Genetic analysis reveals demographic fragmentation of grizzly bears yielding vulnerably small populations.
Ecosystem conservation requires the presence of native carnivores, yet in North America, the distributions of many larger carnivores have contracted. Large carnivores live at low densities and require large areas to thrive at the population level. Therefore, if human-dominated landscapes fragment remaining carnivore populations, small and demographically vulnerable populations may result. Grizzly bear range contraction in the conterminous USA has left four fragmented populations, three of which remain along the Canada-USA border. A tenet of grizzly bear conservation is that the viability of these populations requires demographic linkage (i.e. inter-population movement of both sexes) to Canadian bears. Using individual-based genetic analysis, our results suggest this demographic connection has been severed across their entire range in southern Canada by a highway and associated settlements, limiting female and reducing male movement. Two resulting populations are vulnerably small (< or =100 animals) and one of these is completely isolated. Our results suggest that these trans-border bear populations may be more threatened than previously thought and that conservation efforts must expand to include international connectivity management. They also demonstrate the ability of genetic analysis to detect gender-specific demographic population fragmentation in recently disturbed systems, a traditionally intractable yet increasingly important ecological measurement worldwide.
Proctor
Michael F
MF
University of Calgary, Department of Biological Sciences, Calgary, Alberta, Canada T2N 1N4. mproctor@netidea.com
McLellan
Bruce N
BN
Strobeck
Curtis
C
Barclay
Robert M R
RM
D025041:Animal Migration; D000818:Animals; D002170:Canada; D017753:Ecosystem; D005260:Female; D014644:Genetic Variation; D008297:Male; D011157:Population Dynamics; D014481:United States; D001503:Ursidae / Q000235:genetics* / Q000502:physiology*