Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations

1-1-1982 An analysis of male-male aggression in guanaco male groups Paul E. Wilson Iowa State University

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Recommended Citation Wilson, Paul E., "An analysis of male-male aggression in guanaco male groups" (1982). Retrospective Theses and Dissertations. 17460. https://lib.dr.iastate.edu/rtd/17460

This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. An analysis of male-male aggression in

guanaco mal~ groups

by

Paul E. Wilson, Jr.

A Thesis Submitted to the

Graduate Faculty in Partial Fulfillment of the

Requirements for the Degree of MASTER OF SCIENCE

Major: Animal Ecology

Signatures have been redacted for privacy Signatures have been redacted for privacy

Iowa State University Ames, Iowa

1982

1 417353 ii

TABLE OF CONTENTS PAGE

ABSTRACT • • • • • • • • • • • • • • • • • • • • • • • • 1

INTRODUCTION • • • • • • • • • • • • • • • • • • • • • 3

METHODS • • • • • • • • • • • • • • • • • • • • • • • • 7

Study Area • • • • • • • • • • • • • • • • • • • • • 7

Male Identification and Age Classes • • • • • • • • • 8

Male Group Dynamics • • • • • • • • • • • • • • • • 10

Focal Animal Sampling • • • • • • • • • • • • • • • 11

RESULTS • • • • • • • • • • • • • • • • • • • • • • • • 15

Male Group Dynamics • • • • • • • • • • • • • • 15

Aggressive Behavior Patterns •••• • • • • • • • • • 19

Analysis of Male-Male Aggression • • • • • • • • • • • 26 Rates of interaction •••••••• • • • • • • 26 Rates of aggressive displays •••• • • • • • • • 29 Mean duration of aggressive encounters • • • • • • 32 Intensive encounters •••••••• • • • • • • 37 Playfights • • • • • • • • • • • • • • • • 38 Dominance fights •••••••••• • • • • • • • 40 Outcomes of aggressive encounters •• • • • • • 43

DISCUSSION • • • • • • • • • • • • • • • • • • • • • 46

Male Group Dynamics • • • • • • • • • 46 Age structure and male group sizes • • • • • • • • 48 Male movements from the male group • • • • 49 Presence of females • • • • • • • • • • • • • 51

Analysis of Male-Male Aggression • • • • • • • • • • • 52 Rates of aggression and displays •• • • • • 52 Mean duration of displays and encounters • • • • • 54 Intensive encounters ••••••••• • • • • • • 55 Fighting behavior • • • • • • • •• • • • • • • 56

CONCLUSIONS • • • • • • • • • • • • • • • • • • • • • • • 59

LITERATURE CITED • • • • • • • • • • • 61

ACKNOWLEDGEMENTS • • • • • • • • • • • • • • • • • • 67 iii

LIST or TABLES

PAGE

TABLE 1. Number of hours of focal sampling during the six month study of guanaco male-male aggressive behavior ••••••••••••••••••• 14

TABLE 2. Observed monthly means and ranges of guanaco male group sizes in Torres del Paine National Park, Chile (n=n umber of groups) • • • • • • • 16

TABLE 3. Behavior patterns used in aggressive encounters 20

TABLE 4. Mean durations of three guanaco ear threat displays for male social age classes (sample size in parentheses) ••••••••••••• 36 TABLE s. Sample size, mean, standard error, and range of playfight durations (in seconds) for three social age classes of guanaco males (n=number of playfights) • • • • • • • • • • • • • • • • 39

TABLE 6. Number and mean duration, range, and standard error (in seconds) for playfight components in an age class (n =sample size) ••••••••• 41

TABLE 7. outcomes of aggressive encounters for initiator's social age class (number of encounters in parentheses) •••••••••• 44 iv

LIST OF FIGURES

PAGE FIGURE 1. Map of the study area in southern Chile . . . 9 FIGURE 2. Maximum number of yearlings observed in any one male group during two week periods {clear bar is first half of month, shaded bar is second) ••••••••••••••••••• 18 FIGURE 3. Chase with legbite ••••• ...... • 23 FIGURE 4. Body-slam during dominance fight • • • • • • • 23

FIGURE s. Neckwrestling with unbalanced opponent •••• 24

FIGURE 6. Neckbite during a playfight • • • • • • • 24

FIGURE 1. Horizontal Ear Threat (HET) • • • • • • • • • 25 FIGURE 8. Below Horizontal Ear Threat {BHET) . . . . . • 25 FIGURE 9. Head-Up Tilt Threat {HUTT) • • • • • • • • • • 25

FIGURE 1 0. Mean rate of aggressive encounters per month (number of focal observations in parentheses) 27

FIGURE 11. Mean rate of aggressive encounters per male social age class (number of focal observations in parentheses) ••••••••••••••• 28

FIGURE 12. Percentage of aggressive interactions (threats and playfights) initiated (clear bar) and received (shaded bar) by social age classes (number of encounters in parentheses) •••• 30

FIGURE 13. Percentage of encounters when the focal animal did not respond to a received threat or playfight (number of encounters when the focal animal was recipient in parentheses) ••••• 31

FIGURE 14. Monthly mean number of ear threat displays (HET=Horizontal Ear Threat, BHET=Below Horizontal Ear Threat, HUTT=Head-Up Tilt Threat) ••••••••••••••••••• 33 v

FIGURE 15. Mean number of ear threat displays for six social· age classes of guanaco males {HET=Horizontal Ear Threat. BHET=Below Horizontal Ear Threat, HUTT=Head-Up Tilt Threat) • • • • • • • • • • • • • • • • • • • 34

FIGURE 16. Mean monthly durations and standard errors for three guanaco ear threat displays for all age classes (sample size in parentheses, ear threats abbreviated in Figure 15) •••••• 35 ,

ABSTRACT

A six month study was conducted in southern Chile to describe and quantify aggressive behavior within guanaco

(~~ fil!.ani£Q!!) male groups. Aggressive behavior was quantified via focal sampl~ng of identified males.

Aggressive behavior patterns were classified as indirect aggression (dominance displays) or direct aggression

(contact or fighting behavior). The majority of immigrating yearling males moved into male groups in December and

January, while adult males moved out to establish territories in January and February. Aggressive activity rates peaked in January and older males were more aggressively active than younger males. As guanaco males became older, they initiated more threats and received fewer, and utilized all ear threat displays more frequently than younger males. Mean durations of encounters were not affected by the age of the interacting males or by the type of ear threat. Time of year may have affected mean durations of encounters as durations of two ear threat displays increased while the rate of aggressive activity decreased. Increased durations of ear threats were hypothesized to be a sign of increased aggressiveness, replacing energy-costly fighting. Guanaco fighting style was similar to the equids, as both fight in an unpredictable manner to unbalance and bite the opponent. A comparison of 2 .

guanaco aggressive behavior with o~her ungulates indicated that guanacos use more dominance displays and interact more frequently than horned ungulates. who interact less frequently and with greater ritualization. The guanaco chest-ram was hypothesized to be a more ritualized behavior that evolved convergently with the large camelid canine teeth. 3

INTRODUCTION

Segregated groups of males have been observed in many species of gregarious ungulates. It has been hypothesized that males are segregated, because 1) if males forage in the same area as the females which bear and nurse their young, they will remove other males from the foraging area in order to reduce competition against the mothers of their offspring

(Crook, 1970; Eisenberg and Lockhart, 1972), and 2) because the different behavior of females will be such as to maximize energy and nutrients for fetal growth and lactation

(Geist, 197q). From these hypotheses, Geist and Petocz

(1977) predicted that males will segregate from females spatially and by habitat selection to maximize male reproductive fitness and reduce competition against females during critical times of the year (e.g. winter}. Segregated males have probably formed conspecific herds for .the same reason many ungulate species form large groups (Leuthold and

Leuthold, 1975): to reduce predation (Jarman, 1974).

