Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The detection and assessment of pain in animals is crucial to improving their welfare in a variety of contexts in which humans are ethically or legally bound to do so. Thus clear standards to judge whether pain is likely to occur in any animal species is vital to inform whether to alleviate pain or to drive the refinement of procedures to reduce invasiveness, thereby minimizing pain. We define two key concepts that can be used to evaluate the potential for pain in both invertebrate and vertebrate taxa. First, responses to noxious, potentially painful events should affect neurobiology, physiology and behaviour in a different manner to innocuous stimuli and subsequent behaviour should be modified including avoidance learning and protective responses. Second, animals should show a change in motivational state after experiencing a painful event such that future behavioural decision making is altered and can be measured as a change in conditioned place preference, self-administration of analgesia, paying a cost to access analgesia or avoidance of painful stimuli and reduced performance in concurrent events. The extent to which vertebrate and selected invertebrate groups fulfil these criteria is discussed in light of the empirical evidence and where there are gaps in our knowledge we propose future studies are vital to improve our assessment of pain. This review highlights arguments regarding animal pain and defines criteria that demonstrate, beyond a reasonable doubt, whether animals of a given species experience pain.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The two studies ask if behaviour may be altered by a noxious stimulus in the medium to long-term (e.g. Sneddon et al. 2014). They involved behavioural responses that could not be part of a nociceptive reflex because they could only occur some time after the noxious stimulus had stopped. ...
... The increased avoidance of light after shock is thus consistent with the idea that noxious stimuli cause a shift to risk aversion. This is consistent with a key prediction of pain in that we should see a change in behaviour that minimises the risk of further damage (Sneddon et al. 2014). Whilst this study and that of Fossat et al. (2015) are noted in the Crump et al.'s review, the focus is not on the behavioural change but on the physiological basis of that change. ...
... Bateson 1991), sometimes specifically for invertebrates (e.g. Elwood , 2019 or for both (Sneddon et al 2014). These lists have been offered as suggestions, or merely to organise reviews of current knowledge about different taxa (Sneddon et al 2014), or to suggest approaches that might prove useful (Elwood , 2019. ...
... One of the few positive results of pollution of the marine environment is the widespread use of glass, plastic, and metal waste for octopus shelter [51][52][53], sometimes allowing them to live in 'urbanized' seascapes [54]. Dark beer bottles are ideal for O. rubescens [55], tires for O. vulgaris [44]. Split coconut shells are light enough to be portable so that O. tetricus can imitate hermit crabs and actually take shelter with them when they forage on the sandy/mud substrate [56]. ...
... There is a widespread debate about whether and which animals can experience pain, as those with simpler nervous systems are often designated as having nociception, solely receiving the sensory component. Sneddon et al. [55] acknowledge this problem and suggest that many pieces of evidence can be accumulated to make a good case for true pain and thus valence in non-human animals. They suggest that there should be a neurobiological, physiological, and behavioral response to a noxious event, that this should result in avoidant and protective responses afterward, and that we should see subsequent changes in motivational state such as place preference and either analgesia self-administration or that the animal pay an energetic cost to access it. ...
... This sensitivity increase was abolished with anesthetic. Interestingly, octopuses showed immediate arm grooming near the injury and persistent arm guarding, criteria expected as part of affective responses [55]. A different octopus species, O. bocki, was given a presumably painful injection of acetic acid in the arm and then confined in a previously positively conditioned chamber [62]. ...
Article
Full-text available
Octopuses may demonstrate perceptual richness, neural unity, temporality, and finally, valence or affective evaluation, as the neural basis for consciousness. Octopuses attach a positive valence to food as ‘specializing generalists’ with long-term learning and flexible choices. They value shelter, yet modify, adapt and even transport it where necessary. They attach a negative valence to what may be described as pain, monitoring and protecting the damaged area and learning to associate locations with pain relief. Finally and surprisingly, octopuses attach a negative value to uncertainty so that they explore their environment before exploiting certain aspects of it and even exhibit motor play. This series of four papers, culminating in the present one, demonstrates in detail why the Cambridge Declaration of Consciousness has suggested octopuses might have the substrate for consciousness, although it is likely not similar to or as complex as that shown by ‘higher’ vertebrate lineages.
... Nociception is the neural process of encoding noxious stimuli and is typically accompanied by a reflex withdrawal response away from the potentially injurious stimulus [1]. If damage occurs this can elicit the experience of pain, which is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage [2]. ...
... All animals are considered capable of nociception, since animals must avoid injury and be able to detect potentially damaging stimuli via nociceptive mechanisms in order to survive [3]. Experiencing pain is detrimental to animal welfare; however, scientific evidence is needed to confirm that pain occurs in an animal [1]. Pain perception in animals must be assessed by methods other than human languages, including an analysis of physiological signs (heart rate, respiratory rate, and body temperature) [4], pain measurement tools (Numerical Rating Scale and Glasgow Composite Measure Pain Scale) [5,6], the measurement of neural activity [7], and behavioural changes that are indicative of pain rather than a nocifensive reflex [1]. ...
... Experiencing pain is detrimental to animal welfare; however, scientific evidence is needed to confirm that pain occurs in an animal [1]. Pain perception in animals must be assessed by methods other than human languages, including an analysis of physiological signs (heart rate, respiratory rate, and body temperature) [4], pain measurement tools (Numerical Rating Scale and Glasgow Composite Measure Pain Scale) [5,6], the measurement of neural activity [7], and behavioural changes that are indicative of pain rather than a nocifensive reflex [1]. In animals, if the injury is accompanied by a negative emotional component, subsequent behaviour should be altered for a prolonged period, and based upon this evidence, we can infer that the animal experiences the discomfort associated with pain [1,3]. ...
Article
Full-text available
Nociception is the neural process of encoding noxious stimuli and is typically accompanied by a reflex withdrawal response away from the potentially injurious stimulus. Studies on nociception in cephalopods have so far focused on octopus and squid, with no investigations to our knowledge on cuttlefish. Yet, these are an important species both in scientific and commercial use. Therefore, the present study demonstrated that a standard pain stimulus, acetic acid, induced grooming behaviour directed towards the injection site in cuttlefish and that the injection of lidocaine reduces grooming behaviours in acetic-acid-injected cuttlefish. Wound-directed behaviour demonstrates that the animal is aware of the damage; thus, when subjecting these animals to any painful treatments in the laboratory, researchers should consider alleviating pain by the administration of pain-relieving drugs.
... Due to the inability of animals to verbally communicate their experiences to humans, and the fact that pain and nociception may occur in the absence of one another (Loeser and Melzack, 1999*;Shriver, 2006*;Wall, 1979*), the presence of an emotional component of pain in animals is often contested (Bermond, 2001*;Rose et al., 2014*). Nonetheless, pigs are recognised as sentient beings by law within the European Union (The Council of the European Union, 1997) and there is a general (though not complete) consensus within the scientific community that mounting evidence suggests animals, and mammals in particular, are capable of experiencing both nociception and pain, albeit not identically to humans, and only when certain physiological and behavioural criteria have been satisfied (Bateson, 1991*;Elwood, 2012*;Flecknell et al., 2011*;Gentle, 2011*;Mason and Mendl, 1993*;Shriver, 2006*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... changes in heart rate, plasma corticosteroid concentrations, etc.) in response to noxious stimuli. These criteria are considered important evidence of the capacity to feel pain and are fulfilled by mammals, including pigs, and at least some species within several other taxa (Elwood, 2012*;Gieling et al., 2011*;Herskin and Di Giminiani, 2018 † ;Sneddon et al., 2014*;Viñuela-Fernández et al., 2011 † (see also sections 1.2.6-1.2.8)). In broad terms, behavioural indicators of pain include avoidance learning, trade-offs between responses to pain and other strongly motivated behaviours, self-stimulation of injury sites, protective / defensive behaviours, changes in sleeping, feeding, social, or explorative behaviours, vocalisations, appearance of abnormal behaviours, and behavioural changes in response to analgesics and attentional shifts (Bateson, 1991*;Dawkins, 1990*;Elwood, 2012*;Gentle, 2001;Herskin and Di Giminiani, 2018 † ;Ison et al., 2016*;Prunier et al., 2013*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... These criteria are considered important evidence of the capacity to feel pain and are fulfilled by mammals, including pigs, and at least some species within several other taxa (Elwood, 2012*;Gieling et al., 2011*;Herskin and Di Giminiani, 2018 † ;Sneddon et al., 2014*;Viñuela-Fernández et al., 2011 † (see also sections 1.2.6-1.2.8)). In broad terms, behavioural indicators of pain include avoidance learning, trade-offs between responses to pain and other strongly motivated behaviours, self-stimulation of injury sites, protective / defensive behaviours, changes in sleeping, feeding, social, or explorative behaviours, vocalisations, appearance of abnormal behaviours, and behavioural changes in response to analgesics and attentional shifts (Bateson, 1991*;Dawkins, 1990*;Elwood, 2012*;Gentle, 2001;Herskin and Di Giminiani, 2018 † ;Ison et al., 2016*;Prunier et al., 2013*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... To address questions of invertebrate sentience, we must rely (at least partly) on behavioural and cognitive markers, coupled with our knowledge about the animal's nervous system (e.g., Smith & Boyd, 1991;Bateson, 1991;AHAW, 2005;Varner, 2012;Sneddon et al., 2014;Broom, 2014). Hypotheses about what sentience does-its adaptive value-can guide the choice of markers (Lindahl, 1997). ...
... Whilst our behavioural criteria are more concrete than Smith & Boyd's (1991), they are less extensive than those listed by Sneddon et al. (2014). This avoids treating very similar behaviours as independent lines of evidence. ...
... Outside our criteria, other lines of evidence for animal sentience have been proposed. Of particular relevance, Sneddon et al. (2014) nominated physiological stress responses to noxious stimuli. Elwood and Adams (2015) showed that, compared to nonshocked controls, shore crabs (Carcinus maenas) exposed to electric shocks had higher haemolymph lactate levels -a physiological measure of stress. ...
Article
We outline a framework for evaluating scientific evidence of sentience, focusing on pain experience. It includes eight neural and cognitive-behavioural criteria, with confidence levels for each criterion reflecting the reliability and quality of the evidence. We outline the rationale for each criterion and apply our framework to a controversial sentience candidate: decapod crustaceans. We have either high or very high confidence that true crabs (infraorder Brachyura) satisfy five criteria, amounting to strong evidence of sentience. Moreover, we have high confidence that both anomuran crabs (infraorder Anomura) and astacid lobsters/crayfish (infraorder Astacidea) meet three criteria—substantial evidence of sentience. The case is, as yet, weaker for other infraorders, such as penaeid shrimps, highlighting important research gaps. Having demonstrated our framework’s application to decapod crustaceans, we hope that future research will apply it to other taxa.
... This is the approach typically taken by those arguing that fish do feel pain. For example, Sneddon et al. (61) developed a list of behavioral, and also physiological, responses (e.g., rubbing, limping, or guarding; self-administration of analgesia; paying a cost to avoid a stimulus; etc.) that they argue would demonstrate pain perception in mammals and so should be assumed to do so in fish. However, this "theory neutral", inductive approach is also problematic. ...
... For one, S.P.U.D. subjects show diverse unconditioned behavioral responses to noxious stimuli, including avoidance or wound attendance, making it hard to argue that similar responses in fish require awareness or demonstrate true pain rather than mere nociception [cf. e.g., (61,187), citing (188) on rocking in trout and (189) on tail-beating in zebrafish]. Furthermore, in S.P.U.D. subjects such responses can be modulated, including by analgesics. ...
... These means that contrary to several authors [c.f. e.g., (61,187), citing (188,190)], the modulation of fish responses to noxious stimuli by analgesics cannot be said to indicate pain over nociception; and the same applies to their modulation by food deprivation [c.f. e.g., (61,187), citing (191)] or conspecific presence [c.f. ...
