OTTER SURVEY OF THE ISLAND OF CORFU 2021

The island provides a diversity of wetland and coastal habitats. The majority of the rivers are relatively small, with any permanent water of significant depth nearer to the estuaries. Many upland reaches are ephemeral streams, often completely dry by mid-summer and only becoming temporary torrents following heavy rainfall. There are also four significant wetlands linked to coastal areas, all designated as Natura 2000 sites: Antiniotissa, Chalkiopoulou, Lake Korisson and the Alikes Wetland. The coastal peninsula from Kassiopi in the northeast ranging south to Agni provides a variety of relatively undisturbed bays, with much pristine back up forest and many potential lying up sites inaccessible to humans amongst rocky shoreline and cliffs. There are three permanent small wetland lagoons within this area providing freshwater marshland habitats set back from the coast.

Otter distribution was assessed by adopting identical principles of standard otter surveys carried out in the UK and many other European countries (Mason and Macdonald 1986). The survey was undertaken by two people working together due to time constraints and difficulties of access and personal safety. On assessing each site wherever possible riverbanks were surveyed for 600 metres and only curtailed if positive otter signs were found. Many sites encountered did not have easy access, with steeply incised riverbanks, and virtually impenetrable bankside vegetation, often dominated by Giant Reed (Arundo donax). High resolution binoculars were an invaluable aid at several sites where access was clearly private or impossible to achieve safely. The access of habitats surrounding the coastal lagoons concentrated on easy access points and freshwater entry or discharge points from the wetlands themselves to the sea. Many sites were accessible from roads, tracks and bridges, where access was clearly private or fenced off, and permission was sought if local people were approached. No access was denied. Where rivers or streams were completely dry, both up- and downstream, only the actual check site was thoroughly surveyed.

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Figure 1. Otter distribution on the island of Corfu, October 2021.

Out of the 103 selected sites that were surveyed, positive otter signs were found at 33 (32%) (Figure 1). These results are very similar to two principal surveys previously carried out on Corfu Island by Ruiz-Olmo (2006) and Galanaki et al. (2019). However, there are some definite subtle changes in distribution which may reflect that this more recent survey was conducted in the autumn period after an extensive period of drought. There had been no rainfall for the previous 166 days, and so many river courses were completely dry or devoid of running water. It is likely from the clusters of evidence that the population is not large; possibly consisting of just a few individuals utilising large areas of the island, particularly the coast, at varying times of the year.

The small, undeveloped sections of coast, particularly in the north, with small river estuaries appear to be important refuge sites. The largely unspoilt peninsula around the northeast coast, from Kassiopi to Kouloura, provides pristine associated wetlands and dense undisturbed forest habitat. This area would provide otters with many

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Otter survey of the island of Corfu 2021

potential breeding sites and coastal feeding opportunities. The area is also very close to the Albanian coast and it is highly likely that otters move naturally between the two countries. This could well be a factor in sustaining a viable small and mobile island population. The three principal wetland systems of Antiniotissa, Chalkiopoulou and Lake Korisson all contained fresh otter evidence, as did the Alikes wetland in the far south.

Of considerable concern throughout the undertaking of this survey was the degradation of many of the coastal wetland areas and particularly the small river estuaries that provide otters with essential access to freshwater riparian habitats, food prey and quiet refuge areas. The presence of extensive areas of fly tipping, particularly of plastics, the over-abstraction of freshwater in general from virtually all river catchments, and ongoing development are all significant pressures. Fish farms and angling interests are also likely to cause considerable disturbance to sensitive areas and lead to possible/perceived conflicts between humans and otters. Accidental persecution of otters is likely to happen in the trapping of non-native species, particularly the introduced coypu (Myocastor coypus), which is widespread around the island.

It is understood that otters possibly survive on only six of the 6,000 Greek islands and unlike most of the Greek islands, Corfu has a range of naturally occurring and varied wetland resources. This makes the very presence of otters on Corfu of national importance to Greece’s natural biodiversity and it is imperative that the importance of safeguarding the future of this native mammal is recognised at all levels.

The aim of the survey is to inform the local people of Corfu and interested environmental organisations about the importance of otters on the island. Hopefully, the local authorities, and potentially the Greek Government, will be further motivated to safeguard this legally protected endangered mammal by ensuring sensitive habitats are fully protected and even enhanced. Furthermore, local, national and international recognition could add to the many recognised natural resources of Corfu that are so greatly valued by locals and tourists alike.

A further survey of the north coast. an important area between Kassiopi and Kouloura, together with some neighbouring islands, is planned for Spring 2022. The results will then be integrated with the 2021 survey to form the basis of the final publication.

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Disclosure Statement

No potential conflict of interest was reported by the author.

Author Biography

GRAHAM ROBERTS is a retired ecologist who has worked on otter recovery for southern Britain for nearly 40 years. He worked with the County Wildlife Trusts of Hampshire and Isle of Wight, Sussex and Kent and represented the Wildlife Trust on the National Otter Steering Group for many years. He has a passion for chalk rivers and all wetlands across the southeast. Currently he is an active Trustee for the Vitacress Conservation Trust and Chair of the Upper Itchen Initiative.

REFERENCES

Galanaki, A, Kominos, T, Zogaris, S, Gasteratos, I and Lymberakis, P, 2019. Presence of the Eurasian otter Lutra lutra on the islands of Greece: A review. Folia Zoological-Praha 68 , 4, 246–252. DOI: 10.25225/fozo.073.2019

Mason, CF and Macdonald, SM, 1986. Otters: Ecology and conservation. Cambridge, Cambridge University Press.

Ruiz-Olmo, J, 2006. The otter (Lutra lutra L.) on Corfu Island (Greece): Situation in 2006. IUCN Otter Specialist Group Bulletin 23, 1, 16–24.