Journal of Zoology227(3),439–452(1992), DOI10.1111/j.1469-7998.1992.tb04405.x. Verified original publisher abstract/byline. Observational comparison of communal warrens: greater pup survival at larger warrens, more collective vigilance despite less sitting-alert time per pair. Initial-only author identities retained; observational association not randomized causal proof.