Anita. Behav., 1974, 22, 256-261

THE SOCIAL BEHAVIOUR OF THE HOARY MARMOT

(MARMOTA CALIGATA)

BY DAVID P. BARASH* Biology Department, State University College, Oneonta, New York 13820

Abstract. The social behaviour of four colonies of hoary marmots (Marmota caligata) was studied in Glacier National Park, Montana, during the summer of 1970. Colony structure involved a dominant male with a few females (3 years or older), 2-year-olds, yearlings and pups. Patterns of burrow use, greetings, play, and aggressive chasing are described, indicating a closely-integrated social structure with reproductive patterns suggesting late dispersal and maturation. A close resemblance to the be- haviour of the Olympic marmot (M. olympus) is proposed.

Marmota caligata is a widespread alpine and sub-alpine inhabitant of western North America. Yet despite its extensive range and great visibility, there have been no technical accounts of its behaviour or ecology. The Marmota group offers great potential for research into the evolution and functional significance of mam- malian social behaviour (Downhower & Armit- age 1971; Barash 1973), paralleling recent cyto- genetic studies of the genus and its probable evolutionary history (Hoffmann & Nadler 1968; Rausch & Rausch 1971). The research described here constitutes an initial attempt to evaluate the basic social characteristics of M. caligata, preliminary to a unified synthetic picture of marmot biology as a whole.

Methods The behaviour of the hoary marmot in Glacier National Park was studied from 1 June to 15 August 1970, obtaining 344 hr of direct observ- ation. The primary study area was at Piegan Cirque, elevation 2200 m, 2 km east of Logan Pass. Observations were also conducted in the Oberlin-Clements basin, 2 km southwest of Logan Pass and at a colony 50 km above the Highline Trail, 3 km west of Logan Pass. The study areas consisted of rock ledge and talus slope, with adjacent sub-alpine meadow char- acterized by sedges (Carex sp.), glacier lilies (Erythronium grandiflorum), alpine arnica (Arnica alpina) and mountain sorrel (Oxyria digyna) with occasional groves of krumpholtz sub- alpine fir (Abies lasiocarpa).

All observations were conducted from con- venient vantage points, with no effort at self- concealment as the animals appeared to habituate

*Present address: Departments of Psychology and Zoology, University of Washington, Seattle, Washing- ton 98195.

to the observer's presence within 30 min. Mar- mots were trapped with steel, folding-door live traps manufactured by the National Live Trap Corp., Tomahawk, Wisconsin, using peanut butter and apples as bait. Each animal was weighed, sexed, marked with ear notches, and released within 3 min of capture. Distinct pelage characteristics enabled positive individual recog- nition of all animals older than yearlings.

Results Colony Composition

The Piegan Cirque study area comprised two marmot colonies with significant interaction occurring between them, while the Oberlin- Clements and Highline Trail colonies were each somewhat isolated. Young, yearlings and adults (at least 3 years old) were easily differentiated by size, but some presumed 2-year-olds may possibly have been unusually small adults. The observed distribution of weights for all animals in June was as follows (in kilogrammes): adult males 2.4 to 2.7 (x ---- 2.5), adult females 1.9 to 2.1 (x = 2.0), 2-year-olds 1.4 to 1.7 (Y ---- 1.5), yearlings 0.3 to 0.5 (x = 0.4) and young (in late July) 0.2 to 0.3 (x = 0.3). The composition of all four colonies is presented in Table I, revealing a basically polygynous society, although with some variation.

The 2-year-olds of Piegan Cirque were not clearly associated with either colony. They occupied burrows roughly intermediate in distance between both and associated during the day with members of either colony, although they concentrated their activity with members of only one colony during any 1 day. These 2-year-olds were accepted without apparent antagonism by the colony residents, although the resident adult male customarily showed high excitation and initiated lengthy greetings (dis-

256

BAR.ASH: SOCIAL BEHAVIOUR OF MARMOTS

Table I. Composition of All Study Colonies

257

Location Adult male Adult female 2-year-olds Yearlings Young

Piegan Cirque A 1 2 3 3 4

Piegan Cirque B 2 3 3 2 3, 4

Oberlin-Clements 1 2 2 4 0

Highline Trail 1 2 0 3 4

cussed below) on fourteen of the sixteen occa- sions when the approach of a 2-year-old was recorded.

