Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

MacDougall-Shackleton, Elizabeth A.

Abstract

I

In many animals, individuals show consistent variation in activity and movement, suggesting the existence of movement-related behavioural syndromes. I assessed the relationship between exploratory behaviour (over a small spatial scale) and migration distance (over a much larger scale) in song sparrows (Melospiza melodia). I quantified exploration using a novel environment test and inferred migration distance (overwintering latitude) using stable hydrogen isotope analysis of winter-grown claw tissue. Exploration was positively related to migration distance. I also investigated candidate mechanisms that if common to both exploration and migration, could explain the correlation between these behaviours. Circulating androgen levels were not associated with either movement behaviour, but at the dopamine receptor gene DRD4 one sequence variant was linked to exploration and another to migration distance. The observed relationship between small- and large-scale movement suggests the existence of a movement syndrome and provides insight into the evolution of movements over multiple geographic scales.

Summary for Lay Audience

Individuals in many animal species show correlated differences in their behaviours and movement, suggesting the existence of behavioural syndromes. Behavioural syndromes are collections of multiple behaviours that show consistencies in different contexts. For example, individuals that are more aggressive than others in certain situations may also be bolder than their counterparts in other circumstances. Accordingly, behaviours related to movement on multiple scales, such as exploration over short distances and migration over longer distances, may show a relationship with each other. I tested the relationship between exploration and migration distance in a breeding population of song sparrows (Melospiza melodia). I placed individuals into a room with features they would not experience in their natural habitats and measured how much they explored this new environment. To quantify migration distance, I analyzed isotope composition of winter-grown claw tissue. The relative proportions of “heavy” and “light” forms of hydrogen in claw tissue reflect those of the area where the tissue was grown. Because these proportions vary predictably with latitude, stable isotope analysis of winter-grown tissue allows estimating how far south each bird migrated. Exploration levels were strongly correlated with latitudinal and total migration distance—more exploratory birds overwintered further south and thus migrated longer distances.

Exploration and migration might be correlated because they are both influenced by the same mechanism, for example the same genetic variant or hormone. I tested two candidate mechanisms that might link exploration to migration: androgen levels and variation at a dopamine gene. Androgen levels were not associated with either small-scale (exploration) or large-scale (migration distance) movement behaviours. However, variation at the dopamine receptor DRD4 was related to both exploratory behaviour and total migration distance. This gene is involved in the motivational and reward pathways. The relationship between small-scale movement (exploration) and larger-scale movement (migration) suggests movement may be a consistent trait, and part of a behavioural or ‘movement’ syndrome. This result improves our understanding of the evolution of movements over multiple geographic scales.

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