Bats in a changing landscape: Linking occupancy and traits of a diverse montane bat community to fire regime

Abstract

Wildfires are increasing in incidence and severity across coniferous forests of the western United States, leading to changes in forest structure and wildlife habitats. Knowledge of how species respond to fire‐driven habitat changes in these landscapes is limited and generally disconnected from our understanding of adaptations that underpin responses to fire. We aimed to investigate drivers of occupancy of a diverse bat community in a fire‐altered landscape, while identifying functional traits that underpinned these relationships. We recorded bats acoustically at 83 sites ( n = 249 recording nights) across the Plumas National Forest in the northern Sierra Nevada over 3 summers (2015–2017). We investigated relationships between fire regime, physiographic variables, forest structure and probability of bat occupancy for nine frequently detected species. We used fourth‐corner regression and RLQ analysis to identify ecomorphological traits driving species–environment relationships across 17 bat species. Traits included body mass; call frequency, bandwidth, and duration; and foraging strategy based on vegetation structure (open, edge, or clutter). Relationships between bat traits and fire regime were underpinned by adaptations to diverse forest structure. Bats with traits adapting them to foraging in open habitats, including emitting longer duration and narrow bandwidth calls, were associated with higher severity and more frequent fires, whereas bats with traits consistent with clutter tolerance were negatively associated with fire frequency and burn severity. Relationships between edge‐adapted bat species and fire were variable and may be influenced by prey preference or habitat configuration at a landscape scale. Predicted increases in fire frequency and severity in western US coniferous forests are likely to shift dominance in the bat community to open‐adapted species and those able to exploit postfire resource pulses (aquatic insects, beetles, and snags). Managing for pyrodiversity within the western United States is likely important for maintaining bat community diversity, as well as diversity of other biotic communities.

The effects of wildfire severity and pyrodiversity on bat occupancy and diversity in fire-suppressed forests

“…In contrast, assessments of fire severity on bats are more limited in number and ability to infer species-level effects. A concurrent study conducted in northern Sierra Nevada forests found bat functional traits associated with open areas were positively correlated with high-severity fire and fire frequency, whereas traits associated with habitat clutter tolerance were negatively correlated with such fire characteristics 7 . Similarly, a previous study in southern Sierra Nevada mixed conifer forests found higher activity rates of small-bodied species within high-severity areas 8 , and a study in Idaho forests found that overall bat activity was higher in high-severity areas than unburned areas 43 .…”

“…Additionally, future work should build on the findings presented here by exploring the relative importance of fire effects on foraging clutter, roost availability in the form of snag creation, and alterations to prey communities 43 . Habitat resources and bat occupancy also likely change with post-fire succession 7 and a more complete understanding of these temporal dynamics would improve our ability to conserve bats across landscapes with complex fire histories.…”

“…In particular, fire influences bat foraging and roosting resources provided by montane forest ecosystems and may be an important driver of habitat quality 6 . However, the effects of wildfire on bat occurrence and diversity within forest landscapes are understudied, creating challenges for bat conservation and management in fire-prone ecosystems 7,8 .…”

Extent, configuration and diversity of burned and forested areas predict bat richness in a fire-maintained forest

“…Insectivorous bats are highly mobile predators that respond to forest structure and fire based on their diverse call and morphological traits (Schnitzler et al 2003;Denzinger and Schnitzler 2013;Blakey et al 2019). At fine spatial scales (B 500 m), bats adapted to open areas and many edge-adapted species benefit from higher burn severity and more frequent fire (Armitage and Ober 2012;Buchalski et al 2013;Inkster-Draper et al 2013;Cox et al 2016;Blakey et al 2019;Steel et al 2019). Bats also use edges and openings created by timber harvest (Law et al 2016b and references therein).…”

Quantifying the impact of severe bushfires on biodiversity to inform conservation

“…We propose the 2019-2020 res will have signi cant population impacts on grey-headed ying foxes through substantial reduction in habitat and feeding resources at speci c roosts. Although there are no other studies of ying fox responses to res, studies of other bat species have shown that res impact populations through the alteration of foraging and roosting habitat 50,51,52 , and other Australian bats (non-Pteropus) have been shown to decrease activity in local areas in the months following bush res and up to one-year after major res 29,52 . The anomalous season of 2019-2020 bush res signi cantly impacted foraging resources for grey-headed ying foxes, which will alter their feeding behavior, and in turn, could delay recovery of Eucalypts that bene t from their pollination.…”