«Item type Thesis or dissertation Authors Davis, Nicolas Citation Davis, N., Schaffner, C. M., & Smith, T. E. (2005). Evidence that zoo visitors ...»
Assuming the animal can resolve the internal conflict, such as they can find food or escape from a rival, then the response and impact on welfare is temporary (Wiepkema & Koolhaas, 1993) and may even mirror the challenges faced by wildliving individuals. Problems occur if the environment does not allow the animal to solve its internal conflicts, and the problem becomes chronic. Behaviours arising from normally transient internal conflicts can turn into disturbed behaviour, and become redirected to abnormal behaviour that is not normally part of an animal’s natural behavioural repertoire. This indicates that the animal can no longer cope and its welfare is being seriously affected. These behaviours can then be used as behavioural indicators of poor welfare (Hughes & Duncan, 1988).
The behavioural indices of poor welfare have been separated into two categories. The first is quantitatively abnormal, whereby a behaviour is performed at a frequency or duration outside the range expressed in the wild, and would include hyperactivity, lethargy, social withdrawal, excessive aggression, over grooming and hyper-aggressiveness (Stevenson, 1983). The second is qualitatively abnormal, which includes behaviour patterns normally only expressed in captivity, and would include atypical postural movements, self mutilation (Hosey & Skyner, 2007), self clasping, cannibalism, sexual disorders, coprophagia, vomiting, eating of vomitus (Kuhar, 2008) and stereotypic movements (Stevenson, 1983). A specific type of abnormal behaviour in which the behaviour is repetitive and non-functioning is termed stereotypy (G. Mason, 1991). The presence of one or more stereotypies is a useful indicator of a sub-optimal or recently sub-optimal environment and considered as an indicator of poor welfare (Hughes & Duncan, 1988; G. Mason, 1991) although caution should be taken when using this in itself as an indicator of welfare. When other welfare indicators are considered stereotypies can in some instances, particularly in sub optimal environments, be associated with an improvement in welfare (G. Mason & Latham, 2004). There is even evidence of stereotypies in some farmed animals being associated with a reduction in cortisol levels (Redbo, 1993;
Vestergaard, Skadhauge, & Lawson, 1997).
1.3.3 Biological functioning The third approach associates animal welfare with the physical and mental wellbeing or biological functioning of animals. Under this approach welfare is reduced by disease, injury and malnutrition (Hughes & Curtis, 1997) and improved welfare is indicated by high levels of growth and reproduction, normal physiological and behavioural processes, and ultimately high rates of longevity and biological fitness (Barnett & Hemsworth, 1990; Duncan & Fraser, 1997). The loss of body weight is also indicative of bad welfare, although for some species this may be a part of an animals’ natural history, e.g. male cotton top tamarins (Saguinus oedipus) lose 10% of their body weight when they share in the carrying of young infants during the first 8 weeks of life (Achenbach & Snowdon, 2002). The biological functioning approach recognises that the welfare of the animal depends on its ability to cope with the response to incoming stimuli from the environment. Failure to cope will lead to a reduction in fitness, either by a reduction in life expectancy, a reduction in the number of offspring or an increase in inter-birth intervals. Furthermore, this approach refers to the state of an individual on a continuum from suffering to pleasure at any particular time throughout the animal’s life. It is easier to scientifically demonstrate changes in biological functioning, although it can be difficult to interpret conflicting measures (Duncan & Fraser, 1997). A range of physiological and biochemical indicators have been used, including heart and respiratory rate, the endocrine system and immunity (Moberg, 2000).
However, physiological indicators can also vary during routine biological functioning, thus it can be difficult to determine welfare based on these measurements alone (Appleby, 1999). The concept of stress has been influential in this field with physiological studies into the endocrine system, and in particular the HPA axis and immune system (Lane, 2006; Mormede, et al., 2007; Veissier & Boissy, 2007). Behavioural assessments can also be useful in the interpretation of levels of glucocorticosteroid hormones, which not only react to levels of stress, but can also be affected by physical activities such as locomotion and copulation (Toates, 1995). Validation of the stress response can also be attained by presenting an animal with a known stressor to ascertain its species-typical stress response and monitoring whether those same responses occur in other contexts (T. E. Smith, McGreerWhitworth, & French, 1998).
It is also possible to correlate measurable physiological or behavioural changes with subjective feelings. This can be done by subjecting an animal to a known stressor and then measuring physiological and behavioural changes. If in another context similar responses occur it could be inferred that the animal finds it correspondingly unpleasant (T. E. Smith, et al., 1998).
1.3.4 An integrative approach While all three approaches to animal welfare have their merits, in isolation they have limitations (Dawkins, 2004). The three approaches also do not always give the same conclusion. When this is the case, more information may lead to a consensus of opinion. However, the conclusion that is drawn will still be open to interpretation because it will depend on how much importance is attached to the different approaches in evaluating the welfare of the animal. One way to increase the objectivity to the three primary approaches in measuring animal welfare is to examine other potential indicators of sub optimal welfare.
While there are numerous methods available to measure particular aspects of animal welfare (Broom, 2007) and a great deal of progress has been made in this area over recent years, a checklist approach analysing a whole raft of physiological and psychological factors should be discouraged (Dawkins, 2004). There are difficulties in interpreting the results, as well as practical, financial and temporal constraints (D.
Fraser, 1995; Lane, 2006). Changes in various indicators may result from unpleasant subjective feelings, but they cannot be directly measured, and do not necessarily provide evidence of suffering. There could be limitations to such a global approach as responses may be dependent on a specific situation, or may only be relevant as short-term or long-term indicators. Furthermore, different measures of assessment may provide contradictory results with repeated assessments giving differing responses (G. Mason & Mendl, 1993).
