Population ecology, life history and conservation biology

– Ringsby Lab

Due to heavy exploitation of natural resources particularly the last centuries we have entered a period of mass extinctions on earth where many wild species experience a steep decline in population sizes towards the brink of extinction.


Photo by Per Harald Olsen/NTNU


More than ever it is now important to understand the processes that drive fluctuations in population sizes, particularly as populations become small and threatened. A thorough understanding of the eco-evolutionary mechanisms that causes population decline may enable us to suggest targeted management measures in order to ensure sustainable populations for the future.

What factors causes variation in time and space?

I seek to understand eco-evolutionary mechanisms that cause changes in species distributions their abundances and how these vary in time which is in the core of population ecology. And in order to understand the mechanisms behind we have to deal with how life history traits (i.e. fitness related traits) vary over among individuals in time and among populations. Next we need to understand how the variation in fitness are influenced both by demographic (for instance population density) as well as environmental effects, such as habitat heterogeneity, seasonal effects and climate change.

Thus, a major part of my research has focused on understanding and quantifying factors that influence individual variation in fitness which may enable us to predict changes in population sizes over time.

The role of parasites

One fascinating area of research is the co-evolutionary interactions between parasites and their hosts. So far we have focused on how a macro parasite, the nematode Syngamus trachea varies in space and time and affects the fitness of the house sparrows negatively by reducing survival rates of juveniles as well as reducing the reproductive output. The role of parasite-host interactions on the population dynamics of host species should be prioritized I the future. Not at least, as many parasite species are extending their geographic ranges as a consequence of global warming, which will utterly emphasize their significance.

The importance of life history trade offs

Another other field of my research seeks to understand how organisms balance their   energy allocation into growth, self-maintenance, and reproduction. These life history trade-offs are fundamental in biology, but still not well understood. In particular I find it interesting to investigate the relationships between growth, body sizes and telomere dynamics at early age, and how these early experiences might interfere with the organism’s lifespan and lifetime reproductive success.

The main study system for my research has been an archipelago located at Helgeland in northern Norway consisting of 18 island populations of House sparrows (Passer domesticus) where the spatial structure of the archipelago form a metapopulation. In addition we conduct experimental studies in several other insular populations along the coast of northern Norway. Since 1993 “the House sparrow project” has collected an impressive data set that provides unique opportunities for in-depth studies within eco-evolutionary disciplines.

The focus in ongoing work

  • Effects of ecto- and endoparasites on variation in individual fitness as well as on population dynamics in House Sparrows
  • How does local phenology (e.g. onset of spring, NDVI) and climate change affect variation in House Sparrows reproductive success
  • Causes and consequences of variation in egg size in House Sparrows
  • Spatial and temporal variation in life history traits: the relationship between body size, growth rate and potential role of telomeres as mediators of lifespan in House Sparrows




Thor Harald Ringsby. Photo by Per Harald Olsen/NTNU

Thor Harald Ringsby

Associate Professor

E-mail: thor.h.ringsby@ntnu.no


Connected to the “House sparrow project”:

Håkon Holand (PhD, researcher, CBD, Dept Biol, NTNU)

Bernt Rønning (PhD, researcher, CBD, Dept Biol, NTNU)

Thomas Kvalnes (PhD student, CBD, Dept Biol, NTNU)

Peter Sjolte Ranke (PhD student, CBD, Dept Biol, NTNU)

Ane Marlene Myhre (CBD, Dept Biol, NTNU)

Bernt-Erik Sæther (Prof, CBD Dept Biol, NTNU)

Henrik Jensen (Assoicate Prof, CBD, Dept Biol, NTNU)

Ingerid Julie Hagen (PhD, Researcher, CBD, Dept Biol, NTNU)

Jonathan Wright (Prof, CBD, Dept Biol, NTNU)

Henrik Pärn (Phd, Senior Engineer, CBD, Dept Biol, NTNU)

Stein Rune Karlsen (Senior researcher, NORUT)

Jarle Tufto (Prof, CBD, Dept Stat Math, NTNU)

Pat Monaghan (Prof, University of Glasgow)


Centre for Biodiversity Dynamics at NTNU