TY  - JOUR
A1  - Naidoo, Robin
A1  - Du Preez, Pierre
A1  - Stuart-Hill, Greg
A1  - Jago, Mark
A1  - Wegmann, Martin
T1  - Home on the Range: Factors Explaining Partial Migration of African Buffalo in a Tropical Environment
JF  - PLoS One
N2  - Partial migration (when only some individuals in a population undertake seasonal migrations) is common in many species and geographical contexts. Despite the development of modern statistical methods for analyzing partial migration, there have been no studies on what influences partial migration in tropical environments. We present research on factors affecting partial migration in African buffalo (Syncerus caffer) in northeastern Namibia. Our dataset is derived from 32 satellite tracking collars, spans 4 years and contains over 35,000 locations. We used remotely sensed data to quantify various factors that buffalo experience in the dry season when making decisions on whether and how far to migrate, including potential man-made and natural barriers, as well as spatial and temporal heterogeneity in environmental conditions. Using an information-theoretic, non-linear regression approach, our analyses showed that buffalo in this area can be divided into 4 migratory classes: migrants, non-migrants, dispersers, and a new class that we call "expanders". Multimodel inference from least-squares regressions of wet season movements showed that environmental conditions (rainfall, fires, woodland cover, vegetation biomass), distance to the nearest barrier (river, fence, cultivated area) and social factors (age, size of herd at capture) were all important in explaining variation in migratory behaviour. The relative contributions of these variables to partial migration have not previously been assessed for ungulates in the tropics. Understanding the factors driving migratory decisions of wildlife will lead to better-informed conservation and land-use decisions in this area.
KW  - Savannas
KW  - utilization distributions
KW  - movement ecology
KW  - predation risk
KW  - animal ecology
KW  - South Africa
KW  - size
KW  - conservation
KW  - Serengeti
KW  - ecosystem
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134935
VL  - 7
IS  - 5
ER  - 
TY  - JOUR
A1  - Grözinger, Franziska
A1  - Thein, Jürgen
A1  - Feldhaar, Heike
A1  - Rödel, Mark-Oliver
T1  - Giants, Dwarfs and the Environment - Metamorphic Trait Plasticity in the Common Frog
JF  - PLOS ONE
N2  - In order to understand adaptation processes and population dynamics, it is central to know how environmental parameters influence performance of organisms within populations, including their phenotypes. The impact of single or few particular parameters in concert was often assessed in laboratory and mesocosm experiments. However, under natural conditions, with many biotic and abiotic factors potentially interacting, outcomes on phenotypic changes may be different. To study the potential environmental impact on realized phenotypic plasticity within a natural population, we assessed metamorphic traits (developmental time, size and body mass) in an amphibian species, the European common frog Rana temporaria, since a) larval amphibians are known to exhibit high levels of phenotypic plasticity of these traits in response to habitat parameters and, b) the traits' features may strongly influence individuals' future performance and fitness. In 2007 we studied these metamorphic traits in 18 ponds spread over an area of 28 km 2. A subset of six ponds was reinvestigated in 2009 and 2010. This study revealed locally high variances in metamorphic traits in this presumed generalist species. We detected profound differences between metamorphing froglets (up to factor ten); both between and within ponds, on a very small geographic scale. Parameters such as predation and competition as well as many other pond characteristics, generally expected to have high impact on development, could not be related to the trait differences. We observed high divergence of patterns of mass at metamorphosis between ponds, but no detectable pattern when metamorphic traits were compared between ponds and years. Our results indicate that environment alone, i.e. as experienced by tadpoles sharing the same breeding pond, can only partly explain the variability of metamorphic traits observed. This emphasizes the importance to assess variability of reaction norms on the individual level to explain within-population variability.
KW  - rana temporaria populations
KW  - prey growth rate
KW  - phenotypic plasticity
KW  - larval density
KW  - amphibian metamorphosis
KW  - ambystoma opacum
KW  - predation risk
KW  - life history
KW  - developmental plasticity
KW  - adaptive plasticity
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117203
SN  - 1932-6203
VL  - 9
IS  - 3
ER  -