Rams

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Anita. Behav., 1976, 24, 818-821 
A U D I E N C E E F F E C T S O N T H E M A T I N G B E H A V I O U R O F R A M S 
Bxr D. R. LINDSAY,~: D. G. DUNSMORE,* J. D. WILLIAMS* & G. J. SYMEt 
*Department of Animal Husbandry, University of Sydney, N.S.W. 2033 
t Department of Psychology, University of Western Australia, Nedlands, W.A. 6009 
Abstract. 'Dominant' rams viewed by an audience of two submissive rams showed no alteration in 
mating behaviour in comparison with their performance when tested alone. Submissive rams, however, 
mounted and ejaculated less when viewed by two dominant rams than when tested alone. Theoretical 
and applied implications of these findings are discussed. 
Several theories of social organization have 
related position in art aggressive or dominance 
order to priorities in mating (van Kreveld 1970; 
Rowell 1974; Wood-Gush 1971). Social position 
in groups of sheep is well correlated with 
success in a competitive mating situation (Hulet 
et at. 1962). 
Environmental context may also influence 
the results obtained in studies with domestic 
animals. The Hulet et al. study was undertaken 
in a restricted setting and it has been suggested 
(Lindsay & Robinson 1961a)' that increased 
space results in a diminished sexual advantage 
to dominant sheep; at least in terms of mounting 
behaviour, low ranking animals may successfully 
avoid their competitors. 
It is possible, though, that the mere presence 
of dominant sheep can inhibit mating behaviour 
when these animals cannot attack other rams. 
For example, sheep breeders have claimed that 
a ram separated from a breeding group of ewes 
can sometimes discourage the sexual activities 
of another ram running with the group. In 
addition, research by Guhl, Coll ias& Allee 
(1945) has demonstrated a 'psychological castra- 
tion' effect in the domestic fowl. 
Maintenance of such sexual advantage without 
physical contact is of interest in that the theoreti- 
cal concept of a sexual priority gains in stature. 
The present study further examines the 
relationship between social status and mating 
behaviour in sheep by investigating the necessity 
for physical aggression by high ranking rams in 
their inhibition of mating behaviour by sub- 
ordinates. Both high and low status rams were 
observed mating by opposite ranked con- 
specifics; the latter animals were physically 
prevented from interfering in the mating process. 
If the inhibitory effects of high social rank 
do not require direct physical intervention sub- 
~Present address: Department of Animal Science and 
Production, University of Western Australia, Nedlands, 
Western Australia, 6009. 
ordinate animals may be expected to be more 
sensitive than dominants to the restraining 
effects on sexual performance of an audience. 
General Methods 
The subjects were twenty-six entire Merino 
rams all of which had had previous sexual 
experience when they were used to detect ewes 
in oestrus. Ten rams were used in the preliminary 
observations and sixteen in the audience experi- 
ment. All twenty-four ewes were ovariectomized 
and were quiet and accustomed to the intensive 
conditions prevailing during the experiment. 
Sixteen ewes were used in preliminary observa- 
tions and eight in the audience experiment. 
While the animals were kept indoors for the 
duration of the study they were fed on sorghum 
grain (0-5 kg/day) with supplementary hay. 
Water was always available. 
The experiments were carried out in a shed 
measuring 8 x 25 m. There was ample light 
supplied through large windows. The sheep 
were run on litter. Experimental pens were either 
3 x 3 m or 3 x 1.5 m. The sheep were placed in 
the holding pens for 1 or 2 days in order to 
habituate them to their surroundings. 
Oestrus was induced in the ewes by the method 
described by Robinson & Moore (1956) and 
used for similar studies by Lindsay & Robinson 
(1961a, b) and Lindsay (1966). Controlling 
oestrus by this method has several advantages 
over the use of ewes experiencing natural oestrus. 
The onset of oestrus takes place over a short 
time, a fact which is essential for the proposed 
experimental design, and which also minimizes 
variations in ewe response due to climate or 
other environmental fluctuations. 
The ewes were primed with progesterone over 
a period of 12 days (six injections each of 20 mg 
in 2 ml arachis oil intramuscularly at intervals 
of 48 hr). Oestradiol benzoate (O.D.B.) was 
injected in 1 ml arachis oil intramuscularly 48 hr 
after the final injection of progesterone. The 
818 
LINDSAY ET AL.: AUDIENCE EFFECTS ON MATING IN RAMS 819 
dosage was always greater than 200 p.g but 
less than 300 gg per sheep. Oestrus resulted 
18 to 22 hr later. More ewes than required were 
injected to ensure that enough were on heat 
for the experiment. 