An important consideration for animal welfare is the ability for an individual to have control over its environment, with poorer welfare if the animal does not have control (Bassett & Buchanan-Smith, 2007). Individual animals also give a high priority to the behaviours that promote and maintain their life conditions (Wiepkema & Koolhaas, 1992). Such behaviours imply learning to predict or control their position within their environment and if there are problems with these processes it could have welfare implications (Wiepkema & Koolhaas, 1993). Many relevant temporal and spatial relationships in nature have a degree of variability. While these may evoke a degree of novelty or uncertainty and could even result in a short term reduction in welfare, their range is normally within the coping capabilities of the individual and would not cause lasting harm. The ability of the individual to cope with some short term reduction in welfare makes it difficult to assess what the acceptable limits of an individual are within a captive environment (D. Fraser & Duncan, 1998).
1.4 Stress and its relationship to welfare
The social and physical environment likely provides a constant source of physical and emotional challenges or stressors to an animal and the animal must respond to each challenge either to remove it, or to adapt to cope with it. This in itself is not necessarily bad and can even be beneficial if it remains within the ability of the individual to cope (Wiepkema & Koolhaas, 1993). However, if the stress levels remain beyond the abilities of the individual to cope or adapt either within the short- or long-term, then its welfare will be affected (Broom, 2007). Therefore, stress refers only to situations when something challenges an individuals mental or physical capacity to cope, and poor welfare refers to the state of the animal when the individual is having difficulty coping (Webster, 2005a). Stress has such a profound impact on animal welfare it is essential that an understanding of the biological response to stress is developed (Moberg, 2000).
1.4.1 Definition of stress Like welfare, the term “stress” has been used broadly in biology and no clear universally accepted definition currently exists (Moberg, 2000). Indeed the word has been used to describe such a wide range of symptoms and levels of suffering that it has even been argued that it has become an essentially useless term (McEwen, 2000).
However, the widespread use of the term necessitates its continued use providing it is clearly defined (Morgan & Tromborg, 2007).
Broom (1999) defined stress as “an environmental effect on an individual which over-taxes its control systems and reduces its fitness or seems likely to do so” (p. 138). Stress has also been defined as a chronic disturbance of the processes that underlie adaptive behaviour, i.e. a long-term failure of regulation by systems that normally exhibit effective negative feedback (Toates, 1995). A similar view captures the definition as the experience of having internal or external demands that exceed an individual’s resources for responding to those demands (Danzter, 1991). The word ‘stress’ should be used for the aspect of poor welfare which involves the failure of that individual to cope (Broom, 1999). Consequences of stress can lead to reduction in general health, which could manifest itself as a reduction in growth rate, and a reduction in the immune system and in turn greater susceptibility to disease.
Moberg (2000) defined stress as the biological response elicited when an individual perceives a threat to its homeostasis. The threat is the ‘stressor’ that can be anything which changes the homeostasis of the animal, although this is an oversimplification as it does not take into account the daily physiological adjustments required to adapt to a changing environment (Goymann & Wingfield, 2004; McEwen & Seeman, 1999). The term stress also refers to both the stimulus that provokes a response as well as the resulting internal changes induced by the stimuli. For clarity, it has been suggested that the word stress should be avoided, and replaced with the terms stressor (the stimuli) and stress response (the change in internal state) (Creel, 2001) and this has been adopted in this study.
1.4.2 Stress response Hans Selye (1946) first identified the ‘General Adaptation Syndrome’ (GAS), to describe the common features of the physiological response of humans to a wide range of physical or physiological challenges he called ‘stressors’. In summary he proposed that a body would respond in a non specific, systematic response on exposure to any type of stress. However, largely due to the work of Mason (1971), it became clear that different stressors can evoke their own specific stress responses (behaviourally and physiologically), possibly resulting in the non-specific response, and that most stressors are characterised by an aspect of novelty that has a great psychological impact. More recently, the early view of a generalised non-specific stress response to all stressors, such as that initially proposed by Selye (1946), has been disproved (Wiepkema & Koolhaas, 1993).
Moberg (2000) identified three general stages in a stress response;
recognition of a stressor; the biological defence to the stressor; and the consequences of the response. It is the last stage that will determine whether the animal is experiencing distress. A ‘stressor’ could be an actual physical challenge to homeostasis, such as a change in temperature, physical restraint, or a threat to a change, such as an approach of a human, or stare of a dominant individual. Whether the stimulus is actually a threat is not important, it is the perception of the threat that is important. This is why psychological stressors can be damaging (McEwen, 2000).
A model of stress, including recognition, responses to and the consequences of stress is presented in Figure 1.1. The first stage of the stress response is the recognition of the threat by the central nervous system (CNS). The body then develops a biological response which involves a cascade of physiological events designed to prepare the body for a threat to its homeostasis, the ‘fight-flight’ response (Cannon, 1929, as cited by Moberg, 2000). This second stage consists of a combination of the four general stress responses (the behavioural response, the autonomic nervous system response, the neuroendocrine response or the immune response).
The behavioural response is normally the first reaction by an animal with an attempt to avoid the stressor by simply removing itself from the threat (Sapolsky, 2000). This is followed by the autonomic nervous system which controls a diverse number of biological systems, including changes in neurotransmitter levels, changes in the cardiovascular system, shutting down the gastrointestinal system, activating the exocrine glands and the adrenal medulla. These have a variety of effects including tachycardia, increases in the rate of respiration and increased glucose metabolism. However, as such effects are very specific, difficult to measure and relatively short in duration the autonomic nervous system has been of only limited interest in the study of an animal’s long term welfare (Moberg, 2000).
Figure 1.1 A model of biological response of animals to stress illustrating the three stages an individual experiences as a result of stress (modified from Moberg, 2000).