Exploiting a readily available but hard to digest resource: A review of exudativorous mammals identified thus far and how they cope in captivity

Gum is a widely available carbohydrate, composed mainly of non‐digestible structural carbohydrates. No mammalian enzymes can digest gum; therefore, a mammal ingesting gum must rely on microbial fermentation to access the energy it possesses. Gums are relatively nutrient poor. Despite this, some mammals have evolved to exploit this food resource. We aim to review the literature for all mammal species which have been recorded to ingest gum, whether quantified or not, and discuss this in the context of their evolutionary adaptations. We also investigated the recommended captive diets for these species to look at whether gum is recommended. We conducted a literature search on ISI Web of Knowledge to tabulate all mammal species observed ingesting gum and classified them as obligate, facultative or opportunistic feeders. We encountered 94 mammal species that eat gum in the wild (27 obligate feeders, 34 facultative feeders and 33 opportunistic feeders). Obligate feeders have entirely evolved to exploit this resource but were found to not be given gum in captivity, which may explain why they are failing to thrive, as opposed to facultative feeders, which have fewer issues. Gum may be necessary for the health of obligate feeders in captivity. Future research should focus on the physiological effects that gum ingestion poses on different digestive systems.     

Trialling nutrient recommendations for slow lorises (Nycticebus spp.) based on wild feeding ecology

Slow loris (Nycticebus spp.) captive diets have been based on routine and anecdotes rather than scientific fact. The growing body of evidence contradicts the high fruit diet supported by such anecdotes. Non‐human primate nutrient requirements are grouped into new (based on the common marmoset Callithrix jacchus) or old world (based on rhesus macaques Macaca mulatta) primates. Slow lorises are known to suffer from many health ailments in captivity such as dental disease, obesity, wasting and kidney issues all of which have been linked to diet. This study aimed to estimate nutrient intake from free‐ranging slow lorises and to determine whether this intake can be used as nutrient recommendations. We collected data of nutrient intake, food passage rate and digestibility of captive slow lorises on three diet treatments 1: current captive type diet which is mostly fruits, 2: wild‐type diet made only of food items from their natural diet, 3: new diet made to reflect wild slow loris nutrient intake. In order to validate our nutrient recommendations, diets 2 and 3 would have to be significantly different to Diet 1 in terms of nutrients, but not different from each other. Captive diets were significantly higher in soluble carbohydrates and lower in minerals and fibre fractions than both diets 2 and 3. Diets 2 and 3 led to a significantly increased food passage time and to more effective fibre and calcium digestion compared to Diet 1. We also observed obese individuals lost weight and underweight individuals gained weight. Our nutrient recommendations have been validated by our trials, and new or old world monkey nutrient recommendations are not consistent with our results. Diets should be high in protein and fibre and low in soluble carbohydrates and fats.