DEN USE AND SOCIAL INTERACTIONS OF POLAR BEARS DURING SPRING IN A DENSE DENNING AREA ON HERALD ISLAND,

NIKITAOVSYANIKOV,1 State , Ushakovskoe,Schmidtovski Region, ChukotskiyAO, Russian Federation

Abstract: Estimatesof the numberof polar bear (Ursus maritimus)maternity dens and observationsof social interactionswere made over 40 days in a dense denning area on HeraldIsland, Russia, following female emergence from dens. Twenty-six dens were found throughoutthe accessible areas of the island (density = 6.2 dens/km2);11 were concentratedin the Main Valley (12.1 dens/km2). Females emerged from dens from 17 March (the first observationday) until 31 March 1993. Sixteen females with cubs-of-the-yearwere observed for 156 hours. Mean litter size was 2.0. Females averaged 15.5 days (range = 8-27) in the denning area from emergence until leaving for the ice. Younger females spent less time outside their dens than older females. Number of dens used other than their own averaged2.4 dens for all females. Younger females were not observed to use any den other than their own, whereas older females averaged 3.2 dens/female. Females spent considerabletime grazing on grasses. Interactionsbetween females defending and competing for dens resulted in spatial separationof family groups and limited access to resources. Presence of other females close to dens sometimes caused a female with cubs to abandonher den. Avoidance of older females by younger females may demonstratehierarchy in dense denning areas. My observationssupport the importanceof protectingHerald Island and the surroundingmarine area as key polar bear breeding and foraging habitats.

Ursus 10:251-258

Key words: Herald island, maternityden, polar bear, social behavior, Ursus maritimus.

Throughout their breeding area, female polar bears Belikov 1982, Amstrup 1986). However, data on the (Ursus maritimus)give birth to their young on land in behavior of females with cubs during the spring are maternaldens made in the snow. Denning and parturi- scarce. The only ethological observationsof polar bears tion on sea ice has been confirmed only for some polar in a denning area were conducted on Kongsoya, bears from the BeaufortSea population(Amstrup 1986). Svalbard,by Hanssonand Thomassen(1983). Very little The majority of pregnant females from the Chukchi- is known about polar bear social interactionsin denning Alaskanpopulation come to Wrangeland Heraldislands, areas with a high density of maternaldens. The objec- northof the ChutkotkaPeninsula, to hibernate. In addi- tives of this study were (1) to estimate the number and tion to the continent,these islands are the only land avail- distributionof polar bear maternitydens and (2) to ob- able to polar bears in this areaof the Arctic Ocean. Both serve, record, and interpret polar bear activities with Wrangel and Herald islands are known as areas with special attentionto the social and territorialbehavior of high densities of polarbear maternal dens (Belikov 1977, breeding females in a dense denning area on Herald Is- 1982). On Wrangel, however, den densities vary sig- land. nificantly over the island (Stishov 1991). This project was funded by the Wrangel Island State Pregnantfemales come to Wrangel Island beginning Nature Reserve, Russian Ministry of the Environment. in late August and continue arriving until November. I wish to thank the former director of the Reserve, A. Usually by the end of October the snow cover is thick Sukhov, for his help in project development. My spe- enough for most females to have settled in dens for hi- cial thanks go to I. Menyushinafor her assistance with bernation. They give birth in December and January the field work. I thankL. McHarguefor her kind edito- and remain in their dens until March-April, although a rial and technical help in preparingthe manuscript. few females emerge from maternaldens at the end of February.Peak emergenceis late Marchand early April. Where polar bear denning has been studied,females not STUDYAREA forced to leave for the ice by disturbancewill often stay Herald Island is situated in the 56 km within the denning area up to several weeks following northeastof WrangelIsland at 71?20'N, 175?45'W. The emergence (Harington 1968, L0n0 1970, Belikov and 8-km2island is a rocky ridge 9.5 km long and 0.1-2.1 km Belikov Kupriyanov 1977, 1982). wide (Fig. 1). Its coast is formedby very steep to nearly Polar bear denning biology has been studied through- vertical cliffs. Top slope inclinationsrange from 25? to out the Arctic (Belikov 1976, Lentfer and Hensel 1980. 60?, alternatingwith numerousgently sloping terracesof

'Present address: Menzinskogo 25, kv. 28, Moscow, 129327, Russian Federation,email: [email protected] 252 Ursus 10:1998

