During the summer, I joined a team of 20 students to participate as a research assistant in a two week wildlife conservation expedition in Croatia. The trip was coordinated by Operation Wallacea, an organisation which partners students with biological research scientists, allowing surveys concerning endangered species to be carried out on a larger scale.
The first week was based in the Krka National Park to investigate populations of terrestrial species. I began by performing bird surveys, where mist nets were set at dawn to perform “mark and recapture” studies, so that the populations of avian species, including the sub-alpine warbler, could be estimated.
Following this, our group learned about mammal surveys. Ink tunnels were used to survey small rodents, where individuals walk through tubes with ink pads at the entrance and paper inside. This allows species to be identified by their footprints and has been used successfully to monitor dormouse populations in the UK. In addition, we inspected wooden poles soaked in valerian solution, designed to act as scratching posts, for hair from wild cats, as well as footage from camera traps.
Electrofishing was performed in the Krka Lake in order to catch invasive species that can then be weighed and measured. Regulations state that any invasive species caught, such as small mosquito fish, originally introduced to the lake to feed on the larvae of malaria-causing mosquitoes, must be euthanised. Following this, we dissected larger pumpkin seed fish to identify their diet; data are collated to analyse how the feeding patterns of invasive species may be affecting the food chain.
Our group then had the opportunity to explore two of the Migaka caves, where we observed horseshoe bats and common toads as well as many unpigmented, blind creatures, such as crickets and isopods, adapted to the zero light levels. Several parameters including temperature, pH, relative humidity and water conductivity were measured to compare pollution levels inside and outside the caves.
The final section of the terrestrial stage of the expedition focussed on herpetology. During the day, we released tortoises and terrapins back into the park, and checked aquatic traps for dice snakes. Back at the base, we took different measurements of previously caught tortoises; this is the first year these species are being studied in the national park, so data collected will provide a baseline for future studies into tortoise populations. Later, a night search for nocturnal creatures was conducted, where we identified the venomous nose horned viper and large numbers of green tree frogs.
At the end of the first week, the team took a ferry to Mljet Island where we were based for marine surveys on Adriatic ecology. After a training session, we were ready to perform snorkelling-based transect surveys into the size and distribution of a range of fish (for example, the Mediterranean rainbow and ornate wrasses) and sea urchin species. These data are important for understanding the interspecies relationships between herbivorous fish species, which compete with the sea urchins for algae, as well as the predator-prey status between carnivorous fish and urchins respectively. Furthermore, data can be compared between sites showing different levels of government protection status against fishing boats. The group also participated in boat surveys for marine mammals and seabirds.
Throughout the expedition, we received lectures on topics ranging from biodiversity to factors causing the decline in fish populations worldwide, such as overfishing, microplastics and invasive species. I thoroughly enjoyed this experience and would love to take part in projects like these in the future. Additionally, I enjoyed having the opportunity to meet like-minded people from across the world and am incredibly grateful for the Gateway funding that made my participation in this venture possible.