To determine whether a ewe was on heat or 
not a test ram was placed in the same holding 
pen. When a ewe stood for this ram she was said 
to be in oestrus. 
Procedure 
Preliminary Observations 
Before beginning experimentation on audience 
effects it was necessary to establish an experi- 
mental period of a suitable duration. It had to be 
short enough to restrict the daily testing period 
to manageable proportions but sufficiently long 
to give a valid estimation of sexual performance 
both within and between rams. 
The rams, which were tested one at a time, 
were placed individually in pens. Soon after, 
one oestrous ewe was introduced to each pen. 
The number of mounts and ejaculations were 
recorded and totalled every 30 rain for a period 
of 8 hr. 
After completion o f 90 min observation the 
number of mounts per ram varied from 0 to 19 
and the number of ejaculations per ram varied 
from 0 to 8. The correlation between the number 
of ejaculations after 90 rain and 8 hr was high 
(r = 0-94, P < 0.01) as was the correlation for 
the mounting response at these two times (r = 
0.85, P < 0.01). 
These results were considered to have demon- 
strated sufficient individual variation and re- 
liability on both the dependent variables (mounts 
and ejaculations) for the audience observations. 
Consequently 90 min was chosen as the experi- 
mental period. 
Audience Experiment 
The study was conducted in two parts using 
the remaining sixteen rams as subjects. 
(a) Social experience. The sixteen rams were 
kept as a separate group for 4 days prior to 
experimentation to allow familiarization among 
animals and with the testing environment. On 
the fifth day the rams were subjected to 24 hr 
food deprivation after which time a bucket of 
feed was placed in the holding pen. This bucket 
allowed only one animal to feed at a time. The 
first ram to eat uninterrupted f rom the bucket 
for more than 1 rain after the ensuing competi- 
tion was noted and then removed from the 
group. This process was repeated with the 
remaining fifteen rams until each animal had 
eaten. In this way a rank ordering of precedence 
to food was obtained daily for six consecutive 
days. 
On the seventh day of competition the 
incentive was changed to that of mounting an 
oestrous ewe. The same elimination procedure 
of ranking was, however, maintained. Because 
of the severe practical difficulties involved in 
handling the subjects the mating experiment 
was not replicated. 
A social order was thus created for all rams 
for both feeding and sexual responses. Those 
in the lower half of the competitive order were 
regarded, for the purposes of the experiment, as 
being 'subordinate' to those at the top. A Kendall 
coefficient o f concordance calculated among 
each of the five feeding orders showed a maxi- 
mum value (w = 1, P < 0-01); i.e. the same 
order was obtained every time. The order of 
precedence for sexual behaviour was identical 
to that for feeding. 
(b) Audience effects on mating. For the 
purposes of establishing our two socially distinct 
audiences the rams were split into 'dominant ' 
and 'subordinate' subgroups comprisingthe 
rams in the top and bot tom halves of the 
competitive order, respectively. The term domi- 
nance in this case is restricted to the competitive 
orders measured only. I t need not imply any 
general social dominance (Rowell 1974; Syme 
1974). This experiment was then divided into 
(1) the effects of a dominant audience on the 
mating performance of submissive rams and 
(2) the effects of a submissive audience on the 
mating behaviour of dominant rams. 
(1) The audience effects for subordinate 
animals were assessed on a related measures 
design with no replication. That is, the number 
of mounts and ejaculations by each ram with an 
oestrous ewe were recorded four times; twice 
when the animal was alone and twice when 
dominant rams were in both adjacent pens. 
The pens in which the 'audience' rams were 
housed had open metal barriers which per- 
mitted unrestricted visual, auditory and olfactory 
contact without allowing dominant rams to 
interfere physically with subordinates. Prior 
exposure to the pen before testing had demon- 
strated to the subject ram that the audience 
pens were physically restraining. 
The eight stimulus ewes were randomly 
distributed amongst the rams with each ram 
being presented to a different stimulus ewe for 
each trial. The same eight ewes were used for all 
tests. 
820 A N I M A L B E H A V I O U R , 24, 4 
For each subordinate ram the audience was 
chosen so that the difference in dominance rank 
between it and its audience rams was 7.5 or 8.5. 
That is, the two most subordinate rams had rams 
ranked 7 and 8 as an audience whereas the rams 
ranked 9 and 10 were tested with rams 1 and 2 
as an audience. In this way a rough control for 
dominance differential was maintained, though 
it is realized that these social relationships were 
not necessarily on an interval scale. 
Hal f the subordinate rams were run in 
'audience-individual-audience-individual' order 
whilst the remainder were tested in the opposite 
condition. 
