Avian Demography Unit
Department of Statistical Sciences
University of Cape Town
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Res Altwegg Res Altwegg
Post-doc student


My research interests

I study the connection between life-history evolution and population/community ecology. The dynamics of food webs are the result of things that happen at the level of the individuals: their survival rates, their reproductive success, their movements, their life-history decisions, the habitat choices they make, how effective they are at gathering food and at avoiding predators. In all these traits, there is variation among individuals in natural populations; genetic variation that can lead to evolutionary change over multiple generations, and phenotypic plasticity that can result in very fast changes within one generation. My main interest is to understand the connection between this variation at the individual level and community processes.
 
Conceptually, I strive to combine field observations with controlled experiments and theoretical concepts. If possible, I aim to directly connect theory and data through statistical methods, and I often use the Akaike Information Criterion (AIC) to evaluate how well my data support different models corresponding to different biological hypotheses.

Short description of current research

I'm about to start a project on range expansions in South African birds. I plan to quantify range changes in several bird species over the past 50 years, and examine the demographic causes that have led to these changes.
 
My recent postdoctoral project at the University of Victoria deals with community level consequences of inducible defence in the ciliate Euplotes. These ciliates react to the presence of predators by growing defensive cell structures. Theory gives us rules for how individuals should balance foraging effort and predator avoidance, and almost all empirical studies investigating risk sensitivity in foraging have found strong reactions at the individual level. There are also many studies now showing that risk sensitive foraging affects competition with other species in a way that makes food-web dynamics difficult to predict: we not only have to know how species interact, but also how these interactions change in the presence of additional species, e.g. predators. However, no study has yet been able to experimentally examine the connection between inducible defence and population dynamics. The aim of my project with Euplotes is to provide such a study. By directly fitting the mathematical models to the population-density counts I obtain from my experimental systems, I expect to be able to test the theory, and to quantify the effect of this type of phenotypic plasticity on the dynamics of my communities.
 
My other current projects use capture-mark-recapture methods and matrix population models for demographic analyses of wild populations of barn owls (Tyto alba), asp vipers (Vipera aspis), and bull frogs (Rana catesbeiana). I estimate age-specific survival, reproduction, and emigration, examine how much these rates are affected by weather, and quantify the effects on population growth. As a general result, these analyses have shown that weather differentially affects different age classes. The connection between weather and population dynamics therefore depends on the demographic composition of these populations, and ultimately on the life history of the species involved.
 
A recently finished project of mine investigated predator-induced plasticity in the life history of water frogs (Rana lessonae / esculenta). Using artificial ponds and terrestrial outdoor enclosures, I was able to manipulate the growth environment and examine the reaction of these animals during two different stages in their complex life cycle. In another project, I investigated dispersal between local populations within a metapopulation of house sparrows (Passer domesticus), and examined how the decision to disperse depended on an individual's age, sex, and morphological characteristics.

Education and occupations
2005 - 2007: Postdoctoral Research fellow, University of Cape Town, South Africa, mentor: Prof. Les G. Underhill, fellowship from the National Research Foundation of South Africa (NRF) and the Swiss National Science Foundation (SNF).
2002 - 2005: Postdoctoral Research fellow, University of Victoria, Canada, mentor: Prof. Bradley R. Anholt, fellowship from the Swiss National science Foundation (SNF).
2001 - 2002: Civil service at the Swiss Ornithological Institute, Sempach: statistical analysis of ring recovery data, and fieldwork.
1997 - 2001: PhD Dissertation at the Zoology Institute, University of Zürich, Switzerland: 'Complex life cycles and predation risk: plastic growth and life-history strategies in water frogs', supervisor: Prof. H.-U. Reyer.
1996 - 1997: Diploma thesis (equivalent to Masters degree) at the Norwegian University of Science and Technology, Trondheim (NTNU), Norway, and University of Basel, Switzerland: 'Causes and consequences of dispersal within a metapopulation of house sparrows (Passer domesticus) in northern Norway', supervisors: Prof. B.-E. Sæther, NTNU, and Prof. S.C. Stearns, University of Basel.
1991 - 1997: Study of Biology I at the University of Basel, Switzerland. Study directions: population biology (supervisor: Prof. S.C. Stearns), invertebrate biology (supervisor: Prof. H. Rowell), plant ecology (supervisor: Prof. C. Körner), vertebrate biology (supervisor: Dr. D.G. Senn), conservation biology (supervisor: Prof. B. Baur).
 
Publications

(please note that the copy right is with the respective publishers)
 
Duquette, S.L., R. Altwegg, and B.R. Anholt 2007 Protozoan functional responses: effects of species, genotype and antipredator defences. Evolutionary Ecology Research 9: 789-800.
 
Erni, B., R. Altwegg, and L.G. Underhill 2007. An index to compare geographical distributions of species. Diversity and Distributions: in press.
 
Roulin, A. and R. Altwegg 2007. Breeding rate is associated with pheomelanism in male and with eumelanism in female barn owls. Behavioral Ecology 18: 563-570.
 
Altwegg, R., R.J.M Crawford, L.G. Underhill, A.P. Martin, P.A. Whittington 2007. Geographic variation in reproduction and survival of kelp gulls Larus dominicanus vetula in southern Africa. Journal of Avian Biology: in press.
 
