Habitat use and spatial dynamics of takhi introduced to Hustai National Park, Mongolia

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1 BIOLOGICAL CONSERVATION Biological Conservation 124 (25) Habitat use and spatial dynamics of takhi introduced to Hustai National Park, Mongolia Sarah R.B. King 1, John Gurnell * School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK Received 27 August 24 Abstract The successful introduction of captive bred takhi or PrzewalskiÕs horse, Equus ferus przewalskii, into Mongolia in the 199s is a good example of the benefits of ex situ conservation and one of the few examples of the recovery of an animal after it became extinct in the wild. This is also particularly interesting because virtually nothing was known about how takhi lived before they died out, and the introductions have enabled us to study how they have settled, and their ecology and behaviour within their former natural range. In this paper, we describe the movement, home range size and shape, and habitat use of takhi at one of the release areas, the 57 km 2 Hustai National Park in Mongolia. Harem home ranges varied between 129 and 2399 ha, with 8% core areas of between 61 and 1196 ha. There was no relationship between range size and harem size, or length of time since release. Initially, harems stayed near their release enclosures, but over time they established home ranges further away. There was little overlap between home ranges of different harems, but neither was there evidence of exclusive range use. The more nutritious vegetation at lower elevations was preferentially selected. Thus the present situation looks good, but, as the population continues to grow, we anticipate that there will be potential problems related to intraspecific competition for water and vegetation resources, and the potential for hybridisation with domestic horses belonging to the local people. We consider the time it may take for takhi to reach carrying capacity within Hustai National Park and emphasise that continual monitoring of the population is essential because interventional management is likely to be required in the future. Ó 25 Elsevier Ltd. All rights reserved. Keywords: Home range; Habitat use; Equus przewalskii; Takhi; Reintroduction 1. Introduction Collections of animals and plants are increasingly being seen as opportunities for ex situ conservation, notably with respect to captive breeding programmes and subsequent release of captive-bred animals back in to the wild. However, to date there have been few successful examples of such a strategy; approximately * Corresponding author. Tel.: addresses: kingsrb@yahoo.com (S.R.B. King), j.gurnell@ qmul.ac.uk (J. Gurnell). 1 Present address: School of Renewable Natural Resources, University of Arizona, Biosciences East, Rm. 325 Tucson, AZ 85721, USA 27% of the 116 reintroductions considered by Fischer and Lindenmayer (2) were classified as failures, with the success of a further 47% not known. Moreover, the respective roles of ex situ and in situ conservation strategies are open to debate (e.g. Balmford, 2; Entwistle and Dunstone, 2). Captive breeding and reintroductions are lengthy, complex and expensive processes (IUCN, 1995; Balmford, 2) but may be vital for the survival of a species in the wild (e.g. Spalton et al., 1999; Kleiman and Rylands, 22). Before reintroduction of captive bred takhi or Przewalski horses, Equus ferus przewalskii, into Mongolia in the 199s, the last authenticated sighting of a takhi in the wild was in 1969, near the Tachyn-shar mountains 6-327/$ - see front matter. Ó 25 Elsevier Ltd. All rights reserved. doi:1.116/j.biocon

2 278 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) in the western Gobi desert (Bouman and Bouman, 1994). The captive population of takhi in European and North American animal collections is descended from animals captured at the beginning of the 2th Century. In 1945, only 31 horses remained in captivity, and only nine of these bred. A species survival plan was set up in the USA in 1979, followed in 1986 by a European breeding programme (Europaisches Erhaltungzucht- Programm or EEP; Bouman and Bouman, 1994). By the start of the 199s, there were more than 15 horses in captivity. In 1992, reintroductions began to Tachyn Tal, by the German Christian Oswald Foundation and the Mongolian government, and to Hustai National Park, by the Dutch Foundation Reserves Przewalski Horse in association with the Mongolian Association for the Conservation of Nature and the Environment (Bouman, 1998). For animals kept in captivity for many generations, there is a potential for loss of genetic variability (Foose, 1986; Ryder, 1986; May, 1991) or attenuation in survival skills (Box, 1991; Brock et al., 1994; Shepherdson, 1994; McPhee, 23; Mathews et al., 25). Thus there was concern that released takhi would not be able to survive after being bred in captivity for 13 generations (Klimov and Orlov, 1982). Moreover, there was no knowledge about the ecology of takhi in the wild before they became extinct, and so it was not clear how the released animals would cope in their new surroundings. Between 