Article
Full-text available
Debates around fishes' ability to feel pain concern sentience : do reactions to tissue damage indicate evaluative consciousness (conscious affect), or mere nociception? Thanks to Braithwaite's discovery of trout nociceptors, and concerns that current practices could compromise welfare in countless fish, this issue's importance is beyond dispute. However, nociceptors are merely necessary, not sufficient, for true pain, and many measures held to indicate sentience have the same problem. The question of whether fish feel pain – or indeed anything at all – therefore stimulates sometimes polarized debate. Here, we try to bridge the divide. After reviewing key consciousness concepts, we identify “red herring” measures that should not be used to infer sentience because also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa (P); spines disconnected from brains (S); decerebrate mammals and birds (D); and humans in unaware states (U). These “S.P.U.D. subjects” can show approach/withdrawal; react with apparent emotion; change their reactivity with food deprivation or analgesia; discriminate between stimuli; display Pavlovian learning, including some forms of trace conditioning; and even learn simple instrumental responses. Consequently, none of these responses are good indicators of sentience. Potentially more valid are aspects of working memory, operant conditioning, the self-report of state, and forms of higher order cognition. We suggest new experiments on humans to test these hypotheses, as well as modifications to tests for “mental time travel” and self-awareness (e.g., mirror self-recognition) that could allow these to now probe sentience (since currently they reflect perceptual rather than evaluative, affective aspects of consciousness). Because “bullet-proof” neurological and behavioral indicators of sentience are thus still lacking, agnosticism about fish sentience remains widespread. To end, we address how to balance such doubts with welfare protection, discussing concerns raised by key skeptics in this debate. Overall, we celebrate the rigorous evidential standards required by those unconvinced that fish are sentient; laud the compassion and ethical rigor shown by those advocating for welfare protections; and seek to show how precautionary principles still support protecting fish from physical harm.
... In other words, conserved opioid receptors are evidence for conscious pain because they are a conserved factor in the pain system that suggests the conservation of other used as evidence--at varying levels of evidential basis--for the existence of conscious pain states [4,5]. Some authors have expressed skepticism of opioid receptors as evidence for conscious pain states [6,7], but nonetheless use them as a point of tenuous evidence. Others have listed opioid receptors as being one of the many biological facets that taken individually are not enough to constitute evidence for conscious pain states [8], but when taken holistically could. ...
... For the reasons mentioned, this is not best practice, as the functional aspect is under question, and the conservation aspect relates to other neurophysiological structures. Others acknowledge the tenuous evidence of opioid receptors, but keep them on evidential lists for conscious pain states [6,7], likely because of the analogy by conservation, which is a mistake, as evidence that merely points elsewhere should be discarded in favor of looking in exactly the place the evidence points at. Even if we modify the evidential criterion from "presence of opioid receptors," to "presence of a pain inhibitory system," this remains a problem for the reasons already mentioned. ...
... Sentientism seems to supply a straightforward criterion: According to sentientism, when we need to know whether a being has PMP, we should test whether it is sentient. According to this criterion, we should resort to the flourishing research programs on animal (Birch et al., 2020;Sneddon et al., 2014) and artificial consciousness (Dehaene et al., 2017;Elamrani & Yampolskiy, 2019;Tononi & Koch, 2015) when we are in doubt regarding the moral status of animals or AI. ...
... According to one interpretation(Shevlin 2020a), the literature on animal pain frequently evades explicit mention of consciousness (e.g.,Sneddon et al., 2014) due to its perceived intractability. If so, then they subscribe to the epistemic objection and propose pain or negative affective states more generally as an alternative criterion of PMP.I thank an anonymous reviewer for pointing out that Coeckelbergh (2009) makes an epistemic argument similar to the ones presented here in the context of the debate on the distribution of moral agency. ...
Article
Full-text available
According to a common view, sentience is necessary and sufficient for moral status. In other words, whether a being has intrinsic moral relevance is determined by its capacity for conscious experience. The epistemic objection derives from our profound uncertainty about sentience. According to this objection, we cannot use sentience as a criterion to ascribe moral status in practice because we won’t know in the foreseeable future which animals and AI systems are sentient while ethical questions regarding the possession of moral status are urgent. Therefore, we need to formulate an alternative criterion. I argue that the epistemic objection is dissolved once one clearly distinguishes between the question what determines moral status and what criterion should be employed in practice to ascribe moral status. Epistemic concerns are irrelevant to the former question and—I will argue—criteria of moral status have inescapably to be based on sentience, if one concedes that sentience determines moral status. It follows that doubts about our epistemic access to sentience cannot be used to motivate an alternative criterion of moral status. If sentience turns out to be unknowable, then moral status is unknowable. However, I briefly advocate against such strong pessimism.
... Bees' ability to trade-off heat avoidance against sucrose preference indicates that conditioned motivational stimuli can influence nocifensive behavior, and the trade-off is mediated in the central nervous system (10,11). As in other animals, such an ability is viewed as consistent with the capacity to feel pain (12)(13)(14), although because of the subjective nature of pain experience, it is not a formal proof. Nonetheless, given the potential ethical implications of our research, the precautionary principle dictates that the possibility of insect pain and suffering should be taken seriously in insect research laboratories as well as insect conservation (14,15). ...
... As in other animals, such an ability is viewed as consistent with the capacity to feel pain (12)(13)(14), although because of the subjective nature of pain experience, it is not a formal proof. Nonetheless, given the potential ethical implications of our research, the precautionary principle dictates that the possibility of insect pain and suffering should be taken seriously in insect research laboratories as well as insect conservation (14,15). ...
Article
Full-text available
Insects are traditionally thought to respond to noxious stimuli in an inflexible manner, without the ability to modulate their behavior according to context. We investigated whether bumblebees’ attraction to high sucrose solution concentrations reduces their avoidance of noxious heat. Bees were given the choice between either unheated or noxiously heated (55 °C) feeders with different sucrose concentrations and marked by different colors. Bees avoided noxious feeders when the unheated feeders contained high sucrose concentrations, but progressively increased feeding from noxious feeders when the sucrose concentration at unheated feeders decreased. This shows a motivational trade-off of nociceptive responses. Bees used learned color cues for their decisions, and thus the trade-off was based on processing in the brain, rather than just peripheral processing. Therefore, bees can use contextual information to modulate nociceptive behavior. This ability is consistent with a capacity for pain experiences in insects.
... Although we focus on visual consciousness, our discussion might be generalized to other sensory modalities; similar issues concerning pain consciousness in fish have been vigorously debated. Some authors have argued that fish experience pain (Braithwaite 2010;Brown 2015;Sneddon et al. 2014;Sneddon 2011). Others have countered that fish lack a neocortex and, therefore, do not experience pain (Key 2015(Key , 2016Rose et al. 2014;Rose 2007). ...
... Such descriptions of agency can be found in many discussions in favor of the existence of sensory consciousness, such as pain, in a wide range of animal species, that emphasize flexible, complex, and adaptive behaviors (e.g., Braithwaite 2010; Brown 2016; Godfrey-Smith 2016a; Mikhalevich and Powell 2020; Powell 2020;Sneddon et al. 2014;Sneddon 2003;2011). Content courtesy of Springer Nature, terms of use apply. ...
Article
Full-text available
Feinberg and Mallatt, in their presentation of neurobiological naturalism, have suggested that visual consciousness was acquired by early vertebrates and inherited by a wide range of descendants, and that its neural basis has shifted to nonhomologous nervous structures during evolution. However, their evolutionary scenario of visual consciousness relies on the assumption that visual consciousness is closely linked with survival, which is not commonly accepted in current consciousness research. We suggest an alternative idea that visual consciousness is linked to a specific class of agency, consequently justifying their phylogenetic claim. We also examine the implication of their phylogenetic claim: visual consciousness is homologous across vertebrates, but its neural basis is not. This apparent incongruence illustrates a general phenomenon of homology, and that the resulting hierarchical view of visual consciousness and its neural basis can be straightforwardly accommodated by neurobiological naturalism. Throughout these discussions, we aim to address the potential theoretical issues in neurobiological naturalism and refine the picture illustrated by Feinberg and Mallatt regarding phylogenetic distribution and trajectories of visual consciousness.
... These measures can be insensitive, often discount the long-term effects of pain, and overlook the cognitive and psychological components of pain (Weary et al., 2006;Steagall et al., 2021;Tschoner, 2021). More recently, the psychological and affective state elements of pain in livestock have been studied to assess the changes in cognition, motivation and decision-making that are known to occur due to higher-order processing of nociceptive signals (Neave et al., 2013;Sneddon et al., 2014;Adcock and Tucker, 2020a;Lecorps et al., 2020;Kleinhenz et al., 2021). ...
... Changes in the sympathetic system can be measured through autonomic responses including heart rate, heart rate variability (von Borell et al., 2007;Stubsjøen et al., 2009), blood pressure (Peers et al., 2002), respiratory rate and ocular temperature (Harris et al., 2021;Stock et al., 2021). These measures are more sensitive for mild pain compared to behavioral assessment and HPA axis changes (Peers et al., 2002), particularly in prey species (Weary et al., 2006;Sneddon et al., 2014). However, they are not specific to pain and can change dramatically with stress (Weary et al., 2006) or other forms of disease such as septic shock or blood loss (Johnson, 2016). ...
Article
Full-text available
Communication between the central nervous system (CNS) and the immune system has gained much attention for its fundamental role in the development of chronic and pathological pain in humans and rodent models. Following peripheral nerve injury, neuroimmune signaling within the CNS plays an important role in the pathophysiological changes in pain sensitivity that lead to chronic pain. In production animals, routine husbandry procedures such as tail docking and castration, often involve some degree of inflammation and peripheral nerve injury and consequently may lead to chronic pain. Our understanding of chronic pain in animals is limited by the difficulty in measuring this pathological pain state. In light of this, we have reviewed the current understanding of chronic pain in production animals. We discuss our ability to measure pain and the implications this has on animal welfare and production outcomes. Further research into the neuroimmune interface in production animals will improve our fundamental understanding of chronic pain and better inform human clinical pain management and animal husbandry practices and interventions.
... Recently there has been much discussion between those who do not believe that fish feel pain (eg, Browman et al. 2019;Diggles 2019;Diggles & Browman 2018;Key 2015;Key et al. 2017;Rose 2002;Rose et al. 2014), and those who believe that there is sufficient evidence of fish pain (eg, Broom 2014;Sneddon, Elwood, Adamo, & Leach 2014;Sneddon et al. 2018). Those who believe we have the evidence already have recently tended to draw on a set of criteria that focus on functional aspects of pain -the role pain plays in relation to motivation, learning, physiological responses, and behaviour. ...
... They attempt to demonstrate pain as opposed to mere reflex or damage-avoidance partly by testing how fish interact with anaesthetics and analgesia. Their criteria are not solely functional, however, in that nociceptive processing must be done centrally, and by the same areas of the central nervous system that regulate motivated behaviour (see, eg, Sneddon et al. 2014;Broom 2014;. ...
... Many scholars have studied biological, cognitive and emotional characteristics of nonhuman animals, comparing them to those of humans, in order to determine the moral status of nonhuman animals (see DeGrazia, 1993;Garner, 2005;Leahy, 1994;Murno, 2005;Murray, 2008;Regan, 1983). In this block of literature, the capacity of nonhuman animals to experience pain (Bermond et al., 1997;Rollin, 2011;Sneddon, Elwood, Adamo & Leach, 2014) and ...
... Singer (2002), as the central figure Bekoff, Allen & Burghard, 2002;Edelman & Seth, 2009;Griffin, 2001;Gutfreund, 2017;Rollin, 2017) and the capacity to experience pain (see Allen, 2004;Bermond et al., 1997, pp. 125-144;Rollin, 2011;Sneddon, Elwood, Adamo & Leach, 2014) as important attributes for (not) assigning animals with moral worth and consideration. One can rightly call in question this approach to moral epistemology as it oversimplifies the phenomenon of ethics and builds its judgements upon narrow facts or assumptions, regardless the context. ...
Thesis
Full-text available
Human-nonhuman animal relationship in tourism reveals a dichotomy between tourism prosperity and ethical concerns. For long nonhuman animals have been involved in different forms of tourism activities with functions ranging from entertainment and profit generation to marketing and education. At the same time, recent talks of animal rights and welfare call to ponder on the moral aspects of nonhuman animal involvement. The currently accelerating wave of social awareness of anthropogenic impacts on our globe’s ecosystems only further pushes both researchers and society to reassess human-nonhuman animal relationship within tourism. Within the field of tourism studies, human-nonhuman animal relationship has been predominantly researched from normative ethics perspectives and viewed either through the context of animal captivity or tourist-animal relationship, with little research taking the worker-animal relationship perspective. Theoretically, this study draws upon the normative discourse of academic literature and major animal ethics theories, joining a critical paradigm which highlights the need to shift the research focus away from justification or application of absolute normative principles towards the inquiry of morally problematic situations. It suggests a turn from a monistic viewpoint towards more intersubjective-interpretive approach. This study aims to explore how cognitive and emotional attributes of animal workers in Northern Europe facilitate moral deliberations of the use of nonhuman animals in tourism. After conducting participatory and non-participatory observations during winter period of 2019-2020, the empirical data was collected through semi-structured in-depth interviews with 6 tourism animal workers in Finnish Lapland in the winter period of 2020-2021. The data was then analysed through the qualitative interpretive content analysis to facilitate the exploratory disposition of the study. The empirical data of the study indicates that emotional motivations and emotional relationship with nonhuman animals facilitate moral positioning of nonhuman animal labour. At the same time, tourism animal workers utilize certain emotional management mechanisms to cope with the difficulties and specifics of the job. Overall, the results of the study on the theoretical level suggest reflective equilibrium as an approach to achieve an endpoint of moral inquiry.
