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University of Otago (2012)

The Functional Responses of European Rabbits (Oryctolagus cuniculus) on Improved and Semi-Improved Pastures in the Semi-Arid Grasslands of Central Otago, New Zealand

Rayner, Elizabeth

Titre : The Functional Responses of European Rabbits (Oryctolagus cuniculus) on Improved and Semi-Improved Pastures in the Semi-Arid Grasslands of Central Otago, New Zealand

Auteur : Rayner, Elizabeth

Université de soutenance : University of Otago

Grade : Master of Science 2012

Résumé
Functional responses describe the relationship between an animal’s consumption rate of food and the abundance of the food resource. They illustrate how consumers cope with declining food resources and provide a greater understanding of plant-herbivore relationships. These play a central role in modelling the dynamics of ecosystems. Modelling helps guide management decisions by allowing predictions about the effects of changes in parts of the ecosystem. Despite the prolonged and significant impacts of rabbits on both conservation values and agriculture in the dry grasslands of Central Otago, there have been no attempts to measure rabbit functional responses in New Zealand. This study is the first to empirically estimate the functional responses of New Zealand rabbits on improved, semi-improved, and ‘rough’ semi-improved pastures in the dry grasslands of New Zealand. Functional response studies of rabbits in Australia have fitted relationships known as ‘type II’ (asymptotic curve) and ‘type II with an ungrazed residue’ responses. In the current study, rabbits exhibited very different patterns of intake between pasture types, with an unsaturating type I response (represented by a linear relationship) on improved pasture, and a saturating (inverted exponential Ivlev relationship) type II response on semi-improved pasture, both with very high intake rates and large ungrazed residues. Intake of green vegetation showed a type V response (although similar in shape to a type II response, the equations differ between the two, with a type V curve including a function quantifying the ungrazed residue). No functional response relationships could be fitted to the data from the ‘rough’ semi-improved pasture. Rabbits on this pasture type showed very high intake rates – far greater than in previous studies. This was probably a result of the high error associated with daily estimates of vegetation biomass on ‘rough’ semi-improved pasture.

Mots clés : Functional response ; European rabbit ; herbivore ; Central Otago ; Ecosystem dynamics

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Page publiée le 25 novembre 2013, mise à jour le 13 juin 2018