An important part of the project will be to describe sex-differences in these traits. It is anticipated that males will increase the size of their home range to a much larger extent than females when they become sexually mature, and that they will do this earlier in the season due to male-male competition for territories (“arms race”). It is also anticipated that males will pay the highest cost of reproduction in terms of reduced survival early in the season when they establish territories and gain access to females, whereas females will have reduced survival while nursing young (usually while being pregnant) later in the season. However, such patterns have yet not been well described.
Another interesting part of the project will be to study the individual level heterogeneity and correlations in the observed traits. How large is the variation in home-range size, body mass, dispersal and risk of mortality among individuals? Can any of this variation be attributed to spatial variation in the microhabitat? Do individuals with large home-ranges have higher survival because they possess more resources, or do they have lower survival because they are more exposed to predation (or live in a nutritionally poor habitat)?
Student requirements:
This project can be carried out by one or two Master students working together in the field but focusing on different questions. If two students are recruited to the project, one student can focus on sex-differences (second paragraph above) while the other student can focus on individual heterogeneity (third paragraph above). The students should have at least some interest in learning statistical modeling. The students will learn to use state-of-the art methods for analyzing spatial capture-recapture data and will have the opportunity to attend international student workshops on this topic. Students with a strong background in statistics will have a chance to make important contributions to a fast developing field. Before starting the field work, students must attend and pass a course on ethical handling of animals, MBV4330 – “Experimental animal studies“ (taught early in both fall and spring semesters) or equivalent.
Fieldwork and logistics:
Field work will be carried out in Kielder forest in the border areas of England and Scotland from early February to mid-June. Live-trapping will be carried out in one large array of traps every 3-4 weeks, each trapping session lasting about one week. Housing will be provided in Kielder village, and students have the opportunity to spend time at University of Aberdeen, hosted by collaborator Professor Xavier Lambin, between trapping sessions (possible housing at Culterty Field Station, just north of Aberdeen).
Some relevant literature:
Ergon T, Lambin X, Stenseth NC. Life-history traits of voles in a fluctuating population respond to the immediate environment. Nature. 2001; 411:1043-5.
Ergon T, Ergon R, Begon M, Telfer S, Lambin X. Delayed density-dependent onset of spring reproduction in a fluctuating population of field voles. Oikos. 2011 Jun;120(6):934-40.
Ergon T, Yoccoz N, Nichols JD. Estimating latent time of maturation and survival costs of reproduction in continuous time from capture-recapture data. In: Thompson D, Cooch EG, Conroy MJ, editors. Modeling Demographic Processes in Marked Populations. Environmental and Ecological Statistics. 3: Springer Verlag; 2009.
Gardner B, Royle JA, Wegan MT. Hierarchical models for estimating density from DNA mark-recapture studies. Ecology. 2009 Apr; 90(4):1106-15.
Ergon, T. & Gardner, B. (2013). Separating mortality and emigration: modelling space use, dispersal and survival with robust-design spatial capture–recapture data.Methods in Ecology and Evolution. ISSN 2041-210X. 5(12), s 1327- 1336 . doi:10.1111/2041-210X.12133