1995 and 2, we carried out a series of studies on the behaviour and ecology of released takhi in Hustai National Park. In this paper, we report on the spatial dynamics and habitat use of the horses. Against the background of changes in population size during the study period, we consider the establishment of home ranges by the harems in relation to their release point, size, interrelationship between the ranges of different harems, and utilisation of the habitat within these ranges. Finally, we consider what might happen in the future as the population continues to increase. By examining these factors we hope to be able to provide information on a reintroduction that currently appears successful, with an aim to helping future reintroduction projects Study site Hustai National Park is 15 km south west of Ulaan Baatar, the capital city of Mongolia. It covers 57 km 2 along a southwestern spur of the Khentei range of mountains (47 41 N, E). It was made a reserve in 1993 and designated a National Park in Hustai National Park borders the Tuul River, with an altitude of between 11 and 1842 m and a continental climate (mean annual temperature =.2 C and yearly rainfall = 27 mm, most of which falls in the summer; Wallis de Vries et al., 1996). During the study, horses were observed in temperatures of between 14 and +34 C. Hustai National Park has a mountain forest steppe habitat that consists of steppe, meadow, grassland, shrub and woodland communities (Wallis de Vries et al., 1996). Water flows down most of the major valleys as streams, which are permafrost fed and covered by gravel at places along their length Study animals Between 1992 and 2, 84 horses were brought to Hustai National Park from reserves in Europe, where they had been kept in large (over 4 ha) grassy enclosures. The horses were released as a harem into acclimatisation enclosures of 4 45 ha; these enclosures were a minimum of 4 km apart and visually separated from each other. Although most of the horses had been kept together in Europe and were released together, others were introduced on arrival in Mongolia. Harems are referred to by the name of the dominant stallion (see Table 1). One harem was given a hard release (TurgenÕs harem), but other releases followed a 6 24 month acclimatisation period. Up to four harems other than the ones studied were also present towards the end of the study period (see Table 1). 2. Methods Mongolian rangers and biologists gathered positional data of the harems at Hustai National Park for the full year from 1995 to 1997, and for the winter months (December to March) from 1998 to 2. Detailed observations were carried out by the first author between June 1998 and July 2, totalling 86 h. The standard procedure was to find a harem at dawn and follow it until 14 h. The same harem was located at 14 h the next day and followed until dusk. Every 1 min during an observation session the position of the harem was recorded with a Global Positioning System and marked on a large-scale map, together with weather details. Once accustomed to the presence of the observer, the horses were watched on foot from a distance of about 15 m and their behaviour recorded; these results will be considered elsewhere (see King, 22). The per capita growth rate per year for harems with more than three years of census data have been estimated using the formula r = [ln(n t /N )]/t, where N t is the number of animals alive t years after reintroduction, and N is the number of animals released (Komers and Curman, 2). Where mares changed harems, for the purposes of this calculation they were included in the harem with which they were released. However, because mares move between harems, and the number of horses per harem is likely to decrease over time as the number

3 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) Table 1 Harem composition and harem range and core areas (ha) in Hustai National Park between 1994 and 1998 Harem Year Release enclosure No. adults and juveniles No. foals Total harem size No. fixes Period Home range Core area Paritet July December January December January August * June October * April November * May June Mean (SD) 832 (387) 277 (156) Bayan 1998 * June October * April October * May June Mean (SD) 69 (455) 292 (219) Margad 1999 * a May October * May June Mean (SD) 48 (288) 235 (155) Khaan April December January December * June October * April June Mean (SD) 949 (231) 42 (121) Ares 1998 * July October Patron April December January December January July Mean (SD) 1985 (38) 936 (242) Turgen 1996 b June December January/April Mean (SD) 44 (44) 164 (135) Bohemian Mark Manlai 1999 a 4 4 Mangir 1999 a Harem range area = 95% kernel estimates, core area = 8% kernel estimates. a = wild born bachelor stallion acquired mares. b = harem hard released from travelling crates near release enclosure 1. There was no difference in mean home range size or mean core area among years, irrespective of harem (home range: F 5, 15 =.56, P = 726; core area: F 5, 15 =.78, P =.578; these include the data for Ares). Mongolian rangers collected data prior to * = data collected by SRBK; = no data.

