In summer 2024, scientists from the A.N. Severtsov Institute for Problems of Ecology and Evolution of the Russian Academy of Sciences (IPEE RAS) conducted the fifth expedition to study the Baikal seal. The fifth expedition to study the Baikal seal was conducted by scientists from the A.N. Severtsov Institute for Problems of Ecology and Evolution of the Russian Academy of Sciences (IPEE RAS). These mammals are endemic to Baikal and a key part of the lake’s ecosystem. A special programme has been developed to study Baikal seals – it is scheduled for 2020-2025 and is financed with the support of the Lake Baikal Foundation. Scientists painstakingly and most importantly – unnoticed by the animal world – study Baikal seals in their natural habitat, trying not to disturb them. The Lake Baikal Foundation shares the results of the research expedition conducted in July and August 2024.
The expedition of IPEE RAS scientists to study Baikal seals took place on the largest summer haulouts, the shores of the Ushkanyi Islands archipelago in the middle part of Lake Baikal, and set several tasks at once.
Thus, it was necessary to visually determine the number of seals and assess the condition of seals by external signs on Tonky Island – to determine the presence of injuries and pathologies, as well as the number of seals that had not moulted, and to compare the data obtained with those obtained in previous years. Secondly, scientists had to count seals on the islands of Tonky, Dolgiy and Kruglyy using drones. Drones were intended to help in the study, first of all because of the inaccessibility of the seal beds, but mainly because of the need not to disturb the peace and rhythm of the seals’ life. The third task the researchers set for themselves is to collect biological material and assess the impact of tourists on seal behaviour, as well as to study the bodies of dead animals, if any are found during the survey.
Thanks to the drones, the scientists were able to conduct 16 overflights and capture 48 videos totalling more than 4 hours and 45 minutes. Each video was later analysed frame by frame, counting the number of seals, marking the locations of the main haulouts and determining what environmental factors influence the distribution of seals on the islands. In addition, the scientists hiked 39 times around Tonky Island to record the number of seals, the number of injured, sick and moulting seals. Dozens of outings resulted in more than 5,000 photographs of the animals, which were later carefully analysed.
Visual counts on foot revealed that the number of seals on Tonky Island varied from 2 to 384 individuals. The maximum number of seals encountered during the expedition was 384. The number of animals in 2024, as in previous survey years, decreased by mid-August, which is probably due to worsening weather conditions, redistribution of animals between islands or their departure to other areas of the lake.
The proportion of sick seals, as well as seals that have not moulted is relatively small and can be assumed to be negligible. The number of animals counted in 2024 is significantly lower than the number of animals counted in the previous years – 2020 and 2022, but not different from the number counted in 2021. This may be due to the increased anthropogenic pressure observed during fieldwork in 2024. For example, boats, inflatable boats, and yachts were repeatedly seen approaching close to animal rookeries,
– the researchers said.
In total, 1,786 individuals were counted during the surveys with the use of equipment (drones) at one time during a single count on three of the four Ushkaniy Islands (a survey of Bolshoy Ushkaniy Island was not conducted due to its remoteness from the other islands). Bolshoy Ushkaniy Island was not covered due to its remoteness from the other islands).
The highest number of seals was recorded on Dolgiy Island and the lowest on Tonky Island. The maximum number of animals recorded at one time was 319 on Tonky Island, 1,060 on Dolgiy Island and 813 on Krugly Island.
An interesting conclusion reached by the researchers is that there are fewer seals on Tonky Island than on the other islands, although it was previously thought that this island had the largest deposit of endemic seals. Researchers had already observed this pattern in previous expeditions and confirmed it again in 2024.
Scientists also had to examine dead individuals to collect biological material – four of them were found during the expedition. For example, samples of hair and vibrissae of one individual helped to assess the level of the stress hormone cortisol in the animal. After the research, the scientists concluded that the dead seal did not experience severe stress before its death. It is worth recalling that according to the results of similar hormonal studies within a five-year programme, the highest values of cortisol concentration were observed in the dead animals of 2020, which was characterised by a large number of dead animals found on the shore of Tonky Island and early melting of ice in winter. At that time, these factors could lead to increased cortisol concentrations in animals during the moulting period.
To analyse the behaviour of the seals, the scientists processed 575 time slices (a time slice is a series of 3 photographs of a seal den, taken every 10 minutes between 6:00 and 12:00), each of which was used to determine the type of behaviour of each individual, as well as the length of time spent on the rock (according to the degree of dryness). Behaviour types were further combined into two categories – calm and anxious. When analysing the behaviour of seals, not only the external natural environment (wind strength and direction, cloud cover, level of lake agitation and so on) was taken into account, but also anthropogenic factors – the number of tourists at the viewing platform and their behaviour.
Nineteen days of behavioural observations were conducted, during which 626 time slices were obtained. For each time slice, weather conditions and the number of tourists at the viewing platform and their behaviour were recorded to further assess the influence of these factors on seal behaviour,
– researchers of IPEE RAS shared.
Thus, we analysed the cases of mass haul-out and identified four scenarios for recovery of the burrow: “rapid return” (5 cases), “prolonged return” (1 case), “return with a decrease in the total number of seals” (9 cases), “no return” (2 cases). The most optimal scenario is the “rapid return” scenario, where the number of seals on the rock is restored after an average of 1 hour 22 minutes.
We assume that the presence of a small number of seals on the rock after a descent is an important condition for a rapid return. We observed both natural and anthropogenic reasons for descent, e.g. active actions of tourists at the seal den (sticking out from behind the wall), passing of swimming vehicles in front of the den. Complete abandonment of the fallow ground was due to both natural and anthropogenic causes and resulted in longer recovery of the fallow ground,
– said in the report.
It is important to note that the most negative scenario, where seals may not return to the rocks for a very long time, e.g. until the end of the day, is related to humans, namely swimming vehicles travelling close to the locations of groups of seals. The scientists emphasise that these cases are unacceptable and require immediate measures to prevent them in the future.
The work to study Baikal seals is carried out in co-operation with the FSBI “Zapovednoe Podlemorye”. In 2024, the project was implemented with the support of private donors of the Lake Baikal Foundation and a charitable donation from the “World Around You” Foundation of Siberian Wellness company.