ANOVA was performed to test for any effects of gender on the type of aggression most often displayed. All correlations were performed one-tailed as the direction of the
correlation was predicted prior to collection of data.
3.3. Spatial relationships The third category of data involved the focal animal’s spatial relationships with other
animals. Every 2 min during each 30-min focal session the following data were recorded:
1. The identities of all animals within 1 m of the focal animal. 2. The identities of all animals greater than 1 m away but within 5 m of the focal
animal. 3. The identities of all animals greater than 5 m away but within 10 m of the focal
animal. These spatial relations were used to determine each mare and foal’s most preferred
associate. The most preferred associate was defined as the animal that was observed within 5 m of the focal animal the greatest percentage of 2-min samples. A t-test for
paired samples was used to test for an effect of the foal’s gender on the gender of its most preferred associate. Only fillies and colts were used for this test as the small
number of early pre-pubertal castrates in the study group precluded their use in these analyses.
In order to test whether or not a foal preferentially associated with the foal of its dam’s most preferred associate, the probability of the focal foal associating with the foal
of the dam’s most preferred associate if association was random was determined. This was tested using a t-test for paired samples. Physical proximity rates were calculated for
mares and foals by taking the total number of animals that were observed within 10 m of the focal animal and dividing by the total number of hours in which spatial data was
recorded. These rates were then correlated with rank in mares and foals. A correlation test was also run between the sociability rates of mares and the sociability rates of their
foals to test for any maternal influence on sociability. Aggression rates to preferred associates were calculated and a t-test for paired samples was used to test for any
differences in aggression towards other foals and preferred associates.
4. Results
Mares were observed for a total of 121.75 h. Foals were observed for 121.75 h pre-weaning and 118.67 h post-weaning. The dominance hierarchies found for mares
Ž .
and foals were not perfectly linear, but did approach linearity Tables 2–4 . Foal rank in Ž
. the dominance hierarchy pre-weaning Table 5 was significantly correlated to the foal
Ž .
rank in the post-weaning dominance hierarchy r s 0.66, p s 0.005 . The foal rank
Ž .
Ž .
pre-weaning Table 6 correlated significantly with the mare rank r s 0.70, p s 0.003 .
Table 2 Field observations of mare dominance–subordinance interactions. Each score represents the number of
win–loss interactions of that pair. Mares appear in order of their rank Winners
45 37
12 24
06 07
100 35
18 30
00 53
57 34
45 X
1 20
1 20
37 48
X 1
12 21
29 X
1 24
19 8
37 X
1 1
06 11
10 6
11 X
4 1
4 07
9 10
11 12
23 X
1 6
100 20
8 11
9 7
8 X
6 1
35 10
6 7
1 7
15 X
18 7
3 3
10 1
6 15
X 5
30 11
9 9
11 6
8 16
4 6
X 3
00 9
6 6
2 9
18 8
8 4
17 X
1 53
2 11
6 7
8 12
9 4
8 2
9 X
22 57
31 11
11 1
5 11
6 5
12 11
14 1
X 1
34 3
4 5
5 3
6 3
1 4
4 4
7 3
X
Ž .
The post-weaning foal rank Table 6 was significantly correlated with mare rank Ž
. Ž
. r s 0.60, p s 0.011 . Birth order Table 7 was significantly correlated with foal rank
Ž .
Ž .
pre-weaning r s 0.66, p s 0.005 but not with the post-weaning foal rank p 0.05 .
