Anthropogenic subsidies mitigate environmental variability for insular rodents

The exogenous input of nutrients and energy into island systems fuels a large array of consumers and drives bottom-up trophic cascades in island communities. The input of anthropogenic resources has increased on islands and particularly supplemented non-native consumers with extra resources. We test...

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Bibliographic Details
Published in:Oecologia 2013-07, Vol.172 (3), p.737-749
Main Authors: Ruffino, Lise, Russell, James, Vidal, Eric
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Animals
Biological and medical sciences
Biomedical and Life Sciences
Birds
Carpobrotus
City states
Demecology
Ecology
Environmental aspects
Finland
Fundamental and applied biological sciences. Psychology
General aspects
Gulls
Habitats
Hydrology/Water Resources
Immatures
Life Sciences
Mammalia
Plant Sciences
Plants
Population Dynamics
POPULATION ECOLOGY
Population ecology - Original research
Rain
Rats
Rats - physiology
Rattus rattus
Reproduction
Sea birds
Shrublands
Subsidies
Summer
Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
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Summary:The exogenous input of nutrients and energy into island systems fuels a large array of consumers and drives bottom-up trophic cascades in island communities. The input of anthropogenic resources has increased on islands and particularly supplemented non-native consumers with extra resources. We test the hypothesis that the anthropogenic establishments of super-abundant gulls and invasive iceplants Carpobrotus spp. have both altered the dynamics of an introduced black rat Rattus rattus population. On Bagaud Island, two habitats have been substantially modified by the anthropogenic subsidies of gulls and iceplants, in contrast to the native Mediterranean scrubland with no anthropogenic inputs. Rats were trapped in all three habitats over two contrasting years of rainfall patterns to investigate: (1) the effect of anthropogenic subsidies on rat density, age-ratio and growth rates, and (2) the role of rainfall variability in modulating the effects of subsidies between years. We found that the growth rates of rats dwelling in the non-subsidized habitat varied with environmental fluctuation, whereas rats dwelling in the gull colony maintained high growth rates during both dry and rainy years. The presence of anthropogenic subsidies apparently mitigated environmental stress. Age ratio and rat density varied significantly and predictably among years, seasons, and habitats. While rat densities always peaked higher in the gull colony, especially after rat breeding in spring, higher captures of immature rats were recorded during the second year in all habitats, associated with higher rainfall. The potential for non-native rats to benefit from anthropogenic resources has important implications for the management of similar species on islands.
ISSN:0029-8549
1432-1939
DOI:10.1007/s00442-012-2545-z