4 28 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) of stallions competing for mares increases (Linklater and Cameron, 2; Linklater et al., 2), changes in numbers of individuals within harems do not reflect overall population growth. Thus, we also consider population growth based on changes in population numbers between 22 and 24 (see Anonymous, 24); no further introductions took place after 21. Home range and habitat use data were analysed using Arcview 3.2. One hundred per cent and 95% kernel harem range areas were calculated (see Worton, 1989; Seaman and Powell, 1996; Hooge and Eichenlaub, 1997), the latter excluded occasional forays outside the areas. Utilisation curves were used to estimate core areas; in all cases these were 8% of the total range area (King, 22). ANOVA was used to test whether the yearly range areas since release changed in a systematic way. Paramatric or non-paramatric correlation techniques were used as appropriate to compare the area overlap of each yearly harem range with the range in its previous year, and the movement of range centres from one year to the next. Harem range use was examined according to season and temperature using Kruskal Wallis tests, because the data were not normal. For analyses of seasonal and altitudinal effects on activity, movement, and range size, the yearly range or core areas for particular harems have been treated as independent. Eleven vegetation categories or habitat types were distinguished within Hustai National Park (Wallis de Vries et al., 1996). The areas covered by the different habitat types within each home range, and those that were grazed or used for shelter or water, were measured, and habitat selection indices (Manly et al., 1993) calculated. Preferences were formulated using v 2 tests. The seasonal (spring March to May, summer June to August, autumn September to November, and winter December to February) use of vegetation was based on data from all years and this was compared with the vegetation available to them within their total range area over all years. 3. Results 3.1. Numbers and density of horses Of 115 foals born between 1994 and 21 (Table 1), 57% were still alive at the end of the study reported here (see Anonymous, 24, for an update of population numbers). Twenty-six per cent of deaths were caused by babesiosis (piroplasmosis), which particularly affected newly released horses (three died from this in 1998 and nine in 1999; previous deaths from this disease are also possible, but were not diagnosed). Most other deaths were foals (63% of all deaths). In each year (1995 2), on average, foals made up 25% of the population, and 12% of the population died. The increase in births in 1998 was mostly produced by three free-ranging harems (19 of the 25 births). Predation by wolves, Canis lupus, was low with a mean of 2.8 horses taken each year, all one year old or less (16% of all foals born between 1994 and 1999). It appears unlikely that predation affected population growth at the time of the study. In July 2 there were 91 free ranging horses, a density of.2 horses km 2 over the entire Park. The yearly mean density of horses within a harem between 1995 and 2 was 1.8 horses km 2 (N = 24 harems, SD = 1.3 horses km 2, range from.5 horses km 2 for Patron in 1995 to 5.4 horses km 2 for Margad in 2). In 1995, 1996 and 1998 the home range and size of every harem was known. The density of horses over the area covered by these harems was.8 horses km 2 in 1995, 1.2 horses km 2 in 1996 and 1.8 horses km 2 in In 1999, density of harems within Hustai National Park was.1 harems km 2 (N = 7). The per capita growth rates (r) of three reintroduced harems with census data spanning more than three years were: Paritet to 2, Patron to 2, and Khaan to Thus, these harems were very successful and doubled in size over these time periods. However, Khaan lost half his harem in 1999 to Margad when numbers dropped from 22 to 11 (Table 1), and he subsequently lost the rest of his harem the year after. A more realistic indication of population growth rate can be obtained by considering population numbers after 21, when no further introductions took place. In 22 there were 142 horses in Hustai National Park, and this increased to 162 horses by June 24, of which 84 were reintroduced (Anonymous, 24). This gives an overall per capita growth rate (r) of.66 per year. This growth rate must be treated with caution since it is based on only three years of data Harem range and core areas Between 1995 and 2, 95% kernel harem range areas ranged from 1.3 to 24. km 2 and 8% core use areas from 61 to 499 ha (Table 1, Fig. 1). There was no difference in range area among years (F 5,15 =.56, P =.726; note, horses were observed for different periods of time within each year). Both mean range and core areas were significantly different among harems (range area: F 5,14 = 6.61, P =.2; core area: F 5,14 = 7.65, P =.1, these exclude the single home range estimate for Ares, Table 1); mainly because PatronÕs mean range and core areas were significantly larger than those of the other harems (Table 1). There was no correlation between number of fixes and size of harem range or core areas (Table 1; range area: r s =.35, N = 21, P =.881; core area: r s =.92, N = 21, P =.691). In addition, there was

