Naturalising diet to reduce stereotypic behaviours in slow lorises rescued from wildlife trade

Providing a natural diet is a key component to improving animal welfare and potentially reducing stereotypic behaviours in captivity. Wild slow lorises (Nycticebus spp.) are threatened by illegal wildlife trade, and in Thailand, confiscations from trade have led to a large number of Bengal (Nycticebus bengalensis) and greater slow lorises (N. coucang) in rescue centers such as Bang Phra Wildlife Domestic Research Station (Bang Phra). Due to limited enclosure space and availability of natural food items, welfare may be compromised for these confiscated animals. Slow lorises in most rescue centres including Bang Phra are mainly fed with fruit and vegetables rather than their natural diet of exudates, nectar and insects. Our project aimed to increase wild-type activities and reduce stereotypic behaviours in captive slow lorises at Bang Phra by modifying the diet (especially adding exudates of gum Arabic) using environmental enrichment devices. From May to August 2019, we implemented four diet conditions on 30 individuals: baseline, gum presented in two feeding devices and insects presented in a box. Diet conditions changed individual behaviours, with more time spent feeding and foraging, less time spent resting, and less stereotypic behaviours. Fixed gum was the most successful device to encourage increased feeding (40.4 % vs ∼ 3.5 % during baseline conditions) and foraging (16.3 % vs ∼2.5 % during baseline conditions), whilst significantly decreasing stereotypic behaviours (3.2 % vs ∼16.5 % during baseline conditions). Animals with small body sizes are often placed in small cages in rescue centres despite their needs in the wild. At the same time, species with specialist diets may not thrive in rescue centres that lack the funds or infrastructure to procure food items perceived to be specialised. With wild numbers declining rapidly, rescue centres must provide adequate space and wild type diets to ensure the health and well-being of these globally threatened primates.