Réhaume Courtois

Effects of sampling effort based on GPS telemetry on home-range size estimations

Home-range size is widely used in wildlife biology to assess animal-habitat relationships. But home-range size estimation largely depends on the estimator and sample size used. Using 3 different estimators (minimum convex polygons, fixed-kernels, clusters), we used data collected on moose (Alces alces), fitted with Global Positioning System (GPS) collars (which allow automatic recording of large data sets with fewer field constraints than VHF telemetry) to investigate to what extent increasing the number of locations affects home-range size estimations. Our results indicated that 100 to 300 locations per animal annually and 30 to 100 locations seasonally were needed to reach an asymptote. High biases occurred below this asymptotic value. Minimum convex polygons consistently underestimated home-range sizes, but fixed-kernel and cluster estimators followed variable trends that often overestimated home-range sizes. Low sampling efforts also affected the number of animals needed to ensure an adequate statistical power of analysis to compare space use between 2 groups. Despite the higher cost, our findings indicate that in most instances, GPS telemetry is better suited than conventional radiotelemetry to estimate home-range sizes precisely and accurately. Moreover, this tracking technique is not limited by meteorological constraints and allows for the collection of similar sample sizes for all tracked animals, which is of major importance for further comparisons of space use among individuals.

Behavioural responses of moose to thermal conditions in the boreal forest

Abstract: Among ungulate species living in boreal regions, moose (Alces alces) are most likely to suffer from heat stress since they have a relatively low upper critical temperature (14 °C in summer and -5 °C in winter). We tested the hypothesis that moose adopt behaviours to reduce thermoregulatory costs. We predicted that moose exposed to high intensities of solar radiation or high air temperatures would 1) seek a type of vegetation association that provides thermal shelter and 2) reduce activity. We also predicted that these behaviours would be most evident in summer. Thermal-shelter use and activity of 30 free-ranging moose were measured over 3 y in a 940-km2 study area of boreal forest using GPS telemetry collars. The effect of solar radiation and air temperature on thermal-shelter use and activity were assessed using logistic and multiple regression analyses. Habitat use and activity rates of moose were related to air temperature but not solar radiation. The probability of finding moose in thermal shelters increased with air temperature in summer and fall. Moose activity did not decrease as air temperature increased, but it increased at night during hot periods. As expected, moose response to thermal conditions was most noted in summer. Our results suggest that moose reduce exposure to thermal stress by using thermal shelters during the day and by increasing nocturnal activity. These behavioural adaptations allow moose to cope with thermal stress on a small temporal scale. Negative effects of heat stress could be important in areas where air temperatures are very high for extended periods of time or where thermal cover is scarce.

Cumulative effects of forestry on habitat use by gray wolf (Canis lupus) in the boreal forest

Forest harvesting involves the creation of roads and cutblocks, both of which can influence animal habitat use. We evaluated the cumulative effects of forestry on habitat selection by six packs of gray wolf (Canis lupus) widely distributed in Quebec’s boreal forest. Resource selection functions were used to evaluate cumulative effects at two levels. First, we studied how the response of wolves to roads and cutblocks varied within their home range (HR level) as a function of the local abundance of these habitat features. Second, we assessed whether differences in the response to roads and cutblocks observed among packs (inter-HR level) could be explained by variations in their average abundance among individual home ranges. At the HR level, we found that cumulative effects shaped habitat selection of wolves, and the nature of the effects varied during the year. For example, we detected a decrease in the selection of roads following an increase in local road density during the rendez-vous and the nomadic periods, but not during the denning period. At the inter-HR level, we found a functional response to logging activity only during the denning period. Packs with home ranges characterized by a larger proportion of recent cutblocks selected these cutblocks more strongly. We conclude that cumulative effects of logging activities occur at multiple levels, and these effects can have profound effects on habitat use by wolves, thereby influencing spatial predator–prey dynamics. Wildlife conservation and management in boreal ecosystems should thus account for cumulative impacts of anthropogenic features on animal distribution.

