Baltic grey seals are originally ice breeders, known for their breeding site fidelity. Baltic grey seals are originally ice breeders, known for their breeding site fidelity. However, due to climate change, the amount of pack ice has decreased in recent years, forcing females to breed on land. This behavioural shift is a known phenomenon in the Baltic Sea, but due to changes in sea ice it became more common and challenges pup survival and female long term reproductive success. The environmental and social conditions driving this change are poorly studied. The PhD project will address this knowledge gap by combining historical data (available since 1990) with modern (collected within this project) behavioural observations of grey seal females. The project will focus on breeding site selection, breeding behaviour synchronization, and reproductive success. Fieldwork will be conducted in Estonia, one of the largest grey seal breeding locations in the Baltic Sea. Spatial analysis of breeding locations, studies of female behaviour, pup counts and their condition assessments will be combined with environmental parameters (e.g. ice thickness, coverage) to model female breeding site selection and reproductive success. The outcomes of this research will contribute to our understanding of Baltic grey seal population dynamics, consequences of climate change for ice-related seals, and will inform effective conservation measures.