spacing and kinship in the formosan squirrel

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International Association for Ecology

Spacing and Kinship in the Formosan Squirrel Living in Different HabitatsAuthor(s): Noriko Tamura, Fumio Hayashi, Kazuyoshi MiyashitaReviewed work(s):Source: Oecologia, Vol. 79, No. 3 (1989), pp. 344-352Published by: Springer in cooperation with International Association for EcologyStable URL: http://www.jstor.org/stable/4218964 .

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Oecologia (1989) 79:344-352 C oIQg? Springer-Verlag989

Spacing and kinshipin the Formosansquirrelliving in differenthabitats

Noriko Tamura,FumioHayashi, andKazuyoshiMiyashitaDepartment of Biology, Faculty of Science, Tokyo MetropolitanUniversity, Fukazawa2-1-1, Setagaya-ku,Tokyo 158, Japan

Summary. Spacing and kinship of the Formosan squirrel,Callosciurus erythraeusthaiwanensis,were studied in twodifferent habitats. One, native habitatin the woods of Kent-ing, southern Formosa, was rich in available food through-out the yearand had several speciesof predators.The other,

a site in Kamakura,centralJapanwheresquirrelshad beenintroduced, had relatively scanty food and few potentialpredators. 1. Home ranges among males and between sexesoverlapped extensively in both habitats. 2. Females occu-pied exclusive home ranges in Kamakura but had smalloverlapping home ranges in Ken-ting. 3. Most males disap-peared from their natal areas at 1 year old in both habitats(86% in Kamakuraand 93% in Ken-ting), but less femalesdisappeared (36% in Kamakura and 35% in Ken-ting).4.In Kamakura, daughterssettled adjacent to the mother orinherited the home range of the mother, but never sharedthe mother's home range. In Ken-ting, 35% of daughtersshared the home range with their mothers. 5. Toleranceamong female kin in Ken-ting was probably facilitatedbythe richness of available food throughout the year, andfunctioned to reduce predation risk via alarm calling andmobbing.

Keywords: Spacing- Kinship- Food - Predation- Callos-ciurus

Intraspecific variations in sociality were detected in somespecies of vertebrates reviewed by Lott 1984). To comparethe sociality of a species living in different habitats is usefulto understand which aspects of sociality are plastic andexhibitvariationthat correlateswith variation in ecological

parameters.In ground-dwellingsquirrels, t was reported that a spe-cies has flexible social structures and life histories with achange of habitats (Barash 1973; Dobson and Kjelgaard1985; Rayor 1985). In due consideration of resultsof suchstudies, the hypothesesof social evolution in ground-dwell-ing squirrels were proposed by Armitage (1981); Dunford(1977),and Michener(1983). Comparedto ground-dwellingsquirrels,the knowledge of social structure n tree squirrelsis scanty, particularly for those species living in tropicalregions. Therefore, the social structure and life history

Offprintrequests o: N. Tamura

adapted to various environments have not been discussedfully in tree squirrels.

Several species of Callosciurus ccur in south-east Asia.Formosan squirrels (C. erythraeus thaiwanensis) nhabittropical monsoon forest in the southern part of Formosa.

This species has been introduced to several parts of Japanand become established n these temperateregions.

We compare the social structureof this squirrelbetweentwo populations, one in native habitat and the other inan introduced area, which differ in food availabilityandpredation pressure. And our purpose is to determine whataspectsof social structureof the Formosan squirrelexhibitchange when they are transposed to the temperateregion.

Materials and methods

Studyareas

One study site was located in tropical monsoon forest in

the woods of Ken-ting national park (22?00'N, 120'45' E),Hen-chung, Pin-tong Prefecture,southern Formosa, nativehabitat of the squirrel. Monthly temperatureranges from20.9 to 28.40 C. In the woods, we establisheda 8.5-ha studyarea in which census routes totalling 2.3 km in length werearranged. Squirrels were observed on 143 days, in De-cember 1985, March, June, September 1986, March, July,October 1987,and February-March1988.Live-trapsbaitedwith banana and peanuts were used to capture squirrelsin a 4-ha portion of the site. A stainless collar with oneor two plastic rings of various colour combinations wasattachedto each squirrel or individual dentification.Bodyweight, sex, and maturity (sexually matured or not) wererecorded.Social relations were studied on an observationarea (3.4 ha) in which all the squirrelswere marked.