Each colony contained an adult male who was clearly the dominant animal and who either occupied a solitary burrow or shared it with the non-parous female and her yearlings. Piegan Cirque colony B included two males, of which one occupied peripheral solitary bur- rows and continually avoided the dominant. The adult females associated in the same burrows with either yearlings or young but not both. This suggests a biennial breeding system in which each female produced young in altern- ate years; these young remain with their mothers through their 2nd (yearling) year until the beginning of their third season (when they are 2-year-olds).

Spatial Behaviour

Each parous female (both before and after parturition) and her infants showed great fidelity to a single sleeping burrow throughout the study period. Other animals generally displayed variable but relatively high burrow fidelity early in the season, with a gradual decline later (Table II). All classes except the young and parous adult females showed a sig- nificant decline in burrow fidelity from June to August (P<0.05, binomial test for pooled data). The adult males consistently showed the lowest burrow fidelity, while the young were highest.

Burrow use patterns typically involved prefer- ential use of a certain burrow by a particular individual, with a declining frequency of use of three or four other select burrows. Thus, in July a non-parous female at Piegan Cirque was seen to use burrow A ten times, burrow C four times, burrow D twice and burrow E once. Comparable utilization practices were character- istic of other colony residents. When super- imposed upon each other, these individual be- haviours produced a complex, kaleidoscopic

Table H. Burrow Fidelity of Age and Sex Classes at the Piegan Cirque Colonies

June July August (9 days) (11 days) (6 days)

Adult 3 0.48 0.33 0.17

Adult $ (parous) 0.92 1.00 0.89

Adult ? (non-parous) 0.89 0.77 0.45

2-year-old 0"76 0"60 0.37

Yearling 0.98 0.69 0.44

Young - - 1.00 1-00

Calculated as the percentage of either morning or evening observations at which night-time occupancy of a particular most-commonly used burrow is confirmed (e.g. six observations of five adult females each, revealing fifteen individual instances of such burrow use would result in an observed fidelity of 15/5 • /6=0.50).

pattern of burrow usage for the colony as a whole.

The Oberlin-Clements colony was unique in that the animals changed their location during the summer. They emerged from hibernation in the relatively snow-free talus and rocky ledges overlooking a basin of rich sub-alpine meadow. This latter area received a heavy snow-pack (3 m in mid-June) compared to the dear, wind- blown meadows near hibernating marmots at the other three locations. As the season pro- gressed, the Oberlin-Clements animals moved down into the basin, following the melting snow into the newly-exposed meadow and utilizing newly-revealed burrows. This seasonal move- ment covered a distance of �89 km and an altitude drop of 200 m. During the movement, burrows en route were utilized by the same animals for periods varying from 1 to 20 days, and the same burrow was often occupied by several animals simultaneously as well as by different animals at different times. By late July a new colony ~ ar- rangement was established in the basin itself,

Q

258 A N I M A L B E H A V I O U R , 22, 1

with patterns of burrow fidelity comparable to those at the other colonies.

Like other marmots (Armitage 1962; Barash 1973) hoary marmots characteristically lounge at the immediate entrances of their burrows both before and after activity periods. However, excluding the parous female and her young, no particular association was apparent during most of the day between specific animals and the region surrounding their burrows or with any region of talus or meadow. Territories were absent, as well as home ranges unique for any individual, since the animals all had equal access to the colony terrain. In fact, they ap- peared distinctly social while feeding, as aggre- gations of three or four foraging animals were common. These animals often appeared to actively seek the company of others. Animals frequently entered another's burrow (one for which another animal demonstrated higher burrow fidelity); 177 observed occasions of this included thirty-one instances of yearlings enter- ing an adult male's burrow. Such intrusions were followed by fights or chases directed by the resident toward the intruder on only five occa- sions; in each case this involved the behaviour of a dominant adult male toward the ,ubordinate male (Piegan Cirque colony B).

Parous females displayed more spatial re- strictiveness than the other animals. Through June all parous females maintained a close association with their burrows, rarely venturing more than 30 m away. The burrows themselves were defended at times against all colony residents, including the adult males. Of twenty- eight aggressive incidents observed between the parous female and other animals within 8 m of her burrow, the former was dominant in all cases, with fifteen aggressive chases as the im- mediate outcome. However, this defence was inconsistent as animals entered parous female burrows forty-nine times with no agonistic response from the female. Thirty-five (71 per cent) of such unopposed visitations occurred during the 2-week period immediately preceding the young's emergence. Only three of seventeen attempted post-emergence visitations were op- posed to parous females.

