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Leadership Behavior in Relation to Dominance and
Reproductive Status in Gray Wolves, Canis lupus

Results


Wolves were visible during 499 h of observation, representing approximately 30% of the winter observation periods. Leadership bouts (N = 591) comprised 64 h, two-thirds of which occurred in early winter and the remainder in late winter. Unless indicated otherwise, "breeder" refers to a dominant breeder, or alpha animal. Individual turnover was low, and pack composition did not fluctuate greatly during the study, so data were pooled across years for each pack. We could identify no influence of snow depth (relatively low in this study) on the tendency of breeders to lead (χ²[1] = 0.02, P = 0.89), so results were pooled across snow categories.

The Leopold pack contained the same dominant breeding wolves in both years of the study. In the Druid Peak pack, the initial breeding male was illegally killed in early December 1997 and was replaced in the pack structure on 8 December by a male that dispersed from the Rose Creek pack. The dominant breeding female in the Druid Peak pack was the same individual (040) in both years of the study. In the Rose Creek pack, the dominant breeding male was the same individual (008) throughout the study, but the dominant breeding female (009) was replaced by her daughter (018) late in 1999 (early-winter study period in 1999). The breeding male (008) was not the father of the new dominant breeding female (018).

Scent-marking

We observed scent-marking 158 times, in all but 3 cases by dominant breeding wolves (Table 1). A subordinate breeding female in the Druid Peak Pack scent-marked 3 times in early winter by scratching when the dominant breeding male and female were not present. In 2 cases, subordinate females replaced dominant females that died or left packs, and the subordinate females initiated double scent-marking with the breeding male at about the same time they exhibited other dominant behavior.

Table 1.  Frequency of scent-marking behavior (N = 158) observed in three free-ranging packs of gray wolves (Canis lupus) in Yellowstone National Park, Wyoming, in early winter (November-December) and late winter (March) of 1997-1999.
  Leopold
pack
Rose Creek
pack
Druid Peak
pack
Total
Early winter
   Dominant pair 13 15 37 65
   Dominant male 6 6 12 24
   Dominant female 0 5 11 16
   Other wolves 0 0 3 3
Late winter
   Dominant pair 5 5 5 15
   Dominant male 14 15 4 33
   Dominant female 1 1 0 2
   Other wolves 0 0 0 0

For each season we found no significant differences in distribution of scent-marking events across social classes among the three packs (early winter: χ²[6] = 6.90, P = 0.33; late winter: χ²[4] = 1.92, P = 0.75), so we pooled the data across packs. In both early and late winter, scent-marking events were not evenly distributed across the four sex and social status classes (early winter: χ²[3] = 79.63, P < 0.0001; late winter: χ²[3] = 55.4, P < 0.0001)). In early winter, 65 of 108 (62%) of all observed scent-marking events involved both dominant males and females (Table 1) compared with 15 of 50 (30%) in late winter. In early winter the dominant males did not scent-mark significantly more often than the dominant females (24 vs. 16; sign test, P = 0.11) but did do so in late winter (33 vs. 2; sign test, P < 0.0001). While we acknowledge the possibility of bias in observing raised-leg urination by males versus females, because males tend to raise their legs somewhat higher, we infer nevertheless that participation in scent-marking by dominant female breeders declines between early and late winter relative to that of their male counterparts.

Leading during travel

The log-linear model analysis of leadership during travel indicated significant differences according to social class, and significant interactions between pack and social class, pack and season, and season and social class (all P < 0.01). This reflects a difference in frontal-leadership distribution across social classes according to pack and season. Consequently we conducted χ² tests for each pack and season, using a Bonferroni adjustment for the six tests while maintaining an overall level of significance of 0.05.

When the number of wolves in each social class was accounted for, we found significant differences between social class/sex categories for all packs and seasons (all P < 0.001): Leopold pack: early winter: χ²[2] = 47.9; late winter: χ²[2] = 43.9); Rose Creek pack: early winter: χ²[3] = 70.9; late winter: χ²[2] = 57.7; Druid Peak pack: early winter: χ²[3] = 178.5; late winter: χ²[3] = 28.4. We note that for three packs and seasons there were no subordinate breeding females. The travel-leading frequency of the dominant breeding male was not significantly greater than that of the dominant breeding female for any of the packs in any season (all P > 0.05/6 = 0.008 (critical value), Bonferonni procedure; minimum P = 0.02 for any single pack) (Table 2). The dominant breeding female led travel significantly more often than subordinate breeding females in the Druid Peak pack in early winter (χ²[1] = 68.1, P < 0.0001), but not in the Rose Creek pack in early winter (χ²[1] = 0.01, P = 0.94) nor in the Druid Peak pack in late winter (χ²[1] = 2.58, P = 0.11).