... Again, extrapolation from human cases to other animals may not be well supported (see e.g. Ginsburg and Jablonka 2019, 98), and disagreement over such underlies recent debates about the presence of fish consciousness (Key 2016;Sneddon et al. 2014). However, even if we use the biological justifications described above to accept that these are useful markers of consciousness in biological organisms, they are too substrate-and context-specific to be considered useful across the board. ...
... Like the lists that Elwood and others have proposed (e.g., Sneddon et al. 2014), our framework aims to organise pre-existing evidence using well-accepted indicators. Building on those lists, the framework includes confidence levels (to assess the strength of evidence) and an approximate grading scheme (to facilitate cross-species comparisons and hypothesis-based evaluations of the evidence). ...
... There are general behavioural patterns associated with poor welfare states (including diseases, infections, fear, pain or negative cognitive states) that are transversal to several taxa (Kent et al., 1992;Sneddon, 2020;Sneddon et al., 2014). The neural networks underpinning these behaviours have even been recently identified (Ilanges et al., 2022). ...
... It is now widely accepted that animals can experience not only negative emotional states and pain (Sneddon et al., 2014), but also positive emotional states (de Vere & Kuczaj, 2016;Birch et al., 2021). Although traditionally, animal welfare science focus has been on pain and suffering, a recent paradigm shift is also addressing quality of life in a broader sense, seeking an understanding of animals' positive affective experiences (Duncan, 1996;Boissy et al., 2007). ...
Article
Full-text available
Advances in animal motion tracking and pose recognition have been a game changer in the study of animal behavior. Recently, an increasing number of works go ‘deeper’ than tracking, and address automated recognition of animals’ internal states such as emotions and pain with the aim of improving animal welfare, making this a timely moment for a systematization of the field. This paper provides a comprehensive survey of computer vision-based research on recognition of pain and emotional states in animals, addressing both facial and bodily behavior analysis. We summarize the efforts that have been presented so far within this topic—classifying them across different dimensions, highlight challenges and research gaps, and provide best practice recommendations for advancing the field, and some future directions for research.
... However, short-term reactions such as changes in respiratory rate and body posture can be assessed (International Whaling Commission, 2020). Long-term impacts of pain in animals have been suggested, such as changes in body weight and steroid hormones, but these are much more difficult to document (Sneddon et al., 2014). ...
... Animals' daily food consumption is often considered as a reliable indicator of welfare state (Johnson, 2002;Millman, 2007;Sneddon, Elwood, Adamo, & Leach, 2014), and a lack of appetite is often the sign of a serious health or welfare issue in captive odontocetes (Waples & Gales, 2002). In addition, participation during training sessions has been shown to be a useful parameter to assess dolphin welfare Delfour et al., 2020). ...
Article
Full-text available
Qualitative ratings are increasingly used to assess animal welfare. We investigated the associations between daily caretakers' ratings of individuals' behavioral style, behavior during free time, participation during training sessions, and environmental variables in captive Yangtze finless porpoises, East-Asian finless porpoises, and bottlenose dolphins. Associations between caretakers' ratings and behavior were found, including social swimming, fast swimming, play, interaction with humans, and agonistic and socio-sexual interactions. Ratings were also associated with participation during training sessions and food intake. Social separation, transport to a new pool, high visitors' density, and holding of a sick conspecific were associated with ratings indicating a deteriorated human-animal relationship, a lower inter-est/fear of the environment, and/or a higher social cohesion depending on the group. Through principal component analyses, new variables that represented both caretakers' ratings and behavior and that could be used for an easier interpretation of the data for welfare monitoring within each group were extracted. Caretaker ratings and behavior should be used as a complement to previously validated indicators to detect changes in welfare state and understand the potential causes of these changes.
... Apart from a small number of commercially cultured species, little is known about their general condition during laboratory maintenance or even their survival. These data, however, have become increasingly important as awareness of decapod welfare has vastly increased, with multiple review articles emerging as a result [5,14,38,39]. Many of these reviews, the primary literature therein, and subsequent commentaries), e.g., [40] suggest the need for increased animal welfare protection for large crustaceans, e.g., [41][42][43][44]. ...
Article
Full-text available
The wide geographic distribution, large size and ease of capture has led to decapod crustaceans being used extensively in laboratory experiments. Recently in the United Kingdom decapod crustaceans were listed as sentient beings, resulting in their inclusion in animal care protocols. Ironically, little is known about how captive conditions affect the survival and general condition of wild decapod crustaceans. We used the green shore crab, Carcinus maenas, to investigate the effects of stocking density and shelter on survival and vitality indices during a 6 month period in the laboratory. Neither stocking density nor the presence of shelter affected survival. Stocking density also had no effect on the vitality indices (limb loss, claw strength, BRIX, righting time, leg flare and retraction). The presence of shelter did affect the number of limbs lost and the leg retraction response, but had no effect on the other vitality indices. All vitality indices changed, and mortality increased over time, independent of treatment: this became most apparent after 8 to 11 weeks storage in the laboratory. This decline in condition may have been due to repeated handling of the crabs, rather than the stocking conditions. In support of this, untracked, non-handled (control) individuals sustained a 4% mortality rate compared with 67% mortality in experimental crabs during the 6 month period. Although simple experimental monitoring of crabs with biweekly vitality tests only produced transient short-term stress events, the repeated handling over time apparently led to a cumulative stress and a deterioration in animal health. Bringing wild crustaceans into the laboratory and holding them, even with modest experimental manipulation, may result in high mortality rates. Researchers and animal care committees need to be aware that wild captive invertebrates will respond very differently to laboratory-bred vertebrates, and plan experiments accordingly.
... Does the wriggling of fish indicate their suffering? The counterargument is that reflexive behaviors (cockroaches scampering to avoid sudden light) are not foolproof pain indicators [29]. In fact, the nervous systems of some animals are not sophisticated enough to carry pain information. ...
Chapter
Full-text available
Empathy for animal suffering can be powerful, but it varies across animal species. In fact, some people empathize as much (or more) with the suffering of certain animals than they do with human suffering. Beginning with Paulhus and Dean, we review research comparing empathic reactions to a diverse array of animal species, as well as to selected humans. Those authors coined the term phyloempathic hierarchy to describe the differential empathy that humans feel toward different species. Sophisticated scaling techniques were applied to determine the unique drivers of empathic responses. Overall, four animal characteristics (the “Big Four”) appeared to drive empathic responses: (1) Perceived intelligence, (2) size, (3) esthetic appeal, and (3) lack of harmfulness. Ranking high were monkeys, elephants, dogs, and cats. Younger versions of the same species (e.g., kittens vs. cats) elicited even more empathy. Sharks, cockroaches, and snakes drew the least empathy. Those results have been replicated across 40 years of research from many laboratories and many countries. This hierarchy presents a challenge to relying on empathy in decisions regarding the treatment of animals. Bottom line: The phyloempathic hierarchy resembles but deviates from the phylogenetic hierarchy.
... Opioids combine reversibly with specific receptors in the brain, spinal cord, and periphery, altering the transmission and perception of pain. In addition to analgesia, opioids can induce other CNS effects that include sedation, euphoria, dysphoria, and excitement (Sneddon et al., 2014). ...
Article
Full-text available
Animal pain management is an important aspect in veterinary medicine.Trauma, illness and surgery can all result in acute pain and good management ofpain is required for animal welfare (i.e., Health, physical and mental wellbeing).Newer classes of drugs are emerging for the management of pain which has lesserside effects and more efficacy than older drugs which were used against pain.Combination of two or more drugs has been proved to be more effective for the management of pain than the single drug usage. Selection of the most suitable drug combination is based on the severity of pain, effectiveness of the drug and also health status of the animal. Management of animals that are under pain needs a combination of good nursing, nondrug therapies (for example, ice packs or heat,bandaging and physical therapy) and drug treatments. The article reviews aboutthe classes of drugs which are used for the management of acute and chronic painin animals, their most common side effects, and the treatment regimen for differentclass of drugs. It is aimed to guide the veterinary practitioner to select and dose the animals with effective analgesics for the management of pain. Keywords:Analgesics, Animal welfare, NSAIDs, Opioids, Pain management
... Nociception is not pain. But the situation may be worse for the Penaeidae because the authors' high confidence level that Penaeidae have nociceptors is not borne out by any of the studies they cite and is questioned by three of them (Puri and Faulkes, 2010;Sneddon et al., 2014;Walters, 2018). With respect specifically to the Penaeidae, the evidence Crump et al. offer seems to be that "nociceptors are widespread across the animal kingdom" and "decapod crustaceans" are "a sister group" to insects, known to have nociceptors. ...
... Pain intensity is estimated based on existing welfare indicators (e.g., behavioral, physiological, neurological [1,6]), as well as knowledge of the importance of the pain signal to promote adaptive behaviors and of the pain-generating mechanisms involved in each challenge. Pain is an influential force in evolution, a warning signal of real or perceived danger that must be noticeable enough to change behavior and prevent survival and reproduction from being compromised [14,[17][18][19]. The greater the threat, the more intense the signal should be [20,21]. ...
Preprint
We describe a recently developed approach to quantify welfare loss in animals, the Cumulative Pain metric. It combines the two most relevant dimensions of negative affective experiences: intensity and duration. The metric enables estimating the time individuals spend in negative affective states of a physical or psychological nature (operationally referred to simply as ‘pain’) of different intensities as the result of one or more challenges (e.g., diseases, injuries, deprivations). A new notation protocol (the Pain-Track) is used in which the duration of the experience is represented along the horizontal axis and intensity is represented by four categories in the vertical axis. Pain experiences are partitioned into temporal segments, where hypotheses for the experienced duration and intensity are proposed based on existing welfare indicators (e.g., neurophysiological, behavioral, anatomical, evolutionary). This structure forces transparency about assumptions and uncertainties, highlights knowledge gaps, and enables estimates to be continuously adjusted. Because the Cumulative Pain metric is based on parameters with a broadly common biological meaning, it provides the much needed interoperability among assessments of animal welfare. It enables comparing the impact of practices and living conditions, policies and interventions, and the calculation of welfare footprints of animal-sourced products using a universal measurement unit.
... Birds display increased heart rate and withdrawal behaviours after being exposed to negative stimuli. The administration of morphine has been shown to reduce animals response to noxious heat in quails (Sneddon, 2014). Finally, Tye (2016) described how there are significant and interesting commonalities between insect brain structures and those of mammals. ...
Article
Animal research remains an important part of science with 2.88 million procedures being carried in 2019 in the UK. Although the number of animals used is declining each year, this is still a significant level of animal use at a time when our understanding of animal sentience is ever increasing. This research work explores the construction of important issues such as open science, animal sentience and culture of care and how these are potentially being seen in terms of animal research ethics responsibilities. Through the lens of empirical ethics, this study explores various actors’ awareness and construction of animal sentience, transparency in reporting standards, and perceptions of a culture of care. Previous studies have focused on these, though little research has been done to examine how institutions respond to the transparency agenda and then link this to researchers’ views of animal sentience and culture of care. This study is being conducted at an important time when the UK government has asked for a public policy review of the current standing on animal usage in research and alongside the introduction of new UK animal welfare legislation which formal recognises animals as sentient. This study comprises of three empirical research streams focusing on an analysis of institutions compliance with the UK Concordat on Openness in Animal Research. The first of which is the assessment of outwards facing animal research information on university webpages. Secondly, an institutional survey targeting university animal research contact points and finally, a survey of researchers within a research network were completed. A thematic analysis was conducted on these data to draw out key themes prevalent across the responses. This work has identified that although there is overall compliance with a number of the core elements of the Concordat, for the majority of the institutes examined, there are still a number of gaps and areas of improvement that the research community should address. For example, clarification and potential standardisation of the definition of the concept of sentience, aiding in translatability. The league table generated in order to allow for comparison between research intensive universities could be used to evaluate compliance to the Concordat and even published to encourage a comparative spirit that may foster improvements and drive transparency across the sector. Perspectives provided by the researchers also indicated a desire to see improvements in overall animal care as well as specific aspects such as animal monitoring technologies. Further work should be done to explore more in-depth perspectives of these important ethical concepts as this may support further reflection on ethical responsibilities and improvements in animal use in experimentation. The recommendations from this study represent small changes in what will continue to be a long path, which should see gradual but sustained advancement and improvement in animal experimentation practice and policies.