Altwegg, R., M. Schaub, and A. Roulin 2007. Age-specific fitness components and their temporal variation in the barn owl. American Naturalist 169: 47-61.[pdf]
 
Bize, P., A. Klopfenstein, J. Gasparini, R. Altwegg, and A. Roulin 2006. Melanin-based coloration is a non-directionally selected sex-specific signal of offspring development in the Alpine swift. Evolution 60: 2370-2380.[pdf]
 
Altwegg, R., and L.G. Underhill 2006. Apparent survival rates of Cape Sugarbirds Promerops cafer at a breeding and a non-breeding site. Ostrich 77: 220-224.[pdf]
 
Altwegg, R., A. Roulin, M. Kestenholz, and L. Jenni 2006. Demographic effects of extreme winter weather in the barn owl. Oecologia 149: 44-51.[pdf]
 
Altwegg, R., M. Eng, S. Caspersen, B.R. Anholt 2006. Functional response and prey defense level in an experimental predator-prey system. Evolutionary Ecology Research 8: 115-128.[pdf]
 
Govindarajulu, P., R. Altwegg, B.R. Anholt 2005. Matrix model investigation of invasive species control: bullfrogs on Vancouver Island. Ecological Applications 15: 2161-2170.[pdf]
 
Duquette, S.L., R. Altwegg, and B.R. Anholt 2005. Factors affecting the expression of inducible defences in Euplotes: genotype, predator density, and experience. Functional Ecology 19: 648-655.[pdf]
 
Sæther, B.-E., R. Lande, S. Engen, H. Weimerskirch, M. Lillegård, R. Altwegg, P.H. Becker, T. Bregnballe, J.E. Brommer, R. McCleery, J. Merilä, E. Nyholm, W. Rendell, R.R. Robertson, P. Tryjanowski, and M.E. Visser 2005. Generation time and temporal scaling of bird population dynamics. Nature 436: 99-102.[pdf]
 
Altwegg, R., S. Dummermuth, B.R. Anholt, and T. Flatt 2005. Winter weather affects asp viper (Vipera aspis) population dynamics through susceptible juveniles. Oikos 110: 55-66.[pdf]
 
Reyer, H.-U., M.-O. Wälti, I. Bättig, R. Altwegg and B. Hellriegel 2004. Low proportions of reproducing hemiclonal females increase the stability of a sexual parasite-host system (Rana esculenta, R. lessonae). Journal of Animal Ecology 73: 1089-1101.[pdf]
 
Altwegg, R., K.B. Marchinko, S.L. Duquette, and B.R. Anholt 2004. Dynamics of an inducible defence in the protist Euplotes. Archiv für Hydrobiologie 160: 431-446.[pdf]
 
Salewski, V., R. Altwegg, B. Erni, K.H. Falk, F. Bairlein, and B. Leisler 2004. Moult of three Palearctic migrants in their West African winter quarters. Journal für Ornithologie 145: 109-116.[pdf]
 
Blanckenhorn, W.U., B. Hellriegel, D.J. Hosken, P. Jann, R. Altwegg, and P.I. Ward 2004. Does testis size track expected mating success in yellow dung flies? Functional Ecology 18: 414-418.[pdf]
 
Altwegg, R. 2003. Multi-stage density dependence in an amphibian. Oecologia 136: 46-50.[pdf]
 
Roulin, A., B. Ducret, P.-A. Ravussin, and R. Altwegg. 2003. Female plumage coloration covaries with reproductive strategies in the tawny owl. Journal of Avian Biology 34: 393-401.[pdf]
 
Altwegg, R., A. Roulin, M. Kestenholz, and L. Jenni. 2003. Variation and covariation in survival, dispersal, and population size in barn owls (Tyto alba). Journal of Animal Ecology 72: 391-399.[pdf]
 
Altwegg, R., and H.-U. Reyer. 2003. Patterns of natural selection on size at metamorphosis in water frogs. Evolution 57: 872-882.[pdf]
 
Altwegg, R. 2003. Hungry predators render predator avoidance behavior in tadpoles ineffective. Oikos 100: 311-316.[pdf]
 
Altwegg, R. 2002. Predator induced life-history plasticity under time constraints in pool frogs. Ecology 83: 2542-2551.[pdf]
 
Altwegg, R. 2002. Trait-mediated indirect effects and complex life cycles in two European frogs. Evolutionary Ecology Research 4: 519-536.[pdf]
 
McElligott, A.G., R. Altwegg and T.J. Hayden. 2002. Age-specific survival and reproductive probabilities: evidence for senescence in male fallow deer (Dama dama). Proceedings of the Royal Society of London B 269: 1129-1137.[pdf]
 
Altwegg, R., T.H. Ringsby, and B.-E. Sæther. 2000. Phenotypic correlates and consequences of dispersal in a metapopulation of house sparrows Passer domesticus. Journal of Animal Ecology 69: 762-770.[pdf]
 
Solberg, E.J., T.H. Ringsby, R. Altwegg, and B.-E. Sæther. 2000. Fertile House Sparrow X Tree Sparrow (Passer domesticus X Passer montanus) hybrids? Journal für Ornithologie 141: 102-104.
 
Ringsby, T.H., B.-E. Sæther, R. Altwegg, and E.J. Solberg. 1999. Temporal and spatial variation in survival rates of a house sparrow, Passer domesticus, metapopulation. Oikos 85: 419-425.


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Last updated: July-2007