5 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) SD = 27%; Table 2). There was no significant correlation between the number of years since release and the degree of overlap (range area r s =.34, N = 11, P =.313; core area r s =.4, N = 11, P =.255;). In general the trend was for a decrease in range overlap over the years (Table 2). The harem range centres did not move very far from one year to the next, with a minimum movement of.4 km and a maximum of 1.8 km (Table 3). However, distance from initial range centre after release to range centres the following years appear to show a movement away from the release enclosure. The harems tended to stay close to their acclimatisation enclosures in the year after release, then move further away to settle in a nearby valley Overlap between the ranges of different harems Fig. 1. Eighty percent core areas of the study harems in (a) 1998 and (b) Ranges show the core area of the entire harem, but the names of the dominant stallions are used. Paritet, Khaan and BayanÕs harems were all released from enclosure 1 (in 1994, 1995 and 1998, respectively). AresÕ harem was released from enclosure 2, and Margad acquired KhaanÕs mares in no correlation between number of months since release and harem range (r =.22, N = 31, P =.235) and core area (r =.1, N = 31, P =.976), or between the number of adults and juveniles in each harem and range (r s =.22, N = 21, P =.337) or core area (r s =.346, n = 21, P =.124). Despite the small sample sizes, we tested for a year effect, but there was no significant difference in range or core area among years (range area: H 5 = 3.56, P =.615; core area: H 5 = 5.9, P =.44) Harem range shifts between years Overlap of individual harem ranges between years varied between 31% and 1% (mean = 59%, N = 11, SD = 26%) (Table 2). Overlap of yearly core areas varied between 11% and 1% (mean = 45%, N = 11, Paritet, Bayan and Khaan were released from enclosure 1, Turgen from outside enclosure 1, and Ares and Patron were released from enclosure 2. MargadÕs was a naturally formed harem (Table 1). Overlap between yearly harem ranges was analysed to see whether harems moved to the same areas of Hustai National Park after release. The degree of range overlap between harems varied from % to 89% (mean = 39%, N = 21, SD = 3%); core areas overlapped % to 66% (mean = 18%, N = 21, SD = 21%) (Table 4). There was no correlation between number of years since release and amount of overlap between harem ranges (r =.26, N = 21, P =.253) or core areas (r =.17, N = 21, P =.459). In 1995, when ParitetÕs harem was first released and KhaanÕs and PatronÕs had been free ranging for one year, there was no overlap between any of the core areas. Core areas overlapped in 1996 after TurgenÕs harem was released. TurgenÕs core area in 1996 and 1997 was overlapped more than any other harem except AresÕ in 1998 (Table 4b). PatronÕs core area did not overlap with any other harem between 1995 and 1997, and did not do so during the rest of this study (SRBK, pers. obs.). The bachelor group moved among the home ranges of all (SRBK, pers. obs.). Changes in overlap among core areas indicate range shifts and/or a change in area used. For example, Bayan overlapped with Ares in 1998, but in 1999 he used a larger area and his harem overlapped with all the other harems. The bachelor stallion Margad took most of KhaanÕs mares in 1999, and although they were using the same valley, their core areas only overlapped by 23%. By mid-summer, KhaanÕs remaining mares were taken over by another stallion and they moved to a different valley. Thereafter MargadÕs harem increasingly used KhaanÕs previous range; in 2, 5% of MargadÕs core area overlapped with KhaanÕs 1998 core area and 57% with KhaanÕs 1999 core area.

6 282 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) Table 2 Harem home range and core area shifts expressed as a percentage of overlap from one year (column) to the previous years (row) Year (a) Overlap of home range Paritet Bayan Margad Khaan * * * * (b) Overlap of core area Paritet Bayan Margad Khaan * * * * * = no data for Khaan harem in In 1999 and 2 there were four other harems in Hustai National Park (Table 1). Although there were no data for these harems, it is possible that total overlap was larger than shown in Table 4. The harems appeared to distance themselves from each other but there was no evidence of exclusive use of an area by any harem. The harems appeared to select a home range in a valley where there were no previous horses, and where the harems were separated by ridges. However, Bayan broke this trend by tending to use the same valley as Margad in 2. Moreover, observations by the Mongolian rangers indicate that all harems sometimes use the same valley during the winter Habitat use within the home range Habitat use within the home range was influenced by several factors including temperature, season, time of day and the presence of flies. Although ranges were slightly larger in winter, there was no significant difference in the size of the ranges or core areas in different seasons (range areas: F 3,39 =.49, P =.693; core areas: F 3,39 =.62, P =.65). In core areas, horses were found more often at a higher altitude during the summer than in spring or autumn (there were too few data for winter; median in summer = 15 m, spring = 1425 m and autumn = 14 m; Kruskall Wallis H 2 = , P <.1). There was also a diurnal trend in the horses movements (Fig. 2). In the morning, when it was cool, the horses spent most of their time grazing in the valleys. As the temperature increased, the horses moved to higher elevations where they could avoid flies and direct solar radiation by standing near rocky outcrops or in forest until the weather cooled enough for them to come down to graze again. This pattern was less marked in spring

