Mammalian dispersal behaviour and its fitness correlates

• Main Author: Johnson, Cheryl A.
• Other Authors: Fryxell, John M., Thompson, I.D.
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: decisions making; juveniles; mortality risk; natal dispersal behaviour; territorial solitary mammals; dispersal; departure; natal area; search; settlement; American marten; Martes americana
• Online Access: https://hdl.handle.net/10214/22160

This thesis is an investigation of the factors influencing the decisions made by juveniles during the three phases of dispersal: departure from the natal area, search and settlement. I used literature data on gregarious and solitary territorial mammals to test whether changes in mortality risk during dispersal and density influenced the probability of leaving the natal area. In gregarious mammals, dispersal probability remained constant with changes in mortality risk and increased with density. These results suggested that increased reproductive success might compensate for high disperser mortality when group membership in the natal area exceeded optimal group sizes among gregarious species. In solitary mammals, the decision to leave the natal area appeared to depend on the fitness costs to dispersal. Few juveniles dispersed when the mortality risk during dispersal was high and when conspecific density was high and competition for territorial sites outside the natal area, presumably, intense. Next, I examined the effect of mortality risk on search and settlement in the solitary, territorial American marten ('Martes americana'). I compared dispersal between a landscape composed of young, regenerating forests, hypothesized to represent suboptimal marten habitat, and an uncut landscape composed of mature, old-growth forests. Juveniles from the regenerating landscape dispersed shorter distances and travelled more slowly than juveniles from the uncut landscape. A more detailed analysis revealed that the accumulation of mortality risk with increasing dispersal distance was two times higher in the regenerating versus uncut landscape. Differences in body condition, supported by previous studies of hunting efficiency, suggested that juveniles from the regenerating landscape were less capable of coping with the energetic demands of dispersal compared to juveniles from the uncut landscape. Neither dispersal cost, nor adult despotism appeared to influence patterns of juvenile settlement. Most juveniles settled <=1 km ...