Measuring motivation in swine: the food-metric scale

Understanding how nonhuman animals such as swine respond to their environment and understanding how to provide them with a good quality of life involves using a range of experimental approaches. More and more, ethological researchers are turning to operant methods to answer some of these questions. Employing an operant such as a lever, researchers can assess how hard animals will work to get access to environmental resources: increased space or social contact. It is difficult, however, to determine how the effort made by the animals relates to the degree to which they need the resource and, in particular, how to interpret intermediate levels of responding. One approach to understanding the level of need is to compare it with familiar states of deprivation such as hunger. Food is an environmental resource known to range from low to high value depending on deprivation level. Depriving animals of a fixed proportion of their daily ad libitum intake allows the animals to demonstrate the levels of responding produced at satiation: 23 hr deprivation and a range of intermediate points. The resulting scale has both empirical and intuitive value and can help in understanding the value of various degrees of operant effort. Ultimately, this information will help in deciding which environmental conditions should be provided to swine as part of routine husbandry.     

Control, choice, and assessments of the value of behavioral management to nonhuman primates in captivity

Many people have devoted considerable effort to enhancing the environments of nonhuman primates in captivity. There is substantial motivation to develop experimental, analytical, and interpretational frameworks to enable objective measurements of the value of environmental enrichment/behavioral management efforts. The consumer-demand approach is a framework not frequently implemented in studies of nonhuman primate welfare but profitably used in studies of the welfare of nonhuman animals in agriculture. Preference studies, in which primates can voluntarily choose to socialize or to participate in training, may be the best current examples of a consumer-demand-like approach to assessing the effects of captive management strategies on primate welfare. Additional work in this area would be beneficial; however, there are potential ethical constraints on purposefully subjecting primates to adverse circumstances to measure their demand for a resource. Primate welfare researchers need to design consumer-demand studies with obstacles that will help measure the relative value of resources to captive primates without compromising the welfare they are attempting to evaluate and enhance.     

Control,Choice, and Assessments of the Value of Behavioral Management to Nonhuman Primates in Captivity

Many people have devoted considerable effort to enhancing the environments of nonhuman primates in captivity. There is substantial motivation to develop experimental, analytical, and interpretational frameworks to enable objective measurements of the value of environmental enrichment/behavioral management efforts. The consumer-demand approach is a framework not frequently implemented in studies of nonhuman primate welfare but profitably used in studies of the welfare of nonhuman animals in agriculture. Preference studies, in which primates can voluntarily choose to socialize or to participate in training, may be the best current examples of a consumer-demand-like approach to assessing the effects of captive management strategies on primate welfare. Additional work in this area would be beneficial; however, there are potential ethical constraints on purposefully subjecting primates to adverse circumstances to measure their demand for a resource. Primate welfare researchers need to design consumer-demand studies with obstacles that will help measure the relative value of resources to captive primates without compromising the welfare they are attempting to evaluate and enhance.     

The effects of environmental control on cognition in rats (Rattus norvegicus)

The aim of this study was to allow nonhuman animals to control their environment using operant conditioning procedures and to assess the effect of control on cognitive tasks. The study tested 4 predictions: (a) rats (Rattus norvegicus) will control a light stimulus; (b) animals will exhibit preferences for particular stimulus strengths; (c) animals who exert control over environmental stimuli will show improved performance on cognitive tasks compared with animals who lack control; and (d) at the end of the operant phase, experimental subjects will have lower corticosterone levels than animals who lack control. Experimental subjects did show control over a light stimulus and performed significantly better over time in a discrimination task compared with subjects who could not control their environment. There was no difference in corticosterone levels between control and experimental subjects. The results will both contribute to our understanding of how control of environmental stimuli affects the welfare of animals in captive environments and aid in designing experimental conditions that will increase validity and reliability in research.     