Behavior of Moose Relative to a Road Network

Abstract Roads often negatively affect terrestrial wildlife, via habitat loss or fragmentation, noise, and direct mortality. We studied moose (Alces alces) behavior relative to a road network, in an area with a history of moose–vehicle accidents, to determine when moose were crossing roadways or using areas near roads and to investigate if environmental factors were involved in this behavior. We tracked 47 adult moose with Global Positioning System collars in a study area crossed by highways and forest roads. We hypothesized that moose would avoid crossing roads but would make occasional visits to roadsides to feed on sodium-rich vegetation and avoid biting insects. Further, we expected moose avoidance to be greater for highways than forest roads. We recorded 196,710 movement segments but only observed 328 highway and 1,172 forest-road crossings (16 and 10 times lower than expected by chance). Moose usually avoided road proximity up to ≥500 m on each side but 20% of collared moose made visits to areas within 50 m of highways, which might have resulted from moose searching for sodium in vegetation and roadside salt pools. In fact, vegetation along highways had higher sodium concentrations and was browsed in similar proportions to vegetation in adjacent forest, despite moose avoidance of these zones. Moose, however, did not use areas near roads more during periods of biting insect abundance. Our results supported the hypothesis of scale-dependent selection by moose; avoidance of highways at a coarse scale may confer long-term benefits, whereas selection of highway corridors at finer scales may be part of a strategy to overcome short-term limiting factors such as sodium deficiency. We found a positive relationship between home-range size and the proportion of road axes they contained, suggesting that moose either compensated for habitat loss or made specific movements along highways to gather sodium. The presence of sodium along highways likely increases moose–vehicle accident risks. Removal of salt pools or use of a de-icing salt other than sodium chloride should render highway surroundings less attractive to moose.

Effects of forest disturbance on density, space use, and mortality of woodland caribou

Abstract Woodland caribou (Rangifer tarandus caribou), a threatened species in Canada, inhabit landscapes dominated by mature and over-mature coniferous stands and tend to avoid areas used by other cervids, wolves (Canis lupus), and humans. We hypothesized that habitat modifications through logging and forest fire alter the space-use pattern of woodland caribou and result ultimately in lowered density. To test this hypothesis, density, distribution, space-use patterns, and mortality of caribou in disturbed landscapes (DLs) and undisturbed landscapes (ULs) of central Québec were quantified by a systematic aerial survey (42 539 km2) and telemetry of 68 adult caribou females. A ground survey of terrestrial and arboreal lichens was carried out to estimate production of lichens in DLs and ULs. Three populations that occupied between 10 000 and 15 000 km2 were identified in the study area. Caribou abundance was not limited by intraspecific competition for food. Production of terrestrial lichens was estimated to support 3 to 4 times the surveyed caribou density (1.2–2.1–100 km−2). Pregnancy rate was almost 100%, indicating that females were not food-limited. Space-use patterns were affected by forest disturbance. In DLs, caribou increased home range sizes and reduced fidelity to seasonal and annual home ranges, probably to avoid disturbed habitats. In response, the probability of surviving decreased with the extent of DL within home ranges. To help keep direct and indirect sources of caribou mortality at very low levels, forest management strategies should be oriented toward the protection of large interconnected blocks of forest to favour caribou spacing away from humans and predators and to maintain adequate space-use strategies.

Temporal and spatial distribution of moose-vehicle accidents in the Laurentides Wildlife Reserve, Quebec, Canada

Abstract Deer-vehicle accidents are an increasing problem in many regions of the world. To elaborate effective mitigation measures, it is necessary to determine environmental factors associated with the occurrence of such accidents. The Lauren-tides Wildlife Reserve in Quebec, Canada, is a prime example of an area having a long-lasting problem of moose-vehicle accidents (MVAs). We tested the effect of the spatial and temporal variables most likely to influence MVAs in this area based on accidents recorded over a 13-year period. Data collected included the date and time of each collision as well as the position of the accident relative to the closest 1-km road marker. We calculated 10 variables to assess moose habitat suitability, moose density, topography and road design for every 1-km road segment. There was a total of 754 MVAs during 1990–2002. The period with the highest number of accidents was the second half of June but accident frequency remained relatively high from mid-May to late August. The risk of accident per vehicle was at least 2–3 times higher at night (when traffic volume was lowest) than during any other time of the day. Also, MVAs were over 42% more frequent on Fridays, when road traffic levels were highest. The probability of an MVA increased when air temperature and atmospheric pressure were high. The MVA rate increased with moose density, in the presence of at least one brackish pool (by 80%) and when a valley traversed the road (by 120%). Implications of our results in the choice of appropriate mitigation measures are discussed. Future work should aim to describe habitat characteristics at the actual collision site.

Landscape management for woodland caribou: the protection of forest blocks influences wolf-caribou co-occurrence

Various management plans have been developed to mitigate the effects of human activities on threatened woodland caribou (Rangifer tarandus caribou) populations. Most plans do not account for the behavior of wolves (Canis lupus), their main predator. The success of caribou recovery plans may nonetheless depend on how landscape management shapes wolf-caribou interactions. We evaluated the species-specific responses of caribou and wolves to a management plan in Québec, and assessed its impact on the probability of wolf-caribou co-occurrence. Landscape management consisted of the protection of large forest blocks, and the spatial aggregation of cutblocks. Based on telemetry data, we modeled animal-habitat spatial relationships with resource selection functions, and then estimate the relative probability of wolf-caribou co-occurrence. We found that caribou selected mature conifer forests with lichen. Wolves selected mixed and deciduous stands. Caribou avoided roads and cutblocks, while wolves selected them, which resulted in a relatively low probability of co-occurrence in harvested areas. Concurrent habitat selection by the two species was such that the highest probability of wolf-caribou co-occurrence took place in protected forest blocks (PB) from December to May. For efficient mitigation measures, the location of PBs should be selected while accounting for differences in habitat selection between wolf and caribou. The blocks should include mature conifer forests with lichen, minimize the abundance of mixed and deciduous stands, and be far from roads and cutblocks. Consideration of predator behavior can improve suitability of landscape management plans for the long-term persistence of threatened prey populations under top-down control.

