Enclosure size
Wild tigers are known for travelling vast distances in search of territory, mates, water and prey [1]. The distances travelled by tigers does depend on the region that they live in, with Amur tigers, who live in colder regions (such as Siberia), usually travelling greater distances than tigers in other parts of the world. Thus, with this natural history, one of the biggest welfare issues for captive tigers is insufficient space from too small enclosures.
It is also believed that this ranging behaviour is partly what causes stereotypic pacing (repetitive walking between two points more than twice without an obvious goal [2]) behaviours in captive tigers [3]. Essentially, the ability to travel long distances is prevented, so the tiger replaces this with moving back and forth in the space that it has in order to emulate the long-range patrolling it would perform in the wild. Some studies have shown that with increased enclosure size, the percentage of time spent pacing decreased [4,5,]. However, another study found that there was no difference in pacing with respect to the size of the enclosure [6]. These conflicting results do not mean that tigers can be kept in small spaces, far from it. Some countries have minimum area standards in place and these should be adhered to, though always providing as large a space as possible. Unfortunately, minimum standards are not provided in many countries, which has a detrimental effect on tiger welfare.
In addition, we need to also consider the quality of the space, instead of solely the size of the space and whether that effects whether tigers pace or not. Tigers, like any animal including humans, need access to meaningful space that provides challenges and stimulation. This is where enrichment is needed, such as food hanging from poles and toys with food hidden inside, all encourage the tiger to work for its food, much as it would in the wild. However, enrichment should never be forced but should rather the tiger is encouraged to engage in enrichment activities of their own choice.
Contrafreeloading
Tigers, like other animals, will choose to engage in enrichment. Studies have shown that the majority of animals are actually contrafreeloaders, which means that they will choose to spend time working to get their food as part of explorative behaviours rather than take the easy option [7]. Tigers have also shown this to be true with pacing reduced in tigers that were given feeding boxes multiple times a day, catering to their need for foraging and providing them with the option of figuring out how to get access to the food [8].
Roaming for a reason
Further evidence suggests that tigers are not simply roaming around for the sake of it, but rather in order to gain the amount of food and water it requires to survive. If the food and water is plentiful, the tiger won’t roam as far. Studies show that animals will only expend the amount of energy necessary for the maximum reward. This can even be seen across the different tiger sub-species, where prey density determines the size of the tiger’s territory [9]. Essentially, some tiger sub-species are travelling long distances because they have to, not because they want to.
Providing a stimulating environment is a lot easier in a large space. The challenge now occurring in zoos is that legislation mandates minimum requirements, which is not the right approach as these smaller areas are liable to become the norm [10]. Regulations such as this can prevent larger enclosures or exhibits from improving. However, Zoo360 Animal Exploration trails at Philadelphia Zoo has demonstrated the success of thinking beyond minimum requirements. The zoo provides trails allowing the tiger to roam around the zoo, passing other animals and even observing the human visitors from various vantage points. This type of enrichment is great for improving animal welfare, but again it must be a novel experience that the tiger can have some control over rather than being forced. A living environment that is changed regularly can also be stressful, much in the way a barren one is, so it’s important to think about this when furnishing the tiger’s environment.
In conclusion, the quality of the space may be the important factor here, rather than just providing huge amounts of it when it comes to captive tiger welfare [11]. The need for mental stimulation focusing on a wide range of behaviours, not just a focus on hunting, is therefore key to improved welfare.
References
1). Szokalski, M.S., Litchfield, C.A., and Foster, W.K. (2012). Enrichment for captive tigers (Panthera tigris); Current knowledge and future directions. Applied Animal Behaviour Science, 139(1-2), pp. 1-9.
2). Mohapatra, R.K., Panda, S. and Acharya, U.R. (2014). Study on activity pattern and incidence of stereotypical behavior in captive tigers. Journal of Veterinary Behavior, 9(4): pp. 172-176.
3). Clubb, R. and Mason, G. (2004). Pacing polar bears and stoical sheep: Testing ecological and evolutionary hypotheses about animal welfare. Animal Welfare. 13, pp. 533-540.
4). White, B.C., Houser, L.A., Fuller, J.A., Taylor, S. and Elliott, J.L.L. (2003). Activity-Based Exhibition of Five Mammalian Species: Evaluation of Behavioral Changes. Zoo Biology, 22: pp. 269–285.
5). Breton, G. and Barrot, S. (2014). Influence of enclosure size on the distances covered and paced by captive tigers (Panthera tigris). Applied Animal Behaviour Science, 154: pp. 66-75.
6). Lyons, J., Young, R.J. and Deag, J.M. (1997). The Effects of Physical Characteristics of the Environment and Feeding Regime on the Behavior of Captive Felids. Zoo Biology, 16: pp.71–83
7). Sambrook, T. D., Buchanan-Smith, H. M. (1997). Control and complexity in novel object enrichment. Animal Welfare, 6(3), pp. 207-216.
8). Jenny, S. and Schmid, H. (2002) Effect of feeding boxes on the behaviour of stereotyping Amur Tigers (Panthera tigris altaica) in the Zurich Zoo, Zurich, Switzerland. Zoo Biolog,y 21: pp. 573-584
9). Simcharoen, A., Savini, T., Gale, G.A., Simcharoen, S., Duangchantrasiri, S., Pakpien, S. and Smith, J.L.D. (2014). Female tiger Panthera tigris home range size and prey abundance: important metrics for management. Oryx, 48(3), pp. 370-377. doi:10.1017/S0030605312001408
10). Young, R.J. (2017). Tigers can roam for hundreds of miles – should they ever be kept in zoos? The Conversation. [Online at: https://theconversation.com/tigers-can-roam-for-hundreds-of-miles-should-they-ever-be-kept-in-zoos-78556].
11).Veasey, J.S. (2020). Can zoos ever be big enough for large wild animals? A review using an expert panel assessment of the psychological priorities of the Amur tiger (Panthera tigris altaica) as a model species. Animals, 10 doi:10.3390/ani10091536