Herald Island

N

w E

Chukchi Sea ,1LK o1J I 01-l~ 0 1000 M i 'i Main Valley

Fig 1. Herald Island, Russia, 1993, showing Main Valley and locations of cabin (square), blinds (x), maternal dens (o), and main blind (circle with x). The solid line indicates the boundary of accessible area. The line with dashes and dots indicates the boundary of the observation area. mostly southern, southeastern, and eastern exposures. terity dens on Herald, however, may be significantly Elevations of the upper slopes are 150-350 m. There are higher, as 100 dens were reportedby Belikov (1982). only 3 deep and narrowvalleys in the wide southeastern part of the island, 2 open to the south and 1 to the east. These valleys provide the only corridorfor polar bears METHODS between the terracesand the ice. The prevailingwind in I observed polar bear activities on Herald Island from autumn is northwest, and deep snow collects along all 17 March to 25 April 1993. Most observationsof polar terracesand on valley slopes with the first snowfall. The bear activities were made from 8 snow blinds; some ob- valleys are well protected from the prevailing northern servationswere also made by an assistant,I. Menyushina, winds. from nearthe cabin (Fig. 1). The main study method was Suitableden sites are found all over the terracesand in direct visual observations combining focal animal snow along the cliff bases. Aerial den surveys on Herald (Altmann 1974) and active scanning (Ovsyanikov 1993) Island conductedby the Wrangel Island Nature Reserve methods. Observationswere made with 12 x 40 binocu- from 1985 to 1989 revealed from 19 to 37 dens for any lars and with 30-60X telescopes. Polar bear behavior single count (Stishov 1991). The actual numberof ma- was recordedverbally in an opportunisticmanner describ- DENUSE OFPOLAR BEARS * Ovsyanikov 253 ing as many details as possible. I also used drawingsand limited visibility occurredon 15 of 37 days. Observa- photographsto recordspatial patterns and behavioralse- tions during snow storms were made as viewing condi- quences duringinteractions. The usual observationdis- tions permitted.Observation time totalled224 hours,with tance was 70-1,000 m in the denningarea and 200-5,000 an averageof 6 hoursof observation/day.The maximum m for bears on the ice. single-day observationwas 10.5 hours. In several cases (n = 11) simultaneousobservations (2 observerssurveyed slopes simultaneouslyfrom different points) were necessary to record an entire sequence of RESULTS bear activity. The majorityof observationswere concen- A total of 16 females with cubs were observed during tratedin 1 large valley (Main Valley) on the southeastern the observationperiod. Mean litter size for the 16 fe- part of the island and were made from the blind on the males was 2.0 cubs; 3 litters consisted of 1 cub, 10 steep slope directly above the outfall of the valley (Fig. litters had 2 cubs, and three litters had 3 cubs. Nine 1). This position provided a broad view of both Main of these females were residential with their maternity Valley and the surroundingice. In additionto observing dens located in the Main Valley viewing area. Fe- from the blinds, I made 1 excursion to the northwestern males whose maternity dens were outside this area are end of the island and 6 trips to the southeasternpart of referred to as non-residential. Of the 7 non-residen- the island west of the Main Valley. tial females, 2 were seen only when they were leaving Dens were located and monitored visually from the the island. same distances and observationpoints from which bear Six residential females and 2 non-residentialfemales activity was recorded. All dens found were markedon a were identified individually and observed continuously 1:25,000 map of Herald Island. I examined dens and when they were visible in the viewing area. The total tracksfor additionalinformation. I examineddens closely time each residential female was seen was: F-P, 45 only after the last female bear with cubs left for the ice. hours; F-SQ, 35 hours 50 minutes; F-WG, 13 hours; A total of 8 snow blinds were built aroundthe cabin to F-SF, 10 hours 15 minutes; F-NR, 14 hours; and F- provide a view of the surrounding area before bears YC, 4 hours 40 minutes. Total time for each non- emerged from maternaldens. All blinds were located residential female was F-MR, 13 hours and F-N, 16 <400 m from the cabin except 1 (Fig. 1). I avoided dis- hours. Other females were distinguished from identi- turbingthe bears by extremely careful behavior and by fied bears by the absence of identifying features. When wearingonly white camouflageclothing outside the cabin. there was a probability that the same female was seen I used no engines or other noise-producingmechanical repeatedly, the observations were excluded from esti- items on the island duringthe observationperiod. I used mation of bear number and litter size. The total view- helicopterstwice-to get to the Islandon 17 March,when ing time for all 16 females was 156 hours. only 1 den was opened in observationarea, and to leave I also saw single pairs of courting polar bears on the island on 25 April, afterthe last female with cubs left the ice on 4, 18, and 23 April for 5 hours 40 minutes, for the ice. 40 minutes, and 1 hour 20 minutes, respectively. In Female bearswere individuallyidentified by theirsize, addition, a courtingpair was recordedfrom fresh tracks body constitution,thickness, fur color, darkspots on the passing near the island on 14 April, which I followed fur (stains from blood, feces, urine,or dirt),and the num- for >3 km. The 3 observed pairs appeared to be dif- ber, size, color, and conditionof accompanyingcubs. To ferent couples; however, I could not confirm this. A verify a bear's identification,the 2 observersdetermined lone male was seen on the ice on 4, 14, 16, and 18 the identityindependently at least twice (up to 7 times for April for 15 minutes, 7 minutes, 1 hour 33 minutes, 1 female) for each of individually recognized females. and 42 minutes, respectively. A lone male was ob- Female age classes were determinedby the animal's ap- served at the cabin on 4 April for 10 minutes. A lone pearance(size, body constitution,foreleg hair length) as female was observed on 19, 20, and 21 April for 3 either young adult (class 1, probably <5-6 years) or hours 50 minutes, 3 hours 45 minutes, and 15 min- middle age-old (class 2, >7 years). Females of smaller utes, respectively, and was judged to be the same in- with size, lighter heads and shorterforeleg hair were as- dividual based on her appearance. The first 2 times to class tall signed 1; large, females with massive heads she was seen in the denning area and entered a den; and longer foreleg hair, to class 2. the third time she was seen at the cabin. Females with Observationswere carried out every day except during cubs approached the cabin only a few times to dis- a 3-day blizzard with zero visibility. Snow storms and tances of 50 m, 5 m, and <1 m. 254 Ursus 10:1998

