VISION AND OTHER
Sheep have panoramic
vision of 330°–360° and binocular vision
of 25°–50°. They are thought to have colour
vision and are able to distinguish between a variety of
colours: black, red, brown, green, yellow and white
(Alexander and Shillito, 1978). They have no accommodation,
so must lift the head to see distant objects. This
also means that they are unable to judge depth.
Sheep eyes possess very
low hyperopia with little astigmatism.
Such physiological optics are likely to produce
a well-focused retinal image of objects in the middle
and long distance (Piggins, et al., 1996).
Sight is a vital part of
communication and when sheep are grazing
they maintain visual contact with each
other (Crofton, 1958; Kilgour, 1977). Each sheep
throws its head to check the position of the other sheep.
This constant monitoring is probably what keeps the
sheep in a mob as they move along grazing.
induced by isolation is reduced if sheep
are provided with a mirror, indicating that the
sight of other sheep has stress-reducing properties
Work has been done by
Franklin and Hutson (1982a,b,c) to find
what stimuli attract sheep to move along a
laneway. They found that olfactory stimuli were
of no use as attractants and that there was no practical
advantage in using sheep calls to attract sheep to move
along a race. The use of a decoy sheep was effective in
attracting sheep to move out of a pen and along a race,
and sheep moved out of a pen faster towards a mirror
that reflected the countryside, or towards open-wire
mesh than towards a covered race ending.
Deprivation of the senses
of smell, sight and hearing
on the mating behaviour of rams indicated that the
absence of sight has the most inhibitory effect on
behaviour and reduced the oestrus detection activity
and dexterity of mating. The loss of hearing has no
marked effect on mating behaviour (Smith, 1975).
Taste is the most
important sense in establishing forage
preferences, with sweet and sour plants being
preferred and bitter plants being more commonly rejected.
Touch and sight are also important in relation to specific
plant characteristics, such as succulence and
growth form (Krueger, et al., 1974).
DOMINANCE HIERARCHIES AND LEADERSHIP
In a flock of grazing sheep there is little or
no sign of dominance. In small domestic flocks, sheep
will compete for small amounts of food by pushing and
shoving rather than active bunting. Dominance–subordination
relationships were assessed in Merinos and
Border Leicesters by Squires and Daws (1975). They
found an almost linear hierarchy in Merinos and a less
rigid structure in Border Leicesters when a competitive
feeding situation was created.
Sheep form strong social groups that are
stable and the social organisation of the flock influences
grazing patterns. Animals are not randomly dispersed in
any environment and free-ranging groups may exhibit
extreme non-randomness in the use of resources, particularly
vegetation. Young lambs form strong social
bonds with each other or other objects (e.g., goats,
humans, dogs, cattle). Sometimes a strong bond forms
between two animals and they become mutually
The number of dominance
fights within flocks is higher in
single-sex, single-age groups than in mixed-sex
groups of varying ages (Stolba, et al., 1990).
The social system of
sheep appears to have been shaped by
anti-predator and foraging strategies that rely
upon learned traditions (Festa-Bianchet, 1991).
Age-effects studies on
cohesive and aggressive behaviour in sheep
indicate that older animals are more
likely to be involved in fights (Stolba, et al., 1990).
Family groups are less
likely to display fighting and
attention-seeking behaviours, indicating that a socially
stable flock may be less affected by environmental
heterogeneity than groups that are not as
well integrated socially (Stolba, et al.,
flock structure. Research has shown
that different breeds have different flock structures
(Arnold et al., 1981):
1. Merinos are a
tightly knit flock and rarely form sub-groups.
They graze close to each other and disperse
into sub-groups only under extreme food shortage,
when sex and age groups segregate out.
2. Southdowns usually
form a few sub-groups and are closely
associated when grazing, but not when camping.
3. Dorset Horns always
form many sub-groups.
