Sheep Migration Patterns and Behavioral Adaptations in Indian Grazing Lands: Understanding Stress Factors and Environmental Adaptation

2.1.1.1 Seasonal migration

Sheep in the Himalayan region often engage in seasonal migration, moving to higher altitudes during the summer months and descending to lower elevations during the winter [13]. This migration pattern is influenced by the availability of fresh pasture at higher elevations during the warmer months and the need to avoid harsh winter conditions at lower altitudes.

2.1.1.2 Altitudinal migration

In mountainous regions like the Himalayas, sheep may migrate vertically, moving between different altitudinal zones in search of suitable grazing areas [14]. They may ascend to alpine meadows and high pastures during the summer and descend to lower slopes or valleys in the winter.

Transhumance: Transhumance is a traditional practice of seasonal movement of livestock between fixed summer and winter pastures [15]. In the Himalayan region, transhumance is common among pastoral communities that follow a seminomadic lifestyle. These communities may move their sheep along established migration routes, taking advantage of the available resources at different times of the year [11].

2.1.1.3 Herding practices

The migration pattern of sheep in the Himalayan region is often guided by herders who know the local terrain and grazing areas [16]. Herders may lead their flocks along well-established routes, which may have been used for generations.

2.1.1.4 Environmental factors

Environmental factors such as snowfall, rainfall, and the condition of grazing lands can also influence the migration pattern of sheep [17]. Unpredictable weather patterns or natural disasters like avalanches may alter migration routes or timing [18].

2.1.1.5 Conservation concerns

Human activities, including infrastructure development, deforestation, and overgrazing, can disrupt traditional migration patterns and impact the availability of grazing lands for sheep [19]. Conservation efforts often aim to preserve these migratory routes and maintain the ecological balance of the Himalayan region [20]. Overall, the migration pattern of sheep in the Himalayan region is a complex interplay of ecological, cultural, and economic factors, shaped by centuries of coexistence between humans and livestock in these rugged landscapes.

2.1.5.1 Habitat loss and fragmentation

Human activities such as agriculture, urbanization, and infrastructure development can lead to the loss and fragmentation of natural habitats for sheep [28]. This can disrupt traditional migration routes and force sheep to alter their movements or inhabit suboptimal habitats.

2.1.5.2 Fencing and barriers

The construction of fences, roads, and other barriers can impede the natural movement of sheep herds [28]. These barriers can disrupt migration patterns, isolate populations, and lead to conflicts with humans when sheep attempt to navigate around them.

2.1.5.3 Land use changes

Changes in land use patterns, such as the conversion of grasslands to croplands or urban areas, can reduce available grazing areas for sheep [29]. This can force them to migrate longer distances in search of suitable forage, leading to increased competition with other wildlife or domestic livestock.

2.1.5.4 Human-wildlife conflict

As human populations expand into sheep habitats, conflicts between humans and sheep can arise [30]. This may result in retaliatory killings of sheep by farmers or shepherds, especially if sheep damage crops or compete with livestock for resources.

2.1.5.5 Climate change

While not directly caused by humans, climate change, largely driven by human activities, can significantly impact sheep migration patterns. Changes in temperature, precipitation patterns, and the availability of water and forage can alter the timing and routes of sheep migrations, leading to challenges in adaptation for both sheep and the communities that depend on them [31].

2.1.5.6 Overgrazing and resource depletion

Unregulated grazing by domestic livestock, including sheep, can lead to overgrazing and depletion of vegetation in certain areas [32]. This can disrupt natural ecosystems, reduce biodiversity, and exacerbate soil erosion and desertification, affecting both sheep migration patterns and the overall health of the landscape [33].

Addressing these issues requires a holistic approach that considers the needs of both humans and wildlife. It involves sustainable land management practices, conservation efforts to preserve critical habitats, community-based natural resource management initiatives, and policies that promote coexistence between humans and wildlife. By mitigating human impacts and promoting sustainable practices, we can help ensure the long-term viability of sheep migrations in India and the ecosystems they inhabit.