... As insects display a diversity of species-specific and complex behavioural responses to the surrounding environment (Hoy, 2019), it is important to understand the relevance of such behavioural responses as indicators of insect welfare. In other words, behavioural responses can indicate 'discomfort' and can cause long-term behavioural changes (Sneddon et al., 2014), and as such, behavioural traits can be used to evaluate insect welfare (Horvath et al., 2013). Insect welfare is a recent concept and underexplored compared to welfare of other animals (Boppré and Vane-Wright, 2019;Van Huis, 2021). ...
Article
Full-text available
The mass rearing of insects as animal feed is a new and rapidly growing component of circular agriculture, which offers the opportunity to develop it in such a way that it promotes insect health and welfare. Behaviour is an important indicator of animal performance and welfare. In this review, we synthesise the current behavioural knowledge on two saprophytic dipteran species that are increasingly being used as mini-livestock, the black soldier fly (Hermetia illucens) and the housefly (Musca domestica). We evaluate which behaviours need to be considered to optimise insect production and welfare under mass-rearing conditions. We distinguish between the different life stages (adults and larvae), and describe their feeding behaviour, social interactions (adult mating, larval aggregation), oviposition behaviour and possible cannibalism. For each species, we review what is known about these behaviours in natural environments, and how this is affected by abiotic factors or interactions with conspecifics and heterospecifics. We also address how the flies’ microbiome and pathogens can influence various aspects of behaviour. Notable differences in natural behaviours between the two species, such as their courtship and mating behaviour and the larval distribution within feed substrates are identified. These behavioural differences have important implications for how we should rear the two fly species in industrial settings, as a mismatch in mass-rearing conditions may induce environmental stress or compromise insect productivity and welfare. Escape behaviour, larval aggregation behaviour, possibly cannibalism in the larval stage and mating frequency and reproduction rate are identified as behaviours providing information on welfare of larval and adult flies. Finally, a number of aspects are identified for which behavioural knowledge is currently still sparse, while this may be important to safeguard insect welfare. We conclude with recommendations for future research to promote insect welfare.
... Although scientists often emphasise what is still unknown, empirical research obviously reveals some information about animal sentience (Birch et al., 2022;Paul et al., 2020;Sneddon et al., 2014). My colleagues and I recently developed eight criteria, each of which provides some evidence for sentience (with a focus on pain; Birch et al., 2021;Crump et al., 2022). ...
Article
Full-text available
Animal sentience research cannot be divorced from its ethical and political implications. For example, discovering which animals are sentient is vital for deciding which require welfare protection. Two legal case-studies illustrate the importance of scientists in such debates: the UK Animal Welfare (Sentience) Act 2022 had input from animal sentience researchers, whereas the US Animal Welfare Act 1966 did not. The former defined sentient animals much more plausibly than the latter. I accordingly argue that sentience researchers should inform policy, and that this is achievable without sacrificing scientific integrity.
... Molecular mechanisms of pain response and analgesic effects between humans and zebrafish are similar (Gonzalez-Nunez and Rodriguez, 2009;Macho Sanchez-Simon and Rodriguez, 2009;Sneddon et al., 2014). Here we studied the effects of ADA and ecto-5 ′ -nucleotidase inhibitors, EHNA and AMPCP, respectively, on behavioral changes induced by the AA-induced pain model in zebrafish. ...
Article
Purinergic signaling is a pathway related to pain underlying mechanisms. Adenosine is a neuromodulator responsible for the regulation of multiple physiological and pathological conditions. Extensive advances have been made to understand the role of adenosine in pain regulation. Here we investigated the effects of purinergic compounds able to modulate adenosine production or catabolism on pain responses induced by Acetic Acid (AA) in zebrafish larvae. We investigated the preventive role of the ecto-5′-nucleotidase inhibitor adenosine 5′-(α,β-methylene)diphosphate (AMPCP) and adenosine deaminase inhibitor erythro-9-(2-Hydroxy-3-nonyl)­adenine (EHNA) on the AA-pain induced model. The pain responses were evaluated through exploratory and aversive behaviors in zebrafish larvae. The exploratory behavior showed a reduction in the distance covered by animals exposed to 0.0025% and 0.050% AA. The movement and acceleration were reduced when compared to control. The treatment with AMPCP or EHNA followed by AA exposure did not prevent behavioral changes induced by AA for any parameter tested. There were no changes in aversive behavior after the AA-induced pain model. After AA-induced pain, the AMP hydrolysis increased on zebrafish larvae. However, the AMPCP or EHNA exposure did not prevent changes in AMP hydrolysis induced by the AA-induced pain model in zebrafish larvae. Although AMPCP or EHNA did not show differences in the AA-induced pain model, our results revealed changes in AMP hydrolysis, suggesting the involvement of the purinergic system in zebrafish larvae pain responses.
... As with many such checklists (e.g., Sneddon et al 2014;Brown & Dorey 2019) there is no single criterion for sentience; rather it is the accumulation of multiple criteria that improves our confidence that an organism is sentient. I would argue, however (and indeed so do the authors) that not all criteria are equal in this respect. ...
... Affective states (emotions) in non-human animals can be hard to assess but are usually measured in terms of valence (positive to negative experience), arousal (strength of response) and motivational intensity (how much the stimulus provokes a corresponding action) (26). There is wide agreement amongst neuroscientists and biologists that animals ranging from primates to fish experience emotions (27)(28)(29)(30), and Balcombe is adamant that humans should not deny animals 'feelings' just because we are unable to prove their existence. Moreover, he cautions: "Because many animals have more acute senses than we do, they may feel certain things more intensely than we do" (31). ...
Article
Full-text available
This paper seeks to expand traditional aesthetic dimensions of design beyond the limits of human capability in order to encompass other species’ sensory modalities. To accomplish this, the idea of inclusivity is extended beyond human cultural and personal identities and needs, to embrace multi-species experiences of places, events and interactions in the world. This involves drawing together academic perspectives from ecology, neuroscience, anthropology, philosophy and interaction design, as well as exploring artistic perspectives and demonstrating how these different frames of reference can inspire and complement each other. This begins with a rationale for the existence of non-human aesthetics, followed by an overview of existing research into non-human aesthetic dimensions. Novel aesthetic categories are proposed and the challenge of how to include non-human aesthetic sensibility in design is discussed.
... Various authors have, therefore, recommended criteria for animal sentience that include both behavioural and neural indicators (e.g. Birch et al., 2021;Smith and Boyd, 1991;Sneddon et al., 2014). ...
Article
We consider the relationship between neural and behavioural evidence for animal consciousness. We critically examine two recent studies: one neural and one behavioural. The first, on crows, finds different neural activity depending on whether a stimulus is reported as seen or unseen. However, to implicate this neural activity in consciousness, we must assume that a specific conditioned behaviour is a report of conscious experience. The second study, on macaques, records behaviours strikingly similar to patterns of conscious and unconscious perception in humans. However, confounds are only ruled out in human subjects, presupposing substantial neural similarity between humans and macaques. Taken together, the two studies reveal a sense in which neural and behavioural research rely on each other. Looking ahead, these two types of evidence could prove to be either mutually reinforcing or mutually undermining. The science of animal consciousness needs both neural and behavioural evidence, ideally obtained as part of a single coordinated programme.
... This includes, but is not limited to, pain (8). While pain and methods to avoid or relieve it are well-understood in some species, they are not in others, including aquatic species (10,11). Nonetheless, precautions have long been taken to putatively reduce suffering, and one of the most frequent treatments of larval zebrafish is the application of anesthetic agents in preparation for invasive procedures or as a method of euthanasia. ...
Article
Full-text available
Tricaine, or MS-222, is the most commonly used chemical anesthetic in zebrafish research. It is thought to act via blocking voltage-gated sodium channels, though its mechanism of action, particularly at the neuronal level, is not yet fully understood. Here, we first characterized the effects of tricaine on both body balance and touch responses in freely swimming animals, before determining its effect on the neural activity underlying the optokinetic response at the level of motion perception, sensorimotor signaling and the generation of behavior in immobilized animals. We found that the standard dose for larvae (168 mg/L) induced loss of righting reflex within 30 seconds, which then recovered within 3 minutes. Optokinetic behavior recovered within 15 minutes. Calcium imaging showed that tricaine interferes with optokinetic behavior by interruption of the signals between the pretectum and hindbrain. The motion sensitivity indices of identified sensory neurons were unchanged in larvae exposed to tricaine, though fewer such neurons were detected, leaving a small population of active sensory neurons. We then compared tricaine with gradual cooling, a potential non-chemical alternative method of anesthesia. While neuronal tuning appeared to be affected in a similar manner during gradual cooling, gradual cooling induced a surge in calcium levels in both the pretectum and hindbrain. This calcium surge, alongside a drop in heartrate, is potentially associated with harmful changes in physiology and suggests that tricaine is a better anesthetic agent than gradual cooling for zebrafish laboratory research.
Chapter
The use of primates in regulated research and testing means that they are intentionally subjected to scientific procedures that have the potential to cause pain, suffering, distress, or lasting harm. These harms, combined with keeping primates in restricted laboratory conditions, are balanced against the potential (primarily human) benefits gained from their use. In this chapter, we provide a brief overview of the use of primates in laboratories, the estimated number, and purpose of use, and summarize the evidence that primates are especially vulnerable and deserve special protection compared to other animals. The 3Rs (replacement, reduction, and refinement) framework, underpinning humane science, is described, and we emphasize both the ethical and scientific needs for refinement. Refinement refers to all approaches used (by humans responsible for their care) to minimize harms and improve welfare for those primates that are still used in research after the application of the replacement and reduction principles. There is a growing body of evidence demonstrating an interplay between animals’ welfare and experimental parameters, and that this interplay affects the validity and reliability of scientific output. With this perspective, we argue that it is better to collect no data than to collect poor (e.g., invalid, unreliable) data. It is, after all, unacceptable for primates to suffer in vain and violates utilitarian principles underlying animal use. Furthermore, inconsistency in experimental approach may introduce conflicting results, increasing the likelihood of using more animals, and delaying delivery of promising therapies to the clinic. We focus on mitigating the major welfare issues faced by primates housed in laboratories through coordinated refinements across their life spans. Drawing on examples from cynomolgus macaques (Macaca fascicularis), an Old World monkey commonly used during the development of medical products, we highlight the importance of understanding the critical role humans play in the laboratory, providing environments, performing husbandry, and undertaking procedures that promote welfare and decrease harms. Our theoretical premise is that if primates are to be “fit for purpose” (i.e., well suited for the designated role), we need a proactive, concerted approach for implementing refinement that spans their lifetime.Keywords3RsFit for purposeRegulated research Macaca fascicularis ReliableValid data
Article
Full-text available
It might become possible to build artificial minds with the capacity for experience. This raises a plethora of ethical issues, explored, among others, in the context of whole brain emulations (WBE). In this paper, I will take up the problem of vulnerability – given, for various reasons, less attention in the literature – that the conscious emulations will likely exhibit. Specifically, I will examine the role that vulnerability plays in generating ethical issues that may arise when dealing with WBEs. I will argue that concerns about vulnerability are more matters of institutional design than individual ethics, both when it comes to creating humanlike brain emulations, and when animal-like emulations are concerned. Consequently, the article contains reflection on some institutional measures that can be taken to protect the sims' interests. It concludes that an institutional framework more likely to succeed in this task is competitive and poly-centric, rather than monopolistic and centralized.
Empirical evidence has demonstrated that fish experience pain, and so to ensure their good welfare, it is vital that we can recognize and assess pain. A range of general, behavioral, and physiologic indicators can be used when assessing pain in fish. Many of these can be used at the tank side and are termed operational welfare indicators, whereas some require further computer or laboratory analysis. Behavioral indicators are valid and have been shown to profoundly differ between nonpainful and painful treatments in fish. However, these are not universal, and species-specific differences exist in behavioral responses to pain.
The recognition and assessment of pain in avian species are crucial tools in providing adequate supportive care in clinical, laboratory, zoologic, rehabilitation, and companion animal settings. With birds being a highly diverse class of species, there is still much to be determined regarding how to create specific criteria to recognize and assess pain in these animals. This article provides a clinical review on the physiology of pain in birds, observed behavioral and physiologic alterations with pain, how different sources and degrees of pain can alter behaviors observed, and how this information can be applied in a clinical setting.