Studies of the introduced population were conductedin temperatemixed forest in the woods of Kamakura City(35018' N, 139033'E), Kanagawa Prefecture,central Japan.It was said that the squirrelwas seen in Kamakuracom-monly at least 20 years ago, although the exact time ofintroduction was unknown. Monthly temperature rangesfrom 4.9 to 26.20 C. The 7-ha study area included 2.3 kmof census routes. Squirrelswere observed on 685 days, 2or 3 days a week, from October in 1982 to March in 1988.On a trappingarea (about 3 ha) in the center of the censusarea, squirrelswere marked by the same method as thatin Ken-ting. Individually dentifiedsquirrelswere observedon a 4-ha main observation area around the trappingarea.



345

Social structure

We patrolled census routes four times a day, at dawn, in

the morning, in the afternoon, and at dusk. When we en-

countered squirrels on the census routes, locations were

plotted on maps for each individual. Home ranges were

estimatedby connecting the outermost points obtainedeach

month for each squirrel with at least 5 observations. To

quantifythe extent of overlap, we calculatedthe percentageof each squirrel'sarea overlapped by home ranges of other

squirrels.Percentageoverlapwas calculated only when data

were available for all the surroundinghome ranges. A pre-

vious studyin Kamakura(Tamuraet al. 1988), showed that

home range size of females did not change with seasons

but that size of males changed with frequency of mating

bouts. In orderto analyzesize and overlapof male'sranges,

we used the home range obtained from March to August

when mating bouts occurredmost frequently.Detailedmatingbehaviorwas described n Tamuraet al.

(1988). Matingbouts weredefined as assemblagesof several

males with an estrous female in which males gave specific

rattle calls when chasing each other. On the day a female

was in estrus, several males with home ranges overlapping

that of the female congregated in her home range early

in the morning. In this study, we compared the mating

behaviorbetween two populations on the following points;

the duration of the mating bout, the number of males as-

sembled for the mating bout, the number of males that

copulated with the estrous female, and the duration for

which each male guardedthe female against other males.

At the post-weaning period, young follows the mother.

In this period, we ascertained kinship from the number

of interactions between young and between mother and

young.We defined residents as individuals which established

a home range and reproduced within it. To establish the

lengthof residencyfor each squirrel,we checked theirpres-

ence within the study area.

Food availability

We identified food items being eaten by squirrels.These

itemswere summarizedby month for both study sites. Plant

availability was determined on a 1000 m2 area (2 m in

width, 500m in total length). Each tree > 1.5 m height was

classified by species and its basal area measured. Because

large trees generally bear more seed than small ones, we

used basal area rather than number of trees to quantify

the availability of each species. Relative plant availability

in each study site was estimated by summingthe basal area

of species listed as food items for each month.

Predators

This squirrel gives specific alarm calls for different types

of predators; a single note alarm call to aerial predators,

repeated barks to terrestrialcarnivorous mammals, and

scream-likecalls to snakes. Calls were easily identified up

to distancesof 200m which enabled us to estimateapproxi-

mate encounter rates of the squirrelsto respective preda-

tors. Alarm calls to raptors and mammals were counted

for two hours just before sunset when the frequency was

higher than at other times of day. Scream-likecalls cause

peripheralsquirrelsto gather and mob the snake (Tamura

in press). We estimated the frequency of mobbing events

per month.

Results

Habitat differences

Food items of the Formosan squirrel in both study sites

are listed in Appendix 1. In Kamakura, most plants bore

seed from summerto autumn. Of 374 observations of feed-

ing from July to November, 91% involved seed or fruit.

In the other months, flowers, bark, or leaves replaced seed

in the diet. From Decemberto June,only 25% of 409 obser-

vations involved seed or fruit. In particular, the flower of

Camellia japonica was an important food item during

winter.In Ken-ting, seed or fruit were consumed in all sea-

sons. Seed or fruit accounted for 59-98% of food items

monthly (X = 78%) at Ken-ting.We identified27 and 43 species of trees in the 1000m2

sites in Kamakura and Ken-ting, respectively (Appendix

2). Figure 1 constructedfrom Appendix 1 and 2 shows the

relative amount of available plants in respect of the basal

area abundance in each month. In Kamakura, plant avail-ability increased from summer to autumn and decreased

duringwinter.In contrast,in Ken-ting,availabilitywas high

throughout the year, and even in autumn, availability of

food trees was greaterthan in Kamakura (Fig. 1).