Den Densityand FemaleActivity length of stay in the denning area for the 3 youngest fe- I found a total of 26 maternitydens throughoutthe ar- males was 13.3 days (SD = 4.1), whereas the average eas to which I had access (Fig. 1). Another5 (not shown numberof days they appearedon the surfacewas 5.3 days in Fig. 1) were seen in the snow at the base of cliffs, but I (SD = 3.2). In contrast,3 females thatappeared older (F- could not confirm their use as maternitydens and omit- P, F-SQ, and F-WG) remainedwithin the denning area ted them from den density estimates. Dens were classi- for 27, 17, and 9 days, respectively, for an average of fied as maternityby direct visual observationsof female 17.7 days (SD = 7.3). They were seen on the surfacefor emergence and consequent use and by such identifica- 13 (F-P), 12 (F-SQ), and 7 (F-WG) days for an average tion features as den depth, distributionand characterof of 10.7 days (SD = 2.6). Within the denning area, older snow at the entry, and tracksaround the entry. A mater- females spent more time on the surfaceand entereddens nity den is always deep, has no excavated fresh snow at only in bad weather. the entry, and always has a progressiveaccumulation of Two non-residentfemales, F-MR and F-N, remained bear sign around the entry (footprints, claw scratches, in the Main Valley for 4 and 12 days and were seen on urinespots, andfeces). Temporaldens were also recorded the surfacefor 4 and 5 days, respectively. The last Main within the observationarea. Valley residentfemale, F-NR, left on 16 April. The last A total of 17 maternitydens were located<1.5 km from non-resident female, F-N, left the Main Valley on 24 the cabin. Eleven were in the Main Valley, including 7 April. Outside of the Main Valley, the last female with which were in sight from the main blind and were moni- cubs was seen on 18 April. tored Another monitoredden was on a daily. regularly Den and terracein the Main Valley west of the cabin. Otherdens Use, Competition, Activity were observedperiodically or occasionally. The density Outsidethe Den of maternitydens withinthe accessible area(4.2 km2,Fig. Following den emergence,older females typically but 1.) was 6.2 dens/km2.In the permanentobservation area, temporarilyused maternitydens other than their own. including the core portion of the Main Valley and adja- Female F-P, for example, used at least 3 differentmater- cent areanear the cabin terrace(0.8 km2,Fig. 1.), the den nity dens afterthe originaloccupants left the area (Table density was 12.1 dens/km2 The total density of polar 1). For the 6 residentialand 2 non-residentialfemales, bear dens over the island is unknown,because the snow the average numberof maternitydens used after emer- banks at the base of the coastal cliffs were inaccessible. gence was 2.4 dens/female. Younger females were not On my first observationday, 17 March,I saw 1 female observed to use any maternityden other than their own. with cubs outsideher den; 2 dens were found opened that Older females' average numberof maternitydens used, day. Six of the 17 maternitydens were opened before 20 including their original maternityden, was 3.2 dens/fe- March;all other dens were opened on 20 Marchor later. male (n = 5). The actual number of dens temporarily The last den was opened on 31 March. used after emergence may have been higher, as not all The length of a female's presence in the denning area dens in the Main Valley could be seen from the main from the time of first den emergenceuntil leaving for the snow blind; also, some females moved to areas of the ice varied from 8 to 27 days; average durationwas 15.5 island that I did not monitor. 8 dens I days (SD = 6.3, n = 6). The 2 youngest females (F-YC The numberof differentfemales that used the 1- and F-SF) appearednervous about the presence of other regularlyobserved averaged2.25 females/den (range females near their dens. They were in the denning area 5). The den used the most was occupied in turn by 4 This for 8 and 14 days, respectively,but they were seen on the females with cubs and 1 solitaryfemale (Table 1). an older surface only 3 (F-YC) and 10 days (F-SF). F-YC was den was used by its original occupant, F-SQ, observedout of her den only twice duringthe 8 days fol- female with 2 cubs, for 17 days (24 Mar through9 Apr) the den was lowing emergence(each time withoutcubs) until leaving following den emergence. When F-SQ left, for the ice with her cubs on her thirdappearance. During closed by snow. The next occupantwas F-MR, an older, She the den the 14 days (28 Mar-10 Apr) that F-SF spent in the area non-residentfemale with 3 cubs. occupied F-MR was after emergence, she went far from the den only once. from 14 to 15 April. On 15 April supplanted She was seen at the entranceto the den with cubs 5 times, by F-P, who entered the den when F-MR was out with but she never led her litter far away. her cubs. F-P occupiedthe den from 15 to 16 April. After female on A thirdfemale identifiedas young (F-NR)spent 18 days F-P left the den, it was occupied by a solitary hours in the denning area from the time she was first seen but 18 April. The lone female spent several inside, was observedat the surfaceon only 3 days. The average then left. Finally, from 23 to 24 April, an older, non- DENUSE OFPOLAR BEARS * Ovsyanikov 255

