This paper proposes vulnerability as a decisive lens for rethinking human-animal responsibility in contemporary Islamic ethics. It takes as its point of departure a critical engagement with stewardship-based approaches rooted in the concept of khilāfa, which often presuppose a hierarchical moral order and a privileged form of human agency. While such models emphasise responsibility as delegated authority, they remain limited in their capacity to account for relations marked by asymmetry, exposure, and embodied dependence. Drawing on Taha Abdurrahman's ethical philosophy, particularly his understanding of amāna and the fragility of the moral subject, the paper develops an alternative conception of responsibility grounded not in mastery or control, but in ethical susceptibility and restraint. Animal vulnerability is treated not as a secondary concern or merely empirical fact, but as a theologically significant challenge that repositions the human subject before God and calls into question claims of moral sovereignty. On this basis, the paper outlines a relational account of responsibility that foregrounds interdependence, moral risk, and the limits of human agency. Rather than abandoning Islamic theological categories, it reworks them from within, offering a systematic contribution to current debates in Islamic ethics, animal ethics, and broader philosophical discussions of responsibility and vulnerability.