Moose Movement Rates Along Highways and Crossing Probability Models

Abstract We developed and validated a density-adjusted spatial model to predict moose (Alces alces) highway-crossing probability to see if the model could be used as an index of moose–vehicle collision risk. We installed Global Positioning System telemetry collars on 47 moose in the north of the Laurentides Wildlife Reserve, Québec, for 2–36 months. We recorded only 84 highway crossings in spring (0.29% of 28,967 2-hr steps) and 122 crossings in summer (0.18% of 68,337 2-hr steps), despite a high sampling effort and having captured moose close to highways. Moose movement rates during movement steps crossing a highway were on average 3 times higher than during the steps preceding or following highway crossing. Paths used by moose when crossing a highway were characterized by a high proportion of food stands, low proportion of lakes and rivers, and topography typical of a valley. Highway-crossing sites were located in valleys with brackish pools and forest stands providing coniferous cover but a low proportion of lakes and rivers. We adjusted moose crossing probability for local variation in moose density using aerial survey data and assessed crossing probability along the highways in the entire Laurentides Wildlife Reserve. We tested the model using moose–vehicle accident data from 1990 to 2002. The relationship between the density-adjusted crossing probability and number of accidents was relatively loose at the 1-km scale but improved markedly when using longer highway sections (5–15 km; r > 0.80). Our results demonstrate that roads and their surroundings are perceived as low-quality habitat by moose. We also conclude that road segments installed along secondary valleys could be a highly strategic site to deploy mitigation measures such as fences and that it could be desirable to increase the width of road shoulders to reduce forest cover and to eliminate brackish pools to reduce cervid–vehicle collisions. We suggest using empirical data such as location of vehicle–wildlife collisions to plan mitigation measures at a fine scale.

Avoidance of roads and selection for recent cutovers by threatened caribou: fitness-rewarding or maladaptive behaviour?

The impact of anthropogenic disturbance on the fitness of prey should depend on the relative effect of human activities on different trophic levels. This verification remains rare, however, especially for large animals. We investigated the functional link between habitat selection of female caribou (Rangifer tarandus) and the survival of their calves, a fitness correlate. This top-down controlled population of the threatened forest-dwelling caribou inhabits a managed forest occupied by wolves (Canis lupus) and black bears (Ursus americanus). Sixty-one per cent of calves died from bear predation within two months following their birth. Variation in habitat selection tactics among mothers resulted in different mortality risks for their calves. When calves occupied areas with few deciduous trees, they were more likely to die from predation if the local road density was high. Although caribou are typically associated with pristine forests, females selected recent cutovers without negative impact on calf survival. This selection became detrimental, however, as regeneration took place in harvested stands owing to increased bear predation. We demonstrate that human disturbance has asymmetrical consequences on the trophic levels of a food web involving multiple large mammals, which resulted in habitat selection tactics with a greater short-term fitness payoff and, therefore, with higher evolutionary opportunity.

Significance of caribou (Rangifer tarandus) ecotypes from a molecular genetics viewpoint

Three caribou ecotypes are present in easternNorth America: the mountain caribou which isfound south of the St. Lawrence River, thebarren-ground caribou which calves in thetundra, and in between, the forest-dwellingecotype which lives all year long in the borealforest. Blood and muscle samples were collectedfrom seven populations and characterized ateight microsatellite loci to test thehypotheses that forest-dwelling andbarren-ground ecotypes constitute a singlemetapopulation and that geographical isolationresults in reduced genetic diversity. The meannumber of alleles per locus, allelic richness,and observed and expected heterozygositydeclined from north to south and were thesmallest in isolated forest-dwellingpopulations. Correspondence analysis showedthree groups of samples corresponding to thethree ecotypes. Gene flow estimates weremoderate or high among all forest-dwellingpopulations and particularly between those <200 km apart. Our results suggest that thethree caribou ecotypes represent three distinctgenetic entities and that the forest-dwellingpopulations in the continuous range form ametapopulation. Genetic diversity was lower inisolated populations but does not seem to be ofimmediate concern for conservation. We proposethat management strategies should favorincrease in caribou numbers in order to avoidextinction due to stochastic events and tomaintain local biodiversity. In the continuousrange, conservation strategies of cariboupopulations must be planned on a large scale tomaintain occasional exchanges betweenpopulations, thus preserving genetic diversity.