Predation pressure, estimated indirectly from alarm

calls, was compared between the two habitats (Fig. 2). The

frequency of aerial predators in Ken-ting was higher than

in Kamakura (means 2.69+1.30 and 0.49+ 0.38 times per

2 h, respectively, t= 5.50, P< 0.01). We observedattempted

predation by Spilornis cheela and Butastur indicus in Ken-

ting. In Kamakura,thereseemed to be no aerialpredation;

Milvusmigranswas the only raptor to which the squirrels

gave alarmcalls but we never observed an attack. The fre-

quency of calling to terrestrialmammals was not different

between the two habitats (means 1.91+ 0.71 in Ken-tingand 1.47+0.88 in Kamakura, t=1.13, P>0.05). At both

sites, feral cats were almost the only terrestrialmammal

that attacked squirrels.The frequency of mobbing snakes

in Ken-ting was significantly higher than in Kamakura

(Fig. 3, mean 11.99+ 7.90 in Ken-ting and 1.80+ 2.25 in

70 o Ken-ting

* Kamakura 0 o

6 0 0~~60- o o

0~~~~~~~O-

?t 50 0

_ 4 0-

Z*.= 40

co*

-

o 20-0

10 -

0~~~~~~0 * M A M J

J F M1 A M^ J J A S 0 N D

Mlonths

Fig. 1. Availabilityf foodplants atenby Formosanquirrels



346

a Kamakura Ken-ting4. 4

s 22 2r nnsFig. 2a, b. The frequenciesof alarm

n n n n n0

1 II calls by Formosansquirrels o (a)Z aerialpredatorsand (b) terrestrial

predators. Each type of alarmcallwas counted for 2 h before sunset,0 4 4 and monthlyaverage was shown.

Slashesindicatemonths in whichH! observationswere not conducted. In

2u II 2- Kamakura, data were obtained every

n 0 1 0 0 0 ~~~~~~~~~~~monthrom December 1986 to

J F M A M J J A S O N D J F M A M J J A S 0 N D

Months Months

Kamakura Ken-ting

-20-

0

z

,,10 tO n I I~~~~~101

1Fig. 3. The frequencyof mobbingsnakesby Formosansquirrels.The data from

* r l | f | | | | | 0 0 1 1982 to 1988 were combined inKamakura.Slashes indicate months inwhich observationswere not conducted

J O0 I I I I I I at Ken-tingJ F M ^ M J J ^ S O N O ? J FAA i S O N D

Months Months

Table 1. Numberof adult Formosansquirrelsresidentannuallyat each study site

Kamakura Ken-ting

'83 '84 '85 '86 '87 '88 '86 '87 '88

Observation 3.9 3.9 4.0 4.0 4.0 4.0 3.4 3.4 3.4area(ha)No. males 16 12 13 14 17 16 - 11 11No. females 9 10 10 12 10 10 10 11 12No. males/ha 4.1 3.1 3.3 3.5 4.3 4.0 - 3.1 3.2No. females/ha 2.3 2.6 2.5 3.0 2.5 2.5 2.9 3.2 3.5

Total/ha 6.4 5.6 5.8 6.5 6.8 6.5 - 6.5 6.8

Kamakura, t= 4.23, P <0.01). Elaphe climacophora was the

only snake that climbs treesin Kamakura.This snakehiber-nated during winter so that mobbing did not occur in thisperiod. In Ken-ting, several species of snakes, such as E.taeniura and Trimeresurus mucrosquamatus, were potential

predators. Squirrels in the native habitat were more oftenexposed to predationriskthan those in the introducedarea.

Density

In both study sites, density was 5-7 adult squirrelsper ha(Table 1). Density did not vary annually. Density of adult

females was less in Kamakura than in Ken-ting (t= 3.50,P<0.01), though the total density did not differ betweenhabitats (t = 1.09, P> 0.05).

Home range

Figures4 and 5 show the typical distribution patterns ofhome ranges observed in March 1983 in Kamakura andMarch 1988 in Ken-ting,respectively.Males hadextensivelyoverlapping home ranges in both study sites. The meansize of male home ranges was 2.21+ 0.74 ha (n= 27) in Ka-makuraand 1.40 + 1.08 ha (n= 20) in Ken-ting,and differed



347

100 m

Fig. 4. The typical distributionpatterns of home ranges observed

on March1983 in Kamakura.Home rangesof all 9 residentfemales

and 11 of 16 residentmales are shown

Male

Female

100 m

Fig. 5. The typical distributionpatternsof home ranges observedon March 1988in Ken-ting. Home ranges of all 12 residentfemales

and 8 of 11 residentmales are shown

significantly (t=2.93, P<0.01). Home ranges of femalesoverlapped ess than those of males. The percentage of over-lap was 29.7+ 22.7% in Kamakura (n= 23) and48.2+15.9% in Ken-ting (n= 19), and differed significantlybetween sites (t= 2.92, P< 0.01). Females had smallerhomeranges than males both in Kamakura (Z= -6.53, P<0.01)and Ken-ting (Z= -5.66, P<0.01). The mean size of fe-male home ranges was 0.46 + 0.10 ha (n= 31) in Kamakuraand 0.28+0.11 ha (n=41) in Ken-ting, and the differencebetween the two sites was statistically significant (t=7.06,P<0.01). Each female's home range was overlapped byseveral males. The number of males which overlapped afemale was 8.19+ 1.54 (n= 26) in Kamakura and 8.88+ 2.00(n= 17)in Ken-ting,and did not differsignificantlybetweenthe two sites (t = 1.24, P> 0.20).

