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 th e 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 aspect is helpful for a characterization of the vegetative period into seasons. It is surprising that only a small portion of hay balls are used as nests. This can be interpreted by several explanations. The balls are used as "iron-food" storages, the animals were killed or died in winter or our knowledge about this phenomenon needs revision.

SUMMARY OF OBSERVATIONS OF LEMMINGS KEPT IN CAPTIVITY

A young lemming with a black side stripe along its body, captured below the rubber pontoon storage at the Station house, was kept during nearly three weeks in June/July in a large, flexible, plastic, fine mesh-bag, 3/4-filled by tundra hay and attached to the house ceiling above the desk at which I was dealing with collected specimens, field data and observations. The animal was fed fresh plant forage, mainly flowers, leaf buds, green branches of Salix, and human food such as cheese, biscuits, grains, raisins, coconut, macaroni and others, all supplied in surplus. Small dishes contained milk and water. In the first wee k the tenant was hiding inside the bag and was active when nobody was home, consuming extensively only the wild food. After a week it gradually changed its diet, choosing more of human food-stuff but always with additions of tundra plants, especially parts of flowers and young seeds. Mosses and lichens were not consumed at all. After two weeks the young lemming looked very well, was semi-domesticated and often squeaked and whistled loudly. A piece of wood used as a ramp allowed the youngster access from the mesh-bag to the surface of 212 the desk, where it liked to play with a rubber and to hide between pages of open books. On the other hand it avoided lights from the microscope mirror and condenser, a plastic ping-pong ball and all kinds of shining metals. My colleagues A. Ohmura, J. Whiting, D. Terroux and M. Klin were afraid of disease and were rather unhappy with my house experiments with the lemming. "The ice was broken" when, during a session of loud singing and joking, the lemming stood up on its hind legs and responded to our noise by whistling in its high "C". After this, my colleagues reported to me their observations about lemmings, of which those obtained on glaciers were highly appreciated. At the end of July, a large, mature, partly silver-haired lemming was captured and kept for five days between the panes of the house's double window. Its new home was furnished with a thick, soft floor of tundra hay, a cardboard maisonette with a rounded entrance, a wooden pole 3x3x3 cms, small dishes for water and milk and a supply of air through a broken corner of the inside glass. It was treated in the same manner as the young lemming. This method permitted me to take a number of black and white photographs showing the lemming in various positions and behaviour (Fig. 5). Here thanks are offered to Dr. A. Ohmura who gave me the roll of film and for his care of the lemmings during my long hours of absence in the Station. Miss B. Sarter is thanked for transferring the black and white photos into indian ink-pictures in 1968, presented in Fig. 5. Among many notable observations is the fact that this lemming excreted red urine, which it immediately consumed. It used the cardboard maisonette only in cases of emergency. Quite often it climbed on to the top of the pole and jumped down from there on to the hay-covered floor. It consumed plants, either not using its forefeet or only one of them or both, seated or staying in a upwards position. In the fifth day of observations a pot of fresh snow was dumped in the corner of the between-glass space, which for a few hours, the lemming reworked non-stop. Afterwards, being completely wet, it sat on the maisonette, where it died.

PREDATORS

There are many predators of lemmings in the Canadian High Arctic, as illustrated in Fig. 6. When the annual predation rate is combined with the losses caused by other reasons such as disease, malnutrition, starvation, random fatalities, etc., the lemming population undergoes a great reduction. Nonetheless, this loss is considered by experts to be only a small proportion of the lemming's annual reproductive potential.

