239 ARTICLE Resource selection in a high-altitude rangeland equid, the kiang (Equus kiang): influence of forage abundance and quality at multiple spatial scales Antoine St-Louis and Steeve D. Côté Abstract: Herbivores foraging in arid and seasonal environments often face choices between plant patches varying in abun- dance and nutritional quality at several spatial and temporal scales. Because of their noncompartmented digestive system, equids typically rely on abundant forage to meet their nutrient requirements. In forage-limited environments, therefore, scarcity of food resources represents a challenge for wild equids. We investigated hierarchical resource-selection patterns of kiangs (Equus kiang Moorcroft, 1841), a wild equid inhabiting the high-altitude steppes of the Tibetan Plateau, hypothesizing that vegetation abundance would be the main factor driving resource selection at a large scale and that plant quality would influence resource selection at finer scales. We investigated resource-selection patterns at three spatial levels (habitat, feeding site, and plant (vegetation groups, i.e., grasses, sedges, forbs, and shrubs)) during summer and fall. At the habitat level, kiangs selected both mesic and xeric habitats in summer and only xeric habitats (plains) during fall. At the feeding-site level, feeding sites had higher plant biomass and percentage of green foliage than random sites in the same habitats. At the plant level, grasses were selected over forbs and shrubs, and sedges were used in proportion to their availability during all seasons. Our results indicate that resource-selection patterns in kiangs vary across scales and that both forage abundance and quality play a role in resource selection. Plant quality appeared more important than hypothesized, possibly to increase daily nutrient intake in forage-limited and highly seasonal high-altitude rangelands. Key words: arid environment, equid, Equus kiang, high-altitude steppes, mountains, resource selection, scales, Tibetan Plateau, Tibetan wild ass. Résumé : Les herbivores vivant dans les milieux arides et saisonniers doivent souvent faire des choix entre l’abondance des végétaux et leur qualité nutritionnelle. En raison de leur système digestif non compartimenté, les équidés comptent générale- ment sur une nourriture abondante pour combler leurs besoins nutritionnels. Dans les environnements où la nourriture est limitée, la rareté des ressources alimentaires constitue ainsi un défi pour les équidés. Nous avons étudié la sélection hiérarchique For personal use only. des ressources par le kiang (Equus kiang Moorcroft, 1841), un équidé sauvage qui habite les hautes steppes du plateau tibétain, en posant l’hypothèse que la sélection des ressources est déterminée a` grande échelle par l’abondance de végétation et, a` plus fine échelle, a` la fois par l’abondance de la végétation et sa qualité nutritionnelle. Nous avons étudié les patrons de sélection des ressources a` trois niveaux: le type d’habitat, le site d’alimentation et le groupe de végétation (graminées, cypéracées, herbacées et arbustes), en été et en automne. En été, les kiangs sélectionnaient a` la fois les habitats mésiques et xériques, alors que seuls les habitats xériques (plaines) étaient sélectionnés au cours de l’automne. À l’intérieur de chaque habitat, la biomasse végétale et le pourcentage de feuillage vert étaient plus élevés dans les sites d’alimentation que dans les sites aléatoires. Au sein des sites d’alimentation, les graminées étaient sélectionnées par rapport aux herbacées et aux arbustes, et les cypéracées étaient utilisées en proportion avec leur disponibilité. Nos résultats indiquent que les patrons de sélection des ressources par le kiang varient d’une échelle a` l’autre et selon les saisons et que l’abondance et la qualité de la végétation jouent un rôle dans la sélection des ressources. À cet égard, la qualité nutritionnelle des plantes semble être plus importante que ce que nous envisagions, probable- ment afin d’augmenter leur apport nutritionnel quotidien dans un environnement fortement saisonnier où la nourriture est limitée. Mots-clés : milieu aride, équidé, Equus kiang, hautes steppes, montagnes, sélection des ressources, échelles, plateau tibétain, âne sauvage tibétain. Can. J. Zool. Downloaded from www.nrcresearchpress.com by Université Laval Bibliotheque on 05/16/14 Introduction (McNaughton 1985; Van Soest 1994; Laca et al. 2001). Plants in For mammalian herbivores, predation risk and plant distribu- low-biomass vegetation patches—early in the growing season for tion are fundamental components of resource-selection strategies example—may thus be more digestible than plants in patches (Jarman 1974; Lima and Dill 1990; Wilmshurst et al. 1999). On with high biomass (Klein 1990; Van der Wal et al. 2000; Winnie rangelands, forage abundance and quality are often inversely et al. 2008). On the other hand, stochastic patterns of precipita- related because plant maturation increases biomass but also tions may also increase both plant biomass and greenness simul- fibre content in stems and leaves, lowering forage digestibility taneously, creating a mosaic of heterogeneous vegetation patches Received 6 August 2013. Accepted 18 December 2013. A. St-Louis* and S.D. Côté. Département de biologie and Centre d’études nordiques, Université Laval, Québec, QC G1V 0A6, Canada. Corresponding author: Antoine St-Louis (e-mail: [email protected]). *Present address: Direction de la biodiversité et des maladies de la faune, Ministère du Développement durable, de l’Environnement, de la Faune et des Parcs, 880, chemin Ste-Foy, 2e étage, Québec, QC G1S 4X4, Canada. Can. J. Zool. 92: 239–249 (2014) dx.doi.org/10.1139/cjz-2013-0191 Published at www.nrcresearchpress.com/cjz on 15 January 2014. 240 Can. J. Zool. Vol. 92, 2014 (Fryxell 1991). Herbivores may thus face choices among fluctuating large scale and that plant greenness would influence resource selec- patterns of plant abundance and quality across several spatio- tion at finer scales. Accordingly, (i) habitat types with highest plant temporal scales, potentially leading to scale-dependent resource- biomass should be used in greater proportion than their relative selection patterns (Hebblewhite et al. 2008; Singh et al. 2010). availability within the study area, especially when plants are green; Strategies of resource selection also depend on the anatomy (ii) feeding sites should have higher percentage of green foliage and of the digestive system, as illustrated by the dichotomy between also higher plant biomass than random sites within habitat types; ruminant bovids–cervids and hindgut-fermenter equids (Janis (iii) plants with higher crude protein content should be consumed in 1976; Demment and Van Soest 1985; Duncan et al. 1990; Menard greater proportion than their relative availability within feeding et al. 2002). Because plants are digested poorly and have a fast sites. Moreover, as plant abundance increases but quality declines passage rate in the digestive tract, equids rely on a high forage throughout summer and fall, (iv) patterns of resource selection intake strategy to meet their nutrient requirements (Janis 1976; should be mostly driven by forage abundance early during the grow- Duncan 1992). In arid and highly seasonal environments (e.g., ing season, and shift toward plant quality as summer and fall prog- arctic and alpine ecosystems), the growing season is short, re- ress. sources are generally scarce, and vegetation distribution is hetero- geneous and highly dependent on rainfall or snowmelt patterns Materials and methods (Noy-Meir 1973; Kudo 1991; Moen et al. 2006; Pettorelli et al. 2007). Under such circumstances, forage availability and distribution is Study area likely to be a strong limiting factor for wild equids (Rubenstein We conducted this study in fall 2003 (29 August to 21 November), 1989; Duncan et al. 1990; Ward 2006; Henley et al. 2007). Rettie and summer 2004 (17 June to 25 August), and summer 2005 (26 June to 2 Messier (2000) suggested that hierarchical patterns of resource 20 August) in a 390 km area located in the Tso Kar basin, eastern selection reflect a hierarchy of limiting factors in foraging herbi- Ladakh, India (32°15=N, 78°0=E). This area lies at the westernmost vores. Accordingly, we may expect arid-adapted equids to select limit of the extensive Tibetan Plateau and is similar to the Chang resources primarily to maximize their forage intake (Janis 1976, Tang region of northwest Tibet (Schaller 1998). Elevation within Duncan 1992). Since forage abundance and quality may fluctuate the Tso Kar basin ranges from 4550 to 6000 m. The climate is that heavily across seasons and scales in such an extreme environment of high altitude – cold desert ecosystems, with annual tempera- (e.g., Van der Wal et al. 2000), investigating patterns of resource tures ranging from –40 to 30 °C, and mean annual precipitation selection may bring clues regarding the relative importance of below 100 mm, which represents the most arid and extreme con- forage availability and quality in arid-adapted wild equids, which, ditions encountered by kiangs across their distribution range to our knowledge, has never been attempted. (Mani 1978; Schaller 1998). Fresh water running off from glaciers Here, we assess resource-selection patterns at several spatial was available in the southern part of the study area near mesic scales in kiangs (Equus kiang Moorcroft, 1841), a rarely studied wild habitats, but otherwise water came only from precipitations.