7 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) Table 3 Distance from the centre of the home range in one year to the centre in all other years since release Year Paritet Bayan Margad Khaan * * * * * >1.2 The arithmetic mean of all points was used to find the centre. Figures given are the distance from the centre of the row to the centre of the column. * = no data for Khaan harem in and autumn when the weather was cooler and the horses spent more time at lower elevations Vegetation use within the home range Habitat composition of the different haremsõ ranges varied slightly, but all 11 vegetation classes described by Wallis de Vries et al. (1996) were grazed at some time (Table 5). However, all harems in all years did not randomly select vegetation classes (all v 2 statistics, P <.5; Fig. 3). They most frequently selected vegetation classes from lower elevations (i.e., Meadow I, Tussock grassland and Lowland steppe; Fig. 3). Meadow I (dominated by bentgrass, sedge and Iris lactea) was preferred by Bayan in 1999 and 2, and by Khaan in Although most preferred, Meadow I was not used by Khaan in 1999, and little by Margad. ParitetÕs range did not include Meadow I vegetation and they preferred Tussock grassland (Fig. 3). Tussock grassland contains the needlegrass species Achnatherum splendens and Stipa krylovii which have high levels of crude protein and crude fibre (van Dierendonck and Wallis de Vries, 1993). Tussock grassland was not found in Khaan/MargadÕs home range. Lowland steppe was selected significantly more than most other vegetation classes, and had a high selection index for all harems except Bayan in 1999 and Khaan in 1998 (Fig. 3). This vegetation class includes the wheatgrass Agropyron cristatum, which featured largely in the diets of feral horses, and is dominated by the needlegrass Stipa krylovii. Both Mountain steppe vegetation classes were found in every home range, and one or both were significantly selected by the harems (Fig. 3). These were dominated by Festuca lenensis in Mountain steppe I and Festuca sibirica in Mountain steppe II. Although these species did not have the high crude protein content of needlegrass they had a higher crude fibre content (van Dierendonck and Wallis de Vries, 1993). Grazing was observed in Woodland by most harems in most years (Fig. 3) and understorey vegetation such as Spiraea media and Cotoneaster melanocarpa was eaten rather than trees. The area covered by other vegetation classes (Upland steppe, Shrubland I, Shrubland II, Meadow II and Scrub) was small Seasonal use of the vegetation The harems selected more vegetation classes in spring and autumn than in summer, and few classes were selected in winter (Fig. 4). From spring to autumn vegetation classes at mid to low elevations were used, with the exception of using woodland in the spring. In winter, vegetation at mid elevations was used. Lowland steppe was selected in every season of the year, and Shrubland I and Mountain steppes I and II were selected in every season except winter. Harems observed in winter preferred Lowland steppe. Woodland was not used at all in the autumn and winter, and Tussock grassland and Upland steppe were selected by at least two of the three harems in spring and autumn, but not in summer. 4. Discussion 4.1. Numbers The reintroduced population of takhi increased in size during the study period, and continues to grow (Anonymous, 24). This was despite loss of half the

8 284 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) Table 4 Overlap of home ranges and core areas between harems expressed as a percentage of the area covered in each year Year Harem Home range area (ha) Harem Total % of core area overlapped Paritet Khaan Patron (a) Home range 1995 Paritet Khaan Patron Khaan Paritet Turgen Patron Khaan Paritet Turgen Patron Paritet Turgen Patron Paritet Turgen Patron Khaan Paritet Bayan Ares Khaan Paritet Bayan Ares Paritet Bayan Margad Khaan Paritet Bayan Margad Khaan Paritet Bayan Margad Paritet Bayan Margad (b) Core area Paritet Khaan Patron 1995 Paritet 96 Khaan 469 Patron Khaan Paritet Turgen Patron Khaan Paritet Turgen Patron Paritet Turgen Patron Paritet Turgen Patron Khaan Paritet Bayan Ares Khaan Paritet Bayan Ares Paritet Bayan Margad Khaan Paritet Bayan Margad Khaan Paritet Bayan Margad Paritet 126 Bayan Margad Columns overlap rows. There was no difference among the harems in the overlap of home ranges (F 6,14 = 1.66, P =.24), but there was a difference among the overlap of core areas (F 6,14 = 3.53, P =.24).

