The Canadian High Arctic Lemming - Dicrostonyx Torquatus Groenlandicus (Traill) - As Perceived by a Botanist
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Marian KUC Wyprawy Geograficzne na Spitsbergen Gloucester (Ottawa), Ontario IV Zjazd Geomorfologów Polskich 6 - Lewer St. KIV IG9. CANADA UMCS, Lublin 3-6 czerwca 199B THE CANADIAN HIGH ARCTIC LEMMING - DICROSTONYX TORQUATUS GROENLANDICUS (TRAILL) - AS PERCEIVED BY A BOTANIST INTRODUCTION Small arctic rodents, known as lemmings (for details see taxonomic remarks below), are significant components of the high arctic biota because they link animal and plant relationships more strongly than any other tundra creatures do. They are basic sources of nourishment for many other animals, considerably modify micro-environments and completely dependent on plant growth, chan- ging it greatly. Naturally, they are investigated mainly by zoologists, while other students, especially botanists very rarely publish about them. Apart from general treatments, the author considers Hart's 1880 paper to be the earliest of the Canadian High Arctic literature to contain botanical information about lemmings. On p. 76 he states "lemmings swarm here (Lady Franklin Bay -MK), and subsist entirely on vegetable matter, Saxifraga oppositifolia and Drabas support hosts of lemmings". Between this publication and more contemporary studies there is a long gap in botanical information about these animals. Savile (1961) and Savile & Oliver (1964) mention the importance of lemmings in the nitrification of high arctic habitats. Brassard & Longton (1970) found nitro- philous mosses at entrances to lemming burrows. Freedman et al. (1981) tabulated seedling density around lemming burrows at Alexandra Fiord. Henry & Svoboda (1987) pointed to sedge meadows as major forage communities for lemmings on Ellesmere I. Forbes (1996) listed several vascular plants and mosses which grew on habitats disturbed by lemmings. Bliss has reported much information about these rodents from various Canadian High Arctic islands (1971,1972,1987 & s.d.). Finally, mention should be made of Speller (1972), who presents interesting botanical evidence in his general biological report regarding the small area of Truelove Lowland (Devon I.). In general, however, knowledge of Canadian High Arctic lemmings is meager and based only on fragmentary factual information. Therefore this botanical addition, consisting of year-round observations of a lemming life, should prove reasonably useful. 209 A botanical survey of lemming burrows and their vicinities, called here a lemming yard, in house experiments on living specimens, and a number of occasional observations were performed by the author between late May and the end of August in 1967. It was not a separate research program for relationships between lemmings and plants involved in a web of tundra life but rather observations made mainly during geobotanical field work made by the author with the use of the Base Camp lodgement (at Colour Lake) of the McGill University Expedition, 70°25' N and 90°30' W, located on the Expedition Area (west-central Axel Heiberg I. in the eastern Canadian High Arctic). In addition this article reports on some selected data and observations of lemmings obtained by me on other High Arctic islands between 1967 and 1971. The year 1967 was a so-called "lemming year", or close to it, and probably the second one after 1960, which embraced almost all of the Canadian Arctic (Krebs 1973). THE SURVEY OF THE LEMMING YARD The surveyed lemming yard, 1 x 1.3 m, located about 4 kms west of the Base Camp on the gravel terrace covered by heavy clay of an average thickness 20 cm, was overgrown by loose, tall vascular plants, a discontinuous matting of mosses and small groups of foliose lichens. This spot of vegetation, surrounded by low Salix - moss/lichen tundra appeared as an enclave of luxuriant growth visible from a distance of 75-100 m. The surveyed area was subdivided into 10 x 10 cm squares whose corners were marked by small red stones and measured by a transect method. Plants and substrate features were plotted on a sheet calibrated in millimetres (Fig. 1). When the lemmings were gone, on August 8, 1967, this area was excavated in order to measure the underground lemming labyrinth, its tunnels, burrows and nests and to map to scale the transect shown in Fig. 2. The surveyed object was visited quite often because it was located beside the trail, by which I passed every several days going towards the head of the Expedition Fiord for collections and the checking of phenophases of plants. The clay layer covering the yard was cut by irregular five-angled polygons modified by the lemmings' activities. The underground labyrinth was tunnelled only in the active permafrost layer and was composed of arched, straight or semicircular corridors several cms