213 MISCELLANEOUS OBSERVATIONS ABOUT CANADIAN HIGH ARCTIC LEMMINGS

In the large lemming hay ball built below the falcon cliff at the head of the Expedition Fiord I found the body of a dead ermine (Mustela erminea). Its skin and skeleton is deposited in the zoological collection of the Canadian Museum of Nature. Lemmings can traverse a frozen sea in winter, a fact that is recorded by their excrements seen on sea-ice in summer. In the summer of 1968, in company with Mr. L. Lundgaard, I observed several more or less parallel routes made by lemmings between Fitzwilliam Owen I. and Eight Bears I. (western Canadian High Arctic). These routes, ca. 6 kms apart from one another, were meandering but still within the scope of the shortest distance between these islands. This indicates that lemmings have the ability to orientate themselves when they travel between invisible land masses. A pair of Snowy owls (Nyctea scandiaca) on Sabine Peninsula (N. Melville I. - several kilometres NW of Sherard Bay), whose food is mainly lemmings, accumulated over 200 of their remains around their nest, holding four young, during 33 days in June/July, 1971. Only a small part of this supply was used by the young. While hunting for lemmings, the adults were observed as far as 15 km from their nest. The year 1971 was not a peak "lemming year" but nearly so. In 1971 I experimented with a lemming kept in a large wooden box in the kitchen tent on the tundra of Sherard Bay. The lemming was able to climb on to a smaller cardboard box 25 cms high, installed inside the wooden one. From this height, spreading legs wide, it jumped down, and steadily repeated this activity for many hours, usually from 19.00 to 4.00 or 6.00. After 10 days of experiments the animal was released upon the kind request of the leader of the expedition, Dr. D.M. Barnett, because a fox started to be a frequent guest in our kitchen trying to steal the lemming. Lemming excrements were observed on glaciers above equilibrium lines or close to glacier borders, as reported to me by various observers from Axel Heiberg I., Ellesmere I., Meighen I. and Melville I. During examinations of mosses in rock fissures in cliffs, I several times saw hermit lemmings living on narrow, relatively inaccessible rock shelves. These specimens were old, large, silver haired (not white as those in a winter pallet), with teeth greatly reduced or imperfect, and were probably blind or nearly so. By approaching slowly and without a noise the palm of the hand to such a lemming, it was possible to reach a distance ca. 10 cms from its body. Not until then did it try to escape or start to check for danger by raising it nose to sniff the air. In a great number of samples of postglacial deposits which I examined, lemming excrements were found often and in perfect shape. In interglacial samples they were rare. Deposits of the Beaufort Formation were not found in Late Pliocene. This evidence is a good bio-indicator of tundra environments and tundra-forest communities. 214 ESSENTIAL RECORDS SELECTED FROM LITERATURE ABOUT ARCTIC LEMMINGS

For readers not quite familiar with lemmings, it seems useful to mention basic data about these animals derived from many publications. Lemming taxa and their general occurrence. The term "lemmings" includes two genera: Lemmus and Dicrostonyx of Rodentia. In the Canadian Arctic occur: Lemmus trimucronatus (unknown from the Canadian High Arctic and Ungava; according to Banfield 1974 it is one of three subspecies of L. sibiricus), Dicrostonyx hudsonius (limited to Ungava Peninsula), and D. torquatus sensu lato (occurring throughout the Canadian Arctic). D. tor quatus is represented by seven geographic subspecies (Banfield 1974, Krebs 1973): D. t. clarus (western and low arctic islands of the Canadian Arctic Archipelago), D. t. groenlandicus (Green- land and the eastern Canadian High Arctic), D. t. kilangmiutak (the continental and Low Canadian Arctic), D. t. lentus (the eastern Canadian Low Arctic), D. t. nunatakensis (hitherto known only from central Yukon), D. t. richardsoni (limited to the western regions of Hudson Bay). In the Eurasian Arctic occur: Lemmus obensis, L. lemmus, L. chrysogaster and Dicrostonyx tor quatus sensu lato (Tikhornirov 1959). Russian literature about lemmings is extensive, consisting of disputes and controversies. Lemmings do not occur on the Svalbard Ar- chipelago, which remains an unsolved puzzle. In regions south of the Arctic live some voles are also called lemmings (Banfield 1974), e.g. the Southern Bog Lemming (Synaptomys cooperi) and Northern Bog Lemming (Synaptomys borealis). In the Eurasian subarctic and southwards this problem is much more complicated. Major features of a lemming body. In general appearance it is similar to field mice, being 12-15 cm long, and weighing from 50 to 100 grams depending on species. The tail is very short (ca 2 cm long), ears and eyes are small, legs short with relatively large claws (some species change them in spring time), the fur is dense and brown to greyish-rufous (changed into white in winter by some species) and many adaptations to minimize energy losses could be figured. Reproductivity, mortality, migrations. Lemming are characterized by a very high reproductivity. The females mature at three to four and males four to five weeks of age. The rodents usually have four to eight young at a time, reproduce the year round (with some local exceptions), and deliver a litter every three to four weeks. In the wild they usually live for one year (rarely longer) and in captivity may reach an age of three years. Lemming population fluctuations, also known as "lemming years", occur in 3-4 year cycles, attaining up to 50 specimens per acre of land surface during a peak population season, while in years of a population depression there may be only a few specimens occupying several acres. The population fluctuations are explained by the influence of snow cover, some weather factors, epidemic diseases, predators (this cause correlated graphically is quite convincing), starvation and malnutrition, hormonal im-