2.2.1.1 Adaptation to climate

Sheep migration can have both positive and negative effects on adaptation to climate, depending on various factors such as the specific characteristics of the migration, the local ecosystem, and management practices [40]. Sheep that migrate to higher altitudes during the summer to escape the heat in the plains may exhibit behavioral adaptations such as seeking cooler areas during the day and grazing at night [41]. They may also develop a higher tolerance for cold temperatures. Sheep migration can lead to more efficient utilization of pasture resources, allowing areas to recover and regenerate, which can enhance ecosystem resilience to climate variations [42]. Migration may expose sheep to a wider variety of forage types, which can promote better nutrition and resilience to environmental changes. Through migration, sheep populations may encounter diverse environmental conditions, which can drive natural selection for traits that enhance adaptation to local climates [43].

However, uncontrolled or poorly managed migration can lead to overgrazing in certain areas, exacerbating soil erosion, reducing vegetation cover, and degrading habitats [33]. This can hinder ecosystem adaptation to climate change. Migration can facilitate the spread of diseases between sheep populations, especially if they move between areas with different disease pressures [44]. Climate change may also alter disease dynamics, potentially increasing the risk of transmission. In some cases, sheep migration routes may overlap with habitats of native wildlife. This can lead to competition for resources and disrupt natural ecosystems, affecting the ability of native species to adapt to changing climates.

In management strategies implementing rotational or managed grazing practices can help mitigate the negative impacts of overgrazing associated with migration. Regular monitoring of sheep health, combined with appropriate disease prevention and control measures, can help minimize the spread of diseases during migration [45]. Restoration efforts in areas impacted by overgrazing can enhance ecosystem resilience and support adaptation to climate change. Engaging with local communities, landowners, and stakeholders to develop collaborative management plans for sheep migration can help balance the needs of both human communities and natural ecosystems [46]. The various factors related to sheep migration and their impact on climate adaptation, highlighting management practices, environmental conditions, and interactions between sheep and local ecosystems are summarized in Table 1.

Overall, sheep migration’s impact on climate adaptation can vary widely depending on management practices, environmental conditions, and the interactions between sheep and local ecosystems. Sustainable management strategies that promote ecosystem health and resilience are crucial for ensuring that sheep migration contributes positively to adaptation efforts.

2.2.1.2 Social dynamics

The effect of migration on sheep social dynamics can vary depending on several factors, including the species of sheep, the type of migration, and environmental conditions. Migration can impact the cohesion of sheep groups. During migration, sheep often move in herds, which can strengthen social bonds among individuals within the group [47]. Migration may influence the establishment or reinforcement of social hierarchies within sheep herds. Dominant individuals may assert their leadership during migration, guiding the group and making decisions about when and where to move. Migration can be a stressful experience for sheep, especially if they encounter unfamiliar environments or predators along the migration route [48]. This stress can lead to increased aggression within the group as individuals compete for resources or jostle for positions within the herd hierarchy.

Migration may impact the communication patterns of sheep. During migration, sheep may use vocalizations, body language, and scent marking to maintain contact with group members, navigate their environment, and coordinate movement [49]. Migration provides opportunities for social learning among sheep. Younger individuals may learn migration routes and behaviors from older, more experienced group members, contributing to the transmission of knowledge within the herd [50]. Migration allows sheep to access different grazing areas and seasonal resources. The movement of sheep herds across landscapes can influence vegetation dynamics and ecosystem processes, shaping the availability and distribution of resources for both sheep and other species [51]. Migration can facilitate genetic mixing among sheep populations. As herds move between different areas, they may encounter individuals from other groups or populations, leading to gene flow and genetic diversity within the overall sheep population [52]. Overall, migration plays a significant role in shaping the social dynamics of sheep herds, impacting their behavior, communication, and interactions with both their environment and other individuals within the group.

2.2.1.3 Feeding behavior

Sheep migration can significantly impact their feeding behavior due to various factors such as the availability of forage, competition with other animals, environmental conditions, and the physiological state of the sheep themselves [41]. During migration, sheep may encounter different grazing areas with varying vegetation types and densities. This can influence their feeding behavior as they adapt to the available forage. They may spend more time searching for suitable food sources or adjust their diet based on what is accessible in each location [34]. In areas where multiple herds or species of animals migrate together, there can be increased competition for food resources. Sheep may need to alter their feeding behavior to compete effectively with other grazers, such as by grazing at different times of the day or selecting less-preferred forage if preferred options are scarce (Figure 3) [51]. Sheep have specific nutritional requirements based on factors like age, reproductive status, and stage of production. Migration may affect the availability of forage that meets these nutritional needs, leading to changes in feeding behavior as sheep prioritize obtaining essential nutrients [53].

