Response of Overwintering Caribou to Burned Habitat in Northwest Alaska

Abstract

Caribou (Rangifer tarandus granti) use lichens, when available, as primary forage on their winter range. In boreal forest habitats, wildland fires effectively destroy lichens, and overwintering caribou are known to avoid burned areas for decades while lichen communities regenerate. However, little has been published about caribou response to burned habitat in tundra ecosystems. To assess the relationship between winter caribou distribution and burned areas, we instrumented Western Arctic Herd caribou with satellite telemetry collars and evaluated their locations in relation to recent burns of known age (≤ 55 years old) across northwestern Alaska. We analyzed caribou distribution for different habitat types (tundra and boreal forest), age categories of burns, and possible edge effects. We also reanalyzed the data, limiting available habitat to a uniform traveling distance (5658 m) from daily satellite locations. Using selection indices that compared caribou use of burns and buffers to their availability, we found that caribou strongly selected against burned areas within the tundra ecosystem. Recent burns were selected against at both large (range-wide) and intermediate (5658 m) spatial scales. Caribou particularly selected against 26-to 55-year-old burns and the interior (core) portions of all burns. We found that caribou were more likely to select burned areas in the late fall and early spring than midwinter. Increased fires in northwestern Alaska could decrease the availability and quality of winter habitat available to the herd over the short term (up to 55 years), potentially influencing herd population dynamics and reducing sustainable harvest levels. We recommend that fire managers consider caribou midwinter range condition and extent: however, management that achieves a mosaic pattern of fire history may benefit a wide array of species, including caribou. A better understanding of the current regional fire regime and the distribution of available winter range will be required before practicable management recommendations can be developed for this herd.

Modeling influences on winter distribution of caribou in northwestern Alaska through use of satellite telemetry

“…This result may seem intuitive as caribou tend to avoid habitat that has recently burned (Joly et al, 2007a;Joly et al, 2010), whereas moose select for it (Maier et al, 2005). Furthermore, high moose densities could sup¬ port high wolf densities which would reduce its suit¬ ability for caribou (Bergerud, 2007).…”

“…Caribou can be found throughout their annual range during winter, though use is more concentrated on the Nulato Hills, upper Kobuk River and eastern Seward Peninsula (Joly et al, 2007a). These regions are diverse, with extensive areas of treeless tussock tundra (Eriophorum vaginatum, Carex spp.…”

“…Looking across the northern landscape, caribou ecotype and disturbance (e.g., wildfire and/or industrial development) are also likely to be important factors in determining distribution (Mallory & Hillis, 1998;Johnson et al, 2005;Joly et al, 2007a). The importance of each factor is likely to depend on the scale of the analysis (Wiens, 1989;Rettie & Messier, 2000;Johnson et al, 2004;Gustine et al, 2006;Mayor et al, 2007).…”

Factors influencing the distribution of Bathurst barren-ground caribou (Rangifer tarandus groenlandicus) during winter.

“…Following a major disturbance such as fire or heavy grazing pressure, the recovery of lichen mats may take a lengthy period of time (~45 kg ha" yr" , Auclair 1985) preventing their use by caribou for up to 50 years (Scotter 1964, Kelsall 1968, Klein 1982, Joly et al 2003, 2007a, Jandt et al 2008.…”

“…Although researchers have noted that caribou sometimes forage in recently burned habitats Rowe 1975, Joly et al 2003), they are mostly observed to avoid these areas in favour of older, lichen-rich communities (>55 years of age; Klein 1982, Thomas et al 1996, Joly et al 2003, 2009a. Lichen species preferred by caribou (e.g., Cladina rangiferina, C mitis) are associated with late-successional serai stages in boreal forests (Maikawa and Kershaw 1976), and in the short term are lost following fire (Klein 1982, Thomas et al 1996Joly 2003Joly , 2007aJoly , 2009a.…”