Within these segregated groups of males, conspecifics compete for environmental resources (e.g. food, water, resting sites) , but more frequently compete over "social resources" such as rank, which may result in territory and access to mates. Social competition has been generally related to reproductive success, and aggressive behavior is the means through which competition is achieved. Thus, 4 aggressive behavior in ungulate male groups is universally important among social organized species, and is an essential tool of selection (Leuthold, 1977).

Aggressive encounters often consist of sequences of behaviors, in which clearly aggressive (e.g. overt threats), moderately aggressive (e.g. displays), and essentially nanaggressive elements are interspersed in variable order.

All-out fighting is relatively rare among ungulate conspecifics (Leuthold, 1977). There also appears to be an inverse relationship between "ritualized fighting" (Heymer,

1977) and the amount of displaying in aggressive encounters

(Leuthold, 1977t. Species with "unrefined" fighting methods \ have relatively small, or lack elaborate, weapons and they tend to display more than species with elaborate weapons

(i.e. horns and antlers) and a ritualized fighting style

(Geist, 1966). Thus, display behaviors can be viewed as a form of psychological warfare where an animal may gain superiority without engaging in damaging physical combat

(Walther, 1974). Agonistic displays would be adaptively beneficial as injured individuals are more vulnerable to predation (Schaller, 1972; Kruuk, 1972).

Interactions between males are essential to establishing and maintaining dominance hierarchies within a male group. Rank in hierarchies of adult male impala

C!~ICe£Q§ mel~l!lfil!§) was usually determined by display 5

encoun~ers, and occasionally some fighting. Rank was important, as only males near the top of the hierarchy were in a position to challenge for a territory (Jarman and

Jarman, 1974). Agonistic encounters between young male roan antelope (li~otragys fil!Y.in.!!.~J , between young sable antelope

(li• niq~£ Ysriani) males, and between yearling pronghorn

(!ntilocaprs smeri£g) males, were more frequent among new members than older males in order to establish hierarchies

(Joubert, 1974; Estes and Estes, 1974; Kitchen, 1974).

Sparring matches between male sable antelope became less frequent and more ritualized with age (Estes and Estes,

1974). Similar observations have been reported for pronghorn antelope, where older males interacted less frequently, but for longer durations (Kitchen, 1974).

Kitchen (1974) attributed greater aggressiveness of large pronghorn males to the age when a male would become territorial.

Segregated groups of males have also been reported in the wild South American camelids; vicuna (Vicuqna vic,!lgns) and guanaco (kam.s quanicQ~) (Koford, 1957; Franklin, 1974 and ca. 1982). Sedentary and migratory guanaco populations have been described in two areas of southern Chile

(Franklin, c~. 1982}. In the migratory population at Torres del Paine National Park, separation of family groups and male groups occurred during late spring, summer, and early 6 autumn. Mating took place within the summer territories which were based upon a system of resource defense polygyny.

Guanacos aggregated in large mixed-groQps prior to migrating to a winter range (Franklin, ca. 1982).

The overall goal of this study was to describe and quantify aggressive behavior within guanaco male groups.

Objectives were: 1) to document male group composition as it relates to immigration and emigration of males, 2) to describe and quantify agonistic behavior patterns used by guanaco males, 3) to quantify rates and durations of aggressive encounters as an index of male aggressiveness, and 4) to describe and quantify fighting behavior of male guanacos. The study was limited to the time of year

(September through April) when male groups were spatially segregated from the reproducing family group segment of the population. 7

METHODS

Study Area

The study area was located on the guanaco summer range in Torres del Paine National Park, Magellanes Region, Chile

(72o 55' W, s10 3 1 S) (Figure 1). The 35 km2 summer range consisted of a desert-like shrubland of open terrain with rolling hills and small scattered patches of Nothofa~~2 woodland. The vegetation of the summer range was predominantly Muli.!lJ!m spinQfil!m with graminoids and

A~..tll£2Qh:!llum ~tagoni£~fil and some scattered yerb~n~

!rid.fill.2 and LepidQQhyllum £Y.J2.£g~ifo~ at 500-700 m altitude. Woodlands were generally Nothofagus ~n1~rcti£~ with Berber!2 ~uxifolia brush located in or near moist depressions and valleys.

Censuses in March and April 1981, revealed a total population of 540-550 guanacos on the summer range during the study period. composition of the population was approximately ~or. males, 40r. females, and 2or. young of the year. Other herbivores on the study area were limited to

European hare (Lep.9_2 fil!f.QP~~~2) and Darwin's rhea

(Pterocnni~ J2.g!Ul~ta). The fox, Dusicysm £U1Qg~!!,2, was frequently observed on the guanaco summer range; however, pumas (Fel i ~ £QD.£Q.lQ£) were the only observed natural predator of the guanaco. The majority of observed puma 8 activity was during the winter season when guanacos were congregated in large mixed groups on the winter range

(Figure 1) •

Male Identification and Age Classes

Focal animal sampling was used to quantify aggressive behavior in guanaco male groups. In field behavioral research, recognizable individuals are required to study dominance relationships and to take individual variability of behavior into account (Altmann, 1974). In August and

September of 1980, efforts were made to capture male guanacos with the immobilization gun technique. Due to mechanical difficulties, this approach had to be abandoned.

However,_ I observed that man-y males had temporary and permanent markings in the form of cuts, scars, and notches on their ears and necks. These markings made continuous identification of individual males possible.

Social age classes of male guanacos were based upon pelage characteristics, relative body size and height, and social behavior. Yearlings, or social age class I (10-15 months old during this study) retained their scruffy juvenile pelage, and were readily aged by their small size and short height. Two year olds (Class II and 22-27 months old during this study) had some scruffy pelage on the back and were noticeably smaller than subadult males. Three year 9

N

0 3 6

Kilometers

.-··---· w Int e .~) road --- ./Range w a t e r '""' . fence-··· - I

FIGURE 1. Map of the study area in southern Chile 10 old males (Class III) had adult pelage, but were slightly smaller than subadult and adult males. Ages could not be accurately distinguished for subadult and adult males in this monomorphic species. For data analysis, I subdivided the subadult and adult class into three social age classes: Class IV males were present in the male groups throughout the six-month study. Class V males were not observed after they departed, while Class VI was composed of males that were observed as solo territorial males in other portions of the study area. I postulated that social age class IV was composed of subadults, and Classes V and VI were adult males attempting to establish territories and recruit females.

Male Group Dynamics

Location, "time,. group size and composition were recorded when a male group was located in the field. The number of yearlings in each male group was recorded from

September through March to document the recruitment of young males into male groups from family groups. Additional counts of males were made prior to each focal sample to determine if numbers or composition were changing due to the movements of males in and out of the male group. 11

Focal Animal Sampling

Preliminary observations in October 1980 indicated: 1) that male groups of five or less animals were often widely spaced (>15 m between animals) when engaged in feeding activity, and 2) male group activity peaked in mid-morning

{0900-1100) and in late afternoon and early evening

{1700-2100). During inactive periods, the majority of males were reclining, and did not interact. Thus, three criteria were used for focal sampling: 1) group size had to be greater than five animals, 2) more than two-thirds of the male group had to be actively feeding or moving, and 3) the focal sample started when the focal animal was standing and engaged in some activity. Sampling continued if the focal animal moved away from other animals, or if the focal animal reclined, but m-0re than two-thirds of the male group remained active. Thus, I assumed that normal behavior of male guanacos could include temporary movement away from the male group, and reclining while other males remained active.

