Post-fire movements of Pacific marten (Martes caurina) depend on the severity of landscape change

Abstract

Background Wildfires and forestry activities such as post-fire salvage logging are altering North American forests on a massive scale. Habitat change and fragmentation on forested landscapes may threaten forest specialists, such as Pacific marten (Martes caurina), that require closed, connected, and highly structured habitats. Although marten use burned landscapes, it is unclear how these animals respond to differing burn severities, or how well they tolerate additional landscape change from salvage logging. Methods We used snow tracking and GPS collars to examine marten movements in three large burns in north-central Washington, USA (burned in 2006) and central British Columbia, Canada (burned in 2010 and 2017). We also assessed marten habitat use in relation to areas salvage-logged in the 2010 burn. We evaluated marten path characteristics in relation to post-fire habitat quality, including shifts in behaviour when crossing severely-disturbed habitats. Using GPS locations, we investigated marten home range characteristics and habitat selection in relation to forest cover, burn severity, and salvage logging. Results Marten in the 2006 burn shifted from random to directed movement in areas burned at high severity; in BC, they chose highly straight paths when crossing salvage-blocks and meadows. Collared marten structured their home ranges around forest cover and burn severity, avoiding sparsely-covered habitats and selecting areas burned at low severity. Marten selected areas farther from roads in both Washington and BC, selected areas closer to water in the 2006 burn, and strongly avoided salvage-logged areas of the 2010 burn. Marten home ranges overlapped extensively, including two males tracked concurrently in the 2010 burn. Conclusions Areas burned at low severity provide critical habitat for marten post-fire. Encouragingly, our results indicate that both male and female marten can maintain home ranges in large burns and use a wide range of post-fire conditions. However, salvage-logged areas are not suitable for marten and may represent significant barriers to foraging and dispersal.

Residual forest structure influences behaviour of Pacific marten (

“…We suspect that this similarity was due to salvage logging homogenising large areas of the burn. In effect, marten in the 2010 burn had fewer suitable post-fire habitats (Volkmann and Hodges 2021). Surprisingly, we did not detect marten in unburned forests bordering either study area.…”

“…More recent work suggests that marten use residual structures in salvage blocks for resting and denning, but these features are a poor long-term substitute for forest cover (Wilk and Raphael 2018). GPS-tracked marten in the 2010 burn avoided salvage-blocks (Volkmann and Hodges 2021), and the relative abundances of both marten (Volkmann 2021) Wildfire and post-fire salvage logging are not equivalent disturbances for marten, and create different landscapes (Fig. 5).…”

“…For each burn, we built generalised linear models to separately examine marten selection of foraging and marking ('used') sites compared to burned ('available') sites. We a priori excluded salvaged and unburned sites from models because the 2006 and 2017 burns lacked salvage-logged areas, and because marten in the 2010 burn avoided salvage-blocks (Volkmann and Hodges 2021). We pooled habitat data for all years.…”

“…Marten in the 2010 burn chose sites with substantially more structural complexity than salvaged sites. When crossing open areas, marten took direct routes between available trees and saplings, and rarely approached salvage-blocks (Volkmann and Hodges 2021). Although deadfall was abundant at salvaged sites, these structures were usually stripped of branches and flush with the ground, making subnivean access difficult (Wilbert et al 2000).…”

“…Marten occupy burned landscapes (Magoun and Vernam 1986;Latour et al 1994;Paragi et al 1996;Volkmann and Hodges 2021), but many details of their post-fire habitat use are unclear. Like other carnivores, marten select habitats based on vegetation (Porter et al 2005;Seip et al 2018), prey (Vigeant-Langlois and Desrochers 2011), and conspecifics (Hutchings and White 2000).…”