Mating system

As previously reported in Tamura et al. (1988), matingbouts were observed throughout the year in Kamakura,most frequently from March to August. In Ken-ting, wealso observed mating bouts in every study period but thefrequency ranged from only 1 time per 15 observation daysin September 1987 to 13 times per 17 observation daysin March 1986. The number of assembled males in matingbouts ranged from 9 to 17 with a mean of 12 (n=19) inKamakura, and from 9 to 14 with a mean of 11 (n =8)in Ken-ting. One male guarded the female against othermales then copulated and left. A second male then guardedthe female to copulate and departed. Consequently, a fe-male mated with 4 to 11 different males (X= 8.4, n = 19)in Kamakura and with 7 to 11 different males (X= 8.9,n=8) in Ken-ting. The average duration of guarding permale was 26 min in Kamakura (range 5-60, n= 160) and32 min in Ken-ting (range 10-80, n= 71). The duration ofguarding was known to have no correlation with matingorder (Tamura et al. 1988). Mating bouts lasted 7.5 to

10.5 h with a mean of 9.7 in Kamakura and 8.0 to 10.5 hwith a mean of 9.0 in Ken-ting, and ended early in theafternoon. In these regards, there was no significant differ-ence between the two sites.

Kinship

Figures 6 and 7 show the recruitmentof young from 7 fe-males in Kamakuraand 7 femalesin Ken-ting, respectively.The appearanceof young occurredmore or less throughoutthe year, but in Kamakura most young (58%) were bornin autumn. Of 22 young females in Kamakura, 14 (64%)stayed within their natal or neighbouringarea. In Ken-ting,11 (65%) of 17 young females stayed and recruited aroundthe natal area. Whether the other femalesdispersedor died

was not known.Most

young males, however, disappearedfrom their birthplace within one year in both sites. In Ka-makura, only 5 (14%) of 35 young males stayed aroundthe natal area and attended mating bouts. In Ken-ting, 1

(7%) of 15 young males stayed and recruited.The femaleswhich stayed around their natal areaestab-

lished their own home ranges at about one year old whensexually mature. The relationships between the mother'shome range and the home range of the newly establisheddaughterwerecategorizedaccordingto whetherthe motherwas still present (Table 2). In Kamakura, half of recruitedfemales (7 individuals) established a home range neighbour-ing to their mother, and the other half took over the



348

1983 1984 1985 1986 1987 1988 1985 1986 1987

WG B L

C2 L YKJKW

KW

CRBv LR

-B I L L NM Fig. 6. Kinship and recruitmentof

w r - young in Kamakura.AlphabeticalW _ __________ ~~~~~~~~and numerical symbols identify

W =GBIOG RW L resident females. Double lines

indicate that the female

v I established a home range andU reproductedwithin it. Upper lines

w2= _F_ W derivedfrom the double line

LG3R indicate that the female producedMa I male young, and the length of line

Y2 R2 to right shows the duration ofG2

_

residency around mother home

R YB F range. Lower lines indicate< UM daughters.Daughters separated

GW- by a dashed line from the motherindicate that the daughter

Ya G2 esablishedher own home range

L p adjacentto but exclusive from the-Wk-- LLR-=~~PYmother

BW L FL I Fig. 7. Kinship and recruitment ofEYB | p I | young in Ken-ting. Symbols are

6 t R2 7 ow the same as in Fig. 6

Kamakura Ken-ting

50 50

male malen=60 n~~~~~~~~f=12

F a = 0-) 622 12 18 24

LL Months Months

female female50 n=24 50- n=18 Fig. 8. Residency of adult males and femaleswithin

the study area. Numbers of squirrelsresident for <6,I 1 6-11, 12-17, 18-24, and >24 months are shown

Table 2. Patternsof home range establishmentby female Formosansquirrels

Daughter's ocation Mother's Kamakura Ken-tingstatus

In mother's home range Dead 31.8% 17.6%Alive 0 35.3

Adjacent o mother'shome range Alive 27.3 11.8Disappearedfrom natal area Alive 40.9 35.3N 22 17

mother's home ranges. In the latter case, mothers had al-ways disappeared from the area. In Ken-ting, however,most females (6 individuals)overlappedwith their mothersand shared the whole area. Three females establishedadja-cent to mothers and 2 females took over mother homerangesin Ken-ting.

