Whether running a ranch, managing a zoo or inspecting a pet shop, one of the primary considerations that literally set the scene for any environment is space. But space is not all about dimensions. Expanding our own understanding of space is currently a very big topic both for facility management and animal welfare.
Space and nature
In nature, space for animals is essentially unlimited. This does not imply that animals can or should go anywhere – only anywhere they need or want to go. Aquatic species, such as most fishes and cetaceans, are predictably and fundamentally “restricted” to water, save for the occasional brief excursion into the air or onto land to avoid predation, acquire prey or indulge in play – anything more than that spells doom. Likewise, terrestrial species, such as tortoises and primates, can pretty much wander as far and as wide on land as they wish and include the occasional dip, but again, no matter how expansive that additional watery world, staying in it must be brief. Amphibious species span these environments comfortably, but are typically also occupationally bound by the margin of both. So, no matter how much “extraordinary” natural space is available, no animal wants it all – at least not for long. The key issue here is that the limitations of the spatial environment for animals are set by the species’ evolutionary determinants – the amount and type of space that is good for it!
This does not mean that the great spaces of nature are always beneficial for animals. Tsunamis may strand aquatic species on land or wash terrestrial species into the sea – effectively bringing the wrong environment to the animal and vice-versa, with catastrophic results. Regular drought naturally shrinks some inland water pools diminishing usable space, and governing the lives for so-called “seasonal fish” species and others, again with fatal consequences. The key thing here is that such events, whether aberrant or regular, signal disaster and those elements of space can be considered outside of good welfare, whereas greater space in general signals good welfare.
Space and captivity
By definition, “captivity” includes deliberate spatial restriction over nature. Whilst many species and individual animals occupy extensive home ranges, some others (eg a few invertebrates) are more sedentary. Still, activity patterns vary due to many factors, none of which confirm that spatial drivers can be preset by rule of thumb. Therefore, no keeper can say their animal’s environment is enough. So, what is enough? For a start, there is no maximum for space – contrary to the folklore beliefs of many animal keepers who think some animals are stressed outside of small cages. Enough space also infers more than accommodating an animal’s behaviour and exercise. In particular, for vivarium- or aquarium-held ectothermic species, the spatial environment cannot be considered reasonably addressed unless there are multiple refugia, thermal zones and habitat variants among others – all of which are essential and all of which take up space.
Recently, snakes have headlined the veterinary pages as an example of unjustifiable housing practices – being deprived of the fundamental need to straighten their bodies at will because enclosures commonly have dimensions less than the full length of the animal (Figure 1). This makes snakes the only vertebrates commonly kept in such conditions, despite the fact that plenty of evidence exists to show that free-living snakes occupy large home ranges and are often highly active, and that captive snakes suffer increased risks of stress and disease when restricted to small cages.
Remedying the conundrum of spatial provision within an existing spatially limited environment (society) inevitably implies compromise, and almost invariably such compromise impinges welfare. Also, recommending minimum enclosure sizes has a certain unpalatability because it risks appearance of approval that major restriction of freedom is OK – giving a nod to the jailer. Of course, for humans, imprisonment is a punishment, whereas for most animals – especially exotics – it is an imposed way of life, just not really their way.
Nevertheless, animals are where they are, with all of the attendant problems that captivity and its limitations bring, and simply moaning about the problem does not offer a lot. Bigger is better, and this is something to which many of the best zoological facilities are committed. Standard-raising may be most effective most of the time, hence new guidance principles for some of the worst offenders (eg pet shops and their suppliers). Now, the recommended primary linear dimensions are for at least 10 times body size – nothing less, and rightly more, with no cages less than 100cm length (Figure 2; Warwick et al., 2018), and all animals must be able to use any facility (eg a refuge or water container) at any time.
Conclusions
The spatial itineraries of animals in nature must inform their husbandry in captivity. Undoubtedly, some things that happen in nature ought to stay in nature; captivity already has enough artificial catastrophes to deal with. Once in captivity, animals become our responsibility, and we have obligations to provide them with what they do need or want and to protect them from what they don’t.
Too often, spatial provisions are decided by what is thought convenient for owners rather than what is better for animals – simply because someone occupies a small apartment is no excuse for confining wild animals in a glass box the size of a plant pot. Such a spatially parsimonious mindset actually indicates poor care. Space is vital to welfare. Improving the lives of animals through greater space offers at least one welfare-progressive dimension, and there should be no room for overlooking the spatial needs or wants of captive animals.