Data recorded during focal sampling included: 1) all aggressive encounters initiated or received by the focal animal; 2) duration of the encounter; 3) the sequence of aggressive behaviors for the focal animal and opponeQt; and

4) the outcome of the encounter for the focal animal was noted as dominant, subordinate, stand-off, or no observed result. 12

The majority (80%) of the focal samples were recorded in the late afternoon and early evening hours when animals were most active. The scheduling of focal samples was dependent on which identified males were present in a male group. ~ale groups commonly roamed over the 35 km2 summer range, and all identified males were not always located.

Therefore, an effort was made to schedule age classes on different days for focal sampling. Identified individuals for all age classes present in a male group were recorded and a schedule was listed for the age class that was to be sampled. Individuals that had been missed during the scheduled age class day were sampled opportunistically.

Individuals returning to the male groups after a period of absence were more frequently sampled, as were individuals who were periodically "lost'' during the study period to even out sampling between age classes.

One male was observed during each 15-minute focal sample and a total of 454 focal observations were fecorded between 1 November 1980 and 19 April 1~81 on 47 individually identified males (Table 1). When unidentified males interacted with known focal animals, they were classified by social age class and all unclassified males were recorded as such. Focal sampling was evenly distributed over the six social age classes with the exception of age class II, because of the low number of identified two-year olds. 13

Observation time was reduced in February due to my absence for two weeks, and sampling was terminated in mid-April with the formation of pre-winter mixed aggregations {Table 1}.

For data analysis, the level of statistical significance was

P<.OS and standard error has been abbreviated as S.E. 14

TABLE 1. Number of hours of focal sampling during the six month study of guanaco male-male aggressive behavior

MONTH AGE CLASS n Nov Dec Jan Feb Mar Apr Total ------I 9 2.2s s.sa 8.25 2.75 4.75 1.25 24.75 II 4 1 .so 2.2s 3.00 1.00 2.25 .75 10.75 III 9 2.25 4.25 3.75 2.00 4.00 2.00 18 .25 IV 9 S.50 5.75 2.50 2.75 4.00 1.75 22.25 v 10 4.50 5.50 2.50 2.25 4.00 1.00 19.75

VI 6 5.00 1. 50 3.50 2 .25 4.50 1.00 17. 75 ----, ----- TOTAL 47 21 .oo 24.75 23.50 13.00 23.50 7.75 113.50 ------15

RESULTS

Male Group Dynamics

Guanaco male groups were fluid groups of males of all ages (~1 year old) that frequently split and reunited during the course of their daily activities. These movements resulted in a wide range of male group sizes (Table 2). All males and male groups were not enumerated each day due to movements of the groups over the 35 kmZ summer range (Figure

1). Despite group fluidity, monthly means, ranges, and standard errors of male group sizes were similar during the study period {Table 2).

Guanacos ~oved out of their winter ranges between 20 and 26 August 1980. During September, the winter mixed aggregations broke up as adult males established territories and family groups were formed. Male yearlings joined male groups as territorial males began chasing yearlings out of family groups. The first yearling males observed in a male group were on 5 September 1980 when three yearlings were counted in a group of 57 males. The number Qf yearlings in male groups slowly increased from early September through early December and rapidly increased from late December to late January (Figure 2}. On 29 December 1980, 32 yearlings were counted in six male groups totaling 154 males. The final count of yearlings was over a two-day period in 1 6

TABLE 2. Observed monthly means and ranges of guanaco male group sizes in Torres del Paine National Park, Chile (n=number of groups) ------MONTH MEAN RANGE S.E. n ------October 1980 40 8-130 6.56 23

November 47 6-145 6 .16 30

December 57 7-135 5 .17 31

January , 981 45 6-116 4.36 43

February 53 14-108 5.63 25 riiarch 51 7-156 6.32 33

April 51 18-101 7.42 -14 ------17

February when 44 yearling males were enumerated in three widely separated groups totaling 141 males.

The dispersal of yearlings from family groups into male groups paralleled the time of adult male (Classes V and VI) emigration from male groups. Sixteen of 25 known adult males were absent from the male groups at different periods throughout the six month study. The movements of older males from male groups accounted for the reduced number of males (from 154 to 141) between late December and late

February. The increased number of males in male groups by early April (to 156 males) and in early May (to 167 males) represented the return of solo males and solo territorial males to the male groups.

Females were occasionally seen in male groups. Single young females (yearlings and two-year olds) were observed in male groups four times between 5 October and 2 December 1980 and four times between 27 February and 30 March 1981, during which time females grazed without male harassment. However, between 2 December and 27 February, females were chased by males whenever they approached or entered a male group.

Three adult females with young of the year were observed tranquilly feeding in a male group during a one-day census of the guanaco population on 7 April 1981. Mixed aggregations of males, females, and young formed in late

April and early May as family groups moved into areas 1 8

"' ~(;>'~'!, 24 ,...._...,.. 22

20 ;."

(/) ~ CJ 1 8 z ...J 1 6 a: ~ < n' ··'· w · .. ;.,, 14 ,- ·~ >- u. 0 12 a: w 1 0 al ::::E ::::i 8 ,--- z ,_...... 6

4 ~

~ 2 f---

SEPT OCT NOV DEC JAN FEB MAR MONTH

FIGURE 2. Maximum number of yearlings observed in any one male group during two week periods (clear bar is first half of month, shaded bar is second) 19 usually occupied only by male groups. Mixed aggregations moved toward the winter ranges as snow accumulated in late

May 1981.

Aggressive Behavior Patterns

Two general types of .aggressive behavior have been recognized by Walther (1974) and modified by Schaller

(1977): 1) direct aggression involves warnings of imminent attack or actual physical contact; and 2) indirect aggression is where an animal attempts to achieve dominance not by a test of strength, but by intimidating the opponent solely through the use of dominance displays. Observed aggressive and submissive behavior patterns are summarized in Table 3 (see Pilters, 1954 and Franklin, 1978).

Focal sampling was usually conducted on grazing or moving and grazing male groups. surrounded by conspecifics, a male only needed to raise its head to initiate an encounter with an approaching opponent, or raise and turn the head and/or body to threaten an opponent approaching from the side or rear. Such encounters resulted in two additional behavior patterns: 1) Stop - occasionally an approaching male when threatened would stop and then graze;

2) No Response/Ears Normal - occasionally passing males when threatened would continue walking, apparently oblivious to the threat, or a recipient of a threat would not respond by 20

TABLE 3. Behavior patterns used in aggressive encounters

BEHAVIOR PATTERNS DESCRIPTION

Direct Aggression Chase (Figure 3) Observed as loping chase between two playfighting males, or a dead run in a dominance fight

Spit Common display of the Camelidae observed as a subcomponet in intensive encounters

Rush A quick movement of 2-4 steps toward an opponent, observed as a subcomponent in intensive encounters

Chest-ram Chest-to-chest frontal clash of South American Camelidae, observed in playfights and in intensive encounters

Body-slam (Figure q} When a male chest-rammed an opponent's flank, observed in dominance fights only

Neckwrestle (Figure S} Common in Eguidae ("rearing"} (Klingel, 1967) and in the Giraffidae ("necking") (Coe, 1967) as a tactic to unbalance an opponent during a playfight or dominance fight

Legbite (Figure 3) Biting at the forelegs to unbalance an opponent or at the hindlegs of a fleeing opponent, observed in playfights and in dominance fights

Neckbite (Figure 6) Observed in playfights as a tactic to impede movement of an opponent, and in dominance fights to inflict injury 21

TABLE 3 (continued)