Height was significantly negatively correlated with foal rank both pre and post-weaning Ž
. r s y0.574,
p s 0.033; r s y0.633, p s 0.019 . Weight was not significantly
Table 3 Field observations of pre-weaning dominance–subordinance interactions. Each score represents the number of
win–loss interactions of that pair. Foals appear in order of rank Winners
100F 45F
12F 07F
24F 30F
35F 06F
37F 00F
57F 53F
18F 34F
100F X
1 2
1 L45F
2 X
6 2
1 O12F
1 4
X 1
1 2
2 1
S07F 2
1 X
1 2
1 E24F
1 6
2 X
1 1
R30F 2
X 1
1 S35F
4 6
1 4
X 06F
1 2
2 1
1 X
2 37F
2 1
1 X
00F 1
2 1
1 1
1 X
57F 1
5 1
1 2
1 1
X 1
53F 1
1 2
1 1
3 X
2 1
18F 3
4 3
2 1
1 1
1 X
34F 1
3 1
2 3
1 1
1 1
X
Table 4 Field observations of post-weaning dominance–subordinance interactions. Each score represents the number of
win–loss interactions of that pair. Foals appear in order of their rank Winners
06F 45F
30F 100F
12F 00F
37F 35F
24F 07F
18F 57F
34F 53F
06F X
1 1
2 45F
13 X
12 1
1 7
30F 12
16 X
1 100F
7 1
1 X
1 3
12F 6
11 3
1 X
2 1
1 1
00F 15
20 7
2 11
X 1
3 5
37F 6
22 1
6 2
6 X
1 2
35F 5
12 4
6 3
1 X
1 1
1 1
24F 10
15 5
2 3
4 6
7 X
1 1
2 07F
6 14
1 3
5 5
1 X
2 18F
6 10
5 8
11 9
7 5
15 9
X 2
57F 8
22 3
7 10
9 3
12 12
5 23
X 2
34F 5
13 3
2 8
3 2
6 5
3 9
3 X
53F 1
7 3
1 8
7 9
4 11
9 11
11 2
X
correlated with rank at any time, though the correlation did approach significance Ž
. r s 0.46, p s 0.08 prior to weaning. Gender had no effect on the dominance rank
obtained by the foal either pre or post-weaning. Foal rank was not significantly correlated with weaning order.
Aggression rates were calculated for mares and foals. The rank of a mare was Ž
. significantly correlated
r s 0.93, p s 0.000 with the rate at which the mare gave Ž
. aggression to other herd members
Table 8 . Mare rank was also significantly,
Table 5 Pre-weaning rank order of the foals compared to the post-weaning rank order of the foals. The foal are listed in
descending order of rank Pre-weaning
Post-weaning 100F
06F 45F
45F 12F
30F 07F
100F 24F
12F 30F
00F 35F
37F 06F
35F 37F
24F 00F
07F 57F
18F 53F
57F 18F
34F 34F
53F
Table 6 Mare rank order compared to the pre-weaning rank order and the post-weaning rank order of the foals. The
mares and foals are listed in descending order of rank
a b
Mare rank Pre-weaning foal rank
Post-weaning foal rank 45
100F 06F
37 45F
45F 12
12F 30F
24 07F
100F 06
24F 12F
07 30F
00F 100
35F 37F
35 06F
35F 18
37F 24F
30 00F
07F 00
57F 18F
53 53F
57F 57
18F 34F
34 34F
53F
a
Spearman’s rank correlation coefficient s 0.70, p-0.003.
b
Spearman’s rank correlation coefficient s 0.60, p-0.01.
Ž .
negatively correlated r s y0.55, p s 0.02 with the rate of receiving aggression. Prior to weaning, the rate at which a foal gave aggression was significantly, positively
Ž .
correlated with rank r s 0.93, p s 0.000 , while the rate at which a foal received
aggression was not significantly correlated with rank. The data for foals post-weaning
Table 7 The pre-weaning rank order and post-weaning rank order of foals compared to their order of birth into the
Ž .
herd. The foals are listed in descending order of birth oldest at the top and rank
c d
Pre-weaning rank order Post-weaning rank order
Birth order 100F
06F 100F
45F 45F
35F 12F
30F 24F
07F 100F
12F, 45F 24F
12F 30F, 18F
30F 00F
07F 35F
37F 37F, 57F
06F 35F
00F 37F
24F 53F
00F 07F
06F 57F
18F 34F
53F 57F
18F 34F
34F 53F
c
Spearman’s rank correlation coefficient s 0.055, p-0.055.
d
Spearman’s rank correlation coefficient NSD.
Table 8 Mare’s listed in order of rank, aggressions received per hour, aggression given per hour and percentage of
aggression given up hierarchy
e f
Mare rank Aggression received
Aggression given Percentage up
45 3.29
14.98 37
3.84 9.33
12 5.51
12.22 24
7.14 8.11
06 3.69
4.86 07
6.13 5.96
100 8.48
7.76 4
35 5.94
8.65 47
18 5.41
4.54 23
30 6.84
4.00 5
00 7.49
2.55 13
53 9.30
2.70 72
57 10.67
2.22 81
34 4.84
0.09
e
Receives aggression rate. Spearman’s rank correlation coefficient s 0.55, p-0.02.
f
Gives aggression rate. Spearman’s rank correlation coefficient sy0.93, p-0.01.
