**1. Introduction**

Current extinction rates are outstandingly high (about 1000 times previously valued ones) and likely to be underestimated once biodiversity statistics are affected by a gap of information on species taxonomy, distribution and status [1]. The enhanced role of human actions brings new escalating conservation challenges and emerging diseases, which pressure impaired long-term survival of threatened free-ranging and captive wildlife species, while having hazardous effects on ecosystems and public health [2–4]. Biodiversity conservation currently requires a broader approach, capable of connecting interdisciplinary bridges between the diversity of social, economic, political and biological variables which influence health issues, so to understand their complex interaction and therefore find new solutions bearing in mind human and animal well-being while preserving ecosystems, in what is designated as the "OneHealth" approach. Zoological and wildlife medicine are acknowledged scientific branches within the veterinary profession, which emerged in the 1990s as a response to increasing concerns regarding wildlife protection, and that now fully integrate the transdisciplinary frame that characterizes Conservation Biology [2]. Wildlife veterinarians and the zoological community have a pivotal role to play in the future of biodiversity conservation as, apart from saving numbers of species and understanding

the consequences of animal diseases to human communities, they also encompass the protection of functional and integrated ecosystems, applying their skills and scientific knowledge on the emerging field of Conservation Medicine [5, 6].

Modern zoos and aquariums have a responsibility towards the animals under their protection, through their whole life stages. Captivity can affect drastically animal behavior. By confining animals to a cage or enclosure, we reduce the complexity of their environment, severely narrowing the natural control they should detain over it and restricting the range of behaviors they are able to exhibit [7]. Where animals have very limited choices we are the ones planning almost all aspects of their life (e.g., feeding schedules, what to eat, where to sleep, who to live or to reproduce with). Effects of sensory deprivation and physical variety in the environment may result in aggression, boredom, anxiety, frustration and, ultimately, both physical and physiological illness [8]. Furthermore, preservation of core biological behaviors is essential [to the survival of the individuals targeted for release and reintroduction in the wild and, therefore, for the success of conservation programs [9] Thus, captive establishments have an ethical and legal obligation to provide for the holistic welfare of all animals under their protection. They should work in an organized way in order to achieve high standards of animal welfare (AW), comply with animals' wide range of needs and minimize the incidence of negative states while promoting positive ones [10]. This involves providing: (1) appropriate, safe and naturalistic environments; (2) proper diet; (3) adequate veterinary care; (4) appropriate social contact and (5) environmental enrichment [10, 11]. Overall assessment AW is by no means straightforward and should be carried out in a scientific and objective way, avoiding anthropomorphism and taking no account of ethical topics about the practices or conditions being compared in its evaluation [12, 13].
