Photo by IEE RAS
In the summer of 2024, scientists from the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences (IEE RAS) conducted the fifth expedition to study the Baikal seal. These mammals are endemic to Lake Baikal and a key link in its ecosystem. A special program has been developed to study Baikal seals - it is designed 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 scientists from the Institute of Ecology and Evolution of the Russian Academy of Sciences to study Baikal seals took place at the largest summer rookeries, the shores of the Ushkany Islands archipelago in the middle part of Lake Baikal, and set several tasks at once.
Firstly, it was necessary to visually determine the number and assess the condition of the seals by external signs on Tonkiy Island - to establish the presence of injuries and pathologies, as well as the number of seals that had not yet molted, and compare the obtained data with those obtained in previous years. Secondly, scientists had to count the seals on Tonky, Dolgiy, and Krugly Islands using drones. Drones are intended to help in the study primarily because the seal rookeries are difficult to access, but mainly because of the need to in no way disturb the peace and rhythm of life of the seals. The third task that the researchers set for themselves was to collect biological material and assess the influence of tourists on the behavior of the seals, 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 flights and take 48 videos, with a total duration of more than 4 hours and 45 minutes. Each video was later analyzed frame by frame, the number of seals was counted, the main haulout sites were noted, and the environmental factors that influence the distribution of seals on the islands were determined. In addition, the scientists went on 39 hiking trips around Tonky Island to record the number of seals, the number of wounded, sick, and unmolted individuals. The result of dozens of trips by the researchers was the account of more than 5,000 photographs of the animals, which were later carefully analyzed.
During the visual foot counts, it was possible to establish that the number of seals on Tonky Island varied from 2 to 384 individuals. The number of animals in 2024, as in previous years of research, decreased by mid-August, which is probably due to worsening weather conditions, the 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 molted, is relatively small, and it can be considered that their number is insignificant. The number of animals counted in 2024 is significantly less than the number of animals counted in previous years - 2020 and 2022, but does not differ from the number counted in 2021. This may be due to the increased anthropogenic load observed during field work in 2024. For example, cutters, inflatable boats and yachts were repeatedly noticed approaching animal rookeries,” - the researchers said.
In total, during the technological part of the research (using drones), scientists were able to record 13,384 seals, including 5,390 in the water and 7,994 on land (Note: 13,384 is the total number of accounts, including animals counted repeatedly). The maximum number of seals counted at one time was 1,786 in total on three of the four Ushkany Islands (a flyover of Bolshoy Ushkany Island was not conducted due to its remoteness from the other islands).
The largest number of seals was recorded on Dolgy Island, the smallest - on Tonky Island. The maximum number of animals registered at one time on Tonky Island is 319, on Dolgiy Island - 1060, on Krugly Island - 813.
An interesting conclusion that the researchers came to is that Tonkiy Island has fewer seals than other islands, although it was previously believed that this island had the largest endemic seal rookery. In previous expeditions, the researchers had already observed this pattern, and in 2024 they confirmed it again.
Scientists also had to examine dead individuals to collect biological material - four of these were found during the expedition. For example, hair and whisker samples obtained in this way from one individual helped to assess the level of the animal's stress hormone, cortisol. After conducting the research, scientists came to the conclusion 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 the framework of the five-year program, the highest values of cortisol concentration were observed in dead animals in 2020, which was characterized by a large number of dead animals found on the shore of Tonkiy Island and early melting of ice in winter. Then these factors could have led to an increased concentration of cortisol in animals during the molting period.
To analyze the seals' behavior, scientists processed 575 time slices (a time slice is a series of 3 photographs of a seal rookery, taken every 10 minutes from 6:00 to 12:00), on each of which the type of behavior of each individual was determined, as well as the duration of stay on the stone (by the degree of dryness). The types of behavior were then combined into two categories - calm and agitated. When analyzing the seals' behavior, not only the external natural environment (wind strength and direction, cloudiness, lake agitation level, etc.) was taken into account, but also anthropogenic factors - the number of tourists on the observation deck and their behavior.
“19 days of behavioral observations were conducted, during which 626 time slices were obtained. For each time slice, weather conditions and the number of tourists on the observation deck and their behavior were noted for further assessment of the influence of these factors on the behavior of seals,” - the IEE RAS researchers shared.
Thus, cases of mass migration of seals were analyzed, and four scenarios of rookery restoration were identified: "rapid return" (5 cases), "long-term return" (1 case), "return with a decrease in the total number of seals" (9 cases), "no return" (2 cases). The most optimal scenario is "rapid return", in which the number of seals on the rock is restored on average in 1 hour 22 minutes.
“We assume that an important condition for a quick return is the presence of a small number of seals on the rock after the mass exodus. Both natural and anthropogenic causes of the animals leaving the rock were observed, for example, active actions of tourists at the haulout (sticking out from behind the wall), passage of watercraft in front of the haulout. Complete abandonment of the haulout occurred for both natural and anthropogenic reasons, and led to a longer recovery of the haulout,” - the study says.
It is important to note that the worst-case scenario, when seals may not return to the rocks for a very long time, for example, until the end of the day, is associated with humans, namely, with watercrafts moving near the locations of seal groups. Scientists emphasize that these cases are unacceptable and require immediate measures to prevent them in the future.
Work on studying Baikal seals is carried out in cooperation with the Federal State Budgetary Institution "Zapovednoye 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 to the Siberian Wellness company.
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