Adjustments in habitat selection to changing availability induce fitness costs for a threatened ungulate

Abstract

a Montreal en amenagement forestier durable, Departement des sciences biologiques, Universite du Quebec a Montreal, Montreal, QC H3C 3P8, Canada; 6 Ministere du Developpement durable, de l'Environnement de la Faune et des Parcs, Directeur regional par interim du Saguenay -Lac-St-Jean, 3950 boul. Harvey, Jonquiere, QC G7X 8L6, Canada; and 7 Ministere du Developpement durable, de l'Environnement de la Faune et des Parcs, Direction des operations regionales du Nord-du-Quebec, 951 boul. Hamel, Chibougamau, QC G8P 2Z3, Canada Summary 1. Functional responses in habitat selection occur when individuals adjust their selection of habitat features as a function of the availability of those features. Functional responses in habitat selection are generally assumed to be fitness-rewarding tactics and are used to guide conservation actions. Fitness consequences of functional responses, however, have rarely been evaluated. 2. Eighty-three caribou were followed with GPS collars to establish the link between functional responses in habitat selection and adult female survival, a strong fitness correlate for caribou. We measured how caribou avoidance of mixed/deciduous stands and 6-to 20-yearold clear-cuts varied with the proportion of 6-to 20-year-old clear-cuts within their 100% minimal convex polygon (MCP), and if these functional responses were linked to survival. Mixed/deciduous stands and 6-to 20-year-old clear-cuts are risky for caribou because they are selected by moose, thereby attracting wolves and increasing predation risk for caribou. 3. Caribou avoided mixed/deciduous stands, especially when 6-to 20-year-old clear-cuts comprised a large proportion of their MCP, but this functional response did not differ between caribou that died and those that survived. When the proportion of 6-to 20-year-old clear-cuts in the MCP was low, caribou generally had low odds of occurring near 6-to 20-year-old clear-cuts. However, when the proportion of clear-cuts in the MCP was relatively high, caribou that strongly increased their odds of being near 6-to 20-year-old clear-cuts were generally those that died. 4. Synthesis and applications. Assessing the fitness consequences of how animals respond to habitat disturbances is central to wildlife conservation. We demonstrate that distinct functional responses in habitat selection involve different mortality risks and that population dynamics should depend on the frequency of the different tactics observed within populations. Individuals that persistently select riskier areas should be important drivers of population decline. Caribou mortality could be reduced by decreasing the appeal of 6-to 20-year-old clear-cuts for moose by removing deciduous vegetation through cleaning, which should reduce the selection of wolves for these stands. Removing deciduous vegetation should be especially effective in areas where those clear-cuts comprise a large proportion of the landscape, because this is where a subset of the caribou population experiences high mortality rates by selecting 6-to 20-year-old cle...

Spatial factors influencing northern mountain caribou (Rangifer tarandus) survival and distribution in the Telkwa Range

“…There is empirical evidence of inverse density dependence for woodland caribou as a consequence of altered predator-prey dynamics (Wittmer et al 2005b). Regardless, cutblock density may explain some of the variation in survival among caribou herds ranging across areas with different levels of commercial forestry (Smith 2004, Wittmer et al 2007, Apps et al 2013, Leblond et al 2013, Losier et al 2015.…”

“…Alternatively, it is possible that selection is maladaptive and that areas with high 26-40 year old cutblock densities represent ecological sinks, where evolutionary cues and actual habitat quality diverge, resulting in poor habitat choices by caribou (Schlaepfer et al 2002). Maladaptive choices by caribou have been documented in numerous studies and are proposed as being a result of habituation, range fidelity, maternally learned selection strategies, or an inability of caribou to adjust to a rapidly changing environment (Faille et al 2010, Dussault et al 2012, Beauchesne et al 2013, Losier et al 2015.…”

“…Apparent competition has been demonstrated in populations of other species (Norbury 2001, Courchamp et al 2003, DeCesare et al 2009) and in the context of caribou, is supported by studies showing that survival of adult caribou is correlated with cutblock density and is lower in areas where early seral forest is more common (e.g. Smith 2004, Wittmer et al 2007, Leblond et al 2013, Losier et al 2015.…”

“…Although Apps et al (2013) found that caribou survival was unrelated to the amount of early seral forest, most studies suggest a strong relationship between forestry and caribou survival (e.g. Smith 2004, Wittmer et al 2007, Leblond et al 2013, Losier et al 2015. For example, Wittmer et al (2007) found that survival of mountain caribou was lower in areas where early-and midseral forests were more common.…”

“…Although predation is accepted as the proximate cause of caribou declines across Canada, the relationship between human disturbance and caribou mortality has received relatively little attention (but see Smith 2004, Wittmer et al 2007, Apps et al 2013, Leblond et al 2013, Losier et al 2015. There are even fewer studies that examine how this relationship varies among herds as a factor of landscape change and population trajectory.…”