Intraspecifik aggression mellan gräsänder (Anas platyrhynchos) i urbana och rurala habitat

Sammanfattning: The continuing increase in urbanization is changing the natural habitats of wild animals. Some wildlife have colonized urban areas and are exposed to new stimuli to which they respond differently: some species adapt whereas others thrive. Living in such an environment can lead to increased stress and elevated aggression. The purpose of this study was to examine the intraspecific aggression among mallards (Anas platyrhynchos) in two habitats with different degree of urbanization. Field observations were performed on groups of mallards in urban and rural environments. I predicted that there would be more aggressive behavior among mallards in urban than in rural habitats, based on the hypothesis that increased stress in an urban environment results in elevated aggression. Aggression was defined as the number of attacks, which was classified as chases, nips, and threats. I observed on average more than three times as many attacks (chases, nips and threats) in urban as in rural habitats. In addition, more females relative to males in the groups resulted in more attacks. Wild birds are important to flora, fauna, and man. Because high aggression can affect the fitness of wild urban animals negatively through, for example, physical injuries and increased disease transmission during fights, it is important that humans intervene to prevent this.