The Lower Bug region is the habitat of the Eurasian otter (Lutra lutra¬), which, relying on channel reservoirs as reserves, also exploits the seasonal and permanent resources of small steppe rivers. With the climate-driven decrease in surface runoff, small rivers have become subject to complete or partial drying up, making it difficult for semi-aquatic mammals to live. The survival of the otter in the Southern Steppe is ensured by its use of the static and foraging potential of channel reservoirs and ponds. The latter are the key sites that serve as permanent and off-season reserves for the species, ensuring the survival and sustainable existence of otters in the small river network. The habitat specificity of the otter's sustainable habitats covers areas with different spatial and landscape characteristics, and hydrological, and foraging features, which allows us to distinguish three ecologically and ethologically distinct forms of the species. The first is the primary riverine form, represented by animals inhabiting the Southern Bug, Syniukha, and Ingul rivers, the second is the lyman-estuarine form, and the third is the river-pond form associated with small rivers. The current number of otters in the Lower Pobuzhzhia is estimated at 86–108 individuals, which is 38.5% more than in 2000–2005 and 58.1% more than in 1992–1995. The average breeding density is 0.489 individuals/10 ha of water area (excluding the coastal and marine zone). In some habitats, the local density of otters ranges from 0.181 (Berezansky estuary) to 1.14 individuals/10 ha (lower reaches of the Syniukha River, Kovalivsky plains). At the same time, the main reserves of the species generally remain unchanged—the channel-floodplain habitats of the Southern Bug, Ingul, and Ingulets, from which the animals disperse to the tributaries of these rivers and adult males migrate through local watersheds. Some small otter habitats are associated with the peaks and banks of the Tiligul and Berezan estuaries. The least studied was and remains the Ingulets centre of existence of the species, which was significantly affected by the consequences of hostilities.

The study is dedicated to the development of quantum epidemiology which is the expected next stage in epidemiology transformation as new quantum technologies have emerged. At the present time, epidemiology is entering the digital era and undergoes a paradigm shift from data-driven to value-driven strategy. The epidemiology data are characterized by uncertainty, multidimensionality, and disconnection, which drive to prefer the quantum approach for data exposition, creation of value, and modeling. The Quantum Data Lake concept is proposed. The data about DNA viruses with symptoms and diseases are shown as example of epidemiology data complexity. The Quantum Data Lake concept consists of several layers and quantum tools, including PT-symmetry and non-Hermiticity as intuitive modeling tools. PT-symmetry breaking is able to detect the hidden shift in the information which is permanently updated in the Data Lake. The duality of PT-symmetry breaking can be compared with the estimation of the best and worst scenarios simultaneously. In contrast to the widely discussed advantages of quantum computing such as high-speed performance and very large parallel scale, the proposed approach emphasizes the fundamental uniqueness of quantum theory for modeling. The study highlights the necessity to investigate the native processes of viruses’ interaction with the human population by relying on quantum theory’s natural properties. Implementation of quantum logic and reliance on a quantum theory is the fundamental difference between the current digital epidemiology and future quantum epidemiology.