Length of residency

Duration of residency as an adult on the study area was

compared between the two sites for both sexes (Fig. 8).



349

Most females and a few males recruited nto the natal area.For these squirrels, residency was calculated from sexualmaturation. In Kamakura, 67% of females and 32% ofmales stayed in the study area more than 2 years. About50% of immigrantmales dispersed again within 6 months.However, among males that stayed > 6 months, most werestill resident2 years later. In Ken-ting, the number of both

males and females residingmore than 2 yearswas less thanthat in Kamakura.

Discussion

Formosan squirrels transposed in Kamakura showed thesame social structure as those in Ken-tingin some aspects;(1) adult males had extensively overlapping home ranges,(2) males had much larger home ranges than females, (3)a female mated with eight different males on the average,and (4) the dispersal from natal areas was male-biased.However, spacing among females differed between the twosites. Females in Ken-ting (the native habitat) extensivelyoverlapped each other, whereas in Kamakura (the intro-duced habitat) females occupied exclusive home ranges.

Moreover, home range size was larger in Kamakura thanKen-ting.For these reasons, the number of resident femalesper area was less in Kamakura than Ken-ting.

Females of many squirrel species are more intolerantduring the reproductiveseason, defending the area aroundthe nest site against other females more vigorously thanat other times (Barash 1974; Dunford 1977; Festa-Bianchet1981; Festa-Bianchetand Boag 1982; Michener 1979; Sladeand Balph 1974). Female Formosan squirrels reproducedthroughout the year at both study sites, so the differencein spatial overlap among females at the two sites is nota consequence of a geographicaldifferencein reproductiveactivity. According to Ostfeld (1985), female territorialityin microtine rodents should be food-based because theirreproductivesuccess should be limited by the ability to ac-

quire food and convert it into weaned offspring.Slade andBalph (1974) and Balph (1984) also suggested acquisitionof food as the function of female territoriality. However,Wolff (1985) stressed the importance of defence from theinfanticide. In the present study, the amount of availablefood differed between two sites, and food availability mayaffect femalespacing patterns.

Female Formosan squirrels stayed in or near the natalarea, whereas most males dispersed, and this resembled tosome ground-dwelling squirrels (reviewed by Holekamp1984). In Kamakura, home ranges were exclusively evenbetween mother and maturedaughters.On the other hand,mother and daughter in Ken-ting shared the same area,although the communal nesting was not ascertained. Fe-

males, usuallyclose kin, in some speciescluster and cooper-ate even in reproductive season (King and Murie 1985;McLean 1982; Vestal and McCarley 1984; Wilkinson andBaker 1988). In ground-dwelling squirrels, the cluster offemale kin seems to be an important first step for theirsocial evolution (Armitage 1981; Dunford 1977; Michener1983). However, defence of an area around the natal bur-row is typicaleven for very communal species like the black-tailed prairie dog (Michener and Murie 1983). Barash(1973) and Rayor (1985) showed that the tolerance of fe-male kin in the yellow-bellied marmot and the Gunnison'sprairiedog resulted from short growing season, large bodysize, and delayed maturation. In the present study, the toler-

ance between mother and daughter in the native habitatprobablyresultedfrom the richness of available food.

The Belding's ground squirrelsexhibit nepotism suchas warning calls, co-defence an area, and cooperation forprotecting young among adjacentclose kin (Sherman 1977,1981). In the Formosan squirrel, predation risk was higherin the native habitat in Ken-ting. The shorter residency

period in Ken-ting may have resulted from the high preda-tion pressure. In such circumstances, the development ofcoalitionin antipredatorbehavior, such as predator-specificalarm calls and snake mobbing, is expected to be adaptive.Such nepotisticbehavior was observed more often in Ken-ting than Kamakura.Thus, even in tree squirrels,toleranceamong female kin was probably adaptive in the habitatrich in food and predators.

Among tree squirrels which have been studied, socialsystems varyfromspeciesto species. Heaney (1984) summa-rized the tendency of spacing of North Americantree squir-rels; (1) exclusive territorialitywas observedonly in Tamias-ciurushudsonicus and T. douglasii living in the northernconiferous forest, (2) in other species of temperate regions,males have home ranges larger than those of females and

overlapped extensively each other and with females, andadult femalesoften have nonoverlappinghome ranges.Spa-tial overlap among femalesobserved n the Formosan squir-rel in the native habitat has not been reported.

A mating systemin tree squirrelswas mostly promiscu-ous, but the alphamale in Tamiasciurus uardedthe femalefor 81-95% of times in mating bouts (Koford 1982; Layne1954; Smith 1968). In several species of Sciurus living intemperateregions, dominant males have a mating priorityand a female mated with 2-6 different males (Farentinos1972, 1980; Thompson 1977; Benson 1980). Compared tosuch northern species, dominant males in the Formosansquirreldid not guard the estrous female from other males,and a female mated with much more males than other treesquirrels.