BEHAVIOR PATTERNS DESCRIPTION ------Bite attempt Unsuccessful bite movement, observed in intensive encounters

Mount Sexual mount of another male, occasionally observed during playfights

Indirect Aggression Horizontal Ear Threat Ear display of low aggressive {HET) (Figure 7) intent, used in aggressive encounters; also observed as an ear posture of sternally reclining animals, and in body comfort behavior

Below Horizontal Ear Ear display of intermediate Threat (BHET) intensity, observed only in (Figure 8) aggressive encounters and in dominance fights

Flat Ear Threat Ears held flat against the neck; (FET) a display of higher intensity, rarely observed in this study, but observed in vicuna and other guanaco populations (Franklin, 1978)

Head-Up Tilt Threat Ear display of high intensity, (HUTT) (Figure 9) observed occasionally in aggressive encounters and in dominance fights

Head Turned Towards A subcomponent of an ear threat when an animal turned its head toward an opponent

Bite Intent An intention movement, observed when a male steps or leans toward an opponent as if lunging to bite 22

TABLE 3 (continued)

------~------BEHAVIOR PATTERNS DESCRIPTION

Nasal Contact Observed as a subcomponent of HET displays; used in recognition of males by yearling males

Submissive Displays Head Turn-Away Used by a subordinate male before or after an ear threat

Depart Follows a Head Turn-Away movement and subordinate male usually walks 1-4 steps away from dominant animal; a short run of 5-10 m when receiving a Rush or Bite Attempt

Low-Neck Crouch Displayed occasionally by year­ ling and 2 yr old males as they walk behind a dominant adult male tail is in a forward curl and neck is low, approaching ground level (equals Camelidae Submissive Crouch; Franklin, 197 8) 23

FIGURE 3. Chase with legbite

FIGURE ij. Body-slam during dominance fight 24

FIGURE S. Neckwrestling with unbalanced opponent

FIGURE 6. Neckbite during a playfight 25

FIGURE 7. Horizontal Ear Threat (HET}

FIGURE 8. Below Horizontal Ear Threat {9HE T)

FIG URE 9 . Head-Up Tilt Threat {HUTT) 26

displaying any of the des~ribed submissive behaviors (see

Table 3). If an animal performed either of the above behavior patterns, the outcome of the aggressive encounter could not be ascertained and a "no-observed result" was recorded. In addition, grazing males frequently raised their heads to threaten, bqt the threat was not directed towards an obvious recipient, and/or there was not an obvious response by nearby males. Such encounters were recorded as "no recipient-no result".

Analysis of Male-Male Aggression

]at~2 Qf ini~ctj.Qn Aggressive activity in guanaco male groups peaked in

January (Figure 10~ with a significant effect of month on the number of observed encounters per hour (F=10.22; df=5,25; P(.001). Animal age class also affected the rate of aggressive encounters (F=3.88; df=5,25; P<.05). Analysis of the mean rates of encounters indicated a significant

(F=S.79; df=1,q; P<.05) linear relationship for the main effect due to age. The significant trend indicated an increase in the rate of aggressive encounters with progressively older social age classes (Figure 11).

Older male guanacos were recipients of fewer and initiators of more threats or playfight encounters (Figure

12). The linear trend indicated an inverse relationship of 27

40

35 er J: ...... en er w 30 I- z :::> 0 u z 25 w er w co ~ 20 :::> z

15

NOV DEC JAN FEB (84) ( 9 9) (94) ( 5 2) MONTH

FIGURE 10. Mean rate of aggressive encounters per month (number of focal observations in parentheses) 28

35

30 a: .....J: 25 Cl) a: w ..... z 20 ::::> 0 (.) z w a: 15 w Ill '.:!: ::::> z 10

5

II 111 IV v VI (99) (43) (73) (89) (79) (71) SOCIAL AGE CLASS

FIGURE 11. Mean rate of aggressive encounters per male social age class (number of focal observations in parentheses) 29 age class with the percentage of threats or playfights received (F=41.03; df=l,4; P<.OOS). The trend of receiving fewer threats as male age class increased prompted analysis of the response of the focal animal as the recipient of a threat, revealing that they also responded less frequently to threats they received (F=21.30; df=1 ,4; P<.OS} (Figure

1 3) •

Thus, aggressive encounters and playfight behavior in guanaco male groups peaked during the month of January, and males interacted more frequently, but received fewer threats and responded less often to threats received as social age class increased. l!~§. .Qf ~.!I.!I~ s s iv~ £.ifill la!.§. The basic aggressive encounter between two male guanacos consisted of an ear threat (HET, BHET, FET, or

HUTT} directed toward an opponent. The encounter ended when the ears of the focal animal returned to a normal position.

The rates of aggressive displays were affected by time of year and age class of the focal animal. HET and BHET were both significantly affected (P(.001} by time (Figure

14}. FET displays were uncommonly observed and there was no such relationship for the more intense HUTT display

{F=l.01; df=l0,25; P).46). The rates of HET and BHET showed the same general activity trend as the monthly mean rate of encounters (compare Figure 10 and 14). All three ear 30

100

80

w (!) 60 ....c( z w () a: w 40 a..

20

11 111 IV V VI (513) (337) (484) (536) (642) (543) SOCIAL AGE CLASS

FIGURE 12. Percentage of aggressive interactions (threats and playfights) initiated (clear bar) and received (shad~d b~r) by soci~l age classes (number of encounters in parentheses) 31

45

40

35 w 30 < "I- z 25 LU (.) 20 a: w c.. 1 5

1 o

5

11 Ill IV V VI (207) ( 102) (87) (79) (58) (45) SOCIAL AGE CLASS

FIGURE 13. Percentage of encounters when the focal animal did not respond to a received threat or playfight (number of encounters when the focal animal was recipient in parentheses) 32 threats showed a significant linear trend with increasing social age class (P<.005 for HET and BHET; P<.025 for HUTT) indicating older males utilized all threat displays more frequently (Figure 15).

Thus. two of three ear threats had rates of display with a parallel relationship to the rate of encounters

(Figure 10). and the rates of display for all three ear threats increased with social age class indicating that older males utilized all threats more frequently than younger males.

~~an du rat i 2.11- Q.f s_gg~.i.!~ fill.£.Q. u n t e il Over the six month study. the mean durations for the three different ear threats were similar: HET Y=6.89 sec

(n=1712. range=1-145 sec); BHET Y=6.09 sec (n=630, range=l-174 sec); HUTT Y=4.32 sec (n=106, range=1-39). A breakdown of the duration data by month and social age class showed that 1) over time there was a gradual increase in the duration of the HET display (r=.99. P<.001) and BHET display

(r=.71, P>.10), but not for the more intense HUTT display

(r=-.056, P>.90) (Figure 16), and 2) neither the type of ear threat nor age affected mean durations significantly (F=.65; d f = 7 , 1 0 ; p > • 6 7) ( T ab 1 e 4) • S om e ext rem e v a 1 u es for HUTT mean duration (e.g. age classes II and IV) were due to the smaller sample sizes of the less frequent, but more intense display (Table 4). 33

20

1 6

a: ::c: 1 2 ...... a: HET UJ en :::! ::::> a z

4

HUTT

NOV DEC JAN FEB MAR APR MONTH

FIGURE 1~. Monthly mean number of ear threat displays (HET=Horizontal Ear Threat, BHET=Below Horizontal Ear Threat, HUTT=Head-Up Tilt Threat) 34

LJHET 20 D BHET

[Im HUTT 1 6 a: :t ...... a: UJ 1 2 Ill :E :::::> z 8

4

II 111 IV V VI SOCIAL AGE CLASS

FIGURE 15. Mean number of e~r threat displays for six social age classes of guanaco males {HET=Horizontal Ear Threat, EHET=Selow Horizontal Ear Threat, HUTT=Head-Up Tilt Threat) 35