Table1. Maternaldens and littersize of females polarbears on HeraldIsland, Russia, Mar-Apr 1993.

Original Observation Total Number Daysstayed Number maternal Other periodafter observation of days after FemaleID Statusa of cubs den densused emergence time(hr:min) observed emergence

F-P R 1 D8 D2,D10,D14 21 Mar-16 Apr 45:00 13 27 F-9 R 2 D9 unknown 21 Mar-13 Apr 0:55 3 24 F-SQ R 2 D10 D20 24 Mar-9 Apr 35:50 12 17 F-WG R 2 D12 D1,D2 27 Mar-4 Apr 13:00 7 9 F-2 R 3 D2 unknown 28 Mar 0:45 1 unknown F-SF R 3 D14 none 28 Mar-10 Apr 10:15 10 14 F-3 N 2 D5 unknown 29 Mar 0:20 1 unknown F-NR R 2 Dll none 30 Mar-16 Apr 14:00 3 18 F-YC R 2 D20 none 31 Mar-7 Apr 4:40 3 8 F-11 N 2 unknown unknown 6 Apr 1:20 1 unknown F-12 N 1 unknown unknown 7 Apr 0:07 1 unknown F-N N 2 D6 D14,D10 13 Apr-24 Apr 16:00 5 >12 F-MR N 3 unknown D10,D14 13 Apr-16 Apr 13:00 4 unknown F-15 N 2 D22 unknown 13 Apr 0:10 1 unknown F-16 N 2 D21 unknown 18 Apr 0:15 1 unknown F-17 N 1 unknown unknown 27 Mar 0:10 1 unknown a R = Main Valley resident;N = non-resident. residentfemale with 2 cubs (F-N) occupied the den. At monitoring ice conditions. They approachedthe cliff least 2 females from outside the Main Valley, F-MR and edge, sniffed towardthe sea, and reactedto sounds from F-N, arrivedin the Valley and remainedfor a few days the moving ice and winds from the sea by approaching on their way to the sea, using unoccupied dens of the the edge and surveyingtoward the sea. Main Valley residentfemales. Active den use duration-the time from emergenceof IntraspecificInteractions the first den occupantuntil the last use by any female- Fromthe beginningof mass den emergenceby females for dens used by any female duringthe season is known (28 Mar), often more than 1 female (family group) was for 8 dens and averaged 18.1 days (range = 9-32). Ma- in sight. Up to 5 females were observed in the viewing ternity dens used by only the original female were used area simultaneouslyfor extended periods of time from less thandens used by differentfemales (11.5 days, range 28 March until 16 April. Usually females maintained = 9-14 vs. 20.3 days, range = 10-32, respectively). several dozen meters between each other. However, on All individuallyidentified females were observedgraz- a few occasions distances between interactingfemales ing on grasses. Female bears that spent appreciabletime were 10, 7, and <1 m. F-SQ and F-WG once nursedcubs outside their dens (n = 5, or 62.5%) grazed every day simultaneouslysitting 70 m apart and in plain sight of they were observed. For example, female F-P was seen the other. grazing each of the 11 days she was observed; another When in sight of each other, all females attentively female, F-WG, was observed grazing duringeach of the watched each other. Younger females appearedmore 9 days she was seen. One day F-WG spent 95 minutes disturbedby other females than did older females. I ob- grazingand, following a half-hourbreak nursing her cubs, served 12 directintraspecific interactions between females she spent >40 minutes grazing along the valley bottom. with cubs in the denning area. In 11 cases 1 female She was still grazingwhen she moved out of view. Cubs avoidedthe other;in 1 the avoidancewas mutual. Asym- were also observed grazing. Both young residentialfe- metrical avoidance, where 1 individual is aware of males were observed grazing infrequently. F-SF grazed another'spresence and retreatswhile the other remains only once, on 3 April for 69 minutes;F-NR grazed only ignorant,was typical for young females (F-SF-5 cases, on 31 March and 4 April for 30 and 45 minutes, respec- F-YC-1 case, F-NR-2 cases, or 73% of all asymmetri- tively. cal avoidances). During the time within the denning area spent outside Two interactions involved females guarding or de- of the den, all observed females (except the 2 young fe- fending a den. On 3 April, F-SQ rushed back to her male bears which stayed near their dens) appearedto