Therefore, comparedto the other treesquirrels, he For-mosan squirrelhad mainly two specificitiesin social struc-tures; spacing overlap among females and extensive multi-ple mating. One of the specificities,the mating system didnot change by the transpositionto temperate region in Ka-makura.However, the other, spatialoverlap among femalesin Ken-ting changed with the transpositionto the differenthabitats. Females in the introduced area have nonoverlap-ping home ranges which just resembledto spacing patternobserved n othertemperatespecies.This suggeststhat spac-ing among females shows greater sensitivity to a changein habitat than other aspectsof social structure. Moreover,spacing among females (especiallyamong female kin) wasexpectedto have an importantmeaning for social evolution

not only in ground-dwellingsquirrelsbut also in tree squir-rels.

Acknowledgements.We thank G.R. Michener for giving valuablecomments to improvethis manuscript.Y.I. Chu and F.D. Hwanggave us some advice and convenience of field study in Formosa.H.Y. Lee and other staff of the Taiwan Forestry ResearchInstitute,Heng-chun Branch gave us the facilities for study in Ken-ting.We received assistance with plant classification in Ken-ting fromF.C. Ho and in Kamakura from S. Kobayashi. We also thankT. Suzuki,T. Kusano, and other membersof Laboratoryof AnimalEcology, Tokyo MetropolitanUniversity for the help and advicein many aspects of this investigation. H. Tani and T. Okazakikindly allowed us to use the study site in kamakura.



350

References

Armitage KB (1981) Sociality as a life-history tactic of groundsquirrels.Oecologia48:36-49

Balph DF (1984) Spacial and social behavior in a population ofUinta ground squirrels.In: MurieJO, MichenerGR (eds) Thebiology of ground-dwellingsquirrels.University of NebraskaPress, pp 336-352

Barash DP (1973) Social variety in the yellow-bellied marmot(Marmotaflaviventris).Anim Behav 21:579-584

Barash DP (1974) The social behaviour of the Hoary marmot(Marmotacaligata).Anim Behav22:256-261

Benson BN (1980) Dominancerelationships,mating behaviourandscent marking in fox squirrels (Sciurus niger). Mammalia44:143-160

Dobson FS, KjelgaardJD (1985) The influence of food resourceson life history in Columbia ground squirrels. Can J Zool63:2105-2109

Dunford C (1977) Social system of round-tailedground squirrels.Anim Behav 25:885-906

Farentinos RC (1972) Social dominance and mating activity inthe tassel-eared squirrel, (Sciurus aberti erreus). Anim Behav20:316-326

Farentinos RC (1980) Sexual solicitation of subordinatemales byfemale tassel-eared squirrels (Sciurus aberti). J Mamm

61:337-341Festa-BianchetM (1981) Reproduction n yearling female Colum-

bian ground squirrels Spermophilus olumbianus).Can J Zool59:1032-1035

Festa-Bianchet M, Boag DA (1982) Territoriality n adult femaleColumbianground squirrels.Can J Zool 60: 1060-1066

Heaney LR (1984) Climatic influences on life-historytactics andbehavior of North American tree squirrels.In: MurieJO, Mi-chener GR (eds) The biologyof ground-dwelling quirrels.Uni-versityof NebraskaPress,pp 43-78

Holekamp KE (1984) Dispersal in ground-dwellingSciurids. ibid.pp 297-320

King WJ, Murie JO (1985) Temporal overlap of female kin inColumbiangroundsquirrels Spermophilusolumbianus).BehavEcol Sociobiol 16:337-341

Koford RR (1982) Mating systemof a territorial reesquirrel Ta-

miasciurusdouglasii) n California.J Mamm 63:274-283Layne JN (1954) The biology of the red squirrel, Tamiasciurus

hudsonicusoquax,in centralNew York. Ecol Monogr24:227-I Al7

Lott DF (1984) Intraspecific ariation n the social systems of wildvertebrates.Behaviour18:266-325

McLean IG (1982) The association of female kin in the arcticground squirrel, Spermophilus arryii. Behav Ecol Sociobiol10:91-99

MichenerGR (1979) Spatialrelationshipsand social organizationof adult Richardson'sground squirrels.Can J Zool 57:125-139

MichenerGR (1983) Kin identification,matriarchies, nd the evo-lution of sociality in ground-dwellingsciurids. In: EisenbergJF, Kleiman DG (eds) Advances in the study of mammalianbehavior. Am Soc MammalSpec Publ No. 7 pp 528-572

