Foraging in a landscape mosaic
1994
Wallis de Vries, M. F.
This thesis focuses on two main questions regarding the relation between a large herbivore, Bos taurus, and habitat quality: a) how do differences in habitat quality relate to nutrition and herbivore performance? and b) is herbivore foraging behaviour affected by habitat differences and can it be explained by optimal foraging theory? The study was carried out in the Netherlands using free- ranging steers in an experimental set-up with four combinations of two habitats of contrasting soil fertility: heathland and riverine grassland.A hand-plucking method was developed to estimate forage quality and intake; calibration was carried out using oesophageally fistulated steers.
Показать больше [+] Меньше [-]Cattle performance was significantly affected by habitat quality.
Показать больше [+] Меньше [-]On heathland animals showed relatively low weight gains and slow fat accumulation coupled to high weight loss over winter.
Показать больше [+] Меньше [-]These impairments were caused by deficiencies in sodium and phosphorus which led to a reduced energy retention, bone resorption and pica behaviour.
Показать больше [+] Меньше [-]Animals on riverine grassland demonstrated a performance close to their growth potential.
Показать больше [+] Меньше [-]The treatments with combinations of habitats emphasized these differences.Foraging selectivity increased with differences in forage quality and quantity and with spatial scale.
Показать больше [+] Меньше [-]Selectivity between short, tall and stemmy patches within two grassland communities was low but significant.
Показать больше [+] Меньше [-]Short and tall patches were preferred over stemmy patches.
Показать больше [+] Меньше [-]The preference for short patches was consistent with a daily intake maximization of digestible organic matter but not in agreement with instantaneous maximization.
Показать больше [+] Меньше [-]It is suggested that cognitive limitations reduce selectivity of cattle at lower spatial scales.
Показать больше [+] Меньше [-]At a higher scale level selection between landscape types was distinct and broadly agreed with model predictions assuming daily maximization for the intake of digestible organic matter, sodium and phosphorus.Implications of the relation between habitat quality and herbivore performance are discussed with regard to nature conservation.
Показать больше [+] Меньше [-]Breed differences in cattle are of little consequence in mild climates.
Показать больше [+] Меньше [-]Fragmentation and uniformity of habitats are of much greater importance.
Показать больше [+] Меньше [-]It is argued that the habitat requirements of large herbivores should be used to develop guidelines for basic conditions to the design of nature reserves.
Показать больше [+] Меньше [-]Experiments using free-ranging domestic herbivores can elucidate these habitat requirements.
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