Recognition Behaviour Hoary marmots commonly engaged in con-

spicuous oral behaviour termed greeting in previous studies of sciurid rodents (King 1955; Armitage 1962; Barash 1973). Greeting is pre- sumably associated with individual recognition,

through olfactory and possibly tactile stimuli, with the specific behaviour pattern varying be- tween species. The hoary marmots in my study areas demonstrated a diversity of greeting be- haviours, including sniffing at a distant animal (generally within 3 m), superficial contact of the noses, extensive open-mouthed contact with possible tooth-locking, chewing of the face of the animal being greeted and, occasionally, chewing the neck and back of the greeted animal. These descriptions represent points in a be- havioural continuum, which usually followed this pattern of increasing physical involvement but could be broken off at any stage. The sniffing at greetings were rare (observed eleven times), difficult to detect and are not included in the following data. Nose-to-nose and mouth-to- mouth greetings were commonly observed whenever two animals came into close prox- imity, and thus they serve as a covenient index of sociality. The seasonal and diel variations in greeting frequency are shown in Fig. 1. A bimodal diel pattern (with morning and late afternoon activity periods) is apparent for July and August, preceded by a basically unimodal pattern in June.

Animals of different classes were differen- tially involved in greetings, and these differences varied seasonally as well (Fig. 2). Thus, the adult males were involved in a high percentage of greetings, especially in June, while the 2-year- olds had a low representation, reflecting their lesser social integration. The young also engaged in a high percentage of greetings, many of these occurring between themselves.

Play, Agonistie and Sexual Behaviour Although play is admittedly difficult to define

objectively, hoary marmots commonly engaged in behaviour patterns that intuitively suggested play. Animals would prance stiff-legged toward each other, nipping at legs or tail and rolling over and over together. Two animals commonly faced each other balanced on their haunches and lunged at the exposed belly or chest, or appeared to box with one another using the forelimbs. Such bouts were occasionally fol- lowed by pushing matches, in which the animals stood on their hind legs and apparently strained to push the partners over backward. This often resulted in a peculiar posture, previously ob- served for the olympic marmot (Barash 1973) in which both animals pointed their faces to- ward the sky, with their ventral neck surfaces facing each other. Upright play-fights occurred

BARASH: SOCIAL BEHAVIOUR OF MARMOTS 259

:J o

i

t s

6-9 9-10 10-11 11-12 12.1 1.2 2-3 3-4 4.5 5.8 6-7

(AM) LPM~ T ime o f D~y

Fig. 1. Seasonal and did variations in greeting frequency. Cumulative data for all colonies, based on the following observation regime: June 130 hr, July 141 hr, August (1-15) 73 hr, including a minimum of 4-hr observation for each hour-interval during each month.

o

m H June

I ~ ~ ~ r~ ~ ~ ~ ~ ~ ~ : i i - i

Ju ly Augus t

Fig. 2. Percentage involvement in all observed greetings by each class of animals. Cumulative data for all colonies, based on the observation regime reported for Fig. 1.

260 A N I M A L B E H A V I O U R , 22, 1

at a frequency of 0.27 per animal per observation hr during the entire study period. The participa- tion of each class was as follows (per animal per observation hour): adult male 0-11, adult female 0.08, 2-year-old 0.43, yearling 0-58, young 0.31. The young, yearlings and 2-year- olds are thus clearly the most frequent par- ticipants.

A distinction between play and aggression was difficult among the adults, as upright play- fights occasionally becamo sufficiently energetic to qualify as true fights. Thirty-nine per cent of observed upright play-fights involving adults were immediately followed by a chase, with one animal dearly in retreat and another in pursuit. However, not all chases were preceded by upright play-fights. Often one animal approached another at a run, with the other turning and fleeing when the approacher was about seven metres away. The frequencies of involvement in chases for each class of animal are shown in Fig. 3. Chases were most abundant in June and decreased steadily through the summer. The adult males were the most frequent chasers while the 2-year-olds and yearlings were the most frequent recipients.