MichenerGR, Murie JO (1983) Black-tailedprairiedog coteries:are they cooperativelybreedingunit? Amer Nat 121:266-274

OstfeldRS (1985) Limitingresourcesand territoriality n microtinerodents.Am Nat 126:1-15

Rayor LS (1985) Effects of habitat quality on growth, age of firstreproduction, and dispersal in Gunnison's prairie dogs (Cyn-omys gunnisoni).Can J Zool 63:2835-2840

Sherman PW (1977) Nepotism and the evolution of alarm calls.Science 197:1246-1253

ShermanPW (1981) Kinship, demography,and Belding's groundsquirrelnepotism.Behav Ecol Sociobiol 8:251-259

Slade NA, Balph DF (1974) Population ecology of Uinta groundsquirrels.Ecology 55:989-1003

Smith CC (1968) The adaptive nature of social organizationin

the genus Tamiasciurus. col Monogr38:31-63TamuraN, Hayashi F, Miyashita K (1988) Dominance hierarchy

and mating behavior of the Formosan squirrel, Callosciuruserythraeus haiwanensis. Mamm 69:320-331

TamuraN (1989)Snake-directedmobbing by the Formosansquir-rel Callosciurus rythraeus haiwanensis.Behav Ecol Sociobiol24 (in press)

Thompson DC (1977) Reproductivebehaviourof the grey squirrel.Can J Zool 55:1176-1184

Vestal BM, McCarleyH (1984) Spatialand social relationsof kinin thirteen-lined nd other ground squirrels. n: MurieJO, Mi-chenerGR (eds)Thebiology of ground-dwelling quirrels.Uni-versity of Nebraska Press, pp 404-423

WilkinsonGS, Baker AEM (1988) Communalnesting among ge-neticallysimilar house mice. Ethology77:103-114

Wolff JO(1985) Matternalaggressionas a deterrent o infanticide

in Peromyscus leucopus and P. maniculatus. Anim Behav33: 117-123

Received December8, 1988

AppendixIa, b. Food items and the number of observations for each items

(a) Kamakura(data from 1982 to 1988 werecombined)

Species Parts Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.

Camellia aponica flower 15 35 18 46 1 8seed 1 1 1 4 19 8 7 2 2

bark 2 1 2 2 1Aucuba japonica fruit 5 6 1 1Machilus Thunbergii bark 3 11 2 2 2 1 3 1

flower 1 8 1fruit 2leaf 1

Cornus sp. bark 1 9 1 3 1flower 7 5fruit 6 2

Castanopsis cuspidata bark 1 10 3 4 4 2 2 7 1 5flower 4 4nut 3 20 19 13

Aphananthe aspera fruit 1 17 25 13Celtis sinensis fruit 1 6 1Rhus succedanea seed 1 2 18 12 3 4 5 9

bark

Eurya aponica fruit 5bark



351

Species Parts Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.

PittosporumTobira bark 2 1PuerariaThunbergiana seed 1

bark 5 1 2 5 1 5Irexintegra flower 4

fruitFicus erecta

fruit 1 1 2 2 1bark IPrunussp. bark 1 4 3 1

flower 11fruit 5 4

Stachyuruspraecox flower 1 2seed 3 1

Akebia sp. flower 8 2fruit 5 13 2 4

Morusbombycis fruit 4 2Wistariasp. fruit 2Osmanthussp. flower 1

fruit 2Quercusserrata bark I

nut 4 4Styrax aponicus flower 3

seed 1 34 16 7Elaeagnussp. fruit 4Cinnamomum aponicumflower 4

fruit 2 3 2PrunusPersica fruit IHoveniadulcis flower 1

fruit 6 1 3 1CarpinusTschonoski seed 34 5Acer palmatum flower IEriobotrya aponica fruit 1 3Ficus nipponica fruit 2 3Rhus ambigua seed 3Kadsura aponica fruit 2

Fungus 1 1Insect 6 2 2 2 2 3 2Snail I

Total 35 77 53 112 54 39 44 119 84 80 47 39

(b) Ken-ting

Species Parts Feb. '88 Mar. '86 Mar. '87 Jun. '87 Jul. '86 Sep. '87 Oct. '86 Dec. '85

Aleuritesmoluccana seed 33 35 15 5 9 10bark 1

Ficus septica fruit 22 4 13 4 2flowers 4

Ficuscuspidata fruit 15 4 7 20 12 4 9bark 3

Ficus kingiana fruit 13 10 19 1 6 4Ficus caulocarpa fruit 4 15 9 1Gonocaryumdiospyrosifolium seed 7

