Comportamento de ovinos

História natural e domesticação de ovinos

Sheep (genus Ovis) are small ungulates (hoofed mammals) that have adapted to a wide range of climates. Wild ancestors of sheep ranged from Europe to northern Asia and North and South America. With such a wide range of territory, sheep adapted to multiple habitat types, including deserts, mountains, islands, and lowlands.

Sheep are ruminants and have developed the ability to use diverse diets depending on their breed and the region to which they are adapted.

Sheep were domesticated approximately 11,000 years ago in the Middle East. Many wild sheep species are still found in Europe (mouflon), Asia (argali), and North America (mountain bighorn and Dall sheep). As an agricultural species, sheep are most commonly used for meat, wool, pelts, and milk.  

Estrutura social de ovinos

Sheep are gregarious and have strong herd instincts. Generally, sheep remain in social groups known as flocks, and they synchronize their behavior with other sheep in the flock. Individuals adjust their positions and behaviors to maintain social cohesion. They also perform allelomimetic behavior, mimicking the actions of other sheep in the flock.

Communication between sheep is based on largely visual signals, including stomping, pawing, fleeing, and specific body postures. Individuals in a flock spread out to decrease competition while grazing. However, when they perceive a threat, they organize into tightly packed groups for protection from predators, becoming vigilant, flocking together, and quickly moving to protected areas. Once a threat seems to have been evaded, sheep become immobile and silent.

Multiple factors, including the degree of perceived risk, environmental features, group size, age, sex, and reproductive status, affect vigilance behavior and flight distance.

Outside of ewe-lamb interactions, sheep rarely use vocalization to communicate. Ewes and their lambs perform low-pitched bleats when close to one another, and rams vocalize during courtship. In addition, sheep perform a high-pitched bleat when isolated from their flock and during acute stress.

Social groups of sheep are sexually segregated. Flocks are generally composed of matrilineal groups of older ewes, their daughters, and their offspring. Males leave the groups of ewes and other juveniles at approximately 1–2 years old.

After leaving their familial group, males form bachelor groups with conspecifics of similar ages and sizes. Generally, males have a larger exploratory range than females, and because they are less vulnerable to predation, males spend more time in open areas than females do. 

The social hierarchy in sheep flocks is maintained through visual cues and agonistic interactions such as pushing, foreleg kicking, and displacement from feeding and resting areas by pawing and resting their chins on the backs of subordinate sheep. However, males compete for access to females during the breeding season through head butting and chasing sexually mature males.

Aggression between sheep is rare; however, more agonistic interactions are observed when sheep are housed with limited space, when there are sudden changes in the environment, and when access to feed is limited.

Atividades diárias de ovinos

Sheep have a diurnal behavior pattern. Typically, they rest at night and graze during the day.

Grazing and foraging during the day are generally performed in multiple bouts (20–90 minutes each) that are punctuated by resting bouts (45–90 minutes each).

Time spent foraging can range from 8 to 12 hours per day depending on feed quality and availability.

Comportamento sexual e materno de ovinos

The breeding season for sheep depends on the breed and environment in which they live. Sheep are seasonal breeders, and sexual activity is influenced by day length (activity increases as days grow shorter) in temperate breeds.

Breeding occurs in autumn, when animals are in peak condition, and lambs are born in the spring, to be coordinated with new forage availability. Synchronous breeding within a short window decreases predation pressures on lambs, because the period during which there are vulnerable lambs in the flock is shortened.

Shortly before giving birth, ewes separate themselves from the flock to find a desirable lambing site. Lambs are precocial and typically suckle their dam within 30 minutes to 1 hour after birth.

Ewes form a bond with their own lambs within 30 minutes after birth and discriminate between their lambs and unrelated lambs in the group. Ewes allow only their own lambs to nurse, and they reject unrelated lambs from attempts to suckle. The 30-minute window after birth is a critical bonding time for the ewe-and-lamb dyad; if a ewe is unable to interact with her lambs during this time, she might reject the lambs.

Ewes return to the flock with their lambs within a few days after giving birth. Weaning occurs when lambs are approximately 6 months old. After weaning, juveniles stay in their matrilineal social groups. However, doe-lamb dyads do not continue to interact with each other more than with other nonrelated animals in the group.

Roubo do cordeiro (lamb stealing)

In production settings, many preparturient ewes are housed together before and during parturition, so that they can be monitored. Confinement housing during lambing is inconsistent with ewes’ natural behavior to seek isolation before giving birth.

When many ewes close to parturition are housed together, some preparturient ewes steal lambs from other ewes. Typically, dominant ewes steal lambs from subordinate ewes. Providing cubicles for ewes to isolate themselves during lambing, versus having open pens without cubicles, decreases the frequency of lamb stealing.

Rejeição do cordeiro

In some unusual cases, a ewe refuses to care for her lamb—a behavior referred to as rejection. Ewes that reject their lambs do not allow the lambs to nurse and might display aggressive behaviors toward the lambs.

Primiparous ewes are more likely to reject their lambs than are multiparous ewes. Lamb rejection might also occur more frequently in undernourished ewes than in those with adequate body condition. Undernourished ewes have been shown to have decreased attachments to their lambs, as indicated by decreased performance of maternal grooming and bleating.

Overcrowding lambing pens also decreases maternal grooming of lambs and suckling duration and increases udder refusals by the ewe.

Sucção redirecionada em cordeiros

Artificially reared lambs have been observed to perform redirected sucking on other lambs and pen fixtures. Lambs suck the navels and scrotums of other lambs, even if separated from their dam for only 48 hours after birth. This behavior can be observed for months after birth.

Arrancamento de lã em ovinos

In some settings, when sheep are confined without opportunities to graze, they develop the abnormal behavior of wool pulling, in which they bite wool from other sheep they have access to—a behavior that resembles grazing. Depending on the severity of the behavior, receivers of wool pulling can have sparse wool coverage and bald skin.

Wool pulling is a sheep-specific behavior performed by sheep attempting to compensate for a lack of grazing opportunities or other opportunities for stimulation. Additional factors, such as overcrowding, barren enclosures, and inadequate forage, are also associated with wool pulling.