Chapter
The entomology literature has historically suggested insects cannot feel pain, leading to their exclusion from ethical debates and animal welfare legislation. However, there may be more neural and cognitive/behavioural evidence for pain in insects than previously considered. We use Birch et al. 's (2021) eight criteria for sentience to critically evaluate the evidence for pain in insects. We assess six orders (Blattodea, Coleoptera, Diptera, Hymenoptera, Lepidoptera, and Orthoptera) in at least two life stages (adult and first instar juveniles, as well as other instars where relevant data are found). Other insect orders have not received enough research effort to be evaluated. According to the Birch et al. framework, adult Diptera (flies and mosquitoes) and Blattodea (cockroaches and termites) satisfy six criteria, constituting strong evidence for pain. Adults of the remaining orders (except Coleoptera, beetles) and some juveniles (Blattodea and Diptera, as well as last instar Lepidoptera [butterflies and moths]) satisfy 3–4 criteria, or “substantial evidence for pain”. We found no good evidence that any insects failed a criterion. However, there were significant evidence gaps, particularly for juveniles, highlighting the importance of more research on insect pain. We conclude by considering the ethical implications of our findings where insects are managed in wild, farmed, and research contexts.
Preprint
Full-text available
Commercial and recreational stone crab (Menippe mercenaria) fisheries primarily occur along the Gulf of Mexico and Atlantic coasts of the southeastern United States and the northeastern Caribbean. The fishery is unique in that only the crabs' claws are retained and the animal is returned to the water alive. While the fishery is often regarded as sustainable because it is believed to exploit the crabs' natural ability to voluntarily drop (autotomize) and regenerate lost claws, the post-release survival of de-clawed stone crabs is often low, especially when both claws are harvested. In this study, a controlled laboratory experiment was used to compare a new method of claw removal to the typical method currently used in the fishery. For the two different claw removal methods, we compared crab survival and start time to claw regeneration as a function of harvester and whether one claw or both claws were removed. Overall, we found a significant effect of the removal method, harvester, and whether one claw or both claws were removed on crab survival, but these factors did not influence the time to start of claw regeneration. Although our new method was several seconds slower in processing time than the typical method, it resulted in a 28% increase in survival (up to 92% survival throughout the study) compared to the typical method of claw removal (64% survival throughout the study). Overall, these results suggest that our new method of claw removal significantly increases post-release survival of stone crabs, and most notably does so independent of harvester and whether one claw or both claws are removed.
Article
Full-text available
Some scientific research includes experiments performed using animals. Many of the animals used in research are sentient, which means they have emotions or feelings that are probably similar to the positive and negative emotions that humans experience. Some experiments can cause animals to experience negative emotions like pain or fear. While animals can sometimes be replaced with other methods or used sparingly, in other situations there is no easy way to perform experiments without using animals. In these cases, scientists can protect animals by using refinement, which describes all efforts to improve the housing conditions, care, and scientific procedures that the animals experience. Refinement aims to avoid or lessen negative experiences or pain and to improve the animals’ wellbeing. For example, scientists work hard to develop methods to give drugs to mice without using force, or to pick mice up more gently so the animals do not feel stress.
Article
Full-text available
PURPOSE: With the recognition of animals as sentient beings and the growing research in the field ofanimal welfare the use of live animals for scientific purposes and education has been under question. Thepresent paper focused on the legal framework for the protection of animals used for research andeducation while giving examples on their replacement with alternative methods in undergraduateveterinary courses. METHODS: Analysis is made on the implemented legal framework which lays downthe requirement for animal protection and specifically the 3Rs principles for animal experimentation.Additionally, a short literature review is made to identify the most common educational approaches usedto replace live animals in veterinary training. RESULTS: Based on the review we identified commonethical dilemmas for animal use in education like ethically sourced cadavers, continuous tests andmanipulations during the process of training of veterinary students and presented as well some exampleson alternatives like simulators, artificial models and digital resources. CONCLUSIONS: Through thedevelopment and implementation of modern educational resources aimed at the replacement of liveanimals with non-animal alternatives veterinary students could benefit in their studies both in terms ofsolving ethical issues regarding animal use and in gaining self-confidence, improvement of skills, andperformance.
Article
Which animals have conscious experiences? Many different, diverse and unrelated behaviors and cognitive capacities have been proposed as tests of the presence of consciousness in an animal. It is unclear which of these tests, if any, are valid. To remedy this problem, I develop a list consisting of eight desiderata which can be used to assess putative tests of animal consciousness. These desiderata are based either on detailed analogies between consciousness-linked human behavior and non-human behavior, on theories of consciousness or on methods from human consciousness science. If a test or set of tests satisfies more of these desiderata, passing it provides stronger evidence of consciousness. Moreover, one can design future tests of animal consciousness with the intention of satisfying these desiderata to ensure their evidential strength.
Article
The appropriate recognition and assessment of pain in animals is an essential tool that can be used by veterinary professionals, rehabilitators, household caregivers, and others to provide supportive care and analgesia to patients. Although the use of behavioral, postural, and facial changes to recognize pain have been studied in popular domestic species such as dogs (Canis lupus familiaris), cats (Felis catus), and rabbits (Oryctolagus cuniculus), very little is known relative to avian species. The purpose of this article is to provide a literature review comprising structured searches on the topic of avian pain recognition. The emphasis of the searches were based on the behavioral and postural alterations that have thus far been explored. The literature review was performed in the months of AugustSeptember 2020 over 5 online databases: MEDLINE/ PubMed, CAB Direct, Biosis, Zoological Record, and Scopus. Additional snowballing was incorporated by looking at the references and articles that cited the 126 articles from the initial abstract and full-text screening. Of the 194 full-text articles reviewed, 132 sources of literature were included in the final analysis. From these 132 sources of literature, 31.8% were general review articles in which avian pain behaviors were described irrespective of species, with others being specific to a particular species (chickens 47.8%, turkeys 7.6%, parrots 3.8%, pigeons [Columba livia] 3%, raptors 3%, and other 3%2 on ducks, 1 on emus [Dromaius novaehollandiae], and 1 on Eurasian blue tits [Cyanistes caeruleus]). Pain stimulus varied depending on species, although the vast majority of the pain stimuli involved welfare issues such as beak trimming, limb abnormalities, and keel bone fractures in chickens. Although information regarding this topic remains limited for many avian species, this review provides a more thorough understanding of behavioral indicators of pain in species such as chickens, turkeys, psittacines, pigeons, raptors, and select others. It is the hope that this review will motivate further interest and future analgesia research for the improvement of avian welfare.
Article
Full-text available
In addition to being studied for their exceptional regeneration abilities, planarians (i.e., flatworms) have also been extensively used in the context of pharmacological experiments during the past century. Many researchers used planarians as a model system for the study of drug abuse because they display high similarities with the nervous system of vertebrates at cellular and molecular levels (e.g., neuronal morphology, neurotransmitter ligands, and receptor function). This research field recently led to the discovery of causal relationships between the expression of Transient Receptor Potential ion channels in planarians and their behavioral responses to noxious stimuli such as heat, cold or pharmacological analogs such as TRP agonists, among others. It has also been shown that some antinociceptive drugs modulate these behaviors. However, among the few authors that tried to implement a full behavior analysis, none reached a consensual use of the terms used to describe planarian gaits yet, nor did they establish a comprehensive description of a potential planarian nociceptive system. The aim of this review is therefore to aggregate the ancient and the most recent evidence for a true nociceptive behavior in planarians. It also highlights the convenience and relevance of this invertebrate model for nociceptive tests and suggests further lines of research. In regards to past pharmacological studies, this review finally discusses the opportunities given by the model to extensively screen for novel antinociceptive drugs.
Article
With symptoms such as spontaneous pain and pathologically heightened sensitivity to stimuli, chronic pain accounts for about 20% of physician visits and up to 2/3 of patients are dissatisfied with current treatments. Much of our knowledge on pain processing and analgesics has emerged from behavioral studies performed on animals presenting the same symptoms under pathological conditions. While humans can verbally describe their pain, studies on rodents have relied on behavioral assays providing non-exhaustive characterization or altering animals' original sensitivity through repetitive stimulations. The emergence of what we term "next-generation behavioral sequencing" is now permitting us to quantitatively describe behavioral features on millisecond to minutes long timescales that lie beyond easy detection with the unaided eye. Here, we summarize emerging videography and computational based behavioral approaches that have the potential to significantly improve pain research.
Preprint
Full-text available
Advances in animal motion tracking and pose recognition have been a game changer in the study of animal behavior. Recently, an increasing number of works go 'deeper' than tracking, and address automated recognition of animals' internal states such as emotions and pain with the aim of improving animal welfare, making this a timely moment for a systematization of the field. This paper provides a comprehensive survey of computer vision-based research on recognition of affective states and pain in animals, addressing both facial and bodily behavior analysis. We summarize the efforts that have been presented so far within this topic -- classifying them across different dimensions, highlight challenges and research gaps, and provide best practice recommendations for advancing the field, and some future directions for research.
Article
Full-text available
Decapod crustaceans (crabs, hermit crabs, lobsters, crayfish, shrimps, prawns) are sentient beings, not only responding to noxious stimuli but also being capable of feeling pain, discomfort, and distress. General anaesthesia aims at producing analgesia, immobilization, and unconsciousness, while sedation reduces consciousness, stress, and anxiety, though without analgesia. Anaesthesia is recommended to ensure animal welfare and suppress nociception, pain, and suffering in painful and distressing practice that impairs decapods’ welfare. These include long term restrain, surgical procedures, pain control, examination, diagnostic, sampling, treatment, transportation, and euthanasia. The necessary anaesthetic depth, from sedation to surgical anaesthesia, depends on the procedure type. Anaesthetic bath and injection are commonly used, besides inhalation, local anaesthesia, and intracardiac injection. Agents used for the anaesthetic bath include eugenol, isoeugenol, lidocaine, halothane, and essential oils of lemon balm, lemongrass, lemon verbena, and sandalwood. While alphaxalone, eugenol, ketamine-xylazine, lidocaine, morphine, procaine, tiletamine-zolazepam, and xylazine can be used as injectable agents administered on the arthrodial membrane or intramuscular injection. Halothane can be used on inhalation anaesthesia. Local anaesthetics include lidocaine and benzocaine. Notwithstanding, many others are detrimental or ineffective to decapods, thus discouraged. They include but not limited to hypothermia, carbon dioxide, chlorpromazine, chloroform, ethanol, ether, magnesium salts, tricaine methanesulfonate (MS-222), mint and lavender essential oils, passionflower extract, and valerian. Decapods’ welfare, protection, and veterinary attention should not be neglected, but they must receive ethical treatment, including the best of our knowledge and available tools to ensure they are free of pain and discomfort whenever we deal with them.
Chapter
This chapter examines how Derrida’s destabilizing encounter with another semiotic agent and subject (i.e., his cat) serves as a philosophical catalyst for a radical (re-) conceptualization of the mechanistic tradition in philosophical and linguistic circles. Derrida adopts the biosemiotic vision of a universe teeming with purposeful and meaningful human and other-than-human semiosis in which we are immersed in his posthumous works. In the context of microbial ethics, the Derridean exercise of limitrophy is a reminder that we need to redraw the conceptual boundaries somewhere on a continuing basis when information from the hard sciences becomes available, or perhaps human life would even cease to exist. The greatest insight that can be gleaned from Derrida’s late philosophy is that the future of humanity and every other animot may be determined by our willingness to multiply the limit in order to increase the longevity of our beloved planet exponentially in the Anthropocene.
Article
Full-text available
Article
Full-text available
Pain is an aversive sensation and feeling associated with actual or potential tissue damage. A pain system involving receptors, neural pathways and analytical centres in the brain exists in many kinds of animals. Feelings of pain in many species are indicated by physiological responses, direct behavioural responses and ability to learn from such experiences so that they are minimised or avoided in future. Species differ in their responses to painful stimuli because different responses are adaptive in different species but the feeling of pain is probably much less variable. In early evolution, pain must have involved cell sensitivity and localised responses but efficacy would have improved with efficient communication within the individual and sophisticated brain analysis. Pain systems have probably changed rather little during vertebrate evolution. Pain may be a greater problem for animals with less cognitive ability. The distinction between pain and nociception does not seem to be useful.