Sheep are social animals and often exhibit flocking behavior, especially during migration [6]. Social dynamics within the flock can influence feeding behavior, with dominant individuals accessing preferred forage more readily or influencing the movement patterns of the entire group. Environmental factors such as weather, terrain, and water availability can impact sheep migration routes and grazing patterns. Extreme weather conditions or challenging terrain may necessitate changes in feeding behavior as sheep adapt to the environment to meet their nutritional requirements [54]. During migration, sheep may encounter increased predation risk, especially if they move through areas inhabited by predators. This can influence their feeding behavior, causing them to be more vigilant or selective in their foraging to minimize the risk of predation. The distance and duration of migration can affect sheep feeding behavior. Long-distance migrations may require sheep to prioritize energy conservation, leading to adjustments in feeding patterns, while shorter migrations may allow for more consistent grazing behavior [55]. The factors influencing sheep migration and their impact on feeding behavior are listed in Table 2.

Overall, the effects of sheep migration on feeding behavior are complex and multifaceted, influenced by a combination of ecological, social, and physiological factors. Understanding these dynamics is important for managing grazing lands and ensuring the welfare and productivity of sheep populations.

2.2.1.4 Predator avoidance

Migration can expose sheep to different predators along their routes. This may lead to changes in vigilance behavior, with sheep becoming more cautious or developing strategies to avoid predation, such as traveling in larger groups or utilizing terrain features for protection [48]. When sheep migrate in large groups, there is a dilution effect where individual sheep have a lower risk of predation because predators are less likely to focus on any one individual. Predators may find it difficult to single out and attack prey amidst a large moving flock [56]. Sheep tend to be more vigilant during migration, as they are exposed to a higher risk of predation. This heightened vigilance can make it easier for them to detect predators and take evasive action.

Migration often involves herding behavior, where sheep stick together closely. This group behavior can serve as a form of defense against predators, as larger groups are more intimidating and can collectively defend against attacks [57]. Migration may lead sheep to areas with better natural defenses against predators, such as higher ground or areas with dense vegetation. This can reduce their vulnerability to predation during migration periods. While migration offers some benefits in terms of predator avoidance, it also exposes sheep to different risks [58]. For example, during migration, sheep may have to navigate unfamiliar terrain, which can increase their vulnerability to predators who are more familiar with the area [48]. The movement of large groups of sheep during migration can attract predators, leading to dynamic predator-prey interactions. Predators may actively follow migrating herds, which can influence the timing and route of migration for the sheep [59]. Overall, the effect of sheep migration on predator avoidance is multifaceted and depends on various factors such as the behavior of both predators and prey, the landscape, and the presence of other environmental factors.

2.2.1.5 Human interaction

Migration routes may intersect with human settlements or infrastructure, exposing sheep to various human activities. This could lead to habituation or avoidance behaviors in response to human presence, impacting their grazing patterns and movement. Human activities such as urbanization, agriculture, and infrastructure development can fragment natural habitats, disrupting traditional migration routes for sheep [19]. This fragmentation may force sheep to alter their routes or navigate through unfamiliar territories, which can increase their vulnerability to predation and decrease access to essential resources like food and water [60]. Physical barriers like fences, highways, and other human-made structures can obstruct sheep migration paths [61]. These barriers can disrupt the natural flow of migration and may require sheep to deviate from their usual routes or expend additional energy to navigate around them. These barriers can sometimes lead to injuries or fatalities among migrating sheep. Human presence, including recreational activities such as hiking, camping, and off-road vehicle use, can disturb sheep and cause them to avoid areas of high human activity. This disturbance can lead to changes in migration patterns as sheep seek quieter and less disturbed areas, potentially altering their routes and timing of movement [62]. Human activities can indirectly influence predation risk for migrating sheep. For example, the presence of human settlements or livestock can attract predators to areas that sheep frequent during migration, increasing the likelihood of predation events [63]. In response, sheep may alter their migration routes to avoid areas with heightened predation risk, leading to changes in their overall migration patterns. While not directly related to human interaction, human-induced climate change can have significant impacts on sheep migration routes by altering habitat conditions and resource availability [64]. Changes in temperature, precipitation patterns, and vegetation dynamics can influence the timing and distribution of food and water resources along migration routes, prompting sheep to modify their movements in response to these environmental changes [65]. Overall, human interaction can disrupt the natural behavior of sheep and alter their migration routes, which can have implications for their survival, population dynamics, and ecosystem functioning. Conservation efforts aimed at minimizing human-induced disturbances and preserving critical habitat corridors are essential for maintaining healthy and resilient sheep populations.