Diplocyclos palmatus fruit 3Garciniaspicata fruit 2 13 1flower I

Hyophorbeverschaffeltii seed 2 4 1 3 1Ficus sp. fruit 1 2Macaranga anarius flower 2Bauhiniavariegata seed I 1Lantanacamara fruit 2 2Palaquium ormosamum seed 10 7 31 26 8 8

flower 7Delonix regia seed 5Ficus sp. fruit 5Melia azedarach flower 3 5Semecarpusvernicifera seed 2 1



352

Species Parts Feb. '88 Mar. '86 Mar. '87 Jun. '87 Jul. '86 Sep. '87 Oct. '86 Dec. '85

Diospyros eriantha seed 2Bischofia avanica fruit 1 3 4 11 25

flower 2Erythrina ndica flower 55

seed 1Melanolepsis multigladulosa seed 16 3 3

Carica papaya fruit 1Machilus kusanoi fruit 8 42Terminaliacatappa seed IArtocarpuscommunis fruit 1 8

flower 1 IEuphoria ongana fruit 6Diospyros maritima fruit 1 12 2Cinamomumcamphora fruit 5Ravenala madagascariensis flower 10 21 19

leaf IInsect 30 5 10 4 6 5Fungus 1

Total 137 97 162 55 124 90 66 89

Appendix a, b. The numberof trees and total basal areasof respec-X * 2 ~~~~~~ ~ ~~~~~~~~~Species No. trees Total basal areative species found in 1000 m' area. (M2/1000 m2)

(a) Kamakura

Diospyrosmaritima 186 1.1670Species No. trees Total basal area Ficus caulocarpa 1 0.8153

(m2/1000m2) Machilus kusanoi 40 0.6698Ficus kingiana 8 0.6139

Castanopsis cuspidata 60 1.7434 Ravenalamadagascaliensis 6 0.3003

Machilus Thunbergii 26 1.0894 Palmae 33 0.1708Cornus sp. 13 0.6246 Semecarpusvernicifera 1 0.1523Chamaecyparisobtusa 8 0.5067 Ficus septica 7 0.1448

Camellia aponica 17 0.3377 Champereiamanillana 7 0.1012

Acer palmatum 1 0.3090 Melanolepsismultiglandulosa 6 0.0972

Celtis sinensis 3 0.3080 Alstonia scholaris 3 0.0918Cinamomum aponicum 7 0.2746 Cinamomumcamphora 3 0.0896

CarpinusTschonoskii 5 0.2076 Fraxinusgriffithii 2 0.0833

Styrax aponicus 8 0.1711 Euphoria ongana 20 0.0666

Prunus amazakura 3 0.1384 Diospyrosutilis 7 0.0502P. yedoensis 3 0.1373 Aleuritesmoluccana 4 0.0411

Aucubajaponica 114 0.1320 Aglaia formosana 10 0.0330

Aphananthe aspera 4 0.1075 Laporteapterostigma 4 0.0322

Irexcrenata 2 0.0898 Syzigiumformosana 11 0.0309

Ficus erecta 27 0.0869 Musa formosana 3 0.0237

Querucusserrata 1 0.0653 Fraxinus nsularis 4 0.0216

Neolitsea sericea 16 0.0646 Leucaenaglauca 11 0.0186

Irexintegra 8 0.0452 Evodiamerrillii 7 0.0163

Hovenia dulcis 1 0.0448 Mallotusphilippineneis 3 0.0136

Callicarpa aponica 9 0.0371 Melia azedarach 1 0.0100

Stachyuruspraecox 9 0.0359 Diospyroseriantha 2 0.0090

Rhus succedanea 1 0.0241 Actinodaphnepedicellata 10 0.0088

Morus bombycis 2 0.0171 Radermachera inica 1 0.0072

Eurya aponica 4 0.0059 Durantarepens 1 0.0069

Pasania edulis 1 0.0008 Macaranga anarius 2 0.0041Dendropanaxtrifidus 1 0.0003 Koelreuteria ormosana 2 0.0040

Culton 5 0.0025

Total 354 6.7176 Antidesmakotoense 2 0.0015Callicarpa ormosana 1 0.0011Callicarparemotiserulla 2 0.0009

(b) Ken-ting Viburnumodoratissimum 2 0.0008Drypetesyamadai 2 0.0006

Species No. trees Total basal area Sapindusmukorossi 1 0.0004

Trichodesmakhasianuin 1 0.0002Bischofia javanica 10 1.7612 ____________

Ficus caspidato 42 1.5947 Total 493 9.5234Palaquium formosanum 18 1.2642 _________________________

spacing and kinship in the formosan squirrel

Documents

mothers home range

spacing kinship

exclusive home ranges

formosan squirrel

food predation

international association

small overlapping home

change of habitats barash