Studying the demography of animal and plant populations
What causes shifts in species' ranges
The distribution of animal and plant species in nature is dynamic. We want to understand what drives shifts (including contractions and expansions) in species' ranges, and changes in their abundance. Our main approach is to look at factors affecting reproduction, dispersal and death. These are the basic demographic variables that determine spatial population dynamics.
Demographic diversity is one form of biodiversity, and South Africa is particularly rich in it. Among plants, for example, it ranges from cycads and quiver trees, that can live for hundreds of years, to desert annuals that complete their whole life cycle in one year. Among birds, it ranges from Penduline Tits, with a short life expectancy, to Albatrosses that can live for many decades. Our understanding of demographic biodiversity in South Africa is still very limited.
Methodologies for studying population dynamics
We often use matrix population models to link age-specific reproduction and survival to population dynamics. We are concerned about imperfect detection: the fact that surviving individuals can be missed in capture-mark-recapture studies or species overlooked in places where they occur. We therefore use statistical methods that correct for non-detection when studying survival and range dynamics.
Demography is the key to understanding animal and plant vulnerability
Demography is key to understanding the vulnerability of animals and plants, be it due to climate and land use change, or harvesting. We are involved in a wide range of projects within SANBI and in collaboration with scientists at other institutions.
- Population ecology of hadedas near their expanding range edge: http://www.adu.org.za/hadeda.php
- Vulnerability of birds to climate change
- Vulnerability of plants to climate change
- Developing methods for analysing bird atlas data
- Survival and movement of chameleons
Res Altwegg is an honorary research associate of the Animal Demography Unit at the University of Cape Town.
Kirstenbosch Research Centre, Rm C34
Tel: 021 799 88 09
E-mail: Res Altwegg