wide, ending with many hollows (entrances), oval rooms (largest 12 cm in diameter) and short lateral pockets of tunnels nearly completely filled up by lemming excrements. These had accumulated there during many years of the animals' activities and were in various stages of decomposition, strongly overgrown by moist mould (Phycomycetes) emitting a strong unpleasant odour. About 30 cms to one side of the main labyrinth was 210 another smaller one. A corridor connecting them was not found. It could have belonged to another group of lemmings or could have been an emergency labyrinth. More or less in the middle of the yard was the central place called here a plaza. It was of an irregular shape, completely bare, dry and ploughed by lemmings. From there commenced lemming roads which ran in frost cracks widened by animals between polygons. Those at the plaza had flat bottoms, while those more remote gradually narrowed, becoming "V" - shaped in cross-section, while on their sides were elongate bare spots indicating that an animal running in the cracks with considerable speed used first the left side, then the right side of the road. Beyond the terminal parts of the routes, the tundra was affected by lemming activities in various manners, still traceable at a distance of several tens of meters from the yard. Overgrowing vegetation was composed of 20 vasculare (shown in Fig. 1), 12 common mosses (species of Bryaceae and Polytrichaceae, Hylocomium splendens, Rhacomitrium lanuginosum and Sanionia uncinata were quite abundant) and a few lichens (Stereocaulon and Thamnolia were fairly frequent). Specimens of vasculars growing around the plaza were distinctly taller than those growing on average habitats, while mosses and lichens were in typical morphologic forms or only slightly mechanically destroyed by the animals. On abandoned or less frequented lemming roads, covered by fresh soil, grew acrocarpous, gregarious, usually annual mosses, e.g. Hemiediella heimii, Stego- nia latifolia and Desmatodon sp. Dwarf shrubs such as Cassiope, Dryas, and Salix were distinctly less abundant in the plaza than in its vicinities. Nitrophilous vasculars and mosses were absent. It is amazing that lemmings did not cut these plants in the yard. They seemed to use them as protection against predators and as camouflage. In the optimal conditions of summer numerous mosquito-like insects and, rarely, single arachnids and beetles were observed in the burrows. THE VEGETATIVE PERIOD AND LEMMING ACTIVITIES Summer observations of lemming activities are not difficult for a skilled and searching observer, while winter ones are difficult because of the snow cover in which lemmings live. As a consequence, published data about the winter life of lemmings is unique information. The indirect method of tracing winter lemming activities show lemming nests (also known as "storages, balls of hay, winter hay balls, winter nests, cold nests"). These are balls from 6 to 20 cm in diameter (Fig. 3), constructed by lemmings in snow during winter on surfaces with usually well-developed, species-rich, thicker plant growth and are composed of frag- ments of the plants consumed by lemmings. Components of hay are loose in dry snow, but during a melt period they are soaked by water, which when frozen changes hay balls into hay/ice balls. These forms can persist on snow-free tundra until the ice contained in them melts to let the wind and precipitation destroy 211 them. Laboratory analyses of twelve balls yielded the following results. All accumulated plant fragments were gathered by the lemmings from the vicinity of their nests. Most abundant were parts of vascular plants, less than 20% were mosses (upper portions of stems of Aulacomnium, Bryum, Dicranum, Hypnum, Mnium, Polytrichum, Pogonatum, Sanionia, Timmia and few premature cap- sules) and foliose lichens (mostly Cetraria, Cladonia, Thamnolia) occur in small fragments. Table 1 below, presents the vascular plant organs which are major components of the balls. Most moss stems with apical buds and some branches of vasculars with green bark and buds were living diaspores and ,when spread through the tundra, increase its pattern of diversity. Balls are frequent on lowland and adjacent lower elevations covered in winter by thick snow. Along the north side of the Expedition River for a distance of ca. 3 km, during the first half of June, 117 balls were found. Most often balls are built at the intersections of tunnels under snow, which show traces of lemming activities on growth. Frizzed balls are not visited by lemmings. During the period of the winter snow melt lemmings migrate up the hills to drier environments, where they hide in cracks, rock fissures, between stones or in organized summer nests. The phenomenon of lemming spring activities and the vegetative period is presented in Fig. 4. This phenological