Assessing the well-being of captive brown bears is essential for responsible species management and meeting European and national animal care standards outside their natural habitats. The present study aims to assess the welfare of captive brown bears in Bulgaria, considering environmental parameters, husbandry procedures, and the psychological and physical condition of the animals. The study was conducted on 28 brown bears in 11 zoos in Bulgaria and 19 bears in Bear Sanctuary Belitsa. A specific questionnaire and interviews were conducted with zoo managers and keepers. The welfare of the bears was evaluated based on their living conditions, husbandry, and physical and psychological well-being. The Nature and Animal Protection Center in Dobrich received the highest rating for the welfare of two brown bears among the zoos in the study. The study identified annual veterinary check-ups and enrichment programmes as areas needing improvement.

The possible clastogenic activity of tetrahydrofuran (THF), a synthetic organic substance, was explored employing two cytogenetic endpoints, i.e., chromosome aberrations (CA) and mitotic index (MI) analyses in vivo. The assays were carried out with ICR line laboratory mice as well as some widespread small mammal species in Bulgaria: yellow-necked wood mouse Apodemus flavicollis, mound-building mouse Mus spicilegus, bank voles Clethrionomys glareolus (= Myodes glareolus) and common vole Microtus arvalis. THF was introduced at 3.8 mg/kg b. w. (body weight) (0.01 mg/mL) by a single intraperitoneal (ip) administration. Cells with various structural CA were noted with significant (p < 0.01) differences in the frequencies of CA and MI between THF-treated groups and the negative control groups at dose or time interval used. The results of the present study reflect a positive in vivo clastogenic potential of THF.

The Black Sea harbour porpoise (Phocoena phocoena relicta Abel, 1905) is an endemic cetacean with poorly understood spatial ecology in Bulgarian waters. This study aimed to update knowledge on its distribution, abundance, and habitat use throughout the Bulgarian Exclusive Economic Zone (EEZ). We conducted systematic aerial line-transect surveys in all four seasons between October 2022 and October 2023, combined with distance sampling and MaxEnt habitat modelling. Porpoises were present year-round across the EEZ, with marked seasonal shifts in distribution and habitat preferences. Highest densities were observed in spring, while winter distributions were concentrated offshore. Habitat suitability was dynamic, with key high-use areas identified near Cape Emine and in southern offshore waters near the Turkish border. Overall, about 40% of the EEZ represented high-suitability habitat. These findings provide the first comprehensive, year-round baseline for P. p. relicta in Bulgarian waters, highlighting the species’ flexible habitat use and seasonality. The study was conducted under extraordinary conditions due to regional military activity, which may have influenced porpoise behaviour and spatial patterns. The provided results are critical for designing effective conservation and management measures in the face of both natural and anthropogenic pressures and threats.