The Effects of Cross-Fostering On the Behavior of Two Species of North American Lemmings, Dicrostonyx Groenlandicus and Lemmus Trimucronatus. Iii. Agonistic Behavior

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Abstract
1. The role of the maternal environment in development of species-specific agonistic behavior was investigated by reciprocally cross-fostering two species of lemmings (Discrostonyx groenlandicus and Lemmus trimucronatus). Non-fostered and within-species-fostered (in-fostered) animals served as controls. 2. When adult, cross-fostered male lemmings engaged in more frequent contact social behavior with the foster species than with conspecifics. However, since cross-fostered animals retained their ability to interact with conspecifics in a species-specific manner, cross-fostering appears to have resulted in a broadening of "species identity" to include the foster species. 3. In-fostering reduced the aggressiveness of Dicrostonyx but had little effect on the behavior of Lemmus. 4. Both the intensity and orientation of agonistic behavior were altered as a result of cross-fostering. In Dicrostonyx, a highly aggressive species, cross-fostering resulted in decreased aggression directed at the foster species and increased aggression toward conspecifics. In Lemmus, a less aggressive species, cross-fostering appears to have resulted in a broadening of the response range to stimuli provided by the foster species. When paired with aggressive Dicrostonyx, cross-fostered Lemmus engaged in more frequent and intense aggression than did controls. However, when paired with nonaggressive (in-fostered) Dicrostonyx, cross-fostered Lemmus engaged in less frequent and intense aggression than controls. In contrast, non-fostered and in-fostered Lemmus males had a relatively narrow response range to Dicrostonyx. 5. In general, the results suggested that agonistic behaviour in lemmings is the product of a complex interaction between genotype and maternal environment.