The Effects of Environmental Control on Cognition in Rats (Rattus norvegicus)

The aim of this study was to allow nonhuman animals to control their environment using operant conditioning procedures and to assess the effect of control on cognitive tasks. The study tested 4 predictions: (a) rats (Rattus norvegicus) will control a light stimulus; (b) animals will exhibit preferences for particular stimulus strengths; (c) animals who exert control over environmental stimuli will show improved performance on cognitive tasks compared with animals who lack control; and (d) at the end of the operant phase, experimental subjects will have lower corticosterone levels than animals who lack control. Experimental subjects did show control over a light stimulus and performed significantly better over time in a discrimination task compared with subjects who could not control their environment. There was no difference in corticosterone levels between control and experimental subjects. The results will both contribute to our understanding of how control of environmental stimuli affects the welfare of animals in captive environments and aid in designing experimental conditions that will increase validity and reliability in research.     

Special welfare concerns in countries dependent on live animal trade: the real foreign animal disease emergency for Canada

Any outbreak of an Office International des Epizooties trade-disrupting (previously List-A) disease, such as classical swine fever or foot and mouth disease in a previously disease-free region can have severe consequences for nonhuman animal welfare. In addition to animals destroyed for the purposes of disease eradication, certain preexisting trade patterns may result in welfare slaughter programs affecting many more animals than the disease eradication effort. Welfare slaughter is the destruction of healthy animals to prevent overcrowding on farms under movement restriction and as a consequence of loss of access to live animal export markets. Governments of European countries have anticipated welfare slaughter as part of their disease eradication preparedness. The concept of welfare slaughter and the resource implications thereof have not been included in current, published, livestock disease emergency-planning documents in Canada or the United States. Animal welfare, specifically the killing of healthy animals (not foreign animal disease eradication) has been the focus of public concern in recent disease-eradication efforts in Europe. North American organizations responsible for livestock exotic disease emergency preparedness need to expand their plans to include welfare slaughter.     

Evaluation of the ‘maximum price paid’ as an index of motivational strength for farmed silver foxes (Vulpes vulpes)

To measure farmed foxes’ motivations for full, naturalistic social contact, we constructed an apparatus where they could perform an operant to access stimuli, but then leave freely and thence determine their own bout lengths. Motivational measures based on demand curves can be invalid in such set-ups, and we therefore sought to validate the measure ‘maximum price paid’. This was achieved by measuring six silver fox males’ maximum operant responding for access or proximity to three resources differing in biological significance: food, vixens in oestrus and males. We predicted that if valid, maximum price paid would be highest for food and vixens. Maximum price were 970 ± 399 (S.E.) for food, 677 ± 173 (S.E.) for vixens and 389 ± 101 (S.E.) for other males (P < 0.05). In contrast, our complementary measures of motivation – price elasticity, expenditure and consumer surplus – did not differentiate between the resources, and ranked them in different orders (albeit not significantly). This was because the foxes rescheduled their behaviour with increasing costs, decreasing bout number while increasing bout length, to different extents with the three resources. Additional findings showed that all subjects ‘overpaid’, performing the operant response more than was required. This increased as the costs increased, perhaps due to increasing ‘time outs’ on the time-restricted schedule (DRH) as the task got harder. However, the overpayment was also highest when males were the resource, suggesting that operant responding was slowest and least efficient when working for less-valued resources. The resources present also affected how the foxes used the rest of the apparatus and influenced their behaviour; subjects staying more in the operant compartment when the resource was social (especially a female), but retreating to a distant compartment when it was food. While proximity to oestrous vixens elicited higher levels of tail wagging and only low levels of pacing, indicating a positive motivation, proximity to males elicited relatively high levels of pacing plus agonistic gaping, suggesting that the motives for seeking contact with males related to aggression. Thus, although our operant set-up reveals a drive to approach other males, the possible aggressive motives suggest that this sort of social contact would not necessarily improve their welfare in a traditional housing system. Overall, these results help improve the design and interpretation of preference tests, and confirm maximum price paid as a useful motivational measure for farmed foxes.     