2.2.1.6 Reproductive patterns

Migration can significantly impact the reproductive patterns of sheep due to various factors related to changes in the environment, nutrition, stress levels, and social dynamics and may affect the timing of mating seasons and birthing patterns [26]. Sheep often exhibit seasonal breeding patterns, influenced by factors like day length and temperature. Migration may alter the timing or availability of breeding resources, affecting the synchronization of estrus cycles among ewes [66]. Migration can lead to changes in available forage and water sources. Inadequate nutrition can negatively impact reproductive health, leading to decreased fertility rates, lower conception rates, and increased embryonic loss [67]. The physical exertion of migration, especially over long distances or challenging terrain, can induce stress in sheep. Chronic stress can disrupt hormonal balances, affecting reproductive hormone secretion and leading to irregular estrus cycles or anestrus [68]. Migration often involves the mixing of different sheep populations, introducing new social hierarchies and dynamics. Dominance hierarchies within groups can influence mating behavior and access to mates, potentially affecting reproductive success. Migration routes may expose sheep to increased predation risk, causing heightened stress levels. Fear of predation can trigger physiological responses that impact reproductive hormones and behavior [48].

Migration may expose sheep to varying climates and weather conditions. Extreme temperatures or weather events can induce stress and impact reproductive function, particularly during critical stages such as mating or pregnancy. Migration can increase exposure to parasites such as internal worms, which can affect sheep’s health and reproductive performance. Parasite infestations can lead to nutrient deficiencies, anemia, and overall poor reproductive outcomes. Migration can facilitate genetic exchange between different sheep populations. This genetic mixing may introduce traits related to reproductive performance, such as fertility or fecundity, which can influence future breeding patterns [69]. Overall, the effects of migration on sheep reproductive patterns are complex and multifaceted, depending on various environmental, physiological, and social factors. Management practices that mitigate stress, ensure adequate nutrition, and minimize exposure to disease and predators are essential for maintaining optimal reproductive health in migrating sheep populations. Here is a comprehensive Table 3 summarizing the various factors that influence sheep migration and their impacts on reproductive patterns.

2.2.1.7 Cultural influences

Sheep migration can have various effects on cultural influences, depending on the context and the specific cultural practices of the communities involved. In many pastoralist cultures, sheep migration is a deeply ingrained tradition. The movement of sheep herds from one grazing area to another may be a central aspect of cultural identity and heritage [70]. This tradition can be passed down through generations, shaping cultural practices, rituals, and oral traditions. Sheep migration can significantly influence economic activities in pastoralist societies. The timing and routes of migration can impact trading patterns, market dynamics, and economic relationships with neighboring communities [71]. Economic exchanges related to sheep farming, such as wool and meat production, can also contribute to cultural exchanges and interactions. Sheep migration often involves communal cooperation among pastoralist communities. The coordination required for successful migrations fosters social cohesion and strengthens bonds within the community. Cultural values such as cooperation, reciprocity, and solidarity are reinforced through collective efforts to manage and execute the migration process. Pastoralist cultures develop extensive knowledge about the land, weather patterns, and ecosystems through generations of sheep migration [11].