Article
Full-text available
Beak trimming in laying hens is a routine practice in which about 1/3-1/2 of the upper and lower beak is removed with the aim of reducing cannibalism. This experiment aimed to identify if this procedure causes pain by examining self-administration of an analgesic (carprofen) and pecking behaviour in 80 laying pullets beak-trimmed by two different methods at one day of age using hot-blade cauterisation or infra-red cauterisation. We also tested a control treatment, pullets with intact beaks, and a positive control treatment of pullets beak trimmed at 10 weeks of age which were expected to experience some pain due to recent severing of the underlying nerves in the beak. At 11 weeks of age birds trimmed at 10 weeks of age pecked more (p
Article
Full-text available
The crayfish that was afraid of the dark We tend to assume that complex emotions, such as anxiety, only occur in mammals or other cognitively complex vertebrates. But a heightened sense of awareness and the avoidance of novel or dangerous environments could be helpful for any animal species. Fossat et al. show that crayfish exposed to a stressful electric field refuse to enter dark arms in a light/dark maze, even after the electric field has been removed. The animals calmed down when they were injected with an anxiolytic drug used to treat anxiety in humans, and they entered the dark as normal. The stressed animals had increased levels of the neurotransmitter serotonin in the brain, and injections of serotonin induced anxiety-like behavior in control animals. Thus, these invertebrates display a primitive form of anxiety that shares a mechanism with the more complex emotions displayed by vertebrates. Science , this issue p. 1293
Article
Full-text available
Sublethal injury triggers long-lasting sensitization of defensive responses in most species examined, suggesting the involvement of powerful evolutionary selection pressures [1]. In humans, this persistent nociceptive sensitization is often accompanied by heightened sensations of pain and anxiety [2]. While experimental [3] and clinical [4] evidence support the adaptive value of immediate nociception during injury, no direct evidence exists for adaptive benefits of long-lasting sensitization after injury. Recently, we showed that minor injury produces long-term sensitization of behavioral and neuronal responses in squid, Doryteuthis pealei [5, 6]. Here we tested the adaptive value of this sensitization during encounters between squid and a natural fish predator. Locomotion and other spontaneous behaviors of squid that received distal injury to a single arm (with or without transient anesthesia) showed no measurable impairment 6 hr after the injury. However, black sea bass given access to freely swimming squid oriented toward and pursued injured squid at greater distances than uninjured squid, regardless of previous anesthetic treatment. Once targeted, injured squid began defensive behavioral sequences [7, 8] earlier than uninjured squid. This effect was blocked by brief anesthetic treatment that prevented development of nociceptive sensitization [6, 9]. Importantly, the early anesthetic treatment also reduced the subsequent escape and survival of injured, but not uninjured, squid. Thus, while minor injury increases the risk of predatory attack, it also triggers a sensitized state that promotes enhanced responsiveness to threats, increasing the survival (Darwinian fitness) of injured animals during subsequent predatory encounters.
Article
Full-text available
The assessment of pain is critical for the welfare of horses, in particular when pain is induced by common management procedures such as castration. Existing pain assessment methods have several limitations, which reduce the applicability in everyday life. Assessment of facial expression changes, as a novel means of pain scoring, may offer numerous advantages and overcome some of these limitations. The objective of this study was to develop and validate a standardised pain scale based on facial expressions in horses (Horse Grimace Scale [HGS]). Forty stallions were assigned to one of two treatments and all animals underwent routine surgical castration under general anaesthesia. Group A (n = 19) received a single injection of Flunixin immediately before anaesthesia. Group B (n = 21) received Flunixin immediately before anaesthesia and then again, as an oral administration, six hours after the surgery. In addition, six horses were used as anaesthesia controls (C). These animals underwent non-invasive, indolent procedures, received the same treatment as group A, but did not undergo surgical procedures that could be accompanied with surgical pain. Changes in behaviour, composite pain scale (CPS) scores and horse grimace scale (HGS) scores were assessed before and 8-hours post-procedure. Only horses undergoing castration (Groups A and B) showed significantly greater HGS and CPS scores at 8-hours post compared to pre operatively. Further, maintenance behaviours such as explorative behaviour and alertness were also reduced. No difference was observed between the two analgesic treatment groups. The Horse Grimace Scale potentially offers an effective and reliable method of assessing pain following routine castration in horses. However, auxiliary studies are required to evaluate different painful conditions and analgesic schedules.
Article
Full-text available
Memories relating to a painful, negative event are adaptive and can be stored for a lifetime to support preemptive avoidance, escape, or attack behavior. However, under unfavorable circumstances such memories can become overwhelmingly powerful. They may trigger excessively negative psychological states and uncontrollable avoidance of locations, objects, or social interactions. It is therefore obvious that any process to counteract such effects will be of value. In this context, we stress from a basic-research perspective that painful, negative events are "Janus-faced" in the sense that there are actually two aspects about them that are worth remembering: What made them happen and what made them cease. We review published findings from fruit flies, rats, and man showing that both aspects, respectively related to the onset and the offset of the negative event, induce distinct and oppositely valenced memories: Stimuli experienced before an electric shock acquire negative valence as they signal upcoming punishment, whereas stimuli experienced after an electric shock acquire positive valence because of their association with the relieving cessation of pain. We discuss how memories for such punishment- and relief-learning are organized, how this organization fits into the threat-imminence model of defensive behavior, and what perspectives these considerations offer for applied psychology in the context of trauma, panic, and nonsuicidal self-injury.
Article
Full-text available
Currently artificial emotions are being extensively used in robots. Most of these implementations are employed to display affective states. Nevertheless, their use to drive the robot's behavior is not so common. This is the approach followed by the authors in this work. In this research, emotions are not treated in general but individually. Several emotions have been implemented in a real robot, but in this paper, authors focus on the use of the emotion of fear as an adaptive mechanism to avoid dangerous situations. In fact, fear is used as a motivation which guides the behavior during specific circumstances. Appraisal of fear is one of the cornerstones of this work. A novel mechanism learns to identify the harmful circumstances which cause damage to the robot. Hence, these circumstances elicit the fear emotion and are known as fear releasers. In order to prove the advantages of considering fear in our decision making system, the robot's performance with and without fear are compared and the behaviors are analyzed. The robot's behaviors exhibited in relation to fear are natural, i.e., the same kind of behaviors can be observed on animals. Moreover, they have not been preprogrammed, but learned by real inter actions in the real world. All these ideas have been implemented in a real robot living in a laboratory and interacting with several items and people.
Article
Full-text available
Cephalopod molluscs are the most neurally and behaviorally complex invertebrates, with brains rivaling those of some vertebrates in size and complexity. This has fostered the opinion that cephalopods, particularly octopuses, may experience vertebrate-like pain when injured. However, it is not known whether octopuses possess nociceptors or if their somatic sensory neurons exhibit sensitization after injury. Here we show that the octopus Abdopus aculeatus expresses nocifensive behaviors including arm autotomy, and displays marked neural hyperexcitability both in injured and uninjured arms for at least 24h after injury. These findings do not demonstrate that octopuses experience pain-like states; instead they add to the minimal existing literature on how cephalopods receive, process, and integrate noxious sensory information, potentially informing and refining regulations governing use of cephalopods in scientific research.
Article
Full-text available
It was recently found that transient receptor potential (TRP) channels play an important role in the transduction of thermal, mechanical, and chemical stimuli underlying the somatic sensation. Several types of TRP channels exhibit sensitivity to increases or decreases in temperature, as well as to the action of chemical ligands that elicit similar thermal or painful sensations. These agents include menthol, mustard oil, cinnamaldehyde (CA), gingerol, capsaicin, camphor, eugenol, and others. Cinnamaldehyde is a pungent chemical obtained from cinnamon, which acts as an agonist of the TRPA1 channels; these channels were originally reported to be activated by cold temperatures (below 18°C). TRPA1 is also implicated in cold nociception. However, its role in the formation of cold pain is more controversial, with discrepant reports that TRPA1s do or do not respond to intense cooling. Menthol derived from plants of the mint family enhances the feeling of coldness by interacting with the cold-sensitive TRPM8 channels, but its effect on pain is less well understood. Using behavioral methods, we showed that unilateral intraplantar injection of CA (5 to 20%) induced a significant concentration-dependent decrease in the latency for ipsilateral paw withdrawal from a noxious heat stimulus, i.e., heat hyperalgesia. Cinnamaldehyde also significantly reduced mechanical withdrawal thresholds for the injected paw, i.e., evoked mechanical allodynia. Bilateral intraplantar injections of CA resulted in a significant cold hyperalgesia (cold plate test) and a weak enhancement of innocuous cold avoidance (thermal preference test). In contrast to CA, menthol in a dose-dependent manner increased the latency for noxious heat-evoked withdrawal, i.e., exerted an antinociceptive effect. Menthol did not affect mechanosensation except for a weak allodynic effect when applied in the highest concentration used (40 %), indicating that it did not exert a local anesthetic effect. Menthol had a biphasic effect on cold avoidance. High concentrations of menthol reduced cold avoidance, i.e., induced cold hypoalgesia, while low menthol concentrations significantly intensified cold avoidance. The highest menthol concentration provided cold hypoalgesia (cold plate test), while lower concentrations had no effect. Taken together, our data support the idea that TRPA1 and TRPM8 channels represent promising peripheral targets for pain modulation.
Article
Full-text available
Honeybees constitute established model organisms for the study of appetitive learning and memory. In recent years, the establishment of the technique of olfactory conditioning of the sting extension response (SER) has yielded new insights into the rules and mechanisms of aversive learning in insects. In olfactory SER conditioning, a harnessed bee learns to associate an olfactory stimulus as the conditioned stimulus with the noxious stimulation of an electric shock as the unconditioned stimulus. Here, we review the multiple aspects of honeybee aversive learning that have been uncovered using Pavlovian conditioning of the SER. From its behavioral principles and sensory variants to its cellular bases and implications for understanding social organization, we present the latest advancements in the study of punishment learning in bees and discuss its perspectives in order to define future research avenues and necessary improvements. The studies presented here underline the importance of studying honeybee learning not only from an appetitive but also from an aversive perspective, in order to uncover behavioral and cellular mechanisms of individual and social plasticity.
Article
Full-text available
This chapter discusses the different kinds of feelings and considers the origin and possible function of each feeling. Each of these feelings has a biological role that complements various other anatomical, physiological, and behavioral mechanisms. All have some potential for improving fitness and most are likely to have been the subject of considerable selection pressure, but some aspects of feelings are likely to be just epiphenomena of neural mechanisms. With this view that most aspects of feelings have evolved like other biological mechanisms and that they help significantly in coping and responding, a single view of welfare as the state of an individual as regards its attempts to cope with its environment becomes clearer. Feelings are an important part of the welfare of an individual and should be assessed as well as possible. Other coping procedures and effects of the environment on the individual should also be assessed. An effect on an individual that is adverse in the long term is categorized as stress. Programs for trying to evaluate and improve welfare should combine the use of experiments to assess what is important to the individual by measuring the strengths of preferences, with monitoring studies in which feelings and other aspects of welfare are assessed more directly.
Article
Full-text available
This review examines the neurobehavioral nature of fishes and addresses the question of whether fishes are capable of experiencing pain and suffering. The detrimental effects of anthropomorphic thinking and the importance of an evolutionary perspective for understanding the neurobehavioral differences between fishes and humans are discussed. The differences in central nervous system structure that underlie basic neurobehavioral differences between fishes and humans are described. The literature on the neural basis of consciousness and of pain is reviewed, showing that: (1) behavioral responses to noxious stimuli are separate from the psychological experience of pain, (2) awareness of pain in humans depends on functions of specific regions of cerebral cortex, and (3) fishes lack these essential brain regions or any functional equivalent, making it untenable that they can experience pain. Because the experience of fear, similar to pain, depends on cerebral cortical structures that are absent from fish brains, it is concluded that awareness of fear is impossible for fishes. Although it is implausible that fishes can experience pain or emotions, they display robust, nonconscious, neuroendocrine, and physiological stress responses to noxious stimuli. Thus, avoidance of potentially injurious stress responses is an important issue in considerations about the welfare of fishes.
Article
Full-text available
We review studies claiming that fish feel pain and find deficiencies in the methods used for pain identification, particularly for distinguishing unconscious detection of injurious stimuli (nociception) from conscious pain. Results were also frequently mis-interpreted and not replicable, so claims that fish feel pain remain unsubstantiated. Comparable problems exist in studies of invertebrates. In contrast, an extensive litera-ture involving surgeries with fishes shows normal feeding and activity immediately or soon after surgery. C fiber nociceptors, the most prevalent type in mammals and responsible for excruciating pain in humans, are rare in teleosts and absent in elas-mobranchs studied to date. A-delta nociceptors, not yet found in elasmobranchs, but relatively common in teleosts, likely serve rapid, less noxious injury signaling, trigger-ing escape and avoidance responses. Clearly, fishes have survived well without the full range of nociception typical of humans or other mammals, a circumstance according well with the absence of the specialized cortical regions necessary for pain in humans. We evaluate recent claims for consciousness in fishes, but find these claims lack adequate supporting evidence, neurological feasibility, or the likelihood that consciousness would be adaptive. Even if fishes were conscious, it is unwar-ranted to assume that they possess a human-like capacity for pain. Overall, the behavioral and neurobiological evidence reviewed shows fish responses to nociceptive stimuli are limited and fishes are unlikely to experience pain.
