In February 2021, a report from the regional NGO focusing on conservation of marine mammals «Marine Mammal Council» (SMM) about the results of the second expedition to the Ushkan Islands in the summer 2020, which was part of the comprehensive project on research of the Baikal seal, was received.
The team of the expedition consisted of experienced specialists and undergraduate and graduate students from the Biology Faculty of Moscow State University:
- Solovyeva Maria — Ph.D., specialist in marine mammals, member of the SMM, researcher at the Laboratory of Behavior and Behavioral Ecology of Mammals at the A.N. Severtsov Institute for Ecology and Evolution of the Russian Academy of Sciences (IEE RAS),
- Glazov Dmitry — zoologist, specialist in marine mammals, leading engineer of the laboratory of sensory systems of vertebrates at IPEE RAS, executive director of the IEE RAS,
- Razuvaev Andrey — Senior Researcher of the Federal State Budgetary Institution «Zapovednoe Podlemorye»
- Ilyina Polina, Shibanova Polina and Glazova Taisia are students of the Biology Faculty of Moscow State University.
Researchers were assigned to conduct regular visual counts of number of the Baikal seals and counts using an unmanned aerial vehicle (UAV) to determine the dynamics of distribution of the seals, their sex and age, the presence of wounds and signs of animal diseases. Additional task was obtaining biological materials from found dead animals (hair, vibrissa, cells of skin) for further genetic and hormonal research in laboratories.
The main challenge for an observer conducting visual counts is that the seals are very timid. This factor determined the route and points for conducting visual counts. It turned out that arranging a spotting site from a camouflage net does not solve this problem. During visual counts, it is recommended to use natural shelters and to carry out the counts of the area lying ahead on the way of the observer’s movement.
To cover the daily dynamics of the herd, visual counts were carried out 3 times a day for one hour on average for 28 days in a row. At the same time, besides visual counts, photographs of the herd were taken as a source of additional information of the number of the seals on the herd, which is important in case the seals get timid by the observers and hide in the water. Visual counts showed that the number of the Baikal seals on the northern coast of the Thin Ushkan Islet varies from 0 to 1209 animals. It was found that the level of choppy water of the lake is the main factor affecting the number of seals on the islet. Share of the seals which did not molt is at least 2.9% of the average number of the seals on the Thin Ushkan Islet, and the share of sick and injured seals is at least 3.4%. Analysis of the age structure of the Baikal seals, which was carried out using photographs of the claws of animals (Pastukhov’s method), showed that most of the identified seals on the Thin Ushkan Islet are immature individuals.
The first experience of photo-identification of the seals on the herd showed that diseases and wounds can be used to identify the Baikal endemic. Nevertheless, relatively few animals with bright distinctive features were identified (only 21 animals) and second encounters were rare (no more than 3 encounters of one animal). This can be described as either visits of the seals to the Thin Ushkan Islet very rare, or the photo-identification method is imperfect due to invisibility of animals´ signs to observers when the position of the animal changes. Thus, in terms of tracking individual animals the photo-identification method seems to be less effective compared to individual tagging of them. In addition to visual observations, 12 video filming of the coastline of the Ushkan Islands were made using UAV. Based on the results of counts using UAV, it is revealed that the distribution of the Baikal seals between the islets is uneven, the predominant number of seals was on Long Ushkan Islet (up to 48%) and Round Ushkan Islet (up to 77%), and not on the Thin Ushkan Islet, as previously assumed. The total number of the seals on the islets is not constant. Number fluctuations on the islets are not interrelated, which means that migration of the seals during the summer period include not only migration between these three islets.
Despite the flight altitude of the drone (up to 70 m), in some cases the seals were timid, and animals hid into the water. Therefore, it is recommended to use less noisy devices, as well as to determine the altitude at which the UAV flight will not cause timidness in the seals. In order to minimize the sun glare that interferes with counting, the camera should be directed straight down while shooting. It is also possible to take pictures using a thermal imager. Prior to starting filming, it is recommended to designate the place of the beginning and the end of the recording by stopping the device. For the convenience of counts, the quality of the shooting, the resolution, and the size of the screen on which the photo and video materials from the UAV are played are important. It is recommended to make all counts from screens that are identical in characteristics.
Comparison of visual records and data from UAV made it possible to determine that both methods are fully consistent only when determining the total number of seals on the shore and in the water, and give a similar number for the total sum of animals on the islets. Dynamics of the number of seals on land during the day was recorded. More animals on land were recorded in the morning and afternoon hours. The total number of animals on the Ushkan Islands (Long Ushkan Islet, Thin Ushkan Islet, and Round Ushkan Islet) were changing. The maximum number of seals on all islands was recorded on July 28 and totalled to 3467 animals. On this day, the maximum number of animals was observed on each islet for the entire time of observation. The minimum total number was observed on August 8 and totalled to 308 animals on all islets. In the future, to identify more accurate patterns, it is necessary to conduct more joint counts by both methods (at least 10 joint counts), which allow using a wider range of statistical criteria in data analysis.
During this expedition biological materials were non-invasively obtained from the Baikal seals, which are used for genetic and hormonal analysis later in laboratories.