10 HET 8

6 y:3. 59+. 94 x

4

(290) (444) (408) ( 193) (315) (62) ...... 0 1 0 Qj BHET ....."' 8 z 0 6 I- < 4 a: Y=4.01+.59x ::::> f Cl 2

(79) (7 4) (206) (96) ( 142) (33)

1 0 HUTT 8

6

4

2 f f y•4.42-.05x (23) ( 19) ( 19) ( 13) (23) (9) NOV DEC JAN FEB MAR APR MONTH

FIGURE 16. Mean monthly durations and standard errors for three guanaco ear threat displays for all age classes (sample size in parentheses, ear threats abbreviated in Figure 15) 36

TABLE 4. Mean durations of three guanaco ear threat displays for male social age classes (sample size in parentheses)

------EAR THREAT DISPLAYS SOCIAL AGE ------CLASS HET1 BHETZ HUTT3 ------I 5.26 (196} 7. 91 ( 41} 3.14 ( 7)

II 6. 61 (144) 4.62 ( 54) 9.86 ( 7}

III 5.47 (253) 2.83 ( 81) 4 .15 ( , 3}

IV 6.70 ( 313) 6.63 (11 4) 2.22 ( 18)

v 6.79 (432) 5. 31 (171) 4.46 ( 37)

VI 6. 69 (313) 5.10 (136} 4.75 24) ------lHET =Horizontal Ear Threat. ZBHET=Below Horizontal Ear Threat. 3HUTT=Head-up Tilt Threat. 37

Inten§iv~ ~~nt~~

Intensive encounters were characterized by the addition of some form of direct aggression such as spitting, rushing, etc., (see Table 3) to the basic ear threat display. The vast majority (76%) of the 109 intensive encounters were

BHET displays, while 18% were HET displays and only 7% were

HUTT displays. The most frequently observed form of direct aggression was the spit which was observed in 55% of 85 BHET intensive encounters, in 50% of 19 HET encounters, and in

71% of seven HUTT encounters. The next most frequently observed form of direct aggression was the rush, which was observed in 19% of the BHET encounters, in 25% of the HET encounters, and in 14% of the HUTT encounters. Chases were observed in only two BHET encounters, but six chases were recorded in aggressive encounters where a short, fast chase was the only observed threat (mean duration=8.33 sec; s.E.=l.54 sec).

Analysis of the intensive encounters indicated small differences due to the time of year (F=7.28; df=l,4; p).05) and social age class (F=4.87; df=1,4; p).09). The number of intensive encounters peaked in January, but due to the high rate of aggressive activity (Figure 10) the 34 intensive encounters accounted for only 4% of the 883 observed encounters. The frequency of intensive encounters ranged from 37. of 497 encounters in November to a high of 5% of 347 38 encounters in February. Age may have affected the utilization of direct threats as yearlings participated in only 10 intensive enco~nters (2% of 513 encounters) while social age class VI utilized direct threats in 30 intensive encounters (6% of 543 encounters) • glayfiqbts

Thirty-two playfights were observed during focal sampling. The mean playfight duration was 121 sec

(range=15-593 sec; s.E.=22 sec). Playfights were not observed equally in all social age classes. but were limited to age classes I, II. and III {Table 5). The proportion of playfights was significantly higher for age class II when compared with age classes I (Z=2.45; p(.05) and III (Z=3.13;

P<.002). The proportions of playfights in age classes I and

III were not significantly different (Z=1.02; P).30).

Though age class II males initiated significantly more playfights than classes I or III, the percent of observation time utilized for playfighting did not differ significantly

(P).50) between the three age classes (Table 5}.

Scheff~'s s-test indicated that there were no significant differences between the three playfight mean durations (Table 5) nor in mean durations of individual displays between the three age classes (Table 6). While the mean durations were not significantly different, the proportions of some of these displays differed between the 39

TABLE 5. Sample size, mean, standard error, and range of playfight durations (in seconds) for three social age classes of guanaco males (n=number of playfigh ts)

----~~------SOCIAL % time AGE MEAN # Focal in CLASS n DURATION RANGE S.E. Samples Playfights ------I 13 103 15-593 42 99 1.5

II 13 141 31-402 33 43

III 6 119 32-230 33 73 1 • 1 ------40 three social age classes (Table 6) • Age class I chest­ rammed more frequently than age class II or age class III.

Though age class III males participated in fewer playfights than yearlings or 2 year olds, these males neckbit more frequently than the other two classes (Table 6).

There were no significant differences due to social age class in mean playfight durations or mean durations of playfight components. Thus, the percentage distribution of behavior patterns in a typical playfight consisted of 45% neckwrestling, 167. neckbiting, 17% legbiting, and 22% chasing. The frequencies of chest-ramming and neckbiting within any playfight may be dependent on the age of the participants (see Table 6).

Qominan£~ iiID112 seven dominance fights were observed during focal sampling. Dominance fights were shorter and more intense than playfights. The mean duration was 34.4 sec(S.E.=9 sec; range=3-63 sec). This was not significantly less (P>.25) than the mean duration of a playfight (121 sec; S.E.=22 sec), due to the large variance in playfight durations

(Table 5) and the small sample of dominance fights.

In general, dominance fights consisted of the same components as playfights, but exhibited at a higher intensity. For example, during neckwrestling, males bit at the ears and inflicted serious wounds, while leg bites were 41

TABLE 6. Number and mean duration, range, and standard error (in seconds) for playfight components in an age class (n=sample size)

SOCIAL AGE CLASS (# fights) COMPONENT n MEAN RANGE S.E. ------I Neckwrestle 28 27.4 2-108 5. 41 (13) Neckbite 5 11.6 6- 17 2 .11 Legbite 9 13.3 1- 31 4.31 Chase 19 15.9 2- so 3. 01 Chest-ram 15

II Neckwrestle 28 29.6 10-86 4.36 ( 1 3) Neckbite 7 11. 3 1-32 4.29 Legbite 5 6.6 1-18 3 .14 Chase 23 12.2 1-25 1.66 Chest-ram 10

III Neckwrestle 13 28.1 4-11 0 7.78 ( 6) Neckbite 7 7.0 1- l 0 3.46 Legbite 4 11 • 3 2- 20 3.73 Chase 14 13.6 3- 28 1.85 Chest-ram 5 ---- 42 usually from the head-to-tail position. In all observed dominance fights. the two males continuously spit at each other (3-4 spits/male during a 10-12 sec fight). In addition, a male would body-slam into the flank of an opponent. The body-slam was a more intense performance of the chest~ram as a male charged into his opponent. leaning forward. and driving his knees into the flank or ribs

(Figure 4). During a dominance fight, the ears were held in the more intense BHET position, while in a playfight the ears were in HET or were in a normal position.

Chasing in dominance fights was conducted at a fast pace as the chaser-bit at the heels and flanks of his opponent. The chasee would kick back as the chaser attempted to bite. One dominance fight between two class

III males ended when the chaser was kicked on the lower right mandible. tearing the skin. During chases, either the chaser or the chasee may vocalize (see Epler Wood, 1981}.

In four dominance fights where the dominant animal was identified, only the subordinate male vocalized when chased or chasing. Occasionally a subordinate male vocalized during neckwrestling or as the recipient of a neckbite.

The concluding components of a dominance fight were distinctly different from a playfight. Playfights usually ended when the subordinate male departed from a HET display

(16 of 21 playfights) or departed and began grazing (3 of 21 43 playfights). In comparison, dominance fights ended with both participants standing in HET or BHET displays for )60 sec with the subordinate male facing away from the dominant male.