Overt sexual behaviour had a very incon- spicuous role in hoary marmot social inter- actions during the study period. Since the fully-

furred young emerged 15 to 21 July, insemination probably occurred during mid or late May. Nine mountings were observed, with the follow- ing distribution of participants: adult male- adult female, two; adult female (parous)-adult female (non-parous), three; 2-year-old-2-year- old, four. During these mountings, the bottom animal arched its tail and held it conspicuously to the side, while the top animal grasped the partner's dorsal neck fur in its jaws. These mountings were preceded eight times by greet- ings and three times by the mounter sniffing the ano-genital region of the partner.

Discussion The four hoary marmot colonies studied were basically similar in social organization, one notable exception being the seasonal movements at Oberlin-Clements. This was probably due to topographic features directly, as this was the only colony in which the hibernating burrows were greater than 100 m distant from suitable early-season foraging areas. Seasonal move- ments of this sort have not been described pre- viously for any western North American marmot. Hoary marmot burrow sites appear to be limited to large boulders and this restriction may necessitate seasonal movements when such sites are at a distance from suitable feeding

eh~slng

I=~ June ] F - - I July August

Fig. 3. Seasonal variation in involvement in all observed chases by different classes. Cumulative data for all colonies, based on the observation regime for Figs 1 and 2.

BARASH: SOCIAL BEHAVIOUR OF MARMOTS 261

areas. These movements may well be disadvan- tageous for the animals concerned, particularly in view of the high burrow fidelity normally evidenced by parous females. I t may thus be significant that the Oberlin-Clements colony produced no young in 1970.

Hoary marmot biology shows many similar- ities to that of the olympic marmot (Barash 1973): both are highly colonial consisting prin- cipally of a dominant male and one or several females with their offspring. A high frequency of greetings and lack of territorial restriction are also characteristic of both species. Olympic marmots disperse and mature late (as 2-year- olds and 3-year-olds respectively) and individual females reproduce biennially; circumstantial evidence presented here suggests that a similar reproductive constellation occurs in the hoary marmot. Thus, 2-year-olds were distinguishable by their size, and no cases of breeding by them were recognized. Similarly, although no overt dispersal was observed, 2-year-olds received the brunt of aggressive behaviour. Among yellow bellied marmots (M. flaviventris) in which dis- persal is achieved by yearlings, the yearlings accordingly experience high levels of aggression (Downhower 1968). The aggression directed toward 2-year-old hoary marmots thus suggests that like olympic marmots again, hoary marmots disperse as 2-year-olds. Finally, biennial breed- ing was suggested by the association of adult females with either young or yearlings but never both. Such similarity of closely related species

occupying similar environments should be expected (Crook 1970), indicating the adaptive nature of social organization.

Acknowledgments This research was supported by NSF Grant GB 15-304 to Professor John T. Emlen, The University of Wisconsin.

REFERENCES Armitage, K. A. (1962). Social behavior of a colony of

the yellow-bellied marmot (Marmota flaviventris). Anita. Behav., 10, 319-331.

B,arash, D. P. (1973). The social biology of the Olympic marmot (Marmota olympus). Anim. Behav. Monogr., 6, 3.

Crook, J. H. (1970). Social organization and the environ- ment. Anim. Behav., 18, 197-209.

Downhower, J. F. (1968). Factors affecting the dispersal of yearling yellow-bellied marmots. The Univers- ity of Kansas, Ph.D. Dissertation.

Downhower, J. F. & Armitage, K. A. (1971). The yellow-bellied marmot and the evolution of polygamy. Am. Nat., 105(944), 355-370.

Hoffman, R. S. & Nadler, C. F. (1968). Chromosomes and systematics of some North American species of the genus Marmota (Rodentia: Sciuridae). Experientia, 24, 741)-742.

King, J. A. (1955). Social behavior, social organization, and population dynamics in a black-tailed prairie dog town in the Black Hills of South Dakota. Contr. Lab. vertbr. Biol. Univ. Mich., 67, 123 pp.

Rausch, R. L. & Rausch, V. R. (1971). The somatic chromosomes of some North American marmots (Sciuridae), with remarks on the relationships of Marmota broweri Hall and Gilmore. Mammalia, 35, 85-101.

(Received 13 March 1972; revised 23 August 1972; MS. number: A1304.