Ž .
was similar to that of the mares Table 9 . The foal’s post-weaning rank was signifi- Ž
. cantly, positively correlated
r s 0.67, p s 0.004 with the rate at which the foal
aggressed toward others. The rate at which foals received aggression post-weaning was Ž
. also significantly, negatively correlated
r s y0.67, p s 0.004 with rank in the
Table 9 Foal’s post-weaning rank order, aggressions received per hour, aggression given per hour and percentage of
aggression given up the hierarchy
g h
Foal rank Aggression received
Aggression given Percentage up
06F 0.23
7.96 45F
1.96 12.00
0.7 30F
0.76 2.29
100F 0.46
5.54 34
12F 1.50
4.73 2
00F 3.81
3.46 6
37F 2.08
1.73 11
35F 1.02
2.33 19
24F 0.93
3.62 25
07F 1.27
3.69 41
18F 3.15
2.95 6
57F 7.15
2.54 46
34F 2.65
0.92 53F
4.18 0.44
g
Receives aggression rate. Spearman’s rank correlation coefficients 0.68, p-0.004.
h
Gives aggression rate. Spearman’s rank correlation coefficient sy0.67, p-0.004.
hierarchy. Mare rank for giving aggression was positively correlated with the rank of the Ž
. foals for giving aggression both prior to weaning
r s 0.722, p s 0.002 and after Ž
. weaning r s 0.508, p s 0.032 . A foal’s rank for giving aggression pre-weaning and a
Ž foal’s rank for giving aggression post-weaning were also positively correlated r s 0.790,
. p s 0.000 . The mare herd administered an average of 19 of all aggression up the
hierarchy. Similarly, the foal herd post-weaning administered 15 of all aggression up the hierarchy. Aggression rates per subordinate were not significantly correlated with
rank in either the mares or the foals post-weaning. The mare and foal ranks for receiving aggression were never significantly correlated.
The manner in which an individual ignores aggression may also be affected by the rank of the two individuals involved. Aggression rates were calculated for the focal
ignoring aggression directed at it and for aggression given by the focal animal that is ignored by the recipient. Prior to weaning, the rank of a foal approached a significant
Ž .
correlation r s 0.45, p s 0.054 with the rate at which its aggression was ignored by the recipient, i.e., aggression given by a higher ranking foal was less likely to be ignored
than the aggression given by a lower ranking foal. This correlation was not significant Ž
. for the foals after they were weaned p 0.05 . The rate at which an individual ignored
aggression was not significantly correlated with the rank of a foal either pre- or Ž
. post-weaning
p 0.05 . There was no significant correlation between rank and either rate of ignoring aggression in the mares. Fillies and colts did not differ in the type of
Ž .
aggression exhibited p 0.05 .
Ž .
Ž Sociability rates Table 10 of mares and foals were significantly correlated r s 0.67,
. p s 0.005 prior to weaning, but not after weaning. Rank of an individual did not
influence its sociability rate in any group. Gender was found to have no effect on a foal’s choice of most preferred associate.
This lack of effect was evident in foals prior to as well as after the foals were weaned. The foals had a preferential association with the foal of their dam’s most preferred
Table 10 Sociability rates of mares, pre-weaning foals and post-weaning foals
i
Subject ID number Mares
Pre-weaning Post-weaning
06 26.70
72.00 96.38
07 46.63
58.74 73.88
12 63.47
72.80 66.00
18 43.86
59.20 64.63
24 59.00
68.57 86.33
30 47.78
57.67 53.18
34 33.44
42.00 92.38
35 56.36
60.55 90.19
45 48.19
65.90 80.88
53 45.88
52.82 80.47
57 26.10
36.90 90.38
00 53.00
77.00 94.38
37 37.05
49.52 115.88
100 34.95
29.89 63.00
i
Pre-weaning. Spearman’s rank correlation coefficient s 0.67, p-0.005.
Ž .
associate. This association was significant prior to weaning t s y3.69, p s 0.003 and Ž
. approached significance for the foals post-weaning t s y2.10, p s 0.056 . Foals were
not more likely to aggress to preferred associates than to the other members of the herd Ž
. p 0.05 .
Mares and foals were both observed to share supplemental feed when it was offered. Mares were observed to share a feed bucket with their own foals, other mares, and foals
other than their own. Foals were also observed sharing feed buckets both prior to and after weaning. Foals were observed to share a feed bucket with up to three other
individuals.
5. Discussion