215 balances, infrapopulation competition and some authors postulate extra-terrest- rial or cosmic reasons. None of these theories solves the problem. Local lemming migrations from low-lying land to higher and drier elevations are obvious, especially in spring during the melting of the snow cover, when tundra lowlands are flooded and turbulent waters in streams are high, and also in late summer or early winter from elevated areas to lower areas covered by thick snow. Regional migrations were also observed and documented but hitherto they do not have an unequivocal explanation. Most intriguing for laymen are the long distance migrations from inland to sea shores, from which they commit a mass suicide. This is now considered by experts as a legend and misconception. Some socio-hiological aspects. Eskimos consider a lemming as "kilang- -miutak", which means "one who dropped from the sky". This legend is based on their rapid appearance in a snow melt season of peak population years. In 1968 an Eskimo witch-doctor woman in Tuktoyaktuk told me very seriously about "kilang-miutak" and a local Eskimo teacher assisting us translated a meaning of "sky" as a supernatural power. Lemmings are excellent objects for modern studies about global changes, green-house effects, ozone and nitrogen influences and many others but results of such investigations are not yet published. On the other hand tourists and visitors now frequenting the Arctic are very interested in lemmings. In 1971 large lemming yards were photographed from a Super-cub from ca. 200 m above the flood-plain at Roe Point (E. Melville I.). It points to a possibility of mapping lemming burrows by modern, very precise methods called "geo- matics", that may be useful for an estimation of local lemming populations.

ACKNOWLEDGMENTS

Grateful acknowledgment is due to Dr. C. R. Harrington of the Research Division of the Canadian Museum of Nature for suggesting additional literature. Thanks are given to Ms Linda M. Ley for her comments and aid in the preparation of this article.

REFERENCES

BANFIELD A. W. F., 1974: The Mammals of Canada. University of Toronto Press. 436 pp. BLISS L. С. 1971Devon Island - High Arctic ecosystems. In: O. W. Heal (Ed.), Tundra Biome, pp. 71-70. IBP Working Meeting on Analysis of Ecosystems, Kevo, Finland (1970). London. BLISS L. C. 1972: IBP High Arctic, Ecosystem Study, Devon Island. Arctic 25 (2): 158-161. BLISS L. C. 1987: High Arctic ecosystems: how they develop and are maintained. The Canadian Arctic Islands. Canada's Missing Dimension. Abstracts: 59 pp. BLISS L. C. s.d. Devon Island, High Arctic Ecosystems. Biological Conservation (reprint). Elsevier Publishing Co. Ltd., London 1: 229-231.

216 BRASSARD G. R. & Longton R. E. 1970: The flora and vegetation of Van Hauen Pass, northwestern Ellesmere Island. Can. Field-Natur. 84: 357-364. FORBES B. 1996: Plant communities of archaeological sites, abandoned dwellings, and trampled tundra in eastern Canadian Arctic: a multivariate analysis. Arctic 49 (2): 141-154. FREEDMAN В., HILL N., SVOBODA J., & HENRY G., 1981: Seed banks and seedling occurrence in a high arctic oasis. In: Ecology of a high arctic lowland oasis, Alexandra Fiord (78°53' N, 75°55' W), Ellesmere Island, N.W.T., Canada", p. 135-151. HART H. C., 1880: On the botany of the British Polar Expedition of 1875-6. J. Bot. 9(n.s.): 52-306. HENRY G. H. R. & SVOBODA J., 1987: Grazed and non-grazed High Arctic sedge meadows. The Canadian Arctic Islands. Canada's Missing Dimension. Abstracts: 74 pp. KREBS С. J., 1973: Le lemming. Service cannadien de la fauna. Environment Canada. CW 69 -4/312, pages not numbered. KUC M., 1973: Bryogeography of the Expedition Area, Axel Heiberg Island, N.W.T., Canada. Bryophytorum Bibliotheca 2: 120 p. RAE R. W., 1951: Climate of the Canadian Arctic. Can. Dept. of Transport. Ottawa. 18 p. SAVILE D. В. O., 1961: Bird and mammal observations on Ellef Ringnes Island in 1960. Natl. Mus. Can., Mus. Nat. Hist. Bull. 9: 1-6. SAVILE D. В. O. & Oliver D. R., 1964: Bird and mammal observations at Hazen Camp, Northern Ellesmere Island, in 1962. Can. Field-Natur. 78 (1): 1-7. SPELLER S. W., 1972: Biology of Dicrostonyx groenlandicus on Truelove Lowland. In: L. C. Bliss (Ed.), Devon Island IBP. Dept. Bot., Univ. Alberta, Edmonton, pp. 257-271. TIKHOMIROV B. A., 1959: Vzaimosvyazi zhivotnogo mira i rastitelnogo pokrova tundry. Izdatelstvo Akad. Nauk SSSR. Leningrad. 103 pp. Fig. 1. Transect of Dicrostonyx torquatus groenlandicus burrow (The Expedition Area, Axel Heiberg I., eastern Canadian High Arctic). 1 - Cracks in clay, 2 - Lemming "plaza" (place most frequented by lemmings), 3 - Lairs of lemmings, 4 - Burrows, 5 - Carex nardina, 6 - Luzula nivalis, I - Saxifraga tricuspidata, 8 - Stellaria monantha, 9 - Poa arctica, 10 - Festuca sp. (cf. brachyphylla), II - Poa alpigena, 12 - Papaver radicatum - largest spots only, 13 - Saxifraga oppositifolia, 14 - Alopecurus alpinus, 15 - Arenaria rubella, 16 - Draba glabella, 17 - Oxyria digyna, 18 - Polygonum viviparum, 19 - Potenlilla vahliana, 20 - Salix arctica, 21 - Saxifraga nivalis. Single specimens of Draba sp., Papaver radicatum, Saxifraga cernuus, seedlings, dead and premature specimens, mosses and lichens were not plotted