QJ!tc~ 2! ilg~si~ ~!l£2fill1~ outcomes of encounters were summarized by social age class for all encounters between focal animals and classified opponents as dominant, subordinate, stand-off, and no observed result (Table 7). For analysis of encounter outcomes, I combined social age classes V and VI into a single adult class, assuming only fully adult males would leave a male group to establish a territory (see METHODS).

Yearling males interacted predominantly with males in their cohort, but the majority of encounters had no clear outcome. This was probably due to playfighting which was a result of unsettled dominance hierarchies. The same pattern was observed in encounters initiated by age class II males

{Table 7). In contrast, the increased percentage of dominant outcomes between interacting class III males indicated a possible settling of dominance. In addition, class III males were clearly dominant over the smaller class

I and class II males. Age class III males were dominant over age class IV males in 30% of 106 initiated encounters, but this may be due to the larger class III males interacting with males of a similar size. In comparison, 44

TABLE 7. Outcomes of aggressive encounters for initiator's social age class (number of encounters in parentheses)

------INITIATOR RECIPIENT SOCIAL AGE CLASS SOCIAL AGE CLASS Result1 I II III IV Adult

-----~ ------D 363 0% 0% or. 1 2% s 5 23 0 49 0 I so 1 0 0 0 0 NR 58 77 100 51 88 (261) (26) ( 7) (3 7) ( 8)

D 54% 34% 03 193 0% s 0 5 33 33 43 II so 2 4 0 0 0 NR 44 57 67 48 57 (63) (133) ( 9) (21) ( 7) ------·------D 62% 77% 62% 30% 10% s 0 0 3 21 45 III so 0 0 3 2 0 NR 38 23 32 47 45 (50) (3 0) (34) (106) ( 9) ------D 81% 51% 703 387. 183 s 0 4 2 12 24 IV so 0 0 0 0 2 NR 19 45 28 50 56 (9 3) (51) (40) (13 5) (45) ---- D 60% 68% 933 673 281. s 0 0 0 4 14 Adult so 0 0 0 2 0 NR 40 32 7 27 58 (12 4) (6 3) (14) (2 50) (36) ------lD=Dominant; s=subordinate; SO=Stand-Off; NR=No Observed Result. 45 age class IV dominated age class III (703 of 40 initiated encounters). as it did over the younger age classes.

However. over half of the encounters between class IV males and between class IV males and adult males indicated no clear outcome. which suggests an unsettling of dominance hierarchies among large male guanacos. The adult male class was consistently dominant over a l l other age classes when initiating encounters. but there was no clear outcome in 583 of 36 encounters between adult males (Table 7). 46

DISCUSSION

Male Group Dynamics

Gregarious ungulates form either "closed" groups. i.e. those permanently comprised of the same individuals and excluding strangers, or "open" groups of unstable size and composition (Leuthold, 1977). Among the more gregarious

African antelope species. large female herds and groupings of male antelopes often vary considerably in size and composition over short periods in time. which suggests they are essentially open (Leuthold, 1977). From the data presented in Table 2 and the descriptions of male movements •. guanaco male groups also appear to be open groupings.

Segregated groups of males are common in many species of gregarious ungulates. Male group associations have been observed as small. temporary seasonal aggregations in the infrequently gregarious species such as moose (Ale~~ ~1£~)·

Bull moose aggregations in Alaska and Minnesota (USA) occurred when moose were occupying open areas during the rut and post-rut periods. However, the authors claimed that the use of open areas for social interactions did not explain the tendency of moose to aggregate and it appeared that topography, snow depth, and forage supplies played a major role in aggregating moose (Peek et al., 1974).

Ungulate species living in open habitats form large 47

groups, while those in closed habitats fo~m small groups

(Estes, 1974; Jarman, 1974), with the same principle operating within a species as well {Franklin et al., 1975;

Leuthold and Leuthold, 1975; Hirth, 1977). In East Africa, male group sizes of plains zebra (~fil:!.2 burchelli), Coke's hartebeest {Alcel~EhU~ a~selaphus), impala, and Grant's gazelle {GazelJ.A qran.!i) were significantly higher in more open areas of Tsavo East National Park, Kenya (Leuthold and

Leuthold, 1975). Some African species have seasonal variations in male group sizes; e.g. waterbuck (Koa[2 ellipsiprll!!n~), lesser kudu (Tragel~h~2 imberai§), and gerenuk (Litocrani~ .!!All~ri) which aggregate in the dry season (Leuthold and Leuthold, 1975; Leuthold, 1978).

The range of male group social organization varies from year-round bachelor herds in a year-round territorial species like vicuna (Franklin, 1974} to loose seasonal aggregations, like those described for the North American moose (Peek et al., 1974). Within this range, males of some species segregate spatially from females during climatically harsh seasons (e.g. bighorn sheep (~vis ~nadfill§i~) (Geist and Petocz, 1977), American bison (~ison bi~} (Lott,

1974), water buffalo (Buaglus bubgli§) (Tulloch, 1978), and impala in southern Africa (Anderson, 1972)). Conversely, species like pronghorn antelope, (Gilbert, 1973; Kitchen,

1974; Bruns, 1977), Grevy's zebra (li• g£~YYi} (Klingel, 48

1974), gerenuk (Leuthold, 1978) ' · elk (~~m2 £a!ladensi,2)

(Knight, 1970) and guanaco (Franklin, ca. 1982) aggregate with females during migrations in climatically harsh seasons. Thus, male grouping behavior in ungulates is related to environmental changes, physiological function

(e.g. breeding), defense against predators, and migrations.

,!gg stru£tu~ and male ~!!£ §.i~

The reported age structures of ungulate male groups fall into three categories: 1) males of all age classes, 2) subadult males .only, and 3) males of the same or similar age class only. Males of most species, including the guanaco, are in groups that represent a mixture of all male age classes, but in some species, like impala (Leuthold, 1970;

Jarman and Jarman, 1974), males tend to associate with individuals of a similar age. Species with all-age male groups have variable male group mean sizes and range from small groups of 2-3 male African elephant (Lo!.Q~Qllta a!£1£filla) (Laws et al., 1975) to wide ranging group sizes like 2-100 male Coke's hartebeest (Gosling, 1974), 2-60 male impala in Tanzania (Jarman and jarman, 1974), up to 60 males in the wild goat (~apra ~~£..!!§.) (Schaller and Laurie,

1974}, and up to 50 feral male water buffalo (Tulloch,

1978). Large male groups of up to 150 vicuna have been reported in Peru (Franklin, 1978), but guanaco male groups have the highest mean group size and maximum group size to 49

be reported to date f o~ an ungulate species (Table 2) •

Male groups of subadults only are small groups (2-4, maximum 10) and usually occur in territorial species, like defassa waterbuck CK• defa™ uqandae) (Spinage, 1969 and

1974), gerenuk (Leuthold, 1978), blesbok (Damaliscus ~or~

£hillipsi) (Rowe-Rowe, 1973), sable antelope (Estes and

Estes, 1974), roan antelope (Allsopp, 1979; Joubert, 1974), and blackbuck (!ntilope ~rv].capr,a) (Nair, 1976). Male groups composed of the same or similar age class also have small group sizes (2-6 males) and are of territorial species, like nyala (Tra~~laphus anq~i) (Anderson, 1980), southern mountain reedbuck (li~dunca fulyorufula) (Irby,

1977), springbok (!l!,tidQ£.£~ marsu.£.iali~) (Mason, 1976), and possibly lesser kudu (Leuthold, 1974). However, other species like markhor (Capra falcoruil:i) (Aleem, 1979) and the well-studied African buffalo (~~~ caffer) (Sinclair,

1974 and 1977) are not territorial, but are organized by a dominance hierarchy. In all three categories, the species that inhabit open habitats have larger male group sizes than species of closed habitats.

