Primates (monkeys, apes, lemurs etc) are traditionally regarded as relatively easy to feed in zoos but there is growing recognition that inappropriate diets contribute to several health problems. Most common among these is obesity, which is associated with other illnesses such as heart disease, cancer, diabetes and reproductive problems. Obesity is largely due to zoo diets that are high in energy without the foraging and digestive costs associated with the species’ natural feeding strategies. This commonly results from misconceptions about fruits and frugivory; most zoo diets for frugivorous and omnivorous primates, and even some highly folivorous, insectivorous or exudativorous species, consist of large amounts of fruit. Fruit cultivated for human consumption is very different in terms of nutrient composition to food types, even wild fruits, eaten by free-living primates. Selective breeding and modern cultivation methods produce fruit that is high in sugars and very low in fibre, and therefore high in readily digestible energy. Cultivated fruit is also lower in protein, minerals and vitamins than most foodstuffs consumed by primates in the wild. In addition to contributing to obesity, captive primate diets containing large amounts of cultivated fruit may cause gastrointestinal problems and poor dental health and possible behavioural problems.
Research into the nutrition of zoo primates, particularly fruit-free diets, has been carried at Paignton Zoo Environmental Park since 2003 and Newquay Zoo since 2011. This research has confirmed that fruit-free diets can improve primate physical health: reduction in dental and periodontal health issues, fewer overweight and obese animals, improved body condition, and improved gut function as indicated from faecal consistency. In addition, it has also shown that removal of fruit from primate diets can cause improvements in behaviour, most noticeably significantly less aggression and self-directed behaviour (indicators of social stress or anxiety). As a result of this research indicating such a range of benefits for captive primates, fruit-free diets have been implemented for all primates at both zoos. We have disseminated these research results internally and externally through talks, presentations, academic papers, technical articles and popular media. In addition, since March 2014 we have delivered four EAZA Academy Recognised Courses on primate nutrition to improve awareness of our evidence-based diet formulation across the European zoo community. Post-course surveys to evaluate the impact of the course indicate that as a direct consequence of attending the course, fruit has been reduced or removed and/or other improvements made to the diets of over 490 primate groups in at least 70 zoos. This has potentially led to improved health and welfare of over 4000 individual primates.