Animal welfare science and best practice in animal care should focus on the well-being of individuals, in respect of the fact that positive welfare is not something we give to animals but rather something they experience. Through a holistic approach, professional zoos and aquariums (henceforth zoos) should strive to promote optimal welfare for all animals in their care, utilizing a combination of modern science, best practice, and ethical frameworks, including compassion and empathy [1]. Being professional means having up-to-date theoretical and practical knowledge of animal welfare topics including but not strictly limited to learning, training, housing, environmental enrichment, and nutrition [2]. There is no lack of practical examples nor publications on the ways in which we can improve well-being for those animals living in human care, including in zoos, and it is our moral obligation to ensure that this theoretical knowledge and new best practices are integrated into our every day and systemic processes.

Despite significant advances in the care of captive wild animals and an increased understanding of the importance of individual experiences to overall well-being, suboptimal and outdated handling methods are still used for some species and individuals. For example, chasing small and more skittish animals into holding areas (pers. observation, Max Norman, 2021), or using physical restraint for animals that are easily grabbed or for individuals who are perceived as more aggressive. Flight and fear responses are often used for many taxa (earliest pers. observations Sabrina Brando, 1992) despite advances in animal training methods and the numerous known benefits of training animals to participate in their own care. With respect to growing knowledge as to the benefits of using training over coercive “traditional” methods, how animals are positively handled and trained should be at the core of any animal care and well-being program.

Russel and Burch [3] suggested the “3Rs” principles of Replacement, Reduction, and Refinement in the 1960s as an ethical foundation for using animals in research and, while the 3Rs were developed for animals in research specifically, the concepts proposed have broad potential applications when considering animals housed in other contexts including zoos and aquariums [4]. Although the principles can be interpreted in different ways [5], they are broadly described as follows [6]:

• Replacement: The use of animals should be replaced by non-sentient animals or non-animal methods whenever possible without compromising other objectives, such as education, conservation, and research.
• Reduction: The smallest possible number of animals to meet the objectives of the facility should be used; with the purpose of reducing collective animal harm.

• Refinement: This principle entails that all procedures must be designed to minimize the pain and/or discomfort they cause to the animals, e.g., using anesthesia and analgesia, establishing humane endpoints to avoid suffering which cannot be relieved by other measures, and training animals with positive reinforcement.

• Replacement: The use of animals should be replaced by non-sentient animals or non-animal methods whenever possible without compromising other objectives, such as education, conservation, and research.
• Reduction: The smallest possible number of animals to meet the objectives of the facility should be used; with the purpose of reducing collective animal harm.
• Refinement: This principle entails that all procedures must be designed to minimize the pain and/or discomfort they cause to the animals, e.g., using anesthesia and analgesia, establishing humane endpoints to avoid suffering which cannot be relieved by other measures, and training animals with positive reinforcement.

2. Animal Learning and Training

Animals are learning all the time, whether we are cognizant of it or not. Learning is described as the ongoing, dynamic, and individual process of acquiring new or modifying existing knowledge, behaviors, and preferences [7]. Training animals through positive reinforcement training (PRT) promotes the voluntary participation of animals in practices that are commonly regarded as negative, such as veterinary procedures or transport, through a process of encouraging behavioral change through rewarding animals for exhibiting desired behaviors. This is not at all a new concept; there are many publications on the topic, including explorations of reinforcer preferences and effectiveness ^[8][9][13,14]. However, while the use of PRT has greatly increased globally, it is not widely used as a standard practice but instead often seen as something that is done when there is time. This is particularly true for species beyond the larger, more commonly trained, and charismatic species such as elephants, great apes, and marine mammals ^[10][15]. Nonetheless, the widespread implementation of PRT has shifted common animal handling practices away from imposing coercive physical and chemical restraint practices and towards the willing, voluntary collaboration of the animals. Providing the animals with a degree of control increases the likelihood of handling being perceived as a positive experience while increasing the efficiency of procedures such as health checks and sample collection ^[11][12][13][16,17,18]. It should be recognized that learning occurs during all interactions between animals and their caregivers, both direct and indirect. For example, animals become familiar with indirect and informal actions, such as the daily routines of their caregivers and the clothes the veterinarian wears during medical examinations ^[14][19]. They are also cognizant of and remember the manner in which direct and formal animal care activities, such as feeding and training, are conducted and will learn from such experiences. As an example, during their daily routines care staff may always feed in certain areas and make it predictable for the animals where the food will be delivered, as well as the approximate time, which can be the cause of anticipatory and undesired behaviors ^[15][16][17][20,21,22]. While the focus of learning and training is often on formal training sessions, it is of utmost importance that those involved in the care of animals are attentive to the different processes and procedures happening around the animal on an informal basis as well. Informal training can take many different forms and occur through many different means. Behavioral and environmental changes may act as indicators that allow and provide animals information to predict upcoming events; for example, caretakers can wear different clothing when capturing animals or use sounds and other signals to communicate that a particular event is about to happen. Rimpley et al. ^[18][23] found that making certain husbandry events reliable and predictable through the introduction of a unique signal, such as knocking before entering their enclosure, had a significant positive impact in reducing the prevalence of anxiety-related behaviors in capuchins; in this example, the capuchins learned to associate the knocking with the door opening and a keeper entering. Such approaches are effective and easy to implement without any need for additional costs and are not time-consuming for caregivers. The absence of these signals will also serve as a communicative tool; when the signal is not given, the animals know not to expect the event to occur.