PhD Defence: Jennifer E. Hansen

Jennifer E. Hansen will defend her PhD degree in Ecology. The dissertation is about what decisions brown bears (Ursus arctos) make upon where to go and where to settle after becoming independent from their mother and siblings.


20 Jan

Practical information

  • Date: 20 January 2023
  • Time: 10.00 - 15.00
  • Location: Bø, Auditorium 4-311A and on zoom
  • Download calendar file
  • Link to digital participation 

    Program

    Kl. 10.00 Trial lecture, with topic: The interplay between sociality and social organisation in animal ecology

    Kl. 11.30. PhD defence: The effects of social, familial, and anthropogenic factors on dispersal-related space use and movement in Scandinavian brown bear (Ursus arctos).

    Evaluation committee

    • First opponent: Professor Barbara Zimmermann, Inland Norway University of Applied Sciences (INN)
    • Second opponent: Associated Professor Miha Krofel, University of Ljubljana
    • Administrator: Associated Professor Øyvind Steifetten, University of  South-Eastern Norway

    Supervisors

    • Principal supervisor: Professor Andreas Zedrosser, University of  South-Eastern Norway
    • Co-supervisor: Shane Frank, Wildlife Research Scientist at Colorado Parks & Wildlife. 
    • Co-supervisor: Research scientist Anne Hertel, Ludwig Maximilians University of Munich.
Any questions?

Jennifer E.HansenJennifer E. Hansen is defending her dissertation for the degree philosophiae doctor (PhD) at the University of South-Eastern Norway.

The doctoral work has been carried out at the Faculty of Technology, Natural Sciences and Maritime Sciences.

Title of the dissertation: The effects of social, familial, and anthropogenic factors on dispersal-related space use and movement in Scandinavian brown bear (Ursus arctos).

You are welcome to follow the trial lecture and the public defence.

  • Link to the dissertation  will soon be presented here. 

Summary

There is a lot we don't know about the decisions brown bears (Ursus arctos) make upon becoming independent after a variable period spent with their mother and siblings. During the course of my research, I've been able to add a few pieces to the puzzle regarding the factors related to space use and movement decisions made by brown bears during the dispersal and settlement process.

One of the most exciting and surprising findings was that the social landscape plays a role in where female brown bears settle prior to breeding. It turns out that they prefer to settle where they can overlap females familiar from their natal period. They also tend to select a settlement range that overlaps their mother's range and has higher density than their natal ranges. Discovering that females have an awareness of the social landscape around them indicates that this species might not be as solitary as previously described.

I also found that family matters for females, as seen in the distances they settle away from their natal ranges. Females with living mothers settle farther than those whose mothers died prior to settlement. Besides space conflict with their mothers, female sibling pairs compete for settlement ranges closer to the natal range. Unsurprisingly, the larger sister of the pair tends to win that competition! Does it matter, though? It depends.

Females that settled closer to the natal range had higher lifetime survival, but were less likely to survive to wean at least one offspring. Distance settled from the natal range had no effect on lifetime reproductive success. These rather confusing results point to several complexities in the system, including reproductive suppression by neighboring females and relatively high harvest pressure. While familiarity with the area may aid in survival, it does not lead to an increase in reproduction. Thus, females can live a long time and produce no offspring or live a short time and produce a single offspring.

Lastly, I found that male brown bears movement and habitat selection is influenced by human disturbance. More specifically, resident males (who are familiar with resources in their home ranges) show greater avoidance of human infrastructure in movement and selection. Dispersing males, on the other hand, are relatively naïve to their surroundings and tend to exhibit riskier movement and selection during the dispersal period. These differences in movement and selection patterns indicate that connectivity maps based on dispersing individuals rather than residents may be a more accurate portrayal of potential barriers to movement.