Prolonged microwave irradiation of rats: Effects on concurrent operant behavior

Two measures of performance were used to study the effects of pulse-modulated microwave radiation (PM MWR) on schedule-controlled operant behavior of rats: 1) cued (S^D), fixed-ratio (FR) bar pressing for food reinforcement; and 2) noncued (S^d) bar pressing in the absence of food reinforcement. The animals were irradiated and the behavioral data were obtained concurrently, during daily three-hour sessions, five days per week for six to nine weeks. Each experiment began with a two to three-week baseline interval of sham irradiation; a two to three-week interval of sham irradiation followed the irradiation phase. The irradiated animals were exposed to 1.3-Ghz PM MWR (pulse width of 1 microsecond at 600 pulses per second) at whole-body, average specific absorbed-dose rates of from 1.5–6.7 mW/g. Control and irradiated animals were tested in identical, cylindrical waveguide exposure/behavioral assemblies; different groups of irradiated and sham-irradiated animals were used for each dose rate. At 1.5 mW/g, the levels of S^D operant responding by control and irradiated animals were comparable, and showed similar progressive diminutions over the course of each daily session. S^d operant responding was more variable, but again comparable, with both groups showing similar, progressive declines in rate of responding during each session. At 3.6 mW/g, no specific effects on S^D operant response rates were observed. However, there was an initial and transient increase in the rate of extinction of S^d responding. At 6.7 mW/g, S^D response rates were slightly reduced, whereas there was a major reduction in noncued (S^d) operant responding followed by a sharp rebound during the first post-MWR week. This marked reduction in S^d operant responding at MWR onset was in contrast to the relative stability and persistence of FR responding for food reinforcement.     

From “Us vs. Them” to “Shared Risk”: Can Animals Help Link Environmental Factors to Human Health?

Linking human health risk to environmental factors can be a challenge for clinicians, public health departments, and environmental health researchers. While it is possible that nonhuman animal species could help identify and mitigate such linkages, the fields of animal and human health remain far apart, and the prevailing human health attitude toward disease events in animals is an “us vs. them” paradigm that considers the degree of threat that animals themselves pose to humans. An alternative would be the development of the concepts of animals as models for environmentally induced disease, as well as potential “sentinels” providing early warning of both noninfectious and infectious hazards in the environment. For such concepts to truly develop, critical knowledge gaps need to be addressed using a “shared risk” paradigm based on the comparative biology of environment–host interactions in different species.     

The reactive scope model — A new model integrating homeostasis, allostasis, and stress

Allostasis, the concept of maintaining stability through change, has been proposed as a term and a model to replace the ambiguous term of stress, the concept of adequately or inadequately coping with threatening or unpredictable environmental stimuli. However, both the term allostasis and its underlying model have generated criticism. Here we propose the Reactive Scope Model, an alternate graphical model that builds on the strengths of allostasis and traditional concepts of stress yet addresses many of the criticisms. The basic model proposes divergent effects in four ranges for the concentrations or levels of various physiological mediators involved in responding to stress. (1) Predictive Homeostasis is the range encompassing circadian and seasonal variation — the concentrations/levels needed to respond to predictable environmental changes. (2) Reactive Homeostasis is the range of the mediator needed to respond to unpredictable or threatening environmental changes. Together, Predictive and Reactive Homeostasis comprise the normal reactive scope of the mediator for that individual. Concentrations/levels above the Reactive Homeostasis range is (3) Homeostatic Overload, and concentrations/levels below the Predictive Homeostasis range is (4) Homeostatic Failure. These two ranges represent concentrations/levels with pathological effects and are not compatible with long-term (Homeostatic Overload) or short-term (Homeostatic Failure) health. Wear and tear is the concept that there is a cost to maintaining physiological systems in the Reactive Homeostasis range, so that over time these systems gradually lose their ability to counteract threatening and unpredictable stimuli. Wear and tear can be modeled by a decrease in the threshold between Reactive Homeostasis and Homeostatic Overload, i.e. a decrease in reactive scope. This basic model can then be modified by altering the threshold between Reactive Homeostasis and Homeostatic Overload to help understand how an individual's response to environmental stressors can differ depending upon factors such as prior stressors, dominance status, and early life experience. We illustrate the benefits of the Reactive Scope Model and contrast it with the traditional model and with allostasis in the context of chronic malnutrition, changes in social status, and changes in stress responses due to early life experiences. The Reactive Scope Model, as an extension of allostasis, should be useful to both biomedical researchers studying laboratory animals and humans, as well as ecologists studying stress in free-living animals.     