9 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) Temperature (C) Elevation (m) Hour of day Grazing Resting Moving Mean elevation Mean temperature 125 Fig. 2. Diurnal activity of the horses (% of total) according to mean elevation and temperature (SDs not included). The horses were observed in different activities at different times of day (H = 17.38, d.f. = 4, P <.2), and at different temperatures (H = , d.f. = 4, P <.1) and different elevations (H = 63.21, d.f. = 4, P <.1). The horses were found at higher elevations in the middle of the day (H = 12.35, d.f. = 15, P <.1) and at higher temperatures (H = , d.f. = 15, P <.1). Table 5 Habitat classes at Hustai National Park according to landscape features and dominant plant species (based on Wallis de Vries et al., 1996) Habitat class Dominant species Landscape Altitude Slope Scientific name Common name Meadow I Iris lactea Dwarf iris Streamside Tussock grassland Achnatherum splendens Needlegrass Valley terrace Lowland steppe Artemisia adamsii Wormwood Footslope South Stipa krylovii Needlegrass Upland steppe Thermopsis lanceolatus False lupin Footslope South Stipa krylovii Needlegrass Shrubland I Caryopteris mongholica Bluebeard Rocky slope South Amygdalus pedunculata Sweet almond Mountain steppe I Festuca lenensis Tundra fescue Ridge & topslope >13 Mountain steppe Festuca siberica Siberian fescue Mountain slope >14 North Shrubland II Spiraea aquilegifolia Spiraea Gully Meadow II Geranium pratense Meadow cranesbill Combe >13 Woodland Betula platyphylla Asian white birch Mountain slope >14 North Scrub Betula fusca Birch Topslope >14 North horses released in 1998 to babesiosis. Babesia equi and B. caballi are endemic to Mongolia and transmitted by the tick Dermacentor nutalli. Unless treated, between 25% and 1% of cases are fatal (West, 1992). However, animals can acquire immunity during the course of an infection, and mortality depends on the general immune status of the animal, and the virulence of the piroplasm (Schein, 1988). Foals can be infected during pregnancy, but gain protection from maternal antibodies (Donnelly et al., 1982). Thus local domestic horses and takhi born in Mongolia do not appear affected by the disease. In contrast, newly introduced animals with no immunity and that may become stressed for reasons such as transport, release, or poor body condition in early spring, are likely to be susceptible. In particular there is a high mortality rate during the initial infection of older animals

10 286 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) TG TG.5 Paritet harem (1998, 1999, 2) TG W LS LS MS2 W MS2 S1 S1 25 LS MS1 5 MS1 S2 -.5 A S2 S2 S1 MS2-1 MS1 W -1.5 (a) Area of vegetation i Khaan harem (1998, 1999) 1.5 M1 1.5 LS M2 MS2 S1 LS USW S MS2 -.5 (b) 1.6 Margad (prefix 1; 1999, 2) and Ares (prefix 2, 1998 ) harems.4 2M1 1LS 2MS1.2 2M2 1MS1 1LS 2US 1M1 1US 1US 1S1 1S MS2 1MS2 2MS2 1W -.4 1M2 1W 1M1 2LS 2S M1 M1 Bayan harem (1998, 1999, 2).5 R S2 LS S1 US MS1 LS S1 M2 S1 US MS1 W 15 3 S TG MS1 MS2 W TG LS -.5 US MS2 MS S R S2 W M2 TG S Area of vegetation i -1 (c) S US S2 T G W MS1 MS1 Area of vegetation i (d) M1 1M2 2W Area of vegetation i Fig. 3. Habitat selection indices (w i, logged for presentational purposes) plotted against area of each vegetation type (i). M1 = Meadow I, M2 = Meadow II, TG = Tussock Grassland, LS = Lower Steppe, US = Upper Steppe, S1 = Shrubland 1, S2 = Shrubland 2, MS1 = Mountain Steppe I, MS2 = Mountain Steppe II, W = Woodland, S = Scrub, A = Agricultural Area, R = Rock and Stones. Habitat classification based on Wallis de Vries et al. (1996). A value of log w i > represents positive selection, = represents no selection, < represents avoidance. Squares indicate habitats were not selected at all, but were arbitrarily assigned a value of.5 so that they appear on the figure, circles indicate w i values significantly different to zero (v 2 P <.5), triangles indicate insignificant w i values or where expected values <5. when brought from a country, such as Holland, where B. equi is not endemic (Schein, 1988). Most losses to the population resulted from the death of foals. Diseases such as strangles (infection by Streptococcus equi) accounted for some of these deaths, as well as predation and the harshness of the Mongolian winter Home range use Harem range sizes varied between 1 and 24 km 2 (mean 9.2 km 2, N = 21, SD = 5.64 km 2 ) and are similar in range to feral horse populations in Alberta, Canada ( km 2 ; Salter and Hudson, 1982) and in New Zealand (1 18 km 2 ; Linklater et al., 2), but smaller than those in North America (8 48 km 2 ; Pellegrini, 1971; Feist and McCullough, 1976; Berger, 1977, 1986; Miller, 1983a). Home ranges of horses in England ( km 2 ; Tyler, 