Patterns of Wolf Dispersal Respond to Harvest Density across an Island Complex

Abstract

Wolves are highly mobile predators and can disperse across a variety of habitats and over long distances. However, less is known about dispersal capabilities across water and among islands. The biogeography of island systems fosters spatially structured local populations, and their degree of connectivity may influence the dynamics and long-term viability of the regional population. We sought to quantify wolf dispersal rate, distance, and dispersal sex bias throughout Prince of Wales Island, a 6670 km² island in southeast Alaska, and the surrounding islands that constitute the wildlife management unit (9025 km²). We also investigated patterns of dispersal in relation to hunting and trapping intensity and wolf population density. We used DNA data collected during 2012-2021 long-term monitoring efforts and genotyped 811 wolves, 144 of which (18%) were dispersers. Annual dispersal rates were 9-23% and had a weakly positive relationship with wolf density. Wolves dispersed 41.9 km on average (SD = 23.7 km), and males and females did not disperse at different rates. Of the dispersing wolves, 107 died, and the majority (n = 81) died before they were able to settle. The leading manner of death was trapping (97% of mortalities), and wolves tended to disperse from areas with low harvest density to areas where harvest density was relatively higher. Dispersal occurred both to and from small islands and the larger Prince of Wales Island, indicating bidirectional as opposed to asymmetrical movement, and the genetic overlap of wolf groups demonstrates connectivity throughout this naturally patchy system. Island ecosystems have different predator-prey dynamics and recolonization processes than large, intact systems due to their isolation and restricted sizes; thus, a better understanding of the degree of population connectivity including dispersal patterns among islands in the Prince of Wales archipelago could help inform the management and research strategies of these wolves.

Keywords: Canis lupus; dispersal; islands; noninvasive genetic monitoring.

Figure 1

Wolf sample locations, GMU 2 (including Prince of Wales Island and the outer islands), AK, USA, 2012–2021. Samples from harvested wolves are shown as orange, hair samples are shown as red, scat samples are shown as blue, and blood samples are shown as white.

Figure 2

Wolf groups (a) and straight-line representations of dispersal distances (b), GMU 2 (including Prince of Wales Island and the outer Islands), AK, USA, 2012–2021.

Figure 3

Results of discriminant analysis of principal components (DAPC) with number of axes retained = 40, for wolves on Prince of Wales Island and the outer Islands, AK, USA, 2012–2021.

Figure 4

Difference between wolf harvest densities in the areas a wolf dispersed to and the area the wolf was last known to be a resident in the year before sampling, GMU 2 (including Prince of Wales Island and the outer Islands), AK, USA, 2012–2021. Horizontal lines to the right of zero indicate a wolf dispersed to an area with a greater harvest density, lines to the left indicate dispersal to an area with a lower harvest density. The points indicate sample sizes, the horizontal lines are the difference in harvest density (dispersal destination area–pre-dispersal [resident] area), and the diagonal dashed line indicates an individual dispersed to an area with no harvest in the prior year. Points are scaled to sample size and are semi-transparent so that close values are visible.