The faded stripes of Bengal: a historical perspective on the easternmost distribution of the striped hyena

The striped hyena (Hyaena hyaena) is an understudied large carnivore with no known historic range map. Knowledge of the past and present extent of its easternmost distribution beyond 85° east longitude is dubious. Through a comprehensive review of historical evidence and contemporary records, we investigated striped hyena presence in Bengal, i.e., Bangladesh and the Indian state of West Bengal in South Asia. We found 14 historical records, with the oldest one dating to 1876. Our review establishes Bangladesh as a former striped hyena range country and the striped hyena as one of the first large carnivores to go extinct in Bangladesh. We identified northern Bangladesh as part of its historical range (until ~1965), and south-central Bangladesh as a possible part of its historical range. In West Bengal, India, hyenas were historically present up to the southern tributaries of the Brahmaputra River, but the present range is reduced. The area south of the Damodar River is its last refuge in Bengal. We also found 15 contemporary records (2010–2021) in Bengal, from sites situated on the eastern limit of the Chota Nagpur Plateau. These records noted 25 sightings including 9 deaths due to poaching, train accidents, and retaliatory killings. Our review demonstrates that hyenas are currently present up to 87° east longitude, which extends the currently documented easternmost range for the species by almost 1,000 km. We recommend methods which can be applied to delineate the historical extent of striped hyenas elsewhere as well as for other poorly understood species.

Assessment of Dam-Induced Changes in Ecogeomorphological Behaviour and Fluvial Functionality in the Damodar River, West Bengal, India

Anthropogenic interventions in the form of dams and barrages often alter the fluvial functionality and ecogeomorphological (geomorphology, hydrology, and ecology) behaviour of the river systems. The present work examines the environmental flow, channel metamorphosis, and fluvial functionality of Damodar River in the context of Damodar Valley Corporation (DVC) dams and development. The structural (dams, barrages, weirs, etc.) and non-structural (urban-industrial and agricultural disposal with effluents, sand mining, etc.) interventions hinder the ecological functionality of the river. This study portrays that the eco-geomorphological behaviour and fluvial functionality of the river have changed due to flow alteration and diversion by dams and barrages and due to the urban-industrial and agricultural growth in the basin area. These changes have affected riverine ecological integrity. The ecological functionality level of this study area ranges from 85 to 181 i.e. poor to good-fair. The ecological functionality level in sample channel sections (i.e., immediate upstream and downstream of Durgapur Barrage) is poor, and the value ranges from 61 to 100 due to the hydrological impact of the barrage and the Durgapur urban-industrial belt. This assessment work would help to restore the fluvial environment for humans as well as riverine biota.