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Do immune challenges affect migratory decisions?

Rosberg, Linnea (2020) BIOK01 20201
Degree Projects in Biology
Popular Abstract
Should I stay or should I go?

Every year billions of animals migrate! For different reasons, to different places and different distances but they all have the act of migration in common. In almost all groups of animals migration have evolved time and time again. This raises the question of how and why migration came to be? One possible answer is that it evolved from partial migration, where only some individuals in a group migrate while others stay at home. We investigate the reason why individuals make the choice of either staying or going, by looking at a population of Eurasian blackbirds (Turdus merula). We believe that if they have an infection and therefore an active immune system, they will remain resident and not migrate. Like us... (More)
Should I stay or should I go?

Every year billions of animals migrate! For different reasons, to different places and different distances but they all have the act of migration in common. In almost all groups of animals migration have evolved time and time again. This raises the question of how and why migration came to be? One possible answer is that it evolved from partial migration, where only some individuals in a group migrate while others stay at home. We investigate the reason why individuals make the choice of either staying or going, by looking at a population of Eurasian blackbirds (Turdus merula). We believe that if they have an infection and therefore an active immune system, they will remain resident and not migrate. Like us choosing not to run a marathon when sick.

To investigate this, we used tiny transmitters that birds had on their back from autumn to the next spring. Those allowed us to determine whether a bird had migrated or not. Half of the birds got injected with lipopolysaccharides (LPS) to induce an immune response. LPS are molecules that some bacteria use in their cell membrane and it is recognised by the immune system so an immune response starts. This means that we can induce the immune system in the birds without making them sick.

In our study we did not get any result that supported our hypothesis, there was no difference in the group that got treated with LPS and the control group. There were migrating and resident individuals in both groups at about the same amount. The result we got did not support any of the of the other existing theories of partial migration either. We could not see any difference in size or age between migrants and residents. The only tendency to a difference we got was between the genders where females seemed to be more likely to stay and the males migrate, but it was not enough to be a significant result.

The lack of clear results could be due to the difficulty we experienced in determining if a bird had migrated or not. If the groups are not divided correctly that will affect the result when it is analysed. Another problem we encountered was that the winter this year was milder than it has been in more than a hundred years. If there is no lack in food or cold temperatures that make it hard for the birds to stay during the winter they will not migrate. Migration takes energy and can be risky so if there are no motivating factors it’s better for a bird to stay at home.

Other studies have found some support for the immune system to affect the decision of migration or remaining resident, but it has yet to be proven right or wrong. Therefore, more studies need to be done in the future on the subject. If we think about all the billion animals that migrate every year and how they might be affected if changes to the climate like this winter continues, it might be important to understand why they started migrating in the first place.

Examensarbete för kandidatexamen i Biologi 15 hp 2020
Biologiska institutionen, Lunds universitet

Handledare: Arne Hegemann
Evolutionary ecology and Aquatic ecology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Rosberg, Linnea
supervisor
organization
course
BIOK01 20201
year
type
M2 - Bachelor Degree
subject
language
English
id
9021708
date added to LUP
2020-06-23 15:31:33
date last changed
2020-06-23 15:31:33
@misc{9021708,
  author       = {{Rosberg, Linnea}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Do immune challenges affect migratory decisions?}},
  year         = {{2020}},
}