Trophic network structure emerges through antagonistic coevolution in temporally varying environments

Understanding the mechanisms underlying ecological specialization is central to our understanding of community ecology and evolution. Although theoretical work has investigated how variable environments may affect specialization in single species, little is known about how such variation impacts bipartite network structure in antagonistically coevolving systems. Here, we develop and analyse a general model of victim-enemy coevolution that explicitly includes resource and population dynamics. We investigate how temporal environmental heterogeneity affects the evolution of specialization and associated community structure. Environmental productivity influences victim investment in resistance, which will shape patterns of specialization through its regulating effect on enemy investment in infectivity. We also investigate the epidemiological consequences of environmental variability and show that enemy population density is maximized for intermediate lengths of productive seasons, which corresponds to situations where enemies can evolve higher infectivity than victims can evolve defence. We discuss our results in the light of empirical studies, and further highlight ways in which our model applies to a range of natural systems.     

Some effects of procedural variables on operant choice behavior

Procedural variables are concerned with the way subjects contact stimulus, response, and reinforcer variables and relations in an experiment. Procedural variables may therefore be understood as tools that allow researchers and theorists to explore the generality of their conceptions of independent variables, behavioral processes, and quantitative laws of behavior. The present article reviews data from several studies showing how procedural variables can influence the outcome of operant choice experiments, even when nominal independent variables remain constant. An important theoretical issue raised by these data is whether researchers have most usefully identified the independent variables that they incorporate into their quantitative models. Particular attention is paid to how procedural variables can influence the measure of reinforcement frequency over time that best correlates with the distribution of choice responding over time.     

Bioremediation and Tolerance of Humans to Heavy Metals through Microbial Processes: a Potential Role for Probiotics?

The food and water we consume are often contaminated with a range of chemicals and heavy metals, such as lead, cadmium, arsenic, chromium, and mercury, that are associated with numerous diseases. Although heavy-metal exposure and contamination are not a recent phenomenon, the concentration of metals and the exposure to populations remain major issues despite efforts at remediation. The ability to prevent and manage this problem is still a subject of much debate, with many technologies ineffective and others too expensive for practical large-scale use, especially for developing nations where major pollution occurs. This has led researchers to seek alternative solutions for decontaminating environmental sites and humans themselves. A number of environmental microorganisms have long been known for their ability to bind metals, but less well appreciated are human gastrointestinal bacteria. Species such as Lactobacillus, present in the human mouth, gut, and vagina and in fermented foods, have the ability to bind and detoxify some of these substances. This review examines the current understanding of detoxication mechanisms of lactobacilli and how, in the future, humans and animals might benefit from these organisms in remediating environmental contamination of food.     

Training Nonhuman Primates to Cooperate With Scientific Procedures in Applied Biomedical Research

This report provides a brief overview of aspects of training nonhuman primates who have been, and continue to be, used in this laboratory. The research context involves applied behavioral studies in which animals are trained to perform complex operant behavioral sequences, often in their homecage environment. In such studies, animals have freedom to choose whether to engage in appetitively reinforced behavioral tests that employ neither food deprivation nor fluid management. This background of operant conditioning has provided an insight to, and a context for, animal training both as an adjunct to general laboratory management and as a way to expedite scientific procedures. Thus, training has potential implications for both well-being and scientific quality, although it must be considered an adjunct to the provision of socialization with conspecifics in high quality diverse housing systems and not as an alternative to such provision. The importance of discussion and consideration of alternative procedures cannot be overemphasized.     

Training nonhuman primates to cooperate with scientific procedures in applied biomedical research

This report provides a brief overview of aspects of training nonhuman primates who have been, and continue to be, used in this laboratory. The research context involves applied behavioral studies in which animals are trained to perform complex operant behavioral sequences, often in their homecage environment. In such studies, animals have freedom to choose whether to engage in appetitively reinforced behavioral tests that employ neither food deprivation nor fluid management. This background of operant conditioning has provided an insight to, and a context for, animal training both as an adjunct to general laboratory management and as a way to expedite scientific procedures. Thus, training has potential implications for both well-being and scientific quality, although it must be considered an adjunct to the provision of socialization with conspecifics in high quality diverse housing systems and not as an alternative to such provision. The importance of discussion and consideration of alternative procedures cannot be overemphasized.     