!!ale !!!.QY~n.ts from the ~le .[rou12

It is obvious from the categories described above that ungulate males often move through a series of one or more types of male groups before participating in reproduction as adults. This suggests that males with increasing age and 50 experience will move up in social status or rank. In guanacos, all males reside in male groups as young yearlings until ij-6 years old, at which time they leave to establish a territory (Franklin, ca. 1982). From the changing male group sizes in December through May, absence of older males can be assumed to be associated with change in social status. This is supported by the number of solo males observed establishing territories. In the summer of

1979-80, the number of solo males peaked in January (M.

Ortega, Dept. Animal Ecology, Iowa State University, pers. comm.). In a sedentary population of guanacos on Tierra del

Fuego, the propoction of solo males in the population peaked in November (late spring-early summer) (Raedeke, 1979).

Field studies of some African ungulates indicate that males move from and return to male groups as they compete - for territorial status. Spinage (1969) reported that two male waterbuck left the male group at 6 years of age and shared an area near a 9 year old's territory. In addition, one 6 year old male left the male group and shared an area with an 8 year old male, but the 6 year old returned to the male group after suffering wounds to the shoulder, neck and flank. Guanaco males also returned to the male group with fresh wounds, indicating they may have been challenging for territories. Jarman and Jarman (197ij and 1979) have also reported that defeated territorial male impala returned to a 51

bac~elor herd, as do Coke's hartebeest (Gosling, 1974) , while wildebeest males occasionally return to a male group

(Richter, 1971). Displaced herd stallions of mountain zebra

(~. zebr~ ~br~) joined a bachelor herd and other stallions left the bachelor herds to establish their breeding herds

(Penzhorn, 1979). The coming and going of guanaco males paralleled the reported movements of male impala and zebra.

gI~fill~ of fe.!!l~le§.

Outside the breeding season, immature female guanacos occasionally joined a male group. My observations indicate that this was a temporary behavior. Similar observations have been recorded in bontebok, (Damali~£~ dor~ ~QI£~2.) by Langley and ~iliomee (1974), and in yearling female blesbok, after being evicted from their natal groups by the territorial male (Rowe-Rowe, 1973). Spinage (1969) reported that anestrous females were of ten observed in waterbuck male groups and males would mount them.

During the breeding season of January and February, female guanacos that passed near a male group were vigorously chased. This may explain the absence of females in guanaco male groups during these months. In comparison, large pronghorn bachelor males would chase anestrous females during the rut of the American antelope (Kitchen, 1974).

Male guanacos that chased females were also large, and presumably fully adult or at least of subadult class. 52

Analysis of Male-Male Aggression

,R,gte2 Qf ~U§Si.Q!t and di~lgY§ Rates of interactions peaked in January, the month when the majority of females are bred (Franklin, ca. 1982).

Androgen levels in male dromedaries C~amelus dr.Qmeda£iu2) were highest in January and February during the winter rutting period (Yagil and Etzion, 1980) • They also reported that the extreme aggressive behavior of the male camels was directly correlated with the changes in secretion of androgen. The authors attributed the changes in behavior during the rutting period to either direct attraction of the females or delineation of territory from other males. Adult guanaco males left male groups to establish territories from late December t~ late February when aggressive behavior peaked within male groups (Figure 10).

The increased rate of aggressive interactions in older guanaco males (Figure 11) conflicts with a number of well­ studied species. Kitchen (1974) reported that in pronghorn bachelor herds yearlings interacted significantly more due to unsettled dominance, while 2-year olds interacted more than large male antelope, but less than yearlings. Two year old male sable antelope regularly engaged in sparring matches, which became less frequent and more ritualized as they matured (Estes and Estes, 1974). The rate of male guanaco aggressive behavior seemed to compare more closely 53 with a study of mature male American bison, where the number of interactions initiated correlated significantly with social standing (Lott, 1979). However, the interpretation was unclear, because the high level of aggression could have been the consequence of high position in the hierarchy

(Lott, 1979). Most studies have shown that dominance was related to size and/or age {e.g. Gosling, 1974; Jarman and

Jarman, 1974); thus, the high rate of aggressive encounters in older male guanacos may be a consequence of higher social standing as males approach territorial age.

Older males (classes III, IV, and adult) were dominant in the majority of encounters they initiated (Table 7).

Similar relationships have been reported for male bison

(Lott, 1979) and pronghorn antelope (Kitchen, 1974). The lower rate of agonistic encounters between 2-year old male pronghorn and between large male pronghorn indicated increasing clarity of dominance relationships (Kitchen,

1974). Guanaco males interacted more frequently as they increased in social age class, and the high percentage of no-observed results betweeQ class IV males and between adult males (Table 7) suggests a lack of clarity in dominance relationships within these social age classes. The possible lack of clarity in the dominance relationships of older males may be due to interactions between males that are approaching territorial age. 54

The lower percentage of threats received (Figure 12) and the higher percentage of received threats that older males did not respond to (Figure 13) suggest an increasing clarity of dominance relationships with age. However, this was probably due to threats received from younger males or subordinate males. For the male-group guanaco, the adaptive significance of an increasing clarity of dominance would be to assert dominance over a preferred resource, e.g. feeding sites. Dominant animals, when engaged in an activity like feeding, may not respond to a threat received from a subordinate animal. This would be of adaptive significance in order to continue an important maintenance activity without interruption.

The rates of ear threat displays (Figure 15) and the rate of aggressive encounters (Figure 11) showed the same relationship witfi increasing age or social status. This indicated that the consequence of increased social status or rank would be to utilize all threats more frequently in the assertion of dominance.

!1~ duratiQ.!t of g,istl~ll !!!lg_ ~ll.£QY.!lte~~ There were no significant differences in mean duration of guanaco ear displays due to age (Table 4), but the time of year affected the mean durations of two encounter types

(HET and BHET) (Figure 16). Data on pronghorn antelope male groups indicated that as males became older and larger they 55 interacted less frequently, but for longer durations due to the increased intensity of aggressive encounters (Kitchen,

1974). Guanaco social age classes did not show this relationship, but the effect of time did. As the breeding season passed and males interacted less frequently, the mean durations of HET and BHET encounters increased {Figures 10 and 16). If longer duration is assumed to be representative of increased intensity, then less frequent threats of longer duration would be adaptively beneficial to animals that are spending more time on feeding activity prior to the winter season. Increased duration of an ear display costs little additional energy, in comparison to the higher energy costs of direct aggression. Thus, the decreased aggressive activity would correspond with uninterrupted feeding activity.

I~nsiy~ ~n£Qynters

The frequencies of intensive encounters indicated that older guanaco males may, as a consequence of their increased social status, have utilized direct threats more frequently.

This pattern would be comparable to both significant relationships of rate of aggressive encounters with social age class (Figure 11), and the rates of aggressive ear displays with social age class (Figure 15). Thus, the consequence of higher social status or rank may be to utilize all threats, direct and indirect, more frequently. 56

The frequency of intensive encounters showed a slight peak

(53 of 347 encounters) in February, but, in general, the frequency of intensive encounters varied only slightly - . between 2 and 53 of all encounters from month to month. The · use of direct threats in intensive encounters remained a relatively constant proportion (4-53) of all threats as aggressive activity decreased from January through April.

This suggests that increased duration may have replaced direct threats as an indicator of intensity as the rate of aggressive encounters decreased.