This ecological knowledge forms an integral part of cultural identity and influences decision-making processes related to resource management and adaptation to environmental changes. Sheep migration routes often intersect with trade routes and pathways of cultural exchange. As pastoralist communities move their herds, they may encounter other groups with different cultural practices, languages, and belief systems [72]. These encounters can facilitate cultural exchange, leading to the adoption of new customs, technologies, and ideas. Sheep migration can sometimes lead to conflicts, especially in areas where resources are scarce or contested [73]. Conflicts over grazing rights, water access, or land ownership can arise between pastoralist communities or with sedentary agriculturalists.

However, these conflicts also provide opportunities for cultural negotiation, conflict resolution, and the establishment of customary laws and agreements. In the face of modernization and external pressures, sheep migration serves as a means of preserving traditional cultural practices and knowledge systems [74]. At the same time, pastoralist cultures may also adapt their migration practices in response to changing socio-economic conditions, environmental challenges, and government policies. Overall, sheep migration plays a multifaceted role in shaping cultural influences, contributing to the resilience, adaptation, and diversity of pastoralist societies around the world.

Overall, the effects of migration on the behavioral adaptations of sheep in India are multifaceted and influenced by a variety of factors including environmental conditions, social dynamics, and cultural practices. Understanding these dynamics is crucial for effective sheep management and conservation efforts in diverse landscapes.

2.3.1.1 Predator threats

Environmental predator threats can significantly impact the stress levels of sheep. When sheep perceive a predator threat, their bodies release stress hormones like cortisol [48]. Elevated cortisol levels indicate heightened stress, which can have negative impacts on their health and well-being [79]. Sheep may exhibit altered behavior in response to predator threats. They may become more vigilant, spending more time scanning their surroundings for potential threats. This heightened vigilance can lead to decreased feeding and resting behaviors, which can further impact their health and productivity [48]. Prolonged exposure to predator threats can disrupt reproductive patterns in sheep [48]. Stress hormones can interfere with reproductive hormones, leading to decreased fertility and reproductive success [80]. Chronic stress resulting from persistent predator threats can weaken the immune system of sheep, making them more susceptible to diseases and infections. This can lead to higher mortality rates and reduced overall herd health [48].

Stress can also hinder the growth and development of lambs [81]. Pregnant ewes experiencing stress due to predator threats may produce smaller and weaker offspring, affecting the overall productivity of the flock [48]. Continual exposure to predator threats can result in long-term psychological stress in sheep. This can manifest in various ways, including decreased resilience to future stressors, altered social behavior, and even symptoms of anxiety or depression [82].

To mitigate these effects, sheep farmers often implement predator control measures such as using guardian animals, installing fences, or employing deterrents like lights or sound devices to reduce the risk of predator attacks. Additionally, providing a safe and secure environment for sheep, such as well-designed shelters or pasture management strategies, can help minimize stress levels and promote overall welfare.

2.3.1.2 Social hierarchy

The influence of environmental social hierarchy on sheep migration is an interesting aspect of animal behavior and ecology [6]. Sheep, like many other social animals, exhibit a hierarchical social structure within their groups. This hierarchy often determines access to resources such as food, water, and mates, as well as social interactions within the group [83]. In the context of migration, the social hierarchy can play a significant role in shaping the behavior of individual sheep and the dynamics of the entire flock. Here are some ways in which environmental social hierarchy may impact sheep migration, in sheep groups, dominant individuals often emerge as leaders, guiding the movements of the flock [41]. These leaders may have a greater influence on migration decisions, determining when and where the flock moves based on their knowledge of the environment and available resources. Sheep lower in the social hierarchy may follow dominant individuals to ensure access to resources during migration [84]. Dominant individuals may have priority access to preferred foraging areas or water sources, and subordinate sheep may benefit from following them to gain access to these resources.

Dominant individuals within the flock may also provide a sense of security and protection during migration [85]. Subordinate sheep may feel safer following dominant individuals, especially in unfamiliar or potentially dangerous environments. The social hierarchy can contribute to the cohesion of the flock during migration. Subordinate sheep may be more likely to stay with the group and follow dominant individuals, maintaining the integrity of the flock as it moves across the landscape [41]. In some cases, the social hierarchy within the flock may lead to competition and conflict during migration. Dominant individuals may compete for leadership roles, leading to challenges or aggressive interactions within the group [6]. This competition could influence the direction or pace of migration. Sheep may learn from each other during migration, with dominant individuals playing a key role in transmitting knowledge about the landscape and optimal migration routes. This social learning can help the flock adapt to changes in the environment or respond to challenges encountered during migration [6].