In cases where
sub-groupings occur, the flock maintains a
social entity because membership of sub-groups
is constantly changing. The identification of a flock
structure is important to understand when managing
sheep. One important aspect is that, irrespective of
breed, flocks of sheep drawn from different sources do
not readily integrate into a socially homogeneous group
(Winfield et al., 1981). This means that if the paddock is
large enough, each group will use a different area, even
if the food is better in one part. This can lead to some
sheep being under-nourished.
In a gregarious breed,
such as Merinos, the flock moves as a unit
and is unsuited to grazing in pastures
that are not uniformly abundant. The net effect of such
behaviours, particularly on an extensive scale, is that to
increase or decrease stocking rate will not necessarily
lead to improved animal production of an area. This is
because the non-random spread of animals in that grazing
area makes some sectors virtually psychologically
unavailable to some individuals.
Sheep have a strong bias
for associating with others of their own
breed both when grazing and camping
(Arnold, et al., 1974).
undisturbed flocks shows that group
identity develops when small flocks are established. Breed identity
perception also exists within flocks
composed of groups of sheep of different breeds
(Arnold, et al., 1974).
Squires and Daws (1975) found that position
in a moving flock was highly correlated with social
dominance, but there is no definite study to show consistent
voluntary leadership by an individual sheep.
situations, sheep do not usually associate
with cattle. However, sheep will stay close
to and follow cattle when forced into close association
with cattle at an early age, with wethers staying nearer
to cattle than ewes (Anderson, et al., 1996).
behaviour. If shade is available in summer,
sheep use it, but if it is not available they stand about in
groups, shading their heads under the flanks or
between the hind legs of adjacent lambs rather than
lying down (Schreffler and Hohenboken, 1980). A major
problem in Australia is that about 20% of winter-born
lambs die from lack of shelter. An important research
project has looked at ways in which Merinos can be
forced to take shelter before their lambs are born.
Research has shown that it may be possible to train
sheep to spend resting periods in sheltered areas by
shearing during the cooler months; subsequently, a high
proportion may lamb in shelter, thereby reducing lamb
mortality (Lynch et al., 1980).
The use of-artificial
wind-breaks—either a tall, relatively
unpalatable hybrid phalaris or polythene shade
cloth, provided protection from wind and reduced the
death rate of single lambs from 35.5% without shelter to
8.8% with shelter, when the temperature was less than
5° during the 6 hours after birth (Alexander et al., 1980).
The selection of sites
for shelters is important so the behaviour
of the sheep must be considered and the
shelters placed where the sheep naturally prefer. Sheep
tend to graze into the wind on treeless plains, in hot
weather, but on cold wet days they huddle in the down-wind
corner of the paddock, so shelters can be put
there. They also tend to camp on hilltops in cold weather,
so shelters could be placed on ridge tops. Least-used
shelters are typically near roads, human activity
and paddock ends (Pollard, et al., 1999).
Under most conditions,
sheep tend to spend more of their time
closer to trees than would be expected by
chance. This effect is intensified in paddocks with trees
planted at low density (Sibbald, et al., 1996).
Certain breeds of sheep have definite
‘bedding habits’, known as camping. Choice of
campsite is important and often the sites chosen for day
camps differ from night camps. Sheep have clearly
defined tracks leading from the water points to day
campsites (Squires, 1981). Merinos camp on high
ground during cold weather and near water or under
shade during hot weather. In adjacent small pastures,
camping is along the common boundary or adjacent
corners. Because sheep camp, a large proportion of
faeces is dropped at the campsite and so plant nutrients
are transferred from the pasture to the campsite. The
distribution of plants is also influenced and there can be
a build-up of internal parasite eggs at the campsite. In
the management of pastures it may be necessary to
fence off campsites at times and force the sheep to
move to other areas.
Grazing is a social behaviour like sheltering
and camping. Sheep tend to have two primary grazing
periods, during the early morning and again late in the
afternoon. The period from mid-morning to mid-after-noon
is the least active. Grazing time, which may range
from about 5 1 Ú2–10
hours a day, is affected by many factors,
including day length and other environmental factors,
breed, availability of pasture and water, and topography.