Environmental enrichment decreases responding for visual novelty

Previous research has demonstrated that rats reared in an enriched condition (EC) with novel objects and social partners self-administer less amphetamine compared to rats raised in an isolated condition (IC). However, it is unclear if the enrichment-induced decrease in stimulant self-administration generalizes to non-drug rewards such as those provided by novel environmental stimuli. In the current study, EC, IC, and social condition (SC) rats were raised from 21 to 51 days of age before being tested in a two-lever operant conditioning chamber in which responding on one lever (active lever) resulted in illumination of a cue light. In Experiment 1, rats were initially assessed for baseline responding (no contingency) and then the contingent light was introduced. EC rats responded less than IC rats for the contingent light stimulus; however, EC rats also displayed a lower rate of baseline responding. In Experiment 2, rats were trained initially to lever press for a sucrose reward to decrease differences in baseline responding. While sucrose pretraining decreased baseline response differences between groups, EC rats still responded less for the contingent light stimulus than IC or SC rats. These results suggest that environmental enrichment decreases the incentive value of visual novelty.     

Looking where it's hard to see: a case study documenting rare Eucyclogobius newberryi presence in a California lagoon

Environmental DNA (eDNA) analysis is increasingly used for biomonitoring and research of fish populations and communities by environmental resource managers and academic researchers. Although managers are much interested in expanding the use of eDNA as a survey technique, they are sceptical about both its utility (given that information is often limited to presence/absence of a species) and feasibility (given the need for proper laboratory facilities for sample processing). Nonetheless, under the right circumstances, eDNA analysis is cost-effective compared to many traditional aquatic survey methods and does not disturb habitat or harm the animals being surveyed. This article presents a case study in which eDNA analysis was successfully used to document the presence of a rare fish species in a waterway earmarked for restoration. The authors discuss the conditions that allowed this study to occur quickly and smoothly and speculate on how the goals of researchers and managers can be integrated for efficient and informative use of this tool.     

The dynamical implications of human behaviour on a social-ecological harvesting model

The dynamic aspects of human harvesting behaviour are often overlooked in resource management, such that models often neglect the complexities of dynamic human effort. Some researchers have recognized this, and a recent push has been made to understand how human behaviour and ecological systems interact through dynamic social-ecological systems. Here, we use a recent example of a social-ecological dynamical systems model to investigate the relationship between harvesting behaviour and the dynamics and stability of a harvested resource, and search for general rules in how relatively simple human behaviours can either stabilize or destabilize resource dynamics and yield. Our results suggest that weak to moderate behavioural and effort responses tend to stabilize dynamics by decreasing return times to equilibria or reducing the magnitude of cycles; however, relatively strong human impacts can readily lead to human-driven cycles, chaos, long transients and alternate states. Importantly, we further show that human-driven cycles are characteristically different from typical resource-driven cycles and, therefore, may be differentiated in real ecosystems. Given the potentially dramatic implications of harvesting on resource dynamics, it becomes critical to better understand how human behaviour determines harvesting effort through dynamic social-ecological systems.     

Operant sensation seeking requires metabotropic glutamate receptor 5 (mGluR5)

Pharmacological and genetic studies have suggested that the metabotropic glutamate receptor 5 (mGluR5) is critically involved in mediating the reinforcing effects of drugs of abuse, but not food. The purpose of this study was to use mGluR5 knockout (KO), heterozygous (Het), and wildtype (WT) mice to determine if mGluR5 modulates operant sensation seeking (OSS), an operant task that uses varied sensory stimuli as a reinforcer. We found that mGluR5 KO mice had significantly reduced OSS responding relative to WT mice, while Het mice displayed a paradoxical increase in OSS responding. Neither KO nor Het mice exhibited altered operant responding for food as a reinforcer. Further, we assessed mGluR5 KO, Het and WT mice across a battery of cocaine locomotor, place preference and anxiety related tests. Although KO mice showed expected differences in some locomotor and anxiety measures, Het mice either exhibited no phenotype or an intermediate one. In total, these data demonstrate a key role for mGluR5 in OSS, indicating an important role for this receptor in reinforcement-based behavior.