Distribution , activity and range use of male caribou in early summer in Northern Yukon , Canada

Males of the Porcupine Caribou Herd separated from females from the onset of spring migration until they joined them on the calving grounds in late June or early July, 4-6 weeks later. From late May to late June males spent an average of 50% of their time feeding and less than 2% standing and trotting/running. Males spent an average of 29% of their time lying and 19% walking, except in mid-June (40% lying, 6% walking). The average lengths of active and resting periods were 112 minutes and 104 minutes, respectively, from late May to mid-June, but decreased sharply in late June to 78 minutes and 69 minutes, respectively. Tussock meadows were selected in late May and early June, wet sedge meadows were avoided until late June, dwarf shrub heaths were avoided after late May, and alluvial willow thickets were avoided in late May and early June but were selected in mid-June and late June. Caribou fed primarily on lichens and Vaccinium in late May, lichens and Eriophorum in early June, Eriophorum in mid-June and Salix in late June.


Introduction
The Porcupine Caribou Herd {Rangifer tarandus grand) calves on the Arctic Coastal Plain of northeastern Alaska and northwestern Yukon, and winters primarily in north-central Yukon and adjacent Alaska.Calving occurs from late May to mid-June with a peak in the first week of June.During calving, and for a variable period before and after calving, males are segregated from females.It has been suggested that this segregation occurs because males follow the northward initiation of growth of forage while pregnant females move quickly to the calving grounds for other reasons, such as predator avoidance (Whitten and Cameron, 1979).Recent proposals for a seaport, quarries and roads in northern Yukon in the area used intensively by males in early summer have focused attention on the need for information on that component of the herd.

Study area
Investigations were conducted in northern Yukon, north of the Porcupine River (Fig. 1).The area can be divided from south to north into three broad ecoregion bands: Old Crow Basin, Northern Mountains and Northern Coastal Plain (Wikenet*/., 1981).The Old Crow Basin, which includes the Old Crow Flats and the surrounding pediments, is generally flat or gently undulating terrain covered by boreal forest -tundra transition zone vegetation.The Northern Mountains include the British, Barn and Richardson Mountains with broken, ridged terrain interspersed by river valleys and intermountain basins.Vegetation consists of arctic and alpine tundra communities except for some intrusion of boreal forest along river valleys.The Northern Coastal Plain slopes gently from the mountains to the Beaufort Sea and is covered by arctic tundra vegetation.Three campsites were used for observing caribou in 1983: Sam Lake, 21 May -12 June; King Point, 13 -21 June; Firth River, 22 -30 June (Fig. 1).The Sam Lake camp was at the southern edge of the Barn Mountains and overlooked rolling, tundra-covered pediments.The King Point and Firth River camps both lay on the coastal plain in rolling arctic tundra.Sites for documenting plant phenology (Fig. 1) were established on the Old Crow pediments (Sam Lake, Bonnet Lake), in the intermountain basins (Cottonwood Creek, Anker Creek), on the inner coastal plain (Crow River, Walking River) and at the coast (Stokes Point, King Point).

Distribution
To follow the movements of caribou, radio transmitters on collars were placed on animals on the winter range.Between 5 and 15 caribou were available for relocation each year (1981 -5; 1982 -5; 1983 -15).In 1981 and 1982, four relocation surveys were flown between 3 and 28 June and in 1983 six surveys were flown between 8 May and 1 July.In addition to the locations of radio-collared animals, the locations of all male caribou observed on aerial surveys and reported by other researchers were plotted on maps.

Activity
We observed caribou with 15x -60x zoom spotting scopes from the three field camps.A band of caribou was defined as a socially interacting group of animals spatially distinct from other bands in the area.Activity data were collected using the instantaneous scan method (Altmann, 1974).We scanned each band at 15-minute intervals and tallied the number of caribou engaged in each of five general activities.The proportion of caribou observed in each activity and the estimated 95% confidence limits were calculated by the ratio estimator method (Cochran, 1977).Because of serial correlations among 15-minute observations of a given band of caribou, but not among different bands, estimated 95% confidence limits were based on a single ratio for each band observed.Differences were considered to be significant if the estimated 95% confidence limits did not overlap.

Phenology
We observed snowmelt and the development of vegetation in eight relatively flat cottongrass (Eriophorum vaginatum) tussock meadows (Fig. 1).We estimated the relative stage of development of the flowers of Eriophorum vaginatum (flower bud, early flower, full flower, past flower, seed) for 24 tussocks at approximately 5-m intervals along a transect at each site.Along the same transect we also documented the relative stage of development of the leaves of 24 plants of Salix pulchra, Betula glandulosa and Eedum palustre (leaf bud, leaf unfolding, full leaf).