Article
Full-text available
Accurate assessment of animal emotion (affect) is an important goal in animal welfare science, and in areas such as neuroscience and psychopharmacology. Direct measures of conscious emotion are not available, so assessment of animal affect has relied on measures of the behavioural and physiological components of affective states. These are important indicators but have some limitations (e.g. measuring emotional arousal rather than valence (positivity vs negativity)). Human psychology research suggests that changes in cognitive function (information processing) can also be reliable indicators of emotional state (especially valence). For example, people in negative states attend to threats, retrieve negative memories, and make negative judgements about ambiguous stimuli more than happier people. Here we review a new research area investigating the possibility that such affect-induced ‘cognitive biases’ also occur in animals. We focus on a novel ‘judgement bias’ paradigm in which animals are trained that one cue predicts a positive event and another cue predicts a less positive/negative event, and are then presented with ambiguous (intermediate) cues. The hypothesis is that animals in a negative affective state will be more likely to respond to (‘judge’) these ambiguous cues as if they predict the negative event (a ‘pessimistic’ response), than animals in a more positive state. Recent studies of rats, dogs, rhesus monkeys, starlings and humans provide face-value support for this hypothesis. We discuss the strengths and weaknesses of the affect manipulation treatments used in these studies, and the possibility that treatment-induced changes in feeding motivation, general activity and learning are responsible for the effects observed, and we consider whether the type of bias observed and the precise design of the judgement bias task can provide information about different types of affective state. Judgement biases may result from the influence of affect on decision-making processes including attention to and perception of the ambiguous cue, evaluation of the value and probability (expected utility) of the outcomes of different responses, and action selection. Affect might also modulate general tendencies of loss, risk and ambiguity aversion, hence biasing decisions. We discuss these possibilities in relation to theory and findings from neurobiological and psychological studies of decision-making, in order to better understand the potential mechanisms underlying judgement biases. We conclude with some specific recommendations for study design and interpretation, and suggestions for future research in this area.
Article
Full-text available
Bodily injury in mammals often produces persistent pain that is driven at least in part by long-lasting sensitization and spontaneous activity (SA) in peripheral branches of primary nociceptors near sites of injury. While nociceptors have been described in lower vertebrates and invertebrates, outside of mammals there is limited evidence for peripheral sensitization of primary afferent neurons, and there are no reports of persistent SA being induced in primary afferents by noxious stimulation. Cephalopod molluscs are the most neurally and behaviorally complex invertebrates, with brains rivaling those of some vertebrates in size and complexity. This has fostered the opinion that cephalopods may experience pain, leading some governments to include cephalopods under animal welfare laws. It is not known, however, if cephalopods possess nociceptors, or whether their somatic sensory neurons exhibit nociceptive sensitization. We demonstrate that squid possess nociceptors that selectively encode noxious mechanical but not heat stimuli, and that show long-lasting peripheral sensitization to mechanical stimuli after minor injury to the body. As in mammals, injury in squid can cause persistent SA in peripheral afferents. Unlike mammals, the afferent sensitization and SA are almost as prominent on the contralateral side of the body as they are near an injury. Thus, while squid exhibit peripheral alterations in afferent neurons similar to those that drive persistent pain in mammals, robust changes far from sites of injury in squid suggest that persistently enhanced afferent activity provides much less information about the location of an injury in cephalopods than it does in mammals.
Article
Full-text available
The purposes of the present study were to examine the rate of morphine uptake in goldfish (Carassius auratus (L., 1758)) when administered via the water, to calculate the pharmacokinetics of morphine when administered intraperitoneally, and to determine whether morphine could act as an analgesic. When administered via the water, morphine uptake was very slow, and the concentration accumulated in the plasma was <1% of that in water after 2 h. Furthermore, changing water pH or hardness caused small changes in morphine uptake from the water, but plasma levels remained <1% of water concentrations after 2 h exposure. The pharmacokinetics of morphine administered intraperitoneally (40 mg/kg) revealed a half-time for elimination of 37 h and a mean residence time of 56 h. Finally, morphine acted as an analgesic when administered via the water as demonstrated by significantly decreased rubbing behaviour in response to the presence of a noxious stimulus (subcutaneous injection of 0.7% acetic acid). Although morphine appeared to have analgesic properties in goldfish, morphine administered via ambient water is not recommended because of its slow rate of uptake.
Article
Full-text available
Insects possess miniature brains but exhibit a sophisticated behavioral repertoire. Recent studies have reported the existence of unsuspected cognitive capabilities in various insect species that go beyond the traditionally studied framework of simple associative learning. Here, I focus on capabilities such as attentional modulation and concept learning and discuss their mechanistic bases. I analyze whether these behaviors, which appear particularly complex, can be explained on the basis of elemental associative learning and specific neural circuitries or, by contrast, require an explanatory level that goes beyond simple associative links. In doing this, I highlight experimental challenges and suggest future directions for investigating the neurobiology of higher-order learning in insects, with the goal of uncovering the basic neural architectures underlying cognitive processing.
Article
Pain assessment in fish is particularly challenging due to their evolutionary distance from humans, their lack of audible vocalization, and apparently expressionless demeanour. However, there are criteria that can be used to gauge whether pain perception occurs using carefully executed scientific approaches. Here, the standards for pain in fish are discussed and can be considered in three ways: neural detection and processing of pain; adverse responses to pain; and consciously experiencing pain. Many procedures that we subject fish to cause tissue damage and may give rise to the sensation of pain. Fish are popular as pets, in animal exhibits, and as experimental models, but are also cultured or caught for food. There is little legislation for the protection of fish welfare. Many countries are now exploring the welfare cost to fish, and current practices may need to be reviewed with respect to the current evidence for fish perceiving pain.
Article
Lame and sound broilers, selected from commercial flocks, were trained to discriminate between different coloured feeds, one of which contained carprofen. The two feeds were then offered simultaneously and the birds were allowed to select their own diet from the two feeds. In an initial study to assess the most appropriate concentration of drug, the plasma concentrations of carprofen were linearly related to the birds' dietary intake. The walking ability of lame birds was also significantly improved in a dose-dependent manner and lame birds tended to consume more analgesic than sound birds. In a second study, in which only one concentration of analgesic was used, lame birds selected significantly more drugged feed than sound birds, and that as the severity of the lameness increased, lame birds consumed a significantly higher proportion of the drugged feed.
Chapter
Until recently, the frog telencephalon, like those of other nonmammalian vertebrates, was believed to be dominated by the olfactory system. This misconception may originally have been derived from the relatively large size of the olfactory bulbs and tracts. It was thought that all regions of the telencephalon received olfactory afferents. Domination of the telencephalon by olfaction left little room for telencephalic representation of other sensory modalities: a case in point is vision. The optic tectum was considered to be most important part of the visual system of nonmammalian vertebrates; diencephalic and telencephalic structures were presumed to be little involved in this modality. Herrick (1948) conceived of the amphibian dorsal thalamus as a nucleus sensitivus integrating multimodal afferents and lacking functional subdivisions.
Article
The objective assessment of affective (emotional) state in farm livestock, especially positive states, poses a significant challenge. In human psychology, there is evidence that affective state can alter cognition, with more positive states being associated with an increased likelihood of judging ambiguous information postively (a phenomenon described as optimistic cognitive bias). The aim of this study was to investigate whether judgement biases could be used to assess affective states in pigs housed in environments with different levels of enrichment. Two groups of five gilts were housed in either enriched (E) or barren (B) environments for the first five weeks of the experiment. The enriched group had more space, straw and objects to manipulate. The pigs were trained on a go/no-go task to discriminate two auditory cues, a positive cue that predicted a food reward if the pig approached a hatch, and a negative cue that predicted a mildly aversive experience if the pig approached the same hatch. The quality of the pigs’ environment was then changed over time in a balanced, cross-over design (either EBE or BEB). Tests of cognitive bias were made on individual pigs before and after each change in environment using an unreinforced, ambiguous, auditory cue different from either the positive or the negative cue. In test sessions, positive, negative and amibiguous cues were presented in a randomised sequence, and the pigs’ responses (whether they approached the hatch and latency to approach) were recorded. Both groups were more likely to approach the hatch and were faster to approach the hatch in response to the ambiguous cue when currently housed in the enriched environment. There was also an interaction between current and past environment, whereby pigs that started in the enriched environment were subsequently less likely and slower to approach the hatch when moved to a barren environment than pigs intially housed in the barren environment. These results show that pigs have more optimistic judgement biases in enriched environments indicative of a more positive affective state. Also, pigs that have spent time in an enriched environment react more negatively to being subsequently housed in a barren environment. We conclude that cognitive bias has potential to provide additional information about the effect of various management regimes on farmed animals’ welfare. This will be increasingly important for identifying practices to promote positive affective states in our food producing animals.
Article
Connections of the medial precommissural subpallial ventral telencephalon, i.e., dorsal (Vd, interpreted as part of striatum) and ventral (Vv, interpreted as part of septum) nuclei of area ventralis telencephali, were studied in the zebrafish (Danio rerio) using two tracer substances (DiI or biocytin). The following major afferent nuclei to Vd/Vv were identified: medial and posterior pallial zones of dorsal telencephalic area, and the subpallial supracommissural and postcommissural nuclei of the ventral telencephalic area, the olfactory bulb, dorsal entopeduncular, anterior and posterior parvocellular preoptic and suprachiasmatic nuclei, anterior, dorsal and central posterior dorsal thalamic, as well as rostrolateral nuclei, periventricular nucleus of the posterior tuberculum, posterior tuberal nucleus, various tuberal hypothalamic nuclei, dorsal tegmental nucleus, superior reticular nucleus, locus coeruleus, and superior raphe nucleus. Efferent projections of the ventral telencephalon terminate in the supracommissural nucleus of area ventralis telencephali, the posterior zone of area dorsalis telencephali, habenula, periventricular pretectum, paracommissural nucleus, posterior dorsal thalamus, preoptic region, midline posterior tuberculum (especially the area dorsal to the posterior tuberal nucleus), tuberal (midline) hypothalamus and interpeduncular nucleus. Strong reciprocal interconnections likely exist between septum and preoptic region/midline hypothalamus and between striatum and dorsal thalamus (dopaminergic) posterior tuberculum. Regarding ascending activating/modulatory systems, the pallium shares with the subpallium inputs from the (noradrenergic) locus coeruleus, and the (serotoninergic) superior raphe, while the subpallium additionally receives such inputs from the (dopaminergic) posterior tuberculum, the (putative cholinergic) superior reticular nucleus, and the (putative histaminergic) caudal hypothamalic zone.
Article
Vast numbers of decapods are used in human food and currently subject to extreme treatments and there is concern that they might experience pain. If pain is indicated then a positive change in the care afforded to this group has the potential to produce a major advance in animal welfare. However, it is difficult to determine pain in animals. The vast majority of animal phyla have a nociceptive ability that enables them to detect potential or actual tissue damage and move away by a reflex response. In these cases there is no need to assume an unpleasant feeling that we call pain. However, various criteria have been proposed that might indicate pain rather than simple nociception. Here, with respect to decapod crustaceans, four such criteria are discussed: avoidance learning, physiological responses, protective motor reactions and motivational trade-offs. The evidence from various experiments indicates that all four criteria are fulfilled and the data are thus consistent with the idea of pain. The responses cannot be explained by nociception alone but, it is still difficult to state categorically that pain is experienced by decapods. However, the evidence is as strong for this group as it is for fish but the idea that fish experience pain has broader acceptance than does the idea of decapod pain. A taxonomic bias is evident in the evaluation of experimental data.
Article
The ethical positions, on which attacks on the use of animals in research are based, have depended most commonly on treating the preferences of non-human animals as worthy of equal respect to those of humans. More radically, animals are believed to hold the same rights as humans. Such simplistic views are readily criticized and do not capture all the reasons why many people believe that animals, particularly complex ones, should be treated responsibly and with consideration. Moreover, strong moral arguments can also be mounted for using animals in order to understand the fundamental problems of biology and for helping to alleviate the suffering of humans and other animals. The tensions may be eased in practice by making every effort to minimize the suffering of those animals while ensuring that research is focused on important biological problems and, where possible, that it takes into account the likely benefits to health and well-being that may derive from the research. Assessments along these different dimensions of the moral dilemma are not trivial, but the assessment of welfare has, in particular made big strides in recent years. Behavioral biologists are well placed to advance discussion so that any one moral issue does not dominate the debate.
