Video recordings made inside wolf dens chronicle two episodes of infanticide by different α females within a captive pack of timber wolves (Canis lupus). In one instance, infanticidal behaviour was interspersed with maternal behaviour. These cases are discussed in terms of the proximate causes of infanticide. It is also suggested that the killing of pups born to subordinate females by α females may be a common occurrence in both captive and free-ranging wolf packs.