Overall, the environmental social hierarchy within sheep groups can have significant effects on migration behavior, shaping the decisions of individual sheep and the collective movement of the flock across the landscape. Understanding these dynamics is important for conservation efforts and the management of sheep populations in natural habitats.

2.3.1.3 Physical exertion

Physical exertion can have various effects on sheep migration, depending on factors such as the duration, intensity, and timing of the exertion, as well as environmental conditions and the health and fitness of the sheep involved [86]. Here are some potential effects: Physical exertion can influence the speed at which sheep migrate. If the exertion is strenuous, such as climbing steep terrain or traversing long distances without rest, it may slow down the migration process as the sheep need to conserve energy [87].

Exertion increases the energy expenditure of sheep. They need to consume more food and water to replenish the expended energy, which can affect their grazing patterns and may lead them to seek out rest stops more frequently during migration. Prolonged or excessive exertion without adequate rest can lead to fatigue and physical strain in sheep [88]. This can make them more susceptible to injuries, illnesses, or conditions like heat stress or exhaustion, particularly if they are already in poor health or if environmental conditions are harsh. Sheep may exhibit changes in behavior in response to physical exertion during migration. They may become more restless, vocalize more, or display signs of stress or agitation. Alternatively, they may become more focused and determined as they navigate challenging terrain or obstacles.

Physical exertion can affect the cohesion and dynamics of the sheep group [89]. Fatigue or injury in some individuals may slow down the entire group, while stronger or more resilient individuals may lead the way or provide support to weaker members. The presence of physical exertion may influence the choice of migration routes. Sheep may prefer paths that offer easier terrain or access to resources like food, water, or shelter to mitigate the effects of exertion and conserve energy [4]. Prolonged or intense physical exertion during migration could potentially impact the reproductive success of sheep, particularly if it leads to stress, malnutrition, or injuries that affect fertility or the ability to care for offspring [39].

Overall, while physical exertion is a natural part of sheep migration, its effects can be complex and varied, influenced by a range of factors that interact with each other and with the intrinsic characteristics of the sheep population and their environment.

2.3.1.4 Food and water availability

Competition for resources within the flock or encountering scarcity can cause stress and nutritional deficiencies [90]. Sheep often migrate in response to seasonal changes in vegetation and water availability. During the dry season, they may move to areas where water is more abundant and vegetation is still relatively lush [91]. Conversely, during the wet season, they might migrate to higher elevations where vegetation is more abundant and water is plentiful. Sheep are selective grazers and prefer areas with high-quality forage [92]. They will migrate to areas where food resources are abundant and of good quality. If food availability decreases in one area due to overgrazing or environmental changes, sheep may move to other areas where forage is more plentiful. Access to water is crucial for sheep survival, especially in arid and semiarid regions (Figure 4). Sheep will often follow migration routes that lead to reliable water sources such as rivers, streams, or seasonal waterholes [93]. Migration routes may change depending on the availability of water along the way.

Sheep may also migrate to areas where they can avoid predators. This could mean moving to higher elevations where visibility is better or to areas with natural barriers that make it more difficult for predators to approach [94]. Human activities such as agriculture, urbanization, and fencing can impact the availability of food and water for sheep. In some cases, sheep may be forced to alter their migration routes or adapt to changes in their environment due to human intervention [95].

Overall, food and water availability are primary drivers of sheep migration routes, and these routes can vary widely depending on environmental conditions, seasonal changes, and human activities in the area. Understanding these factors is crucial for conservation efforts and sustainable management of sheep populations.