Article
Heart rate was monitored before and after beak trimming in restrained chickens to measure responses to beak trimming at hatch and at 10 and 42 days of age. Immediately after trimming chickens sham-trimmed (control) and trimmed at 10 and 42 days of age had an increase in heart rate, with the 42-day-old chickens showing the greater change. Chickens sham-trimmed and trimmed at hatch showed no change in heart rate. No difference between trimmed and sham-trimmed chickens occurred at any age for heart rate response. These data indicate that heart rate at trimming may be inadequate as a measure of the stress response associated with beak trimming, especially with the concurrent stressors of handling and restraint. Beak trimming and handling of chickens at hatch is either less stressful than trimming at 10 and 42 days of age, as indicated by the lack of a heart rate response, or heart rate is already at a maximum in chickens at hatch, due to stress associated with hatching. Food intake and body weight were measured for 3-4 weeks after trimming to assess the longer term effects of age and level of trimming on performance of the chicken. Removal of 3 mm of beak at hatch or 4.5 mm at 10 days of age depressed feeding levels and a reduced body weight, indicative of a chronic stress associated with beak trimming.
Article
Factors which influence decisions by hermit crabs concerning whether to approach, investigate and enter another shell have been investigated by systematically varying the size of the shell in possession and the size of the shell being offered. The probability that a crab will approach or enter the shell depends on both variables. Investigation after contact, however, depends only on the size of the shell in possession. Durations of each stage of the sequence are negatively correlated with the numbers of crabs in each experimental group performing the next stage. For the final sequence of aperture investigatory activities, the fewer crabs entering the offered shell, the greater the number of investigatory acts performed by those crabs. In addition to variation in number of acts and duration of investigation, specific use of appendages varies according to the experimental situation. Thus naked crabs use the minor cheliped to investigate shells in preference to the major cheliped, which is normally used by housed crabs, with the major cheliped being reserved for defence by naked crabs. These data are discussed in terms of information collection and decisions made on the basis of that information.
Article
One criterion of pain experience is that the emotional response to pain may be traded-off against other motivational requirements. This was tested in hermit crabs, housed in either preferred or unpreferred species of shells, by subjecting their abdomens to electric shocks of gradually increasing intensity. The first observable response was not affected by shell species but those in preferred shells evacuated at a higher shock level than those in poor quality shells. Thus, they seem to trade-off the requirement to retain a high quality shell with that of avoidance of the noxious stimulus. Some crabs returned to their shells and those that got back into the preferred species did so with less probing of the aperture before getting in and subsequently thrust their abdomen in and out less often in further investigation, thus confirming their shell species preference. Not all crabs returned to the vicinity of the shell and some attempted to climb the wall of the experimental chamber. Others engaged in shell rapping as if in a fight and grooming of the abdomen was noted. These findings are consistent with the idea of a pain experience rather than a nociceptive reflex.
Article
Previous work showed that goldfish learn to avoid a region of an aquarium where they receive a discrete shock to the flank. This avoidance is reduced if another fish is present next to the shock zone, suggesting fish trade-off avoidance against a tendency to associate [Dunlop, R., Millsopp, S., Laming, P., 2006. Avoidance learning in goldfish (Carassius auratus) and trout (Oncorhynchus mykiss) and implications for pain perception. App. Anim. Behav. Sci. 97 (2–4), 255–271]. Only shock intensity was adjusted in those experiments, here we report results where a requirement for food was also altered.Fish were trained to feed at a region of the aquarium where subsequently they would receive a discrete shock to the flank. One experimental group had different shock intensities applied, whereas in the other group shock intensity was consistent but food deprivation was varied.We show the number of feeding attempts and time spent in the feeding/shock zone decreased with increased shock intensity and with increased food deprivation the number and the duration of feeding attempts increased as did escape responses as this zone was entered. These data suggest that goldfish balance their need for food against avoidance of an acute noxious stimulus.
Article
Physiological and behavioral parameters were determined in 27 horses to identify potential indicators of postoperative pain following exploratory celiotomy for colic. Experimental groups were 10 horses that received no treatment (Control), 10 horses anesthetized for a non-painful procedure (Anesthesia), and 7 horses that presented for emergency surgery for acute gastrointestinal disease (Surgery). Physiological and behavioral data were collected on the horses 0, 4, 8, 12, 16, 20, and 24–30h after entry into a stall in the equine intensive care unit of the Veterinary Teaching Hospital at Washington State University. Physiological data included: heart rate, respiratory rate, and plasma cortisol concentration. For the entire period of observation the surgery group had significantly higher plasma cortisol concentration and significantly elevated heart rate compared to the Control and Anesthesia groups, which did not differ for either variable. A numerical rating scale (NRS) of behavior was used to visually score the horses at the same time physiological data were collected. In addition, time budgets of behavior were calculated from 1h segments of real-time video recording beginning at the 0, 4, 8 or 12h, and 20 or 24–30h time points. Time budgets for the Control and Anesthesia groups did not differ in the time spent in locomotor activities and both groups spent significantly more time in locomotion than the Surgery group. The Surgery group spent significantly more time displaying painful behavior compared to the Control and Anesthesia groups; however, the amount of time the Surgery group displayed painful behavior was small compared to the amount of time with no movement. The NRS scores substantiated the video taped behavioral data with significantly different scores for the Surgery group versus the Control and Anesthesia groups for multi-factor ratings of body posture and response to stimuli. We conclude that reduced locomotion, elevated plasma cortisol concentration, and elevated heart rate are potential indicators of postoperative pain in horses.
Article
This paper discusses the evidence for pain perception in fish and presents new data on morphine analgesia in fish. Recent anatomical and electrophysiological studies have demonstrated that fish are capable of nociception, the simple detection of a noxious, potentially painful stimulus and the reflex response to this. To prove pain perception, it must be demonstrated that an animal’s behaviour is adversely affected by a potentially painful event and this must not be a reflex response. The present study examined the acute effects of administering a noxious chemical to the lips of rainbow trout (Oncorhynchus mykiss) to assess what changes occurred in behaviour and physiology. There was no difference in swimming activity or use of cover when comparing the noxiously stimulated individuals with the controls. The noxiously treated individuals performed anomalous behaviours where they rocked on either pectoral fin from side to side and they also rubbed their lips into the gravel and against the sides of the tank. Opercular beat rate (gill or ventilation rate) increased almost double fold after the noxious treatment whereas the controls only showed a 30% increase. Administering morphine significantly reduced the pain-related behaviours and opercular beat rate and thus morphine appears to act as an analgesic in the rainbow trout. It is concluded that these pain-related behaviours are not simple reflexes and therefore there is the potential for pain perception in fish.
Article
Many traditional attempts to show that nonhuman animals are deserving of moral consideration have taken the form of an argument by analogy. However, arguments of this kind have had notable weaknesses and, in particular, have not been able to convince two kinds of skeptics. One of the most important weaknesses of these arguments is that they fail to provide theoretical justifications for why particular physiological similarities should be considered relevant. This paper examines recent empirical research on pain and, in particular, explores the implications of the dissociation between the sensory and the affective pain pathways. It is argued that these results show that the belief that nonhuman animals experience pain in a morally relevant way is reasonable, though not certain. It is further argued that the proposal to explore the relationship between consciousness and various forms of learning challenges the aforementioned skeptics to provide more physiological details for their claims that nonhuman mammals are probably not conscious. * This paper (then titled “Neural Correlates of Suffering”) was the winner of the 2005 William James Prize of the Society for Philosophy and Psychology, awarded for the best paper by a graduate student presented at the Society's annual meeting.
Article
Four groups of Ayrshire calves (n = 8 each) were castrated at 1 week of age by either surgery, crushing by a Burdizzo, rubber ring or a combination of the Burdizzo and rubber ring methods. Responses of castrated calves were compared with a control group (n = 8) of handled calves. Plasma cortisol was measured in blood samples taken during the first 3 h after castration. Observations of behaviour were made for 3 h immediately after castration, and for 3 h each afternoon for the first 4 days and then on every third day to 48 days after treatment. An assessment of the castration site (lesion score) was made after each observation period and the calves were weighed every twelfth day. Acute changes in behaviour and plasma cortisol were consistent with those reported previously, namely that increases in active behaviours, abnormal postures and plasma cortisol occurred in the first 3 h after castration. The behavioural response to both surgical and Burdizzo castration was characterised by immobile postures. The combined Burdizzo and rubber ring method produced a significant reduction in the activity (count per 3 h period) of two behaviours (foot stamping/kicking (11.9) and easing quarters (13.3)) compared with the use of a rubber ring alone (27 and 23.7, respectively). During the 48 days after rubber ring treatments there was an increase in the calves' concern with the site of castration, indicated by a significantly (P < 0.01) increased incidence of licking which was associated with increased abnormal standing, with slow movements of the tail, alternate lifting of the hindlegs and head turning as the integrity of the skin broke down. If these indices are valid, they demonstrate that considerable acute and chronic pain is associated with rubber ring methods of castration of calves and that the chronic pain can last for at least 42 days.
Article
Recent research has shown the possibility of pain perception in fish; therefore, the use of analgesia or “painkillers” should be considered for invasive procedures. However, there is relatively little information on the effectiveness of analgesic drugs nor on the appropriate dose for fish. This study assessed the efficacy of three types of drug: an opioid, buprenorphine, a non-steroidal anti-inflammatory drug (NSAID), carprofen and a local anaesthetic, lidocaine. Each drug was tested at three doses on rainbow trout that were noxiously stimulated and the most effective dose was also given to fish experiencing no pain to investigate side-effects. Ventilation rate and time to resume feeding were used as pain indicators, together with the amount of activity and plasma cortisol concentrations to gauge any detrimental side effects. Buprenorphine at all three doses had limited impact on the fish's response to a painful stimulus. Carprofen ameliorated effects of noxious stimulation on time to resume feeding but activity was reduced more than by noxious treatment alone. Lidocaine reduced all of the pain indicators measured with the lowest, most effective dose being 1mg per fish. None of the analgesics led to raised plasma cortisol compared to control groups. This study demonstrates that lidocaine could be recommended for use in rainbow trout to ameliorate possible pain-related responses.
Article
Suckling piglets are routinely identified to assist with their day-to-day management. A total of 120 suckling piglets were used to determine and compare the short-term pain responses to a number of identification methodologies, including: ear notching, ear tagging and intraperitoneal injection (IP) of a 4mm×32mm glass encapsulated transponder. Two additional groups of piglets were used as controls for the different handling positions (ear or IP treatments). Treatments were applied to suckling piglets during a 90-s period and the pain response was determined using behavioural observations, vocalisation recordings, physiological measurements and growth performance analysis. Saliva samples for cortisol analysis were collected 15min pre- and post-treatment from all animals, and blood samples for lactate analysis were collected at the time of treatment application and after 10min from the ear notched and IP injected groups. Piglet behaviour was observed in the farrowing crate using instantaneous scan sampling with recordings made at 5-min intervals over a 3h period. Pain-related behavioural displays were found to be significantly higher (P
Article
Objective: To evaluate the antinociceptive and sedative effects and duration of action of hydromorphone hydrochloride after IM administration to American kestrels (Falco sparverius). Animals: 11 healthy 2-year-old American kestrels. Procedures: Hydromorphone (0.1, 0.3, and 0.6 mg/kg) and an equivalent volume of saline (0.9% NaCl) solution (control treatment) were administered IM to kestrels in a masked randomized complete crossover study design. Foot withdrawal response to a thermal stimulus was determined 30 to 60 minutes before (baseline) and 0.5, 1.5, 3, and 6 hours after treatment administration. Agitation-sedation scores were determined 3 to 5 minutes before each thermal test. Results: Hydromorphone at 0.6 mg/kg, IM, significantly increased the thermal foot withdrawal threshold, compared with the response after administration of saline solution, for up to 3 hours, and hydromorphone at 0.1, 0.3, and 0.6 mg/kg, IM, significantly increased withdrawal responses for up to 6 hours, compared with baseline values. No significant differences in mean sedation-agitation scores were detected between hydromorphone and saline solution treatments; however, appreciable sedation was detected in 4 birds when administered 0.6 mg of hydromorphone/kg. Conclusions and clinical relevance: Hydromorphone at the doses evaluated significantly increased the thermal nociception threshold for American kestrels for 3 to 6 hours. Additional studies with other types of stimulation, formulations, dosages, routes of administration, and testing times are needed to fully evaluate the analgesic and adverse effects of hydromorphone in kestrels and other avian species and the use of hydromorphone in clinical settings.