be den from a day bed 150 m away and stood at the en- 256 Ursus 10:1998 tranceupon seeing F-WG grazingslowly towardthe den. Between den opening on 28 March and the last sight- Before F-WG started moving toward F-SQ's den, she ing on 10 April, F-SF appearedfrom her maternalden a grazed in view of F-SQ for about 15 minutes, with F- total of 19 times. Nine times F-SF only looked from the SQ appearingat ease. The distance between the 2 fe- entry and did not come out, 4 times she was out without males then was greaterthan between either of them and cubs, but only once (of 4 times out) she went to the creek the den. F-SQ appearedto become calm as it became bottom to graze (duringblizzard, without cubs, when no obvious that F-WG was passing the den. On 15 April, other females were near). I saw cubs looking out of the female F-P with 1 cub occupied a den in use (although den 2 times; they were seen out on the surface only 5 temporarilyunoccupied) by a non-residentialfemale (F- times (31 Mar; 4, 7, 8, 10 Apr). These cubs were very MR) with 3 cubs. When F-MR returnedto the den dur- small and had difficulty following their mother around ing a strong wind she was threatenedat the entranceby the entry. On 8 April F-SF triedto lead cubs to the creek an open mouth display from F-P from inside the den. bottom, but when they remainedat the entry the mother After short confrontationF-MR left the area. returnedto the den. When the family was out at the en- Displacement from a day bed was observed on 16 try, twice F-SF pulled the smallest cub by its skin as it April. F-P displaced F-NR from her overnightday bed could not follow her. These cubs were the smallest of all by approachingher directly. F-NR arose and left her the litters. Cubs of this size could not climb ice blocks day bed urinatingon the snow when F-P came within and swim acrossthe leads while on the ice. The day after 40 m. F-P then occupied the abandonedday bed. the family left, F-P appearedfrom F-SF's maternityden In 1 case, the departureof a young female bear (F- and came down to the outfall of the creek where she at- SF) with 3 cubs from her den may have resulted from tentively watchedthe snow at the base of the cliff next to repeated approaches by an older female, F-P. F-SF the outfall for 14 minutes. While watching the snow at opened her den on 28 March. That same day F-P first the base, F-P several times looked towardF-SF's aban- appearedin the creek bottom beneath F-SF's den. F-P doned den. Previously, no female visiting the valley grazedin the valley nearF-SF's den on subsequentdays, watched the snow at the base of the hollow, suggesting weather permitting. Also, every day at least 2-4 fe- that F-SF might have moved her cubs there. males visited the Main Valley, walking and grazing in Courtship.-During the studyperiod, I observed3 pairs the creek bottom beneath F-SF's den. Every time an- of polar bears engaged in courtshipbehavior pass near other female bear was in sight, F-SF became alert or the island along the foot of the cliffs. Each couple was appearedwary, retreatingto the den if she were out or followed, but not chased, at a distance by a lone male watching the other females from the entrance and not polar bear. No competitionbetween maturemales was allowing her cubs to come out. recordedduring these observations. However, 1 paired On 30 March,F-P closely approachedF-SF's den and male had a fresh, bloody wound on his neck. Courting made a day bed about 50 m from the entrance. F-SF couples did not remain for more than a few hours at 1 reacted by hissing and alarm coughing and closed the spot. entrancewith her body. On 6 April, F-P approachedF- I observed 1 interactionon the ice between a female SF's den even closer, making her day bed <40 m from with cubs (F-WG) and a pair of courtingand copulating the den; she then nursed her cub. This time F-SF bears. On 4 April at 0900 hours a pair of bears was seen watched F-P