Spatial and temporal partitioning of mustelids in Southeast Alaska

Abstract

Abstract As species’ distributions shift in response to changing environmental conditions, novel species interactions are emerging, challenging researchers and managers alike. When new species enter existing ecological communities, their effects on fellow guild members are difficult to predict. Competition between species within the same guild can regulate populations and influence community structure, but niche partitioning is a way for sympatric species to coexist through differential use of space, time, and resources. The fisher (Pekania pennanti) is a carnivore species that has recently colonized Southeast Alaska (SEAK), the northern margin of its range. Although currently considered at low density, the fisher has been expanding its distribution in SEAK in recent years and may impact the native SEAK forest carnivore guild through competitive interactions. We examined the potential for competition between fisher, American marten (Martes americana), and ermine (Mustela erminea) in SEAK during the winter of 2018 by investigating patterns of spatial and temporal overlap between the species at both local and landscape scales. Using data collected from remote‐sensed habitat features, climate characteristics, species detections from 25 systematic camera stations (50 unique cameras), and single‐species occupancy models, we found that fisher occupancy was positively correlated with vegetation height, and detection decreased with increased snow density. Using two‐species occupancy models, we found evidence of temporal, rather than spatial, avoidance patterns among the SEAK mustelid species investigated, although our inference was limited by sample size. Fisher, the largest mustelid evaluated, did not exhibit changes in occupancy or detection in the presence of marten or ermine. Likewise, detection and occupancy parameters of the mid‐sized marten and small‐sized ermine were not affected by the presence of the other mustelids. Instead, analysis of diel activity patterns showed that marten and ermine reduced temporal overlap with fisher, exhibiting less activity during times of peak fisher activity. Overall, these results show that mustelids in SEAK displayed a pattern of hierarchical temporal partitioning during winter, with smaller‐bodied mustelids avoiding larger, more dominant mustelids. However, if the fisher population continues to expand its range and abundance in SEAK, species interactions may shift and increase the potential for competition between the fisher, marten, and ermine mustelid guild.

Keywords

• activity pattern
• competition
• ermine
• fisher
• marten
• mustelid