2.3.1.5 Human interference

Human interference can significantly impact sheep migration routes in various ways. Construction of roads, fences, and buildings can obstruct traditional migration paths, forcing sheep to detour or change their routes altogether [96]. These barriers can disrupt the natural flow of migration and isolate populations, leading to reduced genetic diversity and potential habitat fragmentation. Human activities such as agriculture, urbanization, and industrial development can alter the landscape and disrupt habitats along migration routes [97]. Conversion of natural habitats into farmland or urban areas can reduce available grazing areas for sheep and increase the likelihood of conflicts with human settlements. Pollution, deforestation, overgrazing by livestock, and resource extraction activities can degrade the quality of habitats along migration routes [98]. Loss of vegetation cover, water sources, and shelter can negatively impact sheep populations, making it difficult for them to find food and rest during their migrations. Increased human presence along migration routes can disturb sheep behavior and cause them to avoid certain areas or alter their movement patterns [99]. Activities such as recreational hiking, camping, hunting, and livestock grazing can create disturbances, noise, and potential conflicts with migrating sheep.

Overall, human interference can disrupt the natural processes that govern sheep migration, leading to habitat loss, fragmentation, and increased vulnerability to environmental stressors. Conservation efforts aimed at mitigating human impacts, preserving key habitats, and maintaining connectivity along migration routes are essential for ensuring the long-term survival of sheep populations.

2.3.1.6 Separation from lambs

Separation from lambs during migration can cause significant distress and anxiety among both ewes and their offspring [48]. This separation disrupts the strong bond between the mother and her lamb, leading to various behavioral and physiological stress responses [100]. For ewes, the separation from their lambs can result in increased vocalizations, restlessness, and attempts to reunite with their young [101]. This anxiety stems from their maternal instinct to protect and care for their lambs, and being unable to do so can cause significant stress.

Lambs, on the other hand, also exhibit signs of distress when separated from their mothers. They may bleat frequently, exhibit restlessness, and show decreased activity as they attempt to find their mothers [102]. The lack of maternal care can lead to increased vulnerability, reduced feeding, and overall impaired well-being. In addition to behavioral changes, both ewes and lambs can experience physiological stress responses [103]. Elevated levels of cortisol, a stress hormone, can be detected in their systems, indicating a state of heightened stress [104]. This can affect their immune function, growth, and overall health, making them more susceptible to diseases and other health issues.

Efforts to minimize separation during migration are crucial for maintaining the welfare of both ewes and lambs [105]. Ensuring that they remain together can help reduce stress, promote normal behavior, and support their overall health and well-being during the challenging migration process.

2.3.1.7 Unfamiliar territory

Sheep are creatures of habit and may experience stress when navigating unfamiliar terrain or encountering new obstacles along migration routes [106]. This behavior is rooted in their instincts and social structure. Sheep rely heavily on familiar surroundings and established pathways to feel secure. When faced with new environments or unexpected barriers, they can become anxious or disoriented [88]. This stress response can affect their overall well-being and movement efficiency.

To mitigate these issues, shepherds and farmers often take steps to gradually introduce sheep to new areas, using techniques such as leading with experienced animals or creating temporary enclosures that allow sheep to acclimate at their own pace. Understanding and managing the stress responses of sheep in unfamiliar territory is crucial for maintaining their health and ensuring smooth migrations or transitions between pastures.

2.3.1.8 Transportation

Transportation can indeed be a highly stressful experience for domesticated sheep due to several factors. When sheep are transported, they often face confinement in unfamiliar and sometimes cramped conditions, which can induce anxiety and stress [107]. The noise from the vehicle and external environment, along with the movement and vibrations, adds to their discomfort. If not handled properly, this stress can negatively impact their health and welfare. Proper handling during transportation is crucial to minimize stress, including ensuring adequate space, ventilation, and gentle handling practices [108]. Additionally, reducing the duration of transportation and providing rest periods can help mitigate some of the stress associated with the journey. By addressing these factors and implementing best practices, the welfare of sheep during transportation can be significantly improved, reducing the stress and associated negative impacts on their health and productivity.

2.3.1.9 Health issues

Migration can significantly impact the health of sheep, often exacerbating existing health issues or making them more susceptible to new diseases [109]. The act of migration itself can be highly stressful for sheep. This stress can weaken their immune system, making them more vulnerable to diseases. Stress factors include changes in the environment, handling during transportation, and disruption of their regular routines. Long-distance travel can lead to exhaustion. Fatigue reduces the animals’ ability to fend off illnesses and can exacerbate existing health problems, such as respiratory conditions or joint issues [88]. When sheep are moved to new environments, they may encounter unfamiliar pathogens to which they have no immunity [110]. This exposure can lead to outbreaks of diseases such as foot and mouth disease, bluetongue, or other infectious diseases prevalent in the new location [111].