from the entrance. The next day F-SF courting beneath the cliffs and moving eastward then called her cubs out to walk around the den entrance, southeastwardaway from the island. At 1015 hours, F- but forced them back into the den just as F-P appeared WG passed along the creek bottom, leading her cubs to- the was on in the valley walking along the creek bottom. On 8 wardthe valley outfall. By 1100 hours family from Herald Island eastward. At April a severe snow storm began and continued until the ice heading away tracksleft the court- 11 April. On 10 April F-SF came out of her den and 1123 hours, F-WG encountered by then tried to lead her 3 cubs away. However, the cubs could ing pair. She sniffed in the directionthe tracksled, in the direction. At 1210 hardly withstandthe extremely strong wind, the female hurriedlywalked away opposite was nervous, and, after an 8-minute walk near the en- hours, however, she met the couple resting after copula- The the trance, the family returnedto the den. On 12 April as tion on the field of flat ice. family approached of ice. the snow storm died down, F-P appearedfrom F-SF's pair within 100 m, as the pair was behind blocks the of other bears and den. Apparently,F-SF had left her den and moved the The male recognized presence the fe- cubs to anotherplace during the blizzard and was not rushedtoward the intruders.Upon seeing couple, and ran at to seen again. male F-WG changed direction top speed DENUSE OFPOLAR BEARS * Ovsyanikov 257 escape, leading her cubs away. She quickly slowed her dens were concentratedwithin a 400 m-long snow strip. speed, however, so as not to leave the cubs behind. The Hansson and Thomassen(1983) reported20 dens within male stopped his rush toward them after 70 m, intently 2 km2on Kongs0ya, Svalbard,in 1979 in a rathersmall sniffed the tracks of the family, growled toward them, observationarea surrounded by slopes unsuitablefor dens. then for approximately3 minutes sniffed a piece of ice In 1978, however, there were only 5 dens in the same (possibly markedby urine and surroundedby many bear area. An average den density for Kongs0ya for 4 years tracks) before turning back to his mate. His female (1972, 1973, 1977, and 1980) was 0.4-0.9 dens/km2of watchedthe interactionfrom behind a small block of ice. suitabledenning habitat (Hansson and Thomassen 1983). F-WG continuedsouthward, quickly walking away from On WrangelIsland the averagematernity den density re- the couple until she disappearedfrom the observer'sview. corded in the year with the highest numberof denning Single males near the island were observed mostly on females in the area of the highest den concentration the ice huntingringed seals (Phocahispida). Only 1 male (Dream-Head Mountain) was 0.5 dens/km2 (Belikov was seen on the top of the island(he approachedthe cabin), 1977). An average den density on WrangelIsland for a and 2 times I found fresh tracksof an adultmale visiting numberof yearsin the best denninghabitats, Dream-Head the Main Valley. No males approacheda den. Perhaps and Warring,never exceeded 0.5 and 2.5 dens/km2,re- males were attractedto the top by tracksand urine marks spectively (Unpubl. annual report, Letopis Prirodi, of females in estrous-a lone female was seen on the top Wrangel Island Nature Reserve, Ushakovskoe, Russia, of the island on 18-19 April. By following her tracks I 1985-1992). However, Belikov (1982) reportedan av- found that she came from the ice. A urine marklooking erage density for all of HeraldIsland of 12.5 dens/ km2. like an estrous mark was found on a snow-coveredrock Observedinteractions between female bears guarding on the terrace400 m from the cabin. The markwas rather their dens against other females and competing for tem- large, about 10 cm in diameterand of strong yellow-or- poral use of dens in springmay indicate short-termterri- ange color, and had been left on the upper side of snow torialinteractions. These