The skulls and bones of domestic dog (Canis familiaris) and wolf (Canis lupus) from the Mesolithic site of Star Carr, Yorkshire, England are reviewed in the context of the new find of the cervical vertebrae of a dog from the nearby site of Seamer Carr. Examination of the stable carbon isotope ratio of these vertebrae has revealed that the dog's diet must have consisted mainly of marine food. This surprising result compares closely with the stable carbon isotope ratio for dog bone from the Early Atlantic site of Kongemose in Sjaelland, Denmark. If the domestic dogs were feeding predominantly on the scraps left by coastal people then they must have been living on the sea shore and it can be assumed that they died while on hunting trips inland. This in turn implies that Seamer Carr and Kongemose were temporary hunting camps of Mesolithic people who lived for the greater part of the year on the sea shore. This hypothesis is supported by a review of the butchery and age at death of the animal remains from the three sites.