1972; Gates, 1979), and barrier islands (3 6 km 2 ; Keiper, 1976; Zervanos and Keiper, 1979; Rubenstein, 1981) were generally smaller than at Hustai National Park. In general, differences in home range size are related to vegetation quality and distribution of resources such as water and shelter (Leuthold, 1977). No trends in harem range size with time after release were found, or with harem size (cf. Zervanos and Keiper, 1979; Berger, 1986; Linklater et al., 2), and there was no suggestion that forage was limiting. However, Mongolia suffers from periodic droughts and severe winters and these will affect the vegetation growth. It is possible that harem ranges will be smaller when forage quality is good; this was found in reintroduced Arabian oryx, Oryx leucoryx, whose ranges became smaller in areas where rain had fallen (Corp et al., 1998). Similarity in size of reintroduced takhi home ranges and feral horses under similar circumstances implies not only that feral horse management techniques could potentially be applied to this population, but that they are using similar survival strategies. Thus takhi did not

11 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) (a) Spring 1 2S2 1TG.5 3US 2LS 3LS 2M1 2US 3S1 2TG 2S1 1LS 3M1 1W 1MS MS W 1S1 3MS2 2W 1S2-1 3M2 3S2 2M2 3MS1 1MS1 1US 3TG 2MS2 1M1 3S -1.5 Area of vegetation i (ha) Summer 1.5 3M1 1 2M1.5 1TG 2MS1 1W 2US 3MS2 3US 3S1 2M2 1LS 3M2 3W 2W 2MS2 2S1 2S 1S2 8 1MS2 1MS1 3LS -.5 1S1-1 3S2 1M1 2S2 2LS 3MS1 1US 3TG 2R TG 3S (b) Area of vegetation i (ha) Autumn Winter (c) M1 2R 3M1 3M2 2S2 2TG 1US 3US 2LS 2US -1 1M12M2 2S 3TG 3W 3S 3S2 1W 2W 1S TG 3MS1 2MS1 4 1S1 1MS2 2MS2 3LS 2S1 1MS1 Area of vegetation i (ha) 3S1 3MS2 1LS 8 1 3M1.5 3LS 1LS 3US 1S1 4 3MS2 8 3MS MS1-1 3S1 3S 1M1 1US 3TG 3W 1TG 1MS2 3M2 3S2 1W 1S2-1.5 (d) Area of vegetation i (ha) Fig. 4. Habitat selection indices (w i,, logged for presentational purposes) plotted against area of each vegetation type (i). (a) = spring, (b) = summer, (c) = autumn and (d) = winter. First number 1 = Paritet, 2 = Bayan, 3 = Khaan/Margad. M1 = Meadow I, M2 = Meadow II, TG = Tussock Grassland, LS = Lower Steppe, US = Upper Steppe, S1 = Shrubland 1, S2 = Shrubland 2, MS1 = Mountain Steppe I, MS2 = Mountain Steppe II, W = Woodland, S = Scrub, A = Agricultural Area, R = Rock and Stones. Habitat classification based on Wallis de Vries et al. (1996). A value of log w i > represents positive selection, = represents no selection, < represents avoidance. Squares indicate habitats were not selected at all, but were arbitrarily assigned a value of.5 so that they appear on the figure, circles indicate w i values significantly different to zero (v 2 P <.5), triangles indicate insignificant w i values or where expected values <5. lose an ability to adapt to the wild despite 13 generations in captivity, just as this trait has not been bred out of horses despite 5 years of domestication. Characteristics of the ranges of all harems were that they included a permanent water source, an area of rocky outcrops near a ridge, and patches of forest that were used in the summer. The harems of Ares, Bayan, Khaan and Margad all overlapped at one particular place along the stream where pools were formed and the banks had been eroded to form a salt lick. However, in the main, the home ranges occupied separate valleys, defined by ridges which peaked at about 16 m, but which also joined at passes and along watercourses. As the size and number of harems change through time at Hustai National Park, competition for resources may increase. For example, larger harems have been shown to have priority of access to water holes (Miller and Deniston, 1979), and also tend to be found in areas of better vegetation (Miller and Deniston, 1979; Berger, 1977, 1986). Most studies on feral horses show extensive spatial overlap between ranges (Keiper, 1976; Miller, 1983a; Linklater et al., 2), although horses appear to avoid each other temporally, as they did at Hustai National Park (King, 22). After release, harems stayed near the release enclosure in the first year, then moved a little further away to settle in a valley. The harems selected valleys that were visually separated from each other, but as the population increases and more overlap occurs, more valleys will be colonised and smaller ridges within a valley may separate the harems. In winter harems seemed more tolerant of close proximity to each other (Mongolian rangers, pers. comm.), implying that at this time being near other harems is more important than having exclusive access to a food source. More work needs to be done in this season to examine if lack of spatial segregation between harems is for thermal reasons, or for greater protection against predation.