I.ifill1;.!11g beh,aviQ£ "Ritualized fights" consist of innate fighting patterns which proceed according to a set of rules (Heymer, 1977).

Geist's (1966) -0riginal discussion concluded that clashing of bighorn sheep was a "ritualized fight", because the clash was followed by very predictable behavior patterns. "Less" ritualized (or unritualized) ungulates possess small, primitive weapons which could result in physical damage

(e.g. mountain goat, Or~sm~ ~ric~2>· Thus, these

"unritualized" species utilize non-contact displays more frequently than "ritualized" fighters inorder to avoid damaging contact {Geist, 1966).

Guanaco playfighting and dominance fighting, generally, compared closely with the fighting techniques described for eguids (see Klingel, 1967 and Berger, 1981). Berger (1981) 57 suggested that behaviors that cause an opponent's loss of balance become increasingly important in the offensive repertoires of combatants, because unbalanced individuals were bit more frequently. In equid fights, individuals who bit often won all fights (Berger, 1981). Playfighting guanacos neckwrestled for 45~ of a typical playfight and neckwrestling frequently led to successful neckbites and legbites (41% of 69 neckwrestling bouts}. Thus, the higher proportion of neckbites in Class III playfights (Table 6) may have resulted from two year's experience in neckwrestling. Neckwrestling in guanacos compared closely with "rearing" in equids, as rearing was one of two behaviors most responsible for unbalancing opponents

(Berger, 1981). Neckwrestling was also used to block bite attempts and break neckbites, which also compared closely with functions of rearing in equids (see Feist and

McCullough, 1976).

Dominance fights in guanacos were rarely observed, as also was reported in some equids (Klingel, 1974). The more intense tactics used in such dominance fights, also, would unbalance an opponent, increasing the possibility of a successful bite. Thus, the body-slam would unbalance an opponent quicker than chest-rams or bouts of neckwrestling.

In addition, the guanaco chest-ram may be a more ritualized behavior, similar to clashing in the Caprinae (see Geist, 58

1971; Schaller, 1977}. This ritualized behavior may have evolved to reduce serious wounds from the large camelid canines. In contrast, eguids have evolutionally lost their canines and their blunt incisors rarely inflict damaging injuries (Klingel, 1967 and 1974}. 59

CONCLUSIONS

The six-month study resulted in data and observations that indicate guanaco male group social organization compares closely with other male ungulates that are organized in groups of all age classes, and are of variable size. Yearling males joined a male group after leaving their territorial family group and remained in male groups until reaching an age when they were able to hold, or challenge for, a territory. During this time within the male group, a male interacted most frequently with other males of the same cohort. However, they also interacted with older and younger males as part of the long (3-4 years) socialization process.

Competition between young male guanacos was primarily by displays and playfighting. As males became older, they spent less time playfighting and interacted via displays more frequently. Increased rates of aggressive encounters in older male guanacos may be an indicator of increased aggressiveness or a consequence of higher social status and age. Durations of aggressive encounters are not affected by the ear threat display or age class, but may be affected by the time of year. I hypothesize that longer display durations may indicate greater aggressiveness during critical times of the year when utilization of direct aggression would require greater energy expenditures. 60

Male guanacos differ from many species of horned ungulates in that they interact more frequently as they age; in contrast, horned ungulates utilize few displays and interact less freguently. However, guanacos utilized direct aggression and higher levels of indirect aggression (e.g.

HUTT) less frequently, in comparison to horned ungulates.

Guanaco behavior is characterized by less ritualization and more displays which are performed more frequently as threats. I hypothesize that the chest-ram of the guanaco has evolved as a more ritualized behavior pattern due to the presence of large canine teeth. This would indicate that guanaco aggressive behavior is more ritualized than eguid behavior, but much less ritualized that horned or antlered ungulates. 61

LITERATURE CITED

Aleem, A. 1979. Markhor population dynamics and food availability in Chitral Gol Wildlife Sanctuary. Pak. J. For. 29 (3) :166-181.

Allsopp, R. 1979. Roan antelope population in the Lambwe Valley, Kenya. J. Appl. Ecol. 16:109-115.

Altmann, J. 1974. Observational study of behavior: sampling methods. Behaviour 48:1-48.

Anderson, J. L. 1972. Seasonal changes in social organization and distribution of the impala in Hluhluwe Game Reserve, Zululand. J. South. Afr. Wildl. Manage. Assoc. 2(2):16-20.

Anderson, J. L. 1980. The social organization and aspects of behaviour of the nyala, Traqelae,n~a ~qasi Gray, 1849. Z. Saeugetierkd. 45 (2) : 90-123.

Berger, J. 1981. The role of risks in mammalian , combat: zebra and onager fights. z. Tierpsychol. 56:297-304. Bruns, E. H. 1977. Winter behavior of pronghorns in relation to hab'itat. J. Wildl. Manage. 41 (3) :560-571.

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ACKNOWLEDGEMENTS

Due to the foreign {and somewhat remote) location of my study, I am indebted to a number of Chilean nationals, who made my stay in Chile possible, and very memorable.

I am indebted to numerous administrators and employees of Chile's Corporacion Nacional Forestal in Punta Arenas and

Puerto Natales. I especially thank Regional Director

Mauricio Rosenfelt and Director of Wildlife Claudio Cunazza for granting me permission to work in the Park. I also thank the Park Director, Gerardo Gunkel, and the Chief

Guard, Ren~ Cifuentes, for administrative and logistical assistance during my year of fieldwork. At Park

Headquarters, Jose kindly forwarded my mail, and don Sergi6

Gallardo frequently trucked in mail, food, and much needed vino.

I thank the following Park Guards for assisting with censuses and organizing fiestas: Oscar Guineo, Francisco

Barrientos, Anibol Desoto, Guillermo Santana, Juan Toro, and

Jovita Gonzales. The warm friendship of the guards and their families was the highlight of my year in Chile. I especially thank Mr. Guinea, a kind friend whose knowledge of natural history and assistance with the final censuses made my work easier and my stay more pleasant.

At the Institute of Patagonia, I thank Claudio Venegas and his staff for the kind use of taeir facilities, and I 68 especially thank Carlos Rios and his family for their friendship and hospitality during my visits to Punta Arenas.

In Torres del Paine, I met Gina Michea Anfossi and Gustavo

Cruz, whose friendship and our reunion in Santiago are warmly remembered. The special and continuing friendship of

Bunny Lowman is acknowledged; fate must have decreed our meeting in such a far land. In addition, I thank the other students of Dr. w. L. Franklin's project: Mike Fritz, Morty Ortega, and Gladys Garay, for their assistance with fieldwork and logistics.

At Iowa State University, I thank my advisor, Dr.

William L. Franklin for securing funds and for comments and suggestions during data analysis and writing. I also thank my committee members, Drs. Kenneth Shaw and Marilyn

Bachmann, for their comments, and our conversations on animal behavior. I am especially indebted to Terry

Callanan, and Ors. Paul Hinz and Dave Cox, faculty members of the Department of Statistics, Iowa State University, for suggestions on statistical analyis of behavioral data.

Special gratitude is extended to Mr. Callanan, who wrote the computer programs and acted as consultant through all phases of data analysis.

Funding was provided by grants to Dr. Franklin from the

World Food Institute of Iowa State University (Project no.

31) and the from the National Science foundation. I also 69 thank the Sigma Xi Foundation for a small grant that paid for photographing identified guanacos and their behavior patterns.

Lastly, I would like to express my thanks to Dr. Chris

Wemmer, Conservation and Research Center, National

Zoological Park, for introducing me to the world of animal behavior and the methodolgy used in this study.