Foraging Responses of Kudus to Seasonal Changes in Food Resources: Elasticity in Constraints

摘要: Foraging behavior provides the mechanistic link between species perfor- mance and food resources in environment. I document foraging responses of a browsing ruminant, kudu (Tragelaphus strepsiceros), to changes abundance quality over seasonal cycle interpret results context optimal theory. The study was carried out on hand-reared but free-ranging animals savanna region with summer wet season winter dry Transvaal, South Africa. During season, kudus expanded their diet include evergreen unpalatable deciduous woody neglected during season. acceptability rating plants correlated value expressed terms protein-condensed tannin index, relative handling time ingestion or digestion. However, dietary expansion alone inadequate satisfy daily energy requirement this period. also increased fraction trees palatable that accepted for feeding, extended feeding duration at stations, encounter rate still retaining leaves. Both total active proportion spent Digestive capacity apparently accommodate higher intake, which compensated reduced quality. Only September end when little foliage remained, were compensatory adjustments meet requirements. functional response relating consumption showed variation, despite decline biomass by more than an order magnitude. neither maximizers, nor minimizers, rather targeted requirements least overall cost. Findings demonstrate digestive constraints assumed models are somewhat elastic. Dietary predictions obtained using average parameter settings may be misleading, because become effective only under extreme conditions. Further research is needed establish costs associated stretching physiological towards upper tolerance limits.