Habitat selection
We divided the area of observation at each campsite into six distinct habitat types and determined their availability by mapping them on aerial photographs.The habitat types and their approximate classification according to Viereck and Dyrness (1980) were: Tussock Meadow, 2C2c; Wet Sedge Meadow, 2A3a; Dwarf Shrub Heath, 2D2a and 2A4a; Alpine Barren, 2Elb; Alluvial Willow, 3Ala; and Open White Spruce, lA3d.We also documented the use of late snow patches and sandy beaches at some camps.The areas observed at campsites appeared to be representative of much wider areas based on examination of aerial photographs and observations from aircraft.

Food habits
We collected composite fecal samples at Sam Lake ( 22 May, 4-5 June, 12 June), King Point  (15 -17 June), Firth River (26 -27 June) and  Stokes Point (15 June, 27 June).Each composite sample contained 20 fecal pellets, one from each of 20 different fresh pellet groups.Fecal samples were analyzed (Sparks and Malechek, 1968) at the Composition Analysis Laboratory at Colorado State University, Fort Collins.The relative density of plant fragments was based on 100 fields per sample.All samples were analyzed at the same time by the same technician.The accuracy of fecal analysis is influenced by differential digestion among plant species (Holechek et al., 1982).Therefore, the results represent proportions of discerned fragments in fecal samples rather than actual proportions of the ingested diet.

Distribution
Male caribou follow the females on spring migration along essentially the same routes leading from the two principal wintering areas, the Ogilvie Mountains of north-central Yukon and the Arctic Village region of northeastern Alaska.Females reach the calving grounds in mid to late May while males fan out into the rolling pediments north and east of the Old Crow Flats and into the wide basins near the headwaters of the Firth River (Fig. 2a).In early June, at the time of calving, males are distributed in a broad crescent south and east of the calving grounds (Fig. 2b).By this time, if not earlier, males from both the Alaskan and Yukon wintering areas are well mixed.Males then move eastward south of the British Mountains and northwestward from the Richardson Mountains and by mid-June large aggregations begin to form in the intermountain basins near the headwaters of the Spring, Trail, Babbage and Running rivers as well as, in some years, on the Firth River (Fig. 2c).By late June males are found moving westward and northwestward towards the coast of the Beaufort Sea near the Alaska-Yukon border (Fig. 2d).At this time, band sizes frequently number in the thousands and smaller bands which have lingered behind move quickly to join the larger concentrations.Most males meet and mix with females and young on the Alaska-Yukon coastal plain by early to mid-July before returning eastward to the Richardson Mountains.
Males, therefore, are essentially segregated from females during May and June.The consistent pattern of distribution and movements among years and the formation of aggregations in mid-June prior to joining females and prior to the insect season suggest a response to food resources combined with a form of social facilitation.

Activity
In late May, at Sam Lake, many females were moving through the area and males occurred in both male-dominated and female-dominated bands.Therefore, observations included both types of bands.After that time, only maledominated bands were observed.The average size of bands was relatively constant from late May to mid-June but increased significantly in late June (Table 1).
There was no significant difference in the proportion of time spent feeding or trotting/ running among observation periods (Table 2).In mid-June the proportion of time spent lying was significantly higher than during other periods and the proportion of time spent walking was significantly lower than during other periods.The proportion of time spent standing was significantly lower in late June than during other periods.The rate of movement (Table 1) mirrored the proportion of time spent walking (Table 2) and was conspicuously low during mid-June.
It is not possible to make precise comparisons of activity budgets among studies because of differences in methods of calculation.In general, for the same season, Roby (1978) found that male caribou in north-central Alaska spent less time feeding (39%) and more time lying (47%) than males we observed.
The mean length of both active and resting periods declined significantly from late May to late June (Table 3).The decrease from mid-June to late June was particularly conspicuous.The mean late May to mid-June active period we observed (112 minutes) was shorter than reported for summer for male reindeer (135 minutes) (Segal, 1962), while the mean late May to mid-June resting period (104 minutes) was not significantly different (105 minutes).

Phenology
On 18-19 May 1983, the Old Crow pediments were about 80% snow covered while farther north all sites were about 95% snow covered.By 3 June the snow cover had declined to less than 5% on the Old Crow pediments and the coast but was about 50% (30 -70%) beetween those sites.By 10 June the intermoun¬ tain and inner coastal plain sites were about 10% (5 -20%) snow covered and by 17 June all sites were essentially snow-free.
In general, the development of vegetation was most rapid on the Old Crow pediments (Table 4).In early June, the development of Eriophorum vaginatum was more advanced on the coastal plain than at inland sites but by mid-June plant development on the coast was behind that at other sites and remained so.This was probably due to the temperature gradient which develops between the coast, which is strongly influenced by the ice-covered Beaufort Sea, and the thermal basin surrounding the Old Crow Flats (Pearson and Nagy, 1976).In general, plant development on the Old Crow pediments was at least a week in advance of that on the coast.