Migration often involves changes in diet and water sources. Inadequate nutrition or changes in diet can affect sheep’s health, leading to issues like malnutrition or digestive problems [112]. Moving to a different climate can expose sheep to weather extremes they are not accustomed to, such as extreme heat or cold, which can exacerbate conditions like pneumonia or heat stress [3]. Migration can increase exposure to parasites, both internal and external, such as worms, ticks, and lice. These parasites can thrive in different environmental conditions, leading to increased infestation and subsequent health issues [113]. In conclusion, the process of migration can present significant health challenges for sheep, necessitating careful management and preventive measures to mitigate these risks.

Addressing these stressors requires careful planning and management practices to ensure the welfare of migrating sheep populations. Providing access to adequate food, water, and shelter, and minimizing disturbances can help reduce stress and promote a successful migration.

Sheep, like many other animals, experience a range of physiological responses to cope with stressors during migration. These responses involve changes in hormone levels, heart rate variability, and immune function, which help the animals adapt to the physical and psychological challenges they encounter.

2.4.1.1 Cortisol

Often referred to as the stress hormone, cortisol is released by the adrenal glands in response to stress. In sheep, cortisol levels rise in situations of stress, such as during handling, transportation, or exposure to predators [114]. Cortisol helps mobilize energy reserves by increasing blood glucose levels, ensuring that the sheep have the energy needed to respond to the stressor [39]. It also suppresses nonessential functions such as growth, reproduction, and immune responses temporarily to prioritize survival.

2.4.2.1 Immune function

The immune system plays a crucial role in the physiological responses to stress in sheep, as it does in all mammals [123]. Stress can come from various sources in a sheep’s environment, such as changes in diet, temperature, social interactions, or predator threats. Here is how the immune function intersects with stress responses in sheep:

2.4.3.1 Behavioral responses

2.6.1.1 Urbanization

The expansion of urban areas can encroach upon traditional sheep grazing lands, reducing available habitat and forcing migrations to alternative areas.

2.6.1.2 Agricultural expansion

Controlling natural habitats into agricultural lands can fragment migration routes, disrupt access to seasonal forage, and lead to conflicts between livestock and farmers.

2.6.1.3 Deforestation

Deforestation alters the landscape, reducing the availability of shelter and forage for migrating sheep. It can also increase soil erosion, affecting the quality of grazing lands.

2.6.2.1 Roads and highways

Construction of roads and highways can fragment migration corridors, creating barriers that disrupt traditional migration patterns. Sheep may be reluctant to cross roads due to the increased risk of predation and collisions with vehicles.

2.6.2.2 Fences

Fencing associated with infrastructure development can impede the movement of sheep, obstructing migration routes and leading to population isolation. Moreover, fences can increase the risk of entanglement and injury for migrating animals.

2.6.2.3 Dams and reservoirs

The construction of dams and reservoirs can flood grazing lands and disrupt water sources, altering migration routes and limiting access to essential resources for sheep.

2.6.3.1 Overgrazing

Poorly regulated grazing practices can lead to overgrazing, degrading vegetation, and reducing forage availability along migration routes. This can force sheep to travel longer distances in search of suitable feeding grounds, increasing energy expenditure and vulnerability to predation.

2.6.3.2 Seasonal grazing restrictions

Grazing regulations restricting access to certain areas during critical times of the year can disrupt traditional migration patterns, forcing sheep to alter their routes or remain in less suitable habitats.

2.6.3.3 Predator control

Human interventions aimed at predator control, such as culling or fencing, can indirectly influence sheep migration behavior by altering predator-prey dynamics along migration routes.

Overall, human activities have the potential to significantly impact sheep migration behavior and adaptation by altering habitat availability, fragmenting migration corridors, and disrupting access to essential resources. Sustainable land management practices and conservation efforts are essential to mitigate these impacts and ensure the long-term viability of sheep populations and their migratory behaviors.