted of several lectures regarding research and survey techniques (including an introduction to echolocation software) before our bat mist-netting attempt later that evening. After dinner, I was fortunate enough to witness the documenting and marking of two Eastern Montpelier Snakes (Malpolon insignitus) that had been caught by the herpetology team. The ‘marking’ involved a delicate procedure, whereby several scales were clipped to leave a visible patch, allowing researchers to distinguish between previously documented and new snakes. I then assisted in setting up a mist net outside the house and watched in awe as the resident bats emerged from the rafters. Although no bats were caught, we managed to utilise the ‘bat detector’ echolocation technology to identify their calls (documenting both Myotis nattereri and Myotis myotis species). We were also privileged enough to see them feeding underneath dimly lit streetlights, while we attempted to make the distinction between their echolocation and social calls.

Sunday, 25th July 2021 – 06:30 am. By the third morning, I had begun to adjust to the non-existent sleep schedule. Although shattered, I found myself looking forward to waking up the next day and heading back out into the field. After just six hours of sleep, we took a short drive down to the edge of a cliff, where we made our way cautiously down a narrow, steep pathway that led down to the valley floor. It took about 15 minutes before we arrived at our destination, which turned out to be a small, dark opening. Strapping on my head torch and leaving my rucksack behind me, I crawled into the entrance. The cave was littered with a wide variety of spiders, toads, grasshoppers, and cave crickets (Rhaphidophoridae). We did not travel particularly deep into the cave, but the experience remained rewarding and provided valuable insight into the lives of these organisms. The subsequent week, the research team located an Olm (Proteus anguinus), an aquatic salamander found in caves across Slovenia and Croatia. The Olm is currently regarded as “vulnerable to extinction” and there are estimated to be only just over 400 olms left in the world. Their deep cave dwellings make them incredibly difficult to locate, making a sighting particularly special. Our early afternoon lecture was on “Herpetology” (a branch of zoology concerned with the study of amphibians and reptiles) which was particularly captivating.

Later that same day, we went on a herpetofauna survey walk around the grounds of the Krka Monastery (which is undoubtedly one of the most beautiful places I have visited) to continue gathering data. We managed to stumble across a Hermann’s Tortoise (Testudo hermanni) alongside many Dalmatian Wall Lizards (Podarcis melisellensis), Blue-throated Keeled Lizards (Algyroides nigropunctatus), and Italian Wall Lizards (Podarcis sicula).

Monday, 26th July 2021 – 07:30 am. My day began with another picturesque herpetology walk, this time down to transect five located deep in the valley. This transect was not ideal for data collection but did support a fair share of toads and Podarcis melisellensis. Getting back up out of the valley (especially as the heat began to set in) proved challenging, but we were rewarded with astounding views at the end, making it worthwhile. The lecture on Monday afternoon was delivered by the Chiroptera specialist regarding her research and paper on “The impacts of urbanisation on bat species”. The talk was interesting and detailed, outlining various survey techniques and data gathered from both Krka National Park and regions of the midlands in the UK. Later, I ventured off on an optional group walk through the waterfalls of the national park.

However, the path we took (like most others on the trip) was far from the beaten track, leading to some outstanding views. At the base of one of the waterfalls, the herpetology specialist managed to catch a small female Dice Snake (Natrix tessellata) which we were able to hold before releasing her back into the water (the snake was not documented as the walk was not officially for research and would therefore be introducing inconsistent data). After dinner, we had another hour lecture on the Mammalia found in Europe, with particular emphasis on the Krka region. Finally, at 22:00, I participated in another optional walk – this time focusing on herpetology. We stumbled across a wide array of spiders, with their reflective eyes glistening on almost every patch of grass. We also managed to find several mantis’ and scorpions; however, the highlight of the walk was a Glass Lizard (Pseudopus apodus) also known as the ‘European legless lizard’. I found this particularly interesting as (although dead) a glass lizard is a relatively rare sighting. We rounded off the walk at around 23:00 before dispersing to our rooms for tomorrow, I had a very early start.

Tuesday, 27th July 2021 – 03:30 am. Yes, you read that correctly. Barely four hours of sleep later, I was up again working. By this point, I had grown used to the tiredness and felt relatively sprightly as we began our morning walk.

This time we were on the furthest possible transect that morning, transect three, which took an hour to get to. The walk was brutal, navigating uneven surfaces and scattered rocks in pitch black. Solely reliant on my head torch, we ventured on into the distance, until at 04:30 am, we stopped to collect ourselves and take a break before beginning the point count survey. This day was possibly my favourite of the entire trip; seeing the sunrise over the mountains while sitting in silence listening to the songs of birds was a truly breathtaking experience. We were fortunate to document many birds as we learned their calls and estimated their distance, such as the Common Kingfisher (Alcedo atthis), Eurasian Jay (Garrulus glandarius), Common Buzzard (Buteo buteo), Common Kestrel (Falco tinnunculus), Red-Backed Shrike (Lanius collurio), Common Chaffinch (Fringilla coelebs), and Eurasian Blackcap (Sylvia atricapilla). The point count was based on acoustic and visual surveys, with all data collected being used to assist the researchers.

