Density-dependent switches in diet:A likely mechanism for negative feedbacks on goose population increase?

• Published in: Polar Biology
• Main Authors: Kuijper, Dries Pieter Jan, Ubels, R., Loonen, M. J. J. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2009
• Subjects: Depletion; Grazing pressure; Habitat degradation; Branta leucopsis; Svalbard; Spitbergen; LESSER SNOW GEESE; BROOD-REARING AREAS; ARCTIC SALT-MARSH; BARNACLE GEESE; BLACK BRANT; MIGRATORY CONNECTIVITY; AGRICULTURAL CHANGE; VEGETATION CHANGE; COASTAL MARSHES; GRAZING LAWNS; Arctic; Brant; Polar Biology; Tundra; Spitsbergen
• Online Access: https://hdl.handle.net/11370/3b882272-7c2d-4d69-b1ff-346abfcc44d0; https://research.rug.nl/en/publications/3b882272-7c2d-4d69-b1ff-346abfcc44d0; https://doi.org/10.1007/s00300-009-0678-2; https://pure.rug.nl/ws/files/25463039/art_3A10.1007_2Fs00300_009_0678_2.pdf

Goose grazing on arctic tundra vegetation has shown both positive and negative effects on subsequent foraging conditions. To understand the potential of a density-dependent feedback on herbivore population size, the relation between grazing pressure and future foraging conditions is essential. We studied the effect of increasing grazing pressure of barnacle geese (Branta leucopsis) on Spitsbergen. During the establishment of a breeding colony in the period 1992-2004, the proportion of graminoids decreased in the diet of wild geese, while the percentage of mosses increased. Grazing trials with captive geese in an unexploited area showed a similar shift in diet composition. High-quality food plants were depleted within years and over years. Intake rate declined too and as consequence, metabolisable energy intake rate (MEIR) decreased rapidly with increasing grazing pressure. During three successive years of experimental grazing, MEIR decreased at all levels of grazing pressure and declined below minimal energetic requirements when grazing exceeded natural levels of grazing pressure. This suggests that foraging conditions rapidly decline with increasing grazing pressure in these low-productive habitats. The potential for density-dependent feedbacks on local population increase is discussed.