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

The first week of this two-week expedition is spent in the valley of the Krka National Park. At this site you will be working from dawn until late morning and then again in the late afternoon and evening helping a series of different research teams. During the heat of the midday period you will have a series of lectures about Balkans wildlife and conservation, and help with the follow on lab work from the various surveys and data input. The projects include estimating Hermann’s tortoise (Testudo hermanni) and European pond terrapin (Emys orbicularis) populations, completing standard herpetofauna search transects to look at niche separation in some extremely rare and important species of snake such as the venomous nose horned viper, Vipera ammodytes, and the leopard rat snake, Zamenis situla. The bird team will be concentrating on repeating point count surveys to look at changes in bird communities and to survey some of the semi-improved farmland which seems to be being utilised by species in decline in many other parts of Europe. Other teams will be determining the cricket and grasshopper species communities from meadow transects and the butterfly communities from standardised pollard counts. One of the more difficult groups to determine are the small mammals and a novel approach is being used on this survey to examine the contents of owl pellets for remains of small mammals and comparing these with the small mammal trapping surveys. Otter distribution is being studied throughout the whole 20km study stretch from boat-based surveys of otter spraint distribution and diet from analysis of the sprain contents. Surveys are also completed for both native and invasive fish using traps. Biodiversity surveys of some of the larger cave systems which are also home to the blind cave salamander, Proteus anguinus, are carried out by one of the teams. In addition, there are nocturnal surveys of cat snakes (Telescopus fallax), owl roost sites (to collect owl pellets), herpetofauna transect surveys and bats. In the second week, you will move to the beautiful and peaceful Silba Island. During this week if you are not dive trained you will complete a PADI Open Water dive training course. If you are already dive trained or would prefer to snorkel this week you can complete the Mediterranean ecology and survey techniques course, with two lectures and two practicals each day (either by diving or snorkelling). Alongside these training courses students can assist with some of the research projects, such as estimating and monitoring fish populations and seagrass 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
  • Opwall fee
  • Cost of international flights into and out of Split.
  • Cost of internal travel to and from the start and end point of the expedition, plus any hotels you might require. This costs around £102 or $143. Extra nights’ accommodation in Split costs around £66 or $96.
  • Dive equipment rental – £50 or $75 per week for a full dive kit. If you only wish to snorkel and want to hire snorkel equipment, the cost is £25 or $38 per week. Please note that wetsuits cannot be provided – you should bring your own.
  • Park entrance fees – £26 or $38
  • PADI manual and PIC card (if you are completing your Open Water qualification) – £69 or $87 approx.
  • Vaccinations and prophylactic medicines – cost can vary depending on your healthcare provider.
  • All prices in GBP or USD unless specified.

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
  • Silba
  • Krka National Park

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