(2) An identical experiment was then con- 
ducted for the dominant rams with the sub- 
ordinates being used in the audience condition. 
The same stimulus ewes were employed as for 
tbe subordinate rams. 
Tests were conducted in this submissive- 
dominant order to control for previous sexual 
' reward' in the audience condition. That is, in 
comparison to the dominant rams, previous 
mating success in social conditions had been 
comparatively low for the subordinates; (the 
rams had had previous social mating experi- 
ence). Thus mating success immediately before 
they were used as an audience ensured that the 
subordinate r ams provided as highly motivated 
or 'interested' an audience as the dominant 
rams had been. 
Although it is difficult to measure the 'in- 
terest' of the rams in the audience condition 
this seemed to be high in all animals. All rams 
were oriented towards the middle pen and all 
appeared to be 'agitated'. 
Since four tests could be run simultaneously 
the audience observations were completed in 
4 days. 
Results 
The mean number of mounts and ejaculations 
per ram per session under all conditions are 
shown in Figs 1 and 2. Separate 2 • 2 analyses 
of variance with repeated measures on the 
audience factor were calculated for each measure 
(Winer 1971). 
For the mounting index a significant audience 
main effect (Fz, z4 = 15.43, P < 0.01) was 
demonstrated as well as a significant interaction 
between social rank and the audience effect 
(F1, 14 = 19.77, P < 0-01). No significant rank 
order effect (F], 7 = 0 " 4 0 , P > 0 . 0 5 ) was 
observed. 
Individual comparisons were made between 
the audience and individual conditions for both 
dominant and subordinate rams with related 
t-tests. These calculations showed that, whereas 
there was no significant difference between 
performance in the audience and individual 
conditions for the dominant subjects with a 
subordinate audience (t ---- 0.60, df7, P > 0.05), 
there was a highly significant decrement in 
performance in the audience condition by the 
subordinate rams (t = 9.98, df 7, P < 0.01). 
1 
�9 individ~ 
a m 
DOMINANT 
Fig. I. The mean number of mounts per session by 
dominant and subordinate rams in individual and 
audience test conditions. 
e 
. | 
= i n d i v k l u a i 
.audience 
SUBORDINAI'E DOMINANT 
Fig. 2. The mean number of ejaculations per session by 
dominant and subordinate rams in individual and 
audience test conditions. 
LINDSAY ET AL.: AUDIENCE EFFECTS ON MATING IN RAMS 821 
Identical analyses were undertaken for the 
ejaculation scores. Again a significant main 
audience effect was observed (FI, 14 = 8.7, 
P < 0.05) as well as a significant social rank- 
audience interaction (F1, 14 = 5.09, P < 0.05). 
There was no significant social rank main effect 
(F1, 7 = 1.1, P > 0.05). 
Individual comparisons showed that, for the 
subordinate animals there was a significant 
lower frequency of ejaculation in the audience 
condition compared with the individual con- 
dition (t = 2.73, d f 7, P < 0.05). However, no 
significant difference in the audience and 
individual condition was observed for the domi- 
nant rams (t ~ 0.66, d f 7, P > 0-05). 
Discussion 
The results provide strong support for the 
contention that dominant rams can inhibit 
mating behaviour of subordinates without 
physical contact. Sexual performance of low- 
ranking animals was inhibited by a dominant 
audience but not vice versa. 
The practical consequences of these findings 
are obvious; even if rams are physically separated 
sufficient space must be provided in breeding 
programmes to allow low ranking rams to avoid 
communication with higher ranked competitors 
(Liudsay & Robinson 1961b). 
These results are also interesting from a 
theoretical point of view in that they emphasize 
the strong and persistent effects of social re- 
lationships in this species. Although the study 
has not shown exactly which of the behaviours 
emitted by the high-ranking rams inhibited 
their groupmates, this, perhaps, is not the most 
important issue; we need to know how these 
relationships develop and if they can be modified 
(e.g. Smith & Hale 1959) especially in view of the 
possible practical pay-off. 
The findings are also compatible with those 
of Horn (1974) who assessed the effects of 
aggressiveness in mice on the number of off- 
spring produced in a large semi-naturalistic 
environment. Despite considerable spatial free- 
dom aggressive behaviour was found to be a 
factor determining reproductive success. How- 
ever, this study does not report observational 
data on direct competition between males 
during mating. The sort of 'psychological' 
inhibition observed here in subordinate rams 
could thus have influenced the results obtained. 
Further research with other species and experi- 
mental settings may establish the genetic conse- 
quences of socially mediated sexual priorities. 
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(Received 19 May 1975; revised 23 February 1976; 
MS. number: 1433)