Nora Welti, Patrick Scherler, Martin U. Grüebler

Examples of urban scavengers taken by camera traps. © Swiss Ornithological Institute
Examples of urban scavengers taken by camera traps. © Swiss Ornithological Institute

Urbanisation alters the species composition of ecosystems and often involves habitat deterioration and introduction of new species such as domestic animals. These changes can affect key ecosystem functions such as consumption of dead animal matter. In this study we investigate the effect of urbanisation on the composition of diurnal and nocturnal scavenger communities and on their consumption rate of small mammalian carcasses. In particular, we are interested in the effects of two characteristics of urbanised areas: the presence of introduced free-ranging pets and the increased predictability of carcass occurrence. While the urban scavenger community showed clearly more domestic cats than the rural scavenger community, carrion consumption rate did not differ between the two habitats. These results suggest that introduction of domestic pets into urbanised areas does not affect the consumption of dead animal matter, despite higher density of scavenger individuals. The mechanism is likely a behavioural change of native scavengers in response to the occurrence of domestic pets and thus, a flexible behavioural adjustment of native scavengers to the carcass situations. When we placed carcasses repeatedly at the same location to simulate high predictability of food resources, carrion consumption rates increased with time in both urban and rural habitats, but only native scavengers and not introduced domestic pets showed a reaction to the repeated placement. High predictability of carcass occurrence is therefore advantageous for native scavengers, while scavenging of predictable food resources may play a limited role in the food acquisition of domestic pets due to the additional food provided by their owners. The study suggests that urbanisation shapes scavenger communities without affecting their ecological function.

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