Development of supplemental feeding protocol for koala (Phascolarctos cinereus) at San Diego Zoo

Citation

Jewell PE and Nylander J. 2025. Development of supplemental feeding protocol for koala (Phascolarctos cinereus) at San Diego Zoo. In Treiber K, Brooks M, D’amato-Anderson J, Nylander J, Eds. Proceedings of the Sixteenth Conference on Zoo and Wildlife Nutrition, AZA Nutrition Advisory Group, Oklahoma City, OK.

Abstract

Koalas (Phascolarctos cinereus) are monophagous marsupials whose diet consists entirely of eucalyptus species. In managed care, dietary supplementation has been used for the rehabilitation and management of clinically presenting koalas who are unable to effectively consume or metabolize eucalyptus. Historically, this practice has been used with clinical koalas at San Diego Zoo (SDZ) using protein-based supplemental feed items. Over time, dietary supplementation has been employed during specific life stage transitions when energy demands surpass the nutritional provision of eucalyptus. The goal was to develop a protocol to assist koala care specialists, in collaboration with nutritionists and veterinarians, to better determine when supplementation discussions should be started, recommendations on supplement dosage and duration, and identification of appropriate and practical supplemental feed items.

In addition to unexpected weight loss and clinical presentations, supplementation parameters identified included reproductive energy needs (lactating females and females experiencing prolonged estrus) and life stage changes (growing and geriatric individuals). A body condition score (BCS) chart was developed at SDZ to assess anatomical areas in addition to traditional scapular muscle mass. This was done to increase BCS accuracy, account for life stage muscle tone changes, and identify signs of overconditioning. BCS and life-stage parameters were integrated to establish criteria for initiating discussions on dietary supplementation. Three supplemental feed items were trialed to gauge palatability (Table 1). Supplements were selected based on nutrient data, commercial availability, and the absence of prior trials for clinical supplementation. Supplements were trialed with a subsample of the SDZ koala population (n=19) for two months. For each administration (n=112), individual response was categorized by care staff into positive (easily took supplement), neutral (had little or no reaction to supplement), and negative (did not take supplement or had negative reactions such as spitting or face rubbing). Supplement acceptance was determined by compiling the proportions of neutral and positive responses. Syringes without supplement and syringes with blended eucalyptus were initially introduced to acclimate individuals to administration methods and act as a control. Individuals primarily had a negative response to all supplements trialed with 64% of attempts being categorized as negative followed by neutral and positive at 24% and 11% respectively. The supplement with the highest acceptance was EmerAid Sustain Herbivore, Mint Flavor, Lafeber at 30% while Koala Milk Replacer, Late Lactation, Wombaroo had the highest proportion of negative responses at 80% (Table 2). Koalas with prior exposure to supplementation methods yielded more reliable observations regarding supplement acceptance. Further research is required to evaluate whether acclimatization to administration methods enhances the reliability of assessing supplementation efficacy prior to protocol implementation.

JewellKoalaZN2025S4.pdf     181 KB