HUSBANDRY REPORTS Digestibility of a New Diet for Captive Short-Beaked Echidnas (Tachyglossus aculeatus) Hayley J. Stannard, 1 * Jamie M. Bekkers, 2 Julie M. Old, 3 Bronwyn M. McAllan, 4 and Michelle E. Shaw 5 1 School of Life and Environmental Sciences and Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia 2 University Van Hall Larenstein, Leeuwarden, The Netherlands 3 School of Science and Health, Western Sydney University, Richmond, New South Wales, Australia 4 Discipline of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, New South Wales, Australia 5 Taronga Wildlife Hospital, Taronga Conservation Society Australia, Mosman, New South Wales, Australia Short-beaked echidnas (Tachyglossus aculeatus) are myrmecophages, or ant and termite insectivore specialists, and replicating their exact diet in captivity is problematic. Diets for captive animals often incorporate raw meat, eggs and cat food mixed together with water, and vitamin and mineral supplements. These diets have promoted a number of health problems in captive echidnas, such as gastritis, cystitis, gut impaction, obesity, and diarrhea. A manufactured diet was designed and three echidnas from two zoos were transitioned onto this diet to assess the acceptability and digestibility of this diet for echidnas. The new “test” diet was readily accepted by the echidnas with a 1 week transition period. Daily digestible energy intake was 280 kJ kg 0.75 d 1 , similar to another myrmecophagous species. Digestibility values were above 74% for all macronutrients. It was determined that this diet was an acceptable replacement for the previous diets and it was decided that the remaining echidnas at both institutions would be transitioned to the new diet. The diet will also be used for wild echidnas being rehabilitated in the zoo hospitals prior to release and commercially available within Australia. Further data are being collected to assess the use of this diet for seasonal weight management, transitioning hand-reared puggles and effects on gastrointestinal tract health. Zoo Biol. 36:56–61, 2017. © 2017 Wiley Periodicals, Inc Keywords: insectivore; manufactured diet; nutrition; monotreme; myrmecophage STATEMENT OF THE PROBLEM The short-beaked echidna (Tachyglossus aculeatus) is a monotreme or egg laying mammal, native to Australia and Papua New Guinea. Echidnas are myrmecophages (ant and termite specialists) and their morphology is adapted to this feeding specialization. The echidna has an elongated snout, an elongated tongue and strong claws [Augee et al., 2006]. Adult echidnas may weigh between 2 and 7 kg. Adult body mass varies seasonally by 25% in males and 30% in females, and changes are associated with hibernation (a controlled reduction in metabolic rate and thus body temperature) and reproductive activity [Nicol and Andersen, 2007]. Echidnas can live for up to 50 years in captivity [Augee et al., 2006]. It is likely their low active metabolic rate, low body temperature, and hibernation use contributes to their longevity [Nicol and Andersen, 2007, 2008]. In captivity, replicating the diet of free-ranging echidnas is problematic, because of difficulties providing adequate quantities of ants and termites for food. Captive diets used for echidnas, and for other myrmecophagous species, often include some of the following: raw meat, eggs, bran, vegetable oil, wheat germ and cat or dog food mixed together with water and vitamin and mineral supplements [Jackson, 2003; Augee et al., 2006; Gull et al., 2015; Lin et al., 2015]. Generally the mixture is presented as slurry to Grant sponsor: ARC Linkage Grant; grant number: LP: 140100235.  Correspondence to: Hayley J. Stannard, School of Life and Environmental Sciences and Charles Perkins Centre, University of Sydney, Level 4, East Wing (L4E75), Charles Perkins Centre D17, Sydney, NSW 2006, Australia. E-mail: hayley.stannard@sydney.edu.au Received 03 May 2016; Revised 05 December 2016; Accepted 13 December 2016 DOI: 10.1002/zoo.21347 Published online 23 January 2017 in Wiley Online Library (wileyonlinelibrary.com). © 2017 Wiley Periodicals, Inc. Zoo Biology 36: 56–61 (2017)