interactionsresulted in spatially drifted arounda stone about 0.7 m high. I could see it separatingfamily groups and, on some occasions, limit- very well from a long distance(150-200 m). I have never ing access of one of the participantsto resources (e.g., observed a female bear with cubs in spring or a lone fe- dens, grazing areas). Younger females avoiding older male in autumnurinating on any protrudingobject. ones may also reduce locomotor activity for their cubs. The first ringed seal was seen nearHerald Island on 12 Spatialseparation of family groups and females' interest April. On 16 April as she first entered onto the ice, F- in one another'sdens (which once even resultedin a con- MR and her 3 cubs found a seal carcass that had been frontationat a den entrance)was observedon Kongs0ya, killed by anotherbear approximately 1 km fromthe cliffs. Svalbard(Hansson and Thomassen 1983). However, the Earlierin the a day maturemale was seen huntingin this intensity of spatial conflicts observed on Kongs0ya he have killed the area; may seal. After she finished the seemed lower thanon Herald. On WrangelIsland spatial remains, F-MR also exhibited hunting behavior by in- conflicts between females were not observedeven in the leads vestigating and trying unsuccessfully to break dense denning habitats (Belikov and Kupriyanov1977, throughthe ice. Simultaneously,an adultmale was seen unpubl.data). seal about 300 m from the hunting family. Avoidance of older females by younger females may also indicate a hierarchyin dense denning areas because it reducedactivities of certainfemales on the surfaceand DISCUSSIONAND CONCLUSIONS reduced access to resources such as grazing areas and The of bear high density polar maternitydens encoun- additional dens. Observationson Kongs0ya, Svalbard tered on Herald Island is unique among other breeding (Hanssonand Thomassen 1983), did not reveal any hier- areas of the The bear den species. polar density I report archy among family groupsof polar bearsin denning ar- for Herald Island is a minimumestimate for this season. eas in the spring. I suggest thatfemale-female avoidance The density would be higher if I includeddens along the duringpost emergence and its influence on females' ac- foot of the cliffs. On Island Wrangel similarlyhigh con- tivity in denningareas may varyin differentdenning habi- centrationsof bear maternaldens were polar found only tats and under different densities. A long stay in the in a few locations and in certain only years. Belikov denning area after den emergence may be importantfor for (1977), instance, reportedthat in the spring of 1972 preparingcubs for their move onto the ice. Earlierde- he found 12 dens in a maternity stripof bankedsnow 2.5 parturecaused by disturbancemay influence the survival km long on the Dream-HeadMountains. Six of these of cubs forced to follow theirmother to the ice while they 258 Ursus 10:1998 are still too young and too weak. My observationson ninth working meeting of the IUCN/SSC Polar bear HeraldIsland support previous studies thatconclude that Specialist Group. Int. Union Conserv. Nat. Nat. Resour., female bearsare sensitive to disturbancesduring denning Gland,Switzerland. AND D.P. DEMASTER.1988. Polar bear. Ursus (L0n0 1970, Uspenski and Kistchinski 1972, Belikov , maritimus.Pages 39-55 in J.W.Lentfer, ed. Selectedmarine 1976, Lentferand Hensel 1980, Belikov 1982, Amstrup mammals of Alaska: species accounts with research and and DeMaster 1988). management recommendations. Mar. Mammal Comm. females on were Lactating grazing grasses reported Washington,D.C. fromWrangel Island (Belikov et al. 1977) andKongs0ya, BELIKOV,S.E. 1976. Behavioralaspects of the polarbear, Ursus Svalbard(Hansson and Thomassen 1983). Belikov et al. maritimus. Int. Conf. Bear Res. and Manage. 