• Overview
  • Objectives
  • Skills you gain
  • Costs to Consider
  • Site Conditions

This expedition combines both of these important areas with a week working in the spectacular Krka National Park and a second week on Silba Island.

During glacial times the main biodiversity refuges of Europe were the Iberian, Apennine and Balkans peninsulas which managed to conserve tropical elements of the flora and fauna. For example the nocturnal Cat Snake, which is closely related to other tropical species, is still found in the Balkans. The most important biodiversity elements of the present day Balkan region are the short but very large river valleys through the karst limestone areas and the biogeography of the numerous Adriatic islands.

Week 1: Krka National Park

During this first week the groups will spend a day each working on the following projects:

Fish surveys – this will be done from boat and foot based electrofishing surveys and netting surveys of various habitats along the Krka River. There are a number of endemic species including two endemic trout species (Salmo visovacensis and Salmo obtusirostris krkensi) that are being investigated. All fish captured will be identified, measured and genetic samples taken.

Reptile surveys – these surveys are performed from checking under previously placed cover boards and completing standard search times in different habitats and heights in the valley. The Park authorities are keen to determine how the Four lined snake (Elaphe quatuorlineata) which grows to 2.5m, the venomous Nose horned Viper (Vipera ammodytes) and the Leopard Rat Snake (Zamenis situla) separate their niches. In addition the surveys will be recording the distribution of the giant Glass Lizard (Pseudopus apodus), which grows to a length of 1.2m and tortoises (Testudo hermanni). Night surveys are also done for the Cat Snake (Telescopus fallax) which is the only nocturnally active snake species in the region.

Cave surveys – these surveys will be led by cave biology specialists in caves not open to the public and will involve completing transects and quadrats within the cave systems to estimate diversity of groups adapted to cave living. In addition soil samples from different parts of the cave system will be sorted in the lab to estimate soil biodiversity.

Bird and butterfly surveys – these surveys will involve setting mist nets from 6am to 12 noon at different heights in the valley. In addition point count surveys will be completed either side of the mist net from 7am to 9am each day. Target species for the birds include the Natura 2000 important bird species. After lunch the group will complete pollard surveys for the butterflies.

Mammal surveys – the large mammal species are surveyed using camera traps and searching areas for footprints and faecal samples. Within the Krka valley and surrounding plateau there are 2 large wolf packs and these appear to be reducing the jackal and fox populations. In addition to emptying the camera traps and analyzing the footage these teams will also be setting and emptying small mammal traps and in particular looking for the endemic vole (Dinaromys bogdanovi) found in the Dinaric mountains.

In addition to the fieldwork, the group will have a series of lectures covering Mediterranean Wildlife Ecology and Conservation and including presentations on freshwater fish speciation and survey techniques, reptile communities and niche overlap, apex predators and food webs in Mediterranean mammal communities, cave biodiversity, bird communities of the Mediterranean and threats to Mediterranean fauna and conservation initiatives. There will also be a seminar session on how to pursue a career in wildlife conservation.

Week 2: Silba Island

During their time on Silba Island, students will complete one of the following options:

PADI Open Water dive training course: This course involves a combination of theory lessons, confined water dives and open water dives to gain an official scuba diving qualification.

Adriatic ecology course: Lectures cover topics such as Mediterranean fish and survey techniques, management of Mediterranean fisheries, the ecology and survey techniques for seagrass beds, invasive species and conservation in action – examples from the Mediterranean. Each lecture is accompanied by an in-water practical (diving or snorkelling).

Students will also participate in the following activities:

  • Helping with surveys and analysis of data from stereo video monitoring
  • Transect surveys to monitor tortoise populations in the Park
  • Assisting with seagrass monitoring surveys

Croatia Research Objectives

Krka National Park

The Krka Valley runs from the Dinaric mountains bordering Bosnia to the Adriatic and is only 60km in length. However, since the river runs through limestone there are some spectacular gorges and this is one of the most scenic river valleys in Europe. It is also important from a biodiversity viewpoint containing 20 endemic fish species and spectacular cave systems containing a number of potentially new species to science.

Tourism in the Krka Valley is concentrated in the lower end of the valley and few people visit the central and northern parts of the valley. The Krka National Park authorities have built a research centre and museum in a remote part of the valley, in an attempt to attract more visitors away from the tourist hotspots. This project is working with scientists to provide data on the status of the endemic fish species, describing the cave fauna, examining how so many species of snake are separating their niches in the valley and assessing the impact of wolves moving down the valley and on the surrounding plateaus on the native jackal and fox populations. All these data are being fed back to the Krka valley research centre and the Park authorities hope to use this initial work as a way of attracting additional international researchers to the valley.

Silba Island is in the northern Dalmation archipelago and is a car and hotel free island. The island markets itself as a haven of tranquillity and much of the island is still covered by Mediterranean black oak and maquis. The objective of our partners on this island is to map the marine biodiversity around the island and particularly on the rocky reef islets which are currently protected for their breeding bird colonies, but which have no protection for their fish or seagrass communities.

Silba Island

Silba is a small island with no cars or hotels and is currently protected, along with the neighbouring Islets of Grebena, under the Natura 2000 scheme. This is because it has the largest breeding cology of sea cormorants in the Adriatic. However there is currently no protection for the fish and seagrass communities. The seagrass surrounding the island, Posidonia ocieanica (endemic to the Mediterranean), supports high levels of biodiversity and acts as an important nursery for juvenile fish. The increasing numbers of tourists visiting the island, along with the island’s growing population, is beginning to put pressure on Silba’s natural resources (through increased pollution, litter, and land use changes). At present there is no consistent monitoring of the wildlife in the area and Operation Wallacea is therefore involved in establishing a long-term monitoring programme to accurately record the current state and changes in the biodiversity on an around Silba. This information can then be used to inform future decisions and policy making in the area.


  • Attend lectures/workshops on biodiversity and conservation
  • Learn about the biogeography of the Dinaric karst and mountains
  • Explore unique cave flora and fauna
  • Learn many different survey methods for freshwater fish, birds, snakes and mammals
  • PADI Open water dive qualification
  • Participate in Adriatic ecology course
  • Help in estimating the health of sea grass
  • Help in establishing No-take zones for fishing
  • Learn to estimate population of endemic and endangered Nobel shell
  • Learn to adopt to team work and experience its importance
  • Immerse yourself in beauty of 2 national parks


The costs of a school group expedition can be highly variable. There is a standard fee paid to Opwall for all expeditions but the location you are flying from, the size of your group, and how you wish to pay all impact the overall cost.

You can choose to book the expedition as a package (which includes your international flights) or you can organise your travel yourself and just pay us for the expedition related elements.

If you are booking your expedition as a package, you also have the option of being invoiced as a group, or on an individual basis.

Croatia is hot during this time of the year! In both Krka and Silba the daytime temperature rarely drops below 30 degrees and can reach 40 degrees.

Fitness level required
Moderate. Whilst there are not many steep hikes in the forest, the hikes are still quite long and the temperature can make them tiring.

Creature comforts
At Krka we are in a renovated house in the countryside. You will sleep in dormitories with shared western style bathrooms and toilets, and in Silba it will be in dormitories, again with shared bathroom facilities. There is some limited phone signal in Krka (but not reliable for a data connection), but good phone signal in Silba.


  • Croatia
  • Krka National Park
  • Silba

Want to get involved with this project?


Want to get involved with this project?

Wallace House, Old Bolingbroke, Spilsby, Lincolnshire PE23 4EX, UK
| +44 (0) 1790 763194 | info@opwall.com