Haulout patterns of Saimaa ringed seals and their response to boat traffic during the moulting season

Abstract

Conservation of the Critically Endangered ringed seal Phoca hispida saimensis pop- ulation in Lake Saimaa in Finland requires broader knowledge of the behavioural ecology of this subspecies. Understanding Saimaa ringed seal haulout patterns and their response to boat traffic is crucial for designing sustainable land use and tourism guidelines. Responses of unidentified seals to small outboard motor boat traffic were studied during the moulting season. The median distance at which the seals responded to an approaching boat was 240 m. GPS-phone tags were used to study both circadian and seasonal haulout behaviour patterns of individual seals (n = 8) during the open-water season. The average post-moulting haulout duration was 6 ± 5 h (SD), with a maximum of over 26 h. The seals spent more time hauled out at night (between 21:00 and 06:00 h) after the moult. The time spent hauled out and the haulout frequency declined from early summer to autumn. An individual seal had an average of 13 haulout sites, which were an average of 2.5 km apart. Approximately half of these haulout sites were located in the core 50% of the indi- vidual seals’ home ranges. The high level of site fidelity emphasizes the need to identify suitable haulout areas and to develop measures for protecting the main resting sites of this endangered population. Additionally, guidelines for seal watching should be developed in order to mitigate the potential disturbance caused by increasing tourism on Lake Saimaa.