3:37-40 (1977) showed a certainlevel of grass digestion by bears 1977. Number, distribution,and peculiaritiesof the in an investigation of vegetative material in bear feces structureof female polar bear dens on the model plot in collected at den sites. The authorsof both publications WrangelIsland. Pages 10-30 in S.M. Uspenski and S.E. eds. Polar bear and its in the Soviet however, that Belikov, protection suggested, grass may provide important Arctic. Cent. Lab. Nature Min. mineralsand vitaminsrather than calories. Considerable Conserv., Agri., Moscow, Russia. time HeraldIsland females that spentgrazing by suggests .1982. The polar bear (Ursus maritimusPhipps) in a some bears. In grass may have caloric value for any Wrangel Island region: ecology, behavior, conservation. case, grazing may be importantfor lactating females; CandidateBiol. Sci. Diss., All-Union Res. Inst. Nat. Cons. therefore,limiting a female's access to grazing grounds Res., Moscow. 175pp. may unfavorablyinfluence nutrition. More researchis , N.E. BOGDANOVA,AND V.N. VEKHOV. 1977. needed to clarify the effect of grasses in the polar bear Compositionof the vegetationfood in the lactatingfemales diet. of the polar bear in WrangelIsland. Pages 55-65 in S.M. and observationson HeraldIsland showed that female Uspenskiand S.E. Belikov, eds. Polarbear its protection My in the Soviet Arctic. Cent. Lab. Nature Conserv., Minist. bears with cubs avoided other bears. However, young Agri., Moscow, Russia. this seemed to be a normal threats. precaution against , ANDA.G. KUPRIYANOV.1977. Behavior of the polar Tayloret al. (1985) suggestedthat mature male polarbear bear in WrangelIsland. Pages 40-54 in S.M. Uspenski and predationon cubs may influence cub survival. I did not S.E.Belikov, eds. Polarbear and its protectionin the Soviet observe any evidence of that. However, the presence of Arctic. Cent. Lab. NatureConserv., Minist. Agri., Moscow, maturemales aroundHerald Island may positively influ- Russia. ence females with cubs because the females may scav- HANSSON,R., ANDJ. THOMASSEN.1983. Behaviorof polarbears with cubs in the area. Int. Conf. Bear Res. and on carcassesleft by males. This could help support denning enge 5:246-254. a the critical first weeks on the ice when Manage. family during HARINGTON,C.R. 1968. habitsof the bear(Ursus are limited. Denning polar huntingopportunities maritimusPhipps). Can. Wildl. Serv. Rep. Ser. 5. 30pp. the and the Observedinteraction between courtingpair LENTFER,J.W., ANDR.J. HENSEL. 1980. Alaskan polar bear female with cubs on the ice appearedto be a short-term denning. Int. Conf. Bear Res. and Manage. 4:101-108. territorialinteraction (i.e., protectionof a spatially dis- L0N0, 0. 1970. The polar bear (Ursus maritimus) in the tributedresource-a female in estrous) accompaniedby Svalbardarea. NorwegianPolar Inst. Skrifter.149. 103pp. threateningdisplays from the male and a rapidretreat by OVSYANIKOV,N.G. 1993. Behavior and social organizationof the arctic fox. CNIL Moscow, Russia. the family. The male, however, showed no intentionto Publishers, 244pp. Distributionand numberof bear chase or to hunt the cubs. STISHOV,M.S. 1991. polar maternaldens in Wrangeland HeraldIslands in 1985-1991. These observationsstrengthen the importanceof Her- Pages 91-115 in N.G. Ovsyanikov,ed. Animal populations ald Island and the marine area as essential surrounding and assemblages of Wrangel Island. CNIL Publishers, key breedingand huntinghabitats for the Chukchi-Alas- Moscow, Russia. kan polar bear population. TAYLOR,M., T. LARSEN, AND R.E. SCHWEINSBURG.1985. Observationsof intraspecificaggression and cannibalismin polar bears (Ursus maritimus). Arctic 38:303-309. LITERATURECITED USPENSKI,S.M., ANDA.A. KISTCHINSKI.1972. New data on the of the bear maritimus ALTMANN,J. 1974. Observationalstudy of behaviour:sampling winter ecology polar (Ursus Phipps) 2:181- methods. Behaviour49:227-267. on WrangelIsland. Int.Conf. BearRes. andManage. AMSTRUP,S.C. 1986. Researchon polarbears in Alaska, 1983- 197. 1985. Pages 85-115 in Polar bears: Proceedings of the