12 288 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) Vegetation use Plants change in nutrition and palatability through the year (Novellie and Winkler, 1993), and in Hustai National Park the takhi preferred some species in their early development stages, and avoided others after they had flowered (Salter and Hudson, 1979; Duncan, 1983; Miller, 1983b; Putman et al., 1987; Enkhee, 1998). The takhi selected vegetation classes dominated by grasses and fescues which have a high fibre and crude protein content (van Dierendonck and Wallis de Vries, 1993). Although grazing was observed on all vegetation classes overall, takhi did not select all vegetation classes in every year, nor graze on all vegetation classes present. Vegetation available to takhi affected their altitudinal movements through the year. They spent more time at low to mid elevations to shelter from inclement weather, and to feed on the most nutritious vegetation that was found in the Lowland steppe (Salter and Hudson, 1978). All the takhi had good condition throughout the year, and in the spring tended to have retained more body fat than local domestic horses (SRBK, unpubl.). As the takhi population grows there is potential for overgrazing to occur, especially on vegetation classes in the valleys that are preferred. Thus management will be needed in the future to ensure that this is kept under control. 5. Conclusions and the future of takhi at Hustai National Park So far, the introduction of takhi to Hustai National Park seems to have been successful, although this assessment is based on a time period that only approximates one generation (see Gross, 2). Despite this, there is little evidence that takhi have lost any ability to survive in the wild through many generations in captivity. All harems bar one were given a soft release, and maintained in acclimatisation enclosures for at least six months, thus allowing animals to get used to both the climate and disease vectors. The importance of a sufficient acclimatisation period is shown by the greater success of harems, such as PatronÕs, ParitetÕs and KhaanÕs, which were acclimatised for two years, compared to the those that had a hard release (TurgenÕs harem) or were acclimatised for only six months (Mark and BohemianÕs harems). These harems suffered greater mortality, with only two horses from Turgen and BohemianÕs harem surviving a year after release, and only one from MarkÕs. Local diseases were the main cause of mortality, suggesting knowledge of potential diseases should be obtained before animals are brought to the release site, and continuous monitoring post-release with immediate veterinary attention is desirable. Although target release sites should be surveyed for potential predators, in this case predation was not a major cause of mortality. However this is not true for all introductions (e.g., Matson et al., 24). The horses in this study tended to remain near their acclimatisation enclosure upon release, although they did move further away over time. Thus repeated use of a release enclosure could lead to intraspecific conflict and overexploitation of the nearby habitat. However, this does not seem to have occurred at Hustai National Park (enclosure 1 was used in 1994, 1995 and 1998, and enclosure 2 in 1994 and 1998; enclosures 4 and 5 were only used once); there was little overlap between ranges of different harems, although exclusive range use did not occur. All harem ranges at Hustai National Park contained access to a water source, and this has also been seen in feral horse studies. Releases should therefore be near a permanent water source, and this could be used to encourage animals to move further from a release enclosure. In addition shade areas and access to minerals seemed necessary for each harem. In comparison with feral horse studies, it appears that range size depends on habitat quality, and this should be taken into account in assessing target release sites. Importantly, takhi appear to use their habitat in a similar way to feral horses, so management techniques of feral populations could be applied. It has been suggested that Hustai National Park (area 57 km 2 ) should be able to support a population of 4 5 horses (Bouman, 1998), equivalent to a density of.9 horses km 2 or 42 harems with the currently observed 12 horses harem 1. However, because of the topography and availability of water, Hustai National Park may not support 5 horses. For example, in the western section of Hustai National Park there are streams in most valleys, but in the east (c. 144 km 2 ) there are only three ephemeral streams. Horses require a reliable water source, along with the presence of good quality vegetation and places for resting both by rocks near ridges and among trees. At present, the takhi population appears well below carrying capacity. Taking the rather tentative estimate of per capita growth rate per year of.66, it will take 15.5 years for the population to reach a carrying capacity of 45 horses. A future problem is the likelihood of hybridisation with domestic horses as the takhi expand beyond the Park boundary. Local people value hybrid offspring. Hybrids will need to be identified and either controlled, neutered or prevented from re-joining the population. Contraception may be a better way of limiting the population than removing animals (e.g., Gross, 2). Future studies at Hustai National Park will provide insights into dispersal, harem formation, and the effects of intraspecific competition as the population increases. In addition studies of the horses over the winter may provide more insights into the habitat use and any

13 S.R.B. King, J. Gurnell / Biological Conservation 124 (25) changes in social structure during this critical season. Takhi born in Hustai National Park could be used for future reintroductions in other parts of Mongolia as they will already have immunity to babesiosis and will have acquired the skills necessary to survive the varied seasons. Acknowledgements We thank the Foundation Reserves Przewalski Horse for their financial support and the opportunity of studying the horses at Hustai National Park, as well as access to past data. Thanks to the Mongolian Association for the Conservation of Nature and the Environment and the staff at Hustai National Park for all their help during the study, and thanks especially to the Hustai National Park biologists and rangers for collecting invaluable data, to Tessa Roos, and to Marc Hoogerwerf for advice on using ArcView. Funding for this study also came from IFAW, Queen Mary Expeditions Committee and Marwell Preservation Trust. 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