Conservation biology and animal welfare science are multidisciplinary fields of research that address social concerns about animals. Conservation biology focuses on wild animals, works at the level of populations, ecological systems and genetic types, and deals with threats to biodiversity and ecological integrity. Animal welfare science typically focuses on captive (often domestic) animals, works at the level of individuals and groups, and deals with threats to the animals’ health and quality of life. However, there are many areas of existing or potential overlap: (i) many real-life problems, such as environmental contamination, urban development and transportation, create problems for animals that involve both welfare and conservation; (ii) research methods from each field are needed to address some of the scientific problems of the other; and (iii) policies and practices targeting either conservation or animal welfare may prove unproductive if they do not take account of both areas of concern. Moreover, scientists in both fields face the common challenge of applying science to guide policy and practice, often to issues that are both empirical and ethical, and often under conditions of uncertainty. There are many cases where communication and co-operation between the fields should lead to better science and better practical outcomes.

Since reintroduction programmes involve moving animals from captive or wild environments and releasing them into novel environments, there are sure to be a number of challenges to the welfare of the individuals involved. Behavioural theory can help us develop reintroductions that are better for both the welfare of the individual and the conservation of populations. In addition to modifying captive environments to prepare animals for release to the wild, it is possible to modify the animals’ experience in the post-release environment. For releases to be more successful, they need to better accommodate the ecological and psychological needs of individuals. A better understanding of sensory ecology — how animals acquire and respond to information in their environment — is needed to develop new, more successful management strategies for reintroductions. Sensory ecology integrates ecological and psychological processes, calling for better synergy among researchers with divergent backgrounds in conservation and animal welfare science. This integrative approach leads to new topics of investigation in reintroduction biology, including more careful consideration of post-release stress and the role of social support. Reintroductions are essentially exercises in ‘forced’ dispersal; thus, an especially promising avenue of research is the role of proximate mechanisms governing dispersal and habitat selection decisions. Reintroduction biologists have much to gain from the study of mechanism because mechanisms, unlike function or adaptive value, can be manipulated to enhance conservation and welfare goals.

As the harvesting of fish through commercial fisheries becomes both harder and less economically viable, the world is becoming increasingly dependent on aquaculture to provide fish for human consumption. The closely related activity of stock enhancement, whereby large numbers of fish are reared and then released, is a common practice aimed at increasing the numbers of fish in rivers and along coasts. Aquaculture and stock enhancement practices raise a number of welfare and conservation issues both for fish that are reared within captivity, and for the local populations and habitats that are influenced by fish-rearing activities. In this review, we illustrate how fish farms and hatcheries have directly affected fish welfare. Examples cover on-farm fish husbandry and healthcare, the interactions between farmed and wild fish, and survival of fish released for stock enhancement. These aspects are often intertwined with important conservation issues. Thus, we also review direct effects that aquaculture-generated pollution can have on local habitats, issues associated with feeding reared fish, and problems created by alien fish (either escapees or intentionally released fish). While awareness of fish welfare is certainly growing, so is the rate at which fish are reared. There is, therefore, a pressing need to understand the welfare and conservation issues that are affected by aquaculture and stock enhancement.

Forestry practices may directly kill animals as well as destroy and fragment their habitat. Even without habitat destruction, logging and its associated forest management practices (which include road building, re-forestation, and often increased recreational use) create noise, frighten animals, and may lead to changes in species composition as well as evolutionary responses to the myriad of anthropogenic impacts. Thus, forestry practices may create conservation problems. Forestry practices may also create welfare problems that may act on different temporal and spatial scales than the conservation problems. The individuals affected by forestry may have heightened glucocorticoid levels that may lead to a predictable set of deleterious consequences. Individuals may no longer be able to communicate, or they may no longer be attractive to potential mates. Such welfare problems may generate conservation problems if fitness is reduced. Identifying the set of possible impacts is the first step towards improving welfare and aiding wildlife conservation in managed forests.

At least one-third of the land on earth is used for agricultural production and conflicts with the interests of wildlife are inevitable. These conflicts are likely to escalate as the human population expands and as the scale and intensity of agricultural production increases. This paper argues that the same underlying causes frequently affect both wild animal welfare and conservation. Three key threats are discussed: disease transmission from domestic animals and the interventions used to manage wildlife reservoirs of zoonotic diseases; physical operations such as harvesting and the conversion of wildlife habitat to farmland; and the use of agrochemicals, particularly for pest control. While direct effects, such as accidental poisoning, tend to attract the most public attention, it is argued that indirect effects, such as the reduction in food supplies or the disruption of social structures, are likely to be of greater importance. The suffering of pest animals has traditionally been undervalued. There is a need for broader adoption of integrated, ecologically based strategies which minimise suffering and also minimise the numbers of animals involved by preventing population resurgence. New research is urgently required to compare the effects of alternative, economically viable farming strategies on both wildlife conservation and welfare, possibly within the framework of ecosystem services assessments.

Human activities deprive wild animals of their life requisites by destroying or impoverishing their surroundings, causing suffering of individuals. Yet, the notion that animal welfare applies to wildlife has escaped many animal welfarists and conservationists. A well-accepted and applied ethical foundation for animal conservation that considers animal welfare is lacking. We address this by examining how worldviews of conservationists and animal welfarists are related. The clear conceptual link is that individuals within anthropogenically disturbed populations often endure suffering caused by humans. Accordingly, our objectives are to provide an overview of wildlife conservation, integrate ethical aspects of wildlife conservation and animal welfare, and encourage a ‘wildlife welfare’ ethic among conservationists. We describe the relationship between contemporary socioeconomic and environmental conditions and the impoverished status of North American wildlife. We then describe the ecological plight of large mammalian carnivores in North America. Finally, as a case study, we focus on the tenuous lives of grey wolves (Canis lupus) living in the midst of human-dominated landscapes. We conclude that the suffering wildlife endures because of humans is a collective responsibility that presents a moral imperative for animal welfarists and conservationists alike. Habitat destruction and impoverishment deprives species of life requisites, causing trauma, prolonged suffering, and eventually death. We suggest that a shared doctrine of animal welfare principles is needed, such as a modified version of the internationally recognised Five Freedoms. In essence, this would be an ethical affirmation for conservationists and animal welfarists.