Benefits of migration in a partially-migratory tropical ungulateReport as inadecuate

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BMC Ecology

, 13:36

Community, population and macroecology


BackgroundPartial migration, where one portion of a population conducts seasonal migrations while the other remains on a single range, is common in wild ungulate populations. However the relative costs and benefits associated with the distinct strategies adopted by coexisting migrant and resident individuals have rarely been investigated. Here we compare the body condition of migrants and residents in a partially migratory population of impalas Aepyceros melampus in Zimbabwe. The study was conducted during two consecutive years with highly contrasted population densities 16.4 and 8.6 indiv-km due to harvesting.

ResultsWe first identify a population substructure with a north–south sub-division in two spatial units related to distinct soils and vegetation cover. Impalas in the north range had a consistently higher diet quality and body condition than those in the south range. At the beginning of the dry season about one third of the individuals migrated from the lower i.e. south to the higher i.e. north diet quality range. This partial migration pattern was consistent between the consecutive years, and most individuals showed constancy to their moving strategy migrant or resident. In both years, these migrants had a significantly higher body condition at the end of the dry season than the south residents that remained year-round in the lower diet quality range. Diet quality and body condition of impalas were higher in the year of lower density; however we did not detect any evidence for density-dependence in migration propensity, at the individual or population levels, nor in the benefit associated with migration.

ConclusionsOur findings provide rare evidence for a significant relationship between body condition and seasonal migration strategy in wild ungulates in relation to a difference in the quality of resources acquired between distinct seasonal ranges. This study also constitutes rare evidence of partial migration in a tropical ungulate population.

KeywordsPartial migration Habitat–performance relationships Density dependence Impala Individual variability Spatial heterogeneity Diet quality Savannah Electronic supplementary materialThe online version of this article doi:10.1186-1472-6785-13-36 contains supplementary material, which is available to authorized users.

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Author: Nicolas Gaidet - Philippe Lecomte


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