218 [cm] 0 0-t— 10 20 30 40 50 60 70 ВО 90 100 110 120 130

• 1 2 2 3 U1J4

Fig. 2. Underground lemming labyrinth. 1. Burrows. 2. Tunnels. 3. Deeper tunnels. 4. Pocket tunnels filled by excrements. 5. Inactive tunnels

219 п 1 1 h 1 r JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

llllEliiii

W

VEGETATIVE PERIOD 16 16 1 16 1 16 fl 0 1 11 32 38 28 7 se 0 1 0 10 31 39 40 d! 0 0 0 0 0 10 27

AIR TEMPERATURE

JULY TO 20-

15- a«] S 10- on>i D 5- 0

-5

Fig. 4. Phenological spectrum of vegetation period and lemming hay balls. Sun graph after Roa 1951. A-E. Position of the Expedition Area. 1. Winter snow cover 1966-1967. 2. Melt of the winter snow cover of 1966. 3. Period of late snow patches. 4. Snow-free terrain; a - hay ball under construction, b-c - dry hay balls, d - hay/ice ball, e - disintegrating hay ball, f-last stage of disintegration of hay ball

220 Fig. 5. Lemmings. 1-3. Several postures assumed while eating. 4. Climbing a pole

221 »jjjjljjrTj X-— 7

Fig. 6. Predators of lemmings (Dicrostonyx torquatus groenlandicus) on the Expedition Area, Axel Heiberg I., Canadian High Arctic. Visitors: 1. Nyctea scandiaca (Snowy Owl) - rare, hunting from air or small hillocks, eating whole lemmings; 2. Canis lupus (Wolf) - rare, sometimes digging in lemming burrows, consumes whole animals. Permanent inhabitants: 3. Larus hyperboreus (Glaucous Gull) - rarely nesting but frequent visitor, hunting from ground or very low flying, eating whole lemmings, their parts or abandoned dead bodies; 4. Falco rusticollis (Gyrfalcon) -rare, air hunter taking prey to watch towers or nests, skinning and cleaning it; 5. Stecorarius longicaudatus (Long-tailed Jaeger) - frequent, hunting from ambush, consums whole young lemmings, larger ones chopping in situ; 6. Alopex lagopus (Arctic Fox) - frequent, main predator, eating whole animals, digging in burrows; 7. Mustela erminea (Ermine) - rare but very active, also eating some intestines abandoned by falcons

222 Table 1. Vascular plant components of lemming winter nests/storages. Abbreviations: l=leaf fragments, leaves, leaflets, small tufts; s = stem fragments, sb = stem parts with buds, glomerules, stolons; f=flowers and their parts (calyx, florets, flower buds, involucres, parts of inflorescences, perianths); sc=seed capsules (ovules, parts of panicles, parts of spikes and drupes, siliques, stems with capsules) Proportions Species Fragments of total mass Alopecurus alpinus 1, f, sc average Br ay a sp. 1, f low Cardamine nymanii 1, sb low Carex sp. - several species 1 high Cassiope tetragona s, sb, sc average Cerastium arcticum 1, s low C. berringianum s, sb low Cochlearia groenlandica 1, sb low Draba sp. - several species 1, sb, sc average Dryas integrifolia 1, f, s, sc average Erysimum pallasii 1, s, sc low Luzula sp. 1, s, sc high Oxyria digyna 1 low Poa sp. - more than one species 1, s, sc high Polygonum viviparum 1, S low Salix arctica 1, s, sb, f average Varia indeterminata: grass straw high roots, repents, rhizomes, stolons high-average rosettes low winter buds average indifferent average

223