Habitat selection
Tussock Tundra was weakly selected in late May and early June while Wet Sedge Meadow was strongly avoided until late June (Table 5).Dwarf Shrub Heath began to be avoided weakly after late May and Alluvial Willow shifted from being avoided in late May and early June to being selected in mid-June and late June.Other habitat types were too poorly represented to compare.
Eriophorum and Salix were more similar between Stokes Point and King Point than to Sam Lake.Thompson and McCourt (1981) have previously reported on the diet of the Porcupine Caribou Herd based on fecal analysis.They reported that Eriophorum (56%) and lichens (37%) were the most important components in fecal samples in May and that samples were dominated by Eriophorum (77%) in early June and by Salix (99%) in late June.Although the proportions of lichen in late May and Salix in late June are consistent with our findings, the proportions of Eriophorum are not; they appear high in relation to expected phenological stage, especially in late May.Duquette (1984) reported on diet of females of the Porcupine Caribou Herd based on fecal samples and found that in late (16 -26) May samples were dominated by lichens (41%), Salix (22%) and evergreen shrubs (16%), with Eriophorum making up less than 1%.The high proportion of Salix is noticeably different either from that we observed (0%) or from that reported by Thompson and McCourt (1981) (0.1%).In late May, therefore, caribou of the Porcupine Herd apparently feed primarily on lichens but supplement the diet with whatever palatable green matter is available.

Summary and conclusions
In late May male caribou were distributed south of the mountains where snowmelt was more advanced than farther north.Caribou used tussock meadows, dwarf shrub heaths and alpine barrens but avoided low-lying wet sedge meadows and alluvial willow thickets where snowmelt was slower.Diet consisted primarily of lichens and evergreen shrubs which were widely distributed in the habitat types utilized.By early June, as snowmelt progressed south of the mountains and on the eastern coastal plain, males moved northward to those areas.Intermountain basins, where snowmelt was retarded, were avoided.As the season progressed males continued to use, and avoid, essentially the same habitat types but there was less use of dwarf shrub heaths.They continued to feed on lichens but began to use Eriophorum as it came into flower.In mid-June, males moved into intermountain basins as snowmelt there progressed.Caribou used tussock meadows and alluvial willow thickets as the diet shifted to Eriophorum and Salix.At that time, large aggregations of caribou formed in intermountain basins and they spent more time lying,*less time walking, and had a lower rate of movement than in other periods.By late June, males began to use the western coastal plain where they used tussock meadows, wet sedge meadows and alluvial willow thickets.Salix, which was common in all three habitat types, predominated in the diet.At that time, Salix on the coast was at a similar phenological stage to that at inland sites 2 weeks earlier when it was not used as heavily as Eriophorum.However, by late June Eriophorum was in seed and therefore not as desirable as a food for caribou.In late June average band size increased significantly and rate of movement was greatest as males moved westward towards Alaska.As well, the mean length of active and resting periods decreased by about one-third.This sharp decrease may reflect both the high availability and high digestibility of young willow leaves.
In general, the distribution of male caribou followed the pattern of snowmelt and plant phenology and diet reflected both preference and phenological stage.Activity and movements, however, were not related to snowmelt, plant phenology or diet.Rather, they appeared to follow a temporal pattern.

Fig. 1 .
Fig. 1.Map of northern Yukon showing locations of field camps (triangles) and sites for documenting plant phenology (circles).

Fig. 2 .
Fig. 2. General distribution (shaded) and direction of movement (arrows) of male caribou in northern Yukon in late May (A), early June (B), mid-June (C), and late June (I)).

Table 1 .
Size and rate of movement (km/h) of bands of male caribou in northern Yukon in 1983 1 , 2Rate was measured from the estimated distance moved by bands between 15-minute scans.Table2.Daily activity budgets (% time ± estimated 95% confidence intervals) for male caribou in northern Yukon in 1983.

Table 3 .
Length (minutes) of active and resting periods' (x±SE) for male caribou in northern Yukon in 1983 2 .Sample sizes in parentheses.

Table 4 .
Phenology of vegetation in northern Yukon in 1983.The percentage of plants in each stage of development is presented in sequence.Blank spaces indicate that the plant had not yet begun to develop.

Table 6 .
Average percentages of discerned plant fragments in fecal samples collected from male caribou in northern Yukon in 1983.Sample sizes in parentheses. -0.7