The grazing patterns
adopted by sheep in small experimental
paddocks are likely to be affected by
daylength, lack of grass, and rate of loss of liveweight
(Lynch, et al., 1979).
The satiety mechanism is
of much greater importance in sheep than
the hunger mechanism in stimulating
grazing (Forbes, 1978).
Sheep have a cleft upper
lip that permits very close grazing, lower
incisor teeth and upper dental pad. As the
animal grazes, it jerks its head slightly forward and
up to break stems, leaves and grass blades against the
dental pad and lower incisors.
The intake of herbage by
grazing sheep is influenced by the age,
size, weight and physiological state of
the animal, climatic conditions and the availability and
quality of herbage on offer. Little is known, however,
about the interactions between body condition, cold
stress and pasture availability on the intake of grazing
sheep (Arnold, 1970).
Sheep grazing and
efficiency is affected by paddock shape.
Ewes grazing in rectangular paddocks grazed for
less time, had lower intake levels and used forage less
efficiently than ewes in square paddocks (Sevi, et al.,
In a pen environment it
has been shown that no relationship exists
between dominance and mating behaviour (Schreffler
and Hohenboken, 1974). In open environments
there are conflicting results and although the
dominant ram can prevent others from mating, it did not
necessarily have the highest scores for percentage of
ewes mated, number of mounts per oestrous ewe, or
total number of mounts. Also, competition of ewes for a
ram may have an effect, although there is no evidence
Exposure to recently
mated rams increases the sexual
performance of other rams. Odour cues associated
with the ewe or mating per se is thought to enhance the
sexual efficiency of unmated rams (Maina, et al., 1997).
The odour of the oestrous
ewe stimulates the ram, although it is the
ewe who seeks out the ram and stays close
beside it. The male responds to urination of the
oestrous female by sniffing, extending the neck and
curling the lip. This is the flehmen response. The tongue
goes in and out and the male may bite the female’s
wool, and raise and lower one front leg in a stiff-legged
striking motion. If the female is receptive she will stand
In sheep, the duration of
sexual receptivity in the presence of the
ram is reduced when the ram is continuously present with the ewes
(Romano, et al., 2001).
The continuous presence
of a ram after the removal of progesterone
sponges hastens oestrus onset and reduces
the interval between sponge removal and ovulation,
without modifying oestrus duration and time
between oestrus onset and ovulation in ewes synchronised
during the breeding season (Romano, et al.,
Ewes in oestrus will
often display ram-seeking behaviour,
defined as a ewe being persistent in staying
at the common fence with attention focused on the ram
to the virtual exclusion of grazing (Ortman, 2000).
Mating efficiency may
drop if food is short and ewes disperse
into small sub-groups. In this situation the
rams may not be able to find them at the usual ratio of
4 rams per 100 ewes. This is one reason that under-standing
flock behaviour under various environmental
conditions is so important.
There are several
advantages to using wethers, which include
low cost and convenience of treatment
compared to the cost of vasectomy of the ram, and the
use of wethers to identify ewes for artificial insemination
or in the post-mating period to detect non-pregnant
The use of wethers
(castrated male sheep) treated with
oestrogen or testosterone has been shown to be as
good as vasectomised rams for inducing ewes to ovulate
and for detection of ewes in oestrus (Fulkerson et
Some ewes remain with the
flock during lambing and others seek
isolation. Within seconds of birth the ewe
faces the lamb and begins vigorous licking and eating of
foetal membranes. The young must find the teat within
1–2 hours of birth, and it seems that visual cues are
very important for successful teat location (Bareham,
1975). Strange lambs are accepted immediately after
birth and some ewes adopt new-born lambs if they have
lost one. Adoptions in sheep flocks are more common
than is generally realised and has some consequences
in genetic experiments where lambs are identified with
their mothers many hours or even days after birth. From
about 12 hours after birth, a strange lamb is actively
Add-on fostering is
limited only by the inability to properly
match odour-familiar cues on a ewe’s own and
alien lambs (Price, et al., 1998).
