Life on the edge: habitat fragmentation limits expansion of a restored carnivore

Item Metadata

Dublin Core


Life on the edge: habitat fragmentation limits expansion of a restored carnivore


The successful recovery of imperiled species is dependent on knowledge of how demographic drivers mediate population growth and expansion. One of the largest species restoration projects has been the reintroduction of swift foxes Vulpes velox to southern Canada, where 947 foxes were released between 1983 and 1997. Swift foxes have since increased and expanded their range into northern Montana (USA), but have experienced a population decline and stall in recolonization over the past 10 years. The objective of this study was to estimate the survival and reproductive rates of swift foxes in northern Montana, which constitutes the southern edge of this population. In addition, we evaluated support for two different hypotheses of how environmental factors and several demographic factors influence survival. Although our length of monitoring was relatively short, we found that adult and juvenile annual survival rates were 54% and 74%, respectively, and fecundity was 0.85. We found the most support for the hypothesis that the percentage of native grassland at the 1-km scale influenced survival and found that survival increased, on average, 2.1% for every 5% increase in grassland. Compared to previous estimates of swift fox population growth immediately following the release, our data suggest the population is currently stable. The long-term successful recolonization and connectivity of swift fox populations in this region will likely be dependent on maintaining large tracts of contiguous grassland. Comparing the estimates of demographic rates among different points in space and time should help managers better understand the population dynamics and inform restoration strategies for recovering populations.

Bibliographic Citation

Butler, A.R., Bly, K.L.S., Harris, H., Inman, R.M., Moehrenschlager, A., Schwalm, D., and D.S. Jachowski. 2021. Life on the edge: habitat fragmentation limits expansion of a restored carnivore. Animal Conservation 24:108-119.


Butler, Andrew R
Bly, Kristy L S
Harris, Heather
Inman, Robert M
Moehrenschlager, Axel
Schwalm, Donelle


Swift fox
Conservation translocations
Habitat fragmentation
Vulpes velox


12 pages







Is Part Of

Animal Conservation


This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Date Accepted


Date Issued


Date Submitted




Butler, Andrew R et al., “Life on the edge: habitat fragmentation limits expansion of a restored carnivore,” CPW Digital Collections, accessed April 16, 2024,