Table 2.  Frequency of leading during travel for wolves of different social classes in three free-ranging packs in early winter and late winter of 1997-1999 in Yellowstone National Park.
  Leopold pack Rose Creek pack Druid Peak pack
Early winter Late winter Early winter Late winter Early winter Late winter
No. of
bouts
No. of
wolves
No. of
bouts
No. of
wolves
No. of
bouts
No. of
wolves
No. of
bouts
No. of
wolves
No. of
bouts
No. of
wolves
No. of
bouts
No. of
wolves
Breeding wolves
   Dominant males 25 (2.2) 3 19 (1.7) 2 25 (2.4) 3 35 (4.1) 2 72 (10.2) 3 23 (4.7) 2
   Dominant females 23 (2.5) 3 10 (2.4) 2 17 (1.0) 3 20 (3.5) 2 98 (10.2) 3 13 (1.0) 2
   Subordinate females 0 (0) 0 0 (0) 0 11 (2.1) 2 0 (0) 0 25 (1.6) 4 6 (0.5) 2
Nonbreeders 26 (1.7) 15 9 (0.6) 9 42 (3.9) 29 39 (3.4) 11 46 (4.0) 9 7 (0.7) 4
Total 74 (6.4)   38 (4.7)   95 (9.4)   94 (11.0)   241 (26.0)   49 (6.9)  
Note:  Values show the number of observed leadership bouts and the number of wolves in the class; numbers in parentheses show the total time (h).

Subordinate breeding females led significantly more often than nonbreeders only in the Rose Creek pack in early winter (χ²[1] = 17.96, P < 0.001) (in other cases the differences were nonsignificant: Druid Peak pack in early winter: χ²[1] = 0.66, P = 0.42; Druid Peak pack in late winter: χ²[1] = 0.96, P = 0.33). We therefore pooled data for subordinate breeding females and nonbreeders for the Druid Peak pack tests when comparing breeders with nonbreeders. In all six pack/season comparisons breeders led significantly more often than nonbreeders (all P < 0.0001). Over all packs and seasons, breeders led for 78% of the recorded time (Table 2), ranging from a low of 58% (Rose Creek pack in early winter) to a high of 90% (Druid Peak pack in late winter).

When a large pack (Rose Creek) travels with many adults and subadults, pack size may influence individual roles, perhaps simply because more adults are present. In terms of both overall pack size and the number of subordinate nonbreeding yearlings and adults present, the packs were ranked as follows: Rose Creek > Leopold > Druid Peak. Within seasons (early and late winter), leadership provided by these social subordinates was similarly ranked (Table 2).

We were unable to fully evaluate the influence of experience and age on leadership because most dominant breeding wolves were several years old when packs formed simultaneously in Yellowstone National Park. However, we note that in the one case in which a dominant breeder was recruited from outside the pack, the newly arrived male tended to lead more than any other wolf observed in this study (Table 2), perhaps showing an assertiveness similar to the higher rate of scent-marking documented for newly formed wolf pairs (Rothman and Mech 1979).

Initiating behavior

When data were pooled across packs, pack activities were initiated 40 times by dominant breeding males and 30 times by dominant breeding females. Other wolves, especially subordinate breeding females, initiated activities 34 times. Over both seasons, breeding wolves initiated pack activities in 75% of the 104 observed cases (Table 3); 82% in early winter and 66% in late winter. In the Rose Creek pack, breeders (including subordinate breeding females) initiated behavior less often (64%, N = 22) than in the smaller packs (71% in the Leopold pack, N = 48; 88% in the Druid Peak pack, N = 34).

Table 3.  Frequency of initiation of activity (N = 104), relative to sex and reproductive and social status, observed in wolves in three packs in early winter and late winter of 1997-1999 in Yellowstone National Park.
  Leopold pack Rose Creek pack Druid Peak pack
Early winter Late winter Early winter Late winter Early winter Late winter
Breeding wolves
   Dominant males 12 (0.57) 11 (0.40) 4 (0.45) 2 (0.15) 7 (0.26) 4 (0.57)
   Dominant females 3 (0.14) 8 (0.30) 1 (0.11) 3 (0.23) 15 (0.56) 0
   Subordinate females 3 (0.33) 1 (0.8) 2 (0.7) 2 (0.29)
Nonbreeding wolves 6 (0.29) 8 (0.30) 1 (0.11) 7 (0.54) 3 (0.11) 1 (0.14)
Note:  Numbers in parentheses show the proportion of total observation time for each pack.

Nonfrontal leadership

Nonfrontal leadership was not commonly observed and often difficult to identify. Of the 15 cases recorded, all but 1 occurred with a nonbreeder at the head of the line. One nonbreeding male in the Leopold pack (055M) exhibited nonfrontal leadership 3 times during the winter prior to dispersing from the pack; otherwise all such observations were of breeding individuals. All other observations were of breeding wolves of both sexes who displayed leadership from a nonfrontal position.


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