Lambs recognise their
mothers’ voices by individual differences
(Shillito-Walser, 1980) and ewes recognise
their lambs by a variety of cues. These cues may be
vocal recognition (Shillito-Walser et al., 1981). Other
workers (Morgan, et al., 1975) suggested that recognition
depended mainly on smell, while other studies
(Alexander and Stevens, 1981) showed that ewes could
recognise their lambs from auditory and visual cues
alone, but that the correct olfactory cues are required for
suckling to be permitted. These cues may be of differing
importance depending on the breed of sheep, size of
groups, and the environment they are running in.
Litter size has a strong
effect on the time spent grooming by the
ewe. The birth of the second-born twin
results in a dramatic reduction in grooming of the first-born
twin (O’Connor, et al., 1989).
Analysis of lamb
behaviour found that singles were more
active, lying for less time and having a greater
number of suckling attempts than twins (O’Connor, et
Offspring behaviour has
no effect on the onset of bonding
behaviours of the ewe, and neonatal lamb
activity is largely independent of the behaviour of the
dam (Dwyer, et al., 1999).
Suckling behaviour is
modified by ewe behaviour and this affects
the strength of the bond between ewe and
lamb (Dwyer, et al., 1999).
The sheep is a follower
species and in the first day of life the
ewe remains within one metre of the lamb, so
the placement of water, food and shelter is important.
The distance between ewe and lamb when both are
grazing increases rapidly over the next 10 days of life,
reaching a plateau with an average distance of 20
metres. Accidental separation in the first few days causes
great agitation of both lamb and ewe, and reunion is
immediately followed by suckling.
In the first 24 hours
after birth, lambs identify their mothers
at close quarters only (less than 50 cm), and
discrimination at a distance of several metres becomes
established only when the lambs are between 2 and 3
days old (Nowack, 1991). This helps to account for the
prevalence of cross-suckling and mismothering in the
early days of life.
Suckling has strong
rewarding properties in the establishment
of a peferential relationship with the
mother by the lamb but the maintenance of this preference
does not rely strongly on suckling (Nowack, et al.,
The strength of the
ewe–lamb bond is determined mainly by milk
yield with a threshold level below which
weaning occurs (Arnold et al., 1979).
Lambs become familiar
with and recognise individuals (twins and
non-twins) as a result of direct association.
They also discriminate between novel scents and
artificial odorants associated with their familiar age-mates,
but such odors neither mask nor substitute effectively
for lambs’ individually recognisable phenotypes
(Porter, et al., 2001).
The management of the
maternal-offspring bond is important in
the husbandry of lambing ewes. The main
1. To produce lambs
capable of finding teats and suck-ling
2. To produce ewes
whose behaviour facilitates suck-ling.
Some circumstances delay
suckling which will reduce the chances of
successful suckling. These include:
1. mother remains lying
2. mother circles;
3. mother is absent—she
may be attending to one twin at the
expense of the other; and
4. the weather may be
too hot or too cold.
The sheep producer can
help to ensure that suck-ling is
successful in several ways:
control such as positioning of shade,
shelter, food and water;
2. supervision of
3. selection of
suitable breeds who make good mothers.
The most important
abnormal behaviour is concerned with
maternal behaviour. Sometimes a ewe may wander
away from her lamb, butt the lamb or move away as the
lamb approaches to suckle. These behaviours are more
common in ewes with twins, who seem unable to recognise
that they have more than one lamb.
Aggressive behaviours are
preferentially directed towards members of
the same flock (Ruiz-d-la-Torre, et al.,
A small percentage of
rams commonly will not mate with oestrous
females and, if given a choice, will display
courtship behaviour towards another ram in preference
to a female. This partner-preference behaviour of rams
may be traceable to foetal development and could represent
a phenomenon of sexual differentiation (Resko,
et al., 1998).
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