Returning to the house around 08:00, I crashed onto my bunk, exhausted. Our daily lecture was on Insecta and delivered by the Lepidopterist. I rested for a period of the afternoon as I had managed to secure a limited place on a Chiroptera mist-netting survey later that evening. Over a period of three hours, we caught eight bats (including Myotis nattereri, Pipistrellus kuhlii, and Hypsugo savii), and I assisted in measuring, photographing, and documenting the individuals before releasing them back into the wild. I also assisted in collecting bat flies (from the Nycteribiidae family) with the master student to see which ecological and individual traits influence the frequency of bat flies.

Wednesday, 28th July 2021 – 08:30 am. On the last day at the terrestrial site, we visited a tourist hotspot in Krka National Park called Roski Slap. This was designated as a day to recharge and enjoy the landscape before travelling to the marine site. I went swimming in the valley and hiked around the mountains of the national park before enjoying an evening meal at the local restaurant.

Thursday, 29th July 2021 – The journey to Silba Island from the terrestrial site was relatively lengthy. After spending a few hours in the car and some more on the ferry, we were greeted by several members of the marine team as soon as we disembarked the ferry. Upon our arrival at the house (which was slightly more in touch with modern society), we received an introductory lecture on the Mediterranean and Adriatic, which included medical and safety advice. There were five boys in the room I was staying in, which was conveniently equipped with an en-suite bathroom. The bunk beds remained very compacted, but the room was not where I spent most of my time.

Friday, 30th July 2021 – 08:00 am. We began the day with an hour-long lecture on “Sea urchin methodology”. The talk outlined the variety of sea urchin species in the region and surveying techniques. The predominant species of sea urchin in the region are Purple Sea Urchin (Paracentrotus lividus), Black Sea Urchin (Arbacia lixula), and the Violet Sea Urchin (Sphaerechinus granularis). I was unable to scuba dive as planned due to an injury that I sustained on my shoulder before the trip. Fortunately, I managed to snorkel throughout my time at the marine site, which proved to be an insightful and rewarding experience. Immediately after the lecture, we ventured down to the water to assist with a sea urchin survey, monitoring their movement, density, and habitat change regarding the impact on sea urchin populations. The water was warm and clear, making the conditions ideal for surveying marine organisms. We then had a lecture regarding fish methodology and survey techniques in the Mediterranean. Similar to the format in the morning, we again took to the water shortly after the talk, this time focusing on Sea Breams (namely Diplodus annularis, Diplodus vulgaris, Diplodus puntazzo, and Diplodus sargus). On the evening of the 30th, I went out to celebrate my birthday with dinner in the main hub of the island.

Saturday, 31st July 2021 – 08:00 am. Saturday started with another fish survey, monitoring the habitat change (distinguishing between barren, algae, and seagrass (Posidonia oceanica)) alongside the number of schools of Sea Breams. The period between the morning snorkel and lunch (from around 11:30-13:00) was designated for reading through research papers and preparing a presentation to deliver to the rest of the group at the end of the week. Free time throughout the week was given to this project, along with familiarising yourself with other research papers, both in their content and their format. The research paper I received was titled “Ecological effects of full and partial protection in the crowded Mediterranean Sea: A regional meta-analysis” and discussed the impacts and difficulties of implementing Marine Protected Areas (MPAs). In the afternoon, I participated in another fish and habitat survey snorkel, this time taking a boat to the other side of Silba Island to gain accurate data for the entire circumference. In the evening, we had a lecture on Lionfish research from a PhD student who had been gathering data from Opwall’s marine site in Honduras.

Sunday, 1st August 2021 – 09:30 am. This morning we participated in a shore clean-up for several hours. All members took part and, between us, we managed to collect a disturbing amount of rubbish and general waste. That afternoon we went for another fish mapping research survey near where we were based, again focusing on Sea Breams in particular. I then devoted more time to the MPA research papers before our lecture on “Biodiversity and factors affecting ecosystem health”.

Monday, 2nd August 2021 – 10:00 am. The day commenced with another clean-up, this time of the main pier area on Silba island in the small boat harbour. The water was murky and swamped with litter, leading to some undesirable circumstances that I will not go into further detail on. Between the group, we managed to collect several bags of various rubbish, which was then deposited in the correct location. We spent the rest of the morning focusing on a variety of research papers. Later in the day, I participated in a “Marine ID Workshop” in which we closely examined samples sourced from the morning. These included Arbacia lixula, Sphaerechinus granularis, Sea Cucumber (Holothuria), and Red Starfish (Echinaster sepositus). The Marine ID Workshop was particularly fascinating, as it allowed us to witness (and handle in some cases) the marine organisms that we had been surveying. The evening lecture was entitled “Fish Mapping and MPAs”, which fittingly complemented my interest in the research papers on this topic. 

Tuesday, 3rd August 2021 – 08:00. On my last day at the marine site, we had no official work to assist with. In the morning, we hiked to a more desolate part of the island for a recreational snorkel session, in which we found a young Common Octopus (Octopus vulgaris). For the rest of the day, I took the opportunity to explore the range of research papers on offer, including: “Biological effects within no-take marine reserves: a global synthesis”, “Climate change and Mediterranean seagrass meadows: a synopsis for environmental managers”, and “Large-scale Assessment of Mediterranean Marine Protected Areas Effects on Fish Assemblages”. Finally, in the early evening, my group delivered a series of presentations to the rest of the camp on a topic of our choice, which in my case was “Marine Protected Areas”. 

Wednesday, 4th August 2021 – 05:30. I caught the morning ferry back to the mainland and was transported to Split Airport by Opwall. I slept for almost all of the journey to London. My expedition was over.