• Body size and sexual selection in the koala

      Ellis, William A.; Bercovitch, Fred B. (2011)
      ...Koalas are sexually dimorphic in multiple domains, yet are absent from the literature on sexual selection and the structure of their mating system is unclear. We provide the first documentation of the strength of sexual selection in koalas by using microsatellite markers to identify sires....
    • Climate change and the koala Phascolarctos cinereus: water and energy

      Ellis, William A.H.; Melzer, A.; Clifton, I.; Carrick, F.; (2010)
      We studied two groups of koalas during a drought in central Queensland to investigate potential impacts of climatic variability on the physiology and behaviour of this species. The tree use, water turnover, field metabolic rate and diet of koalas during autumn and spring were compared to a similar study of koalas in summer and winter, also in central Queensland, to generate a seasonal picture of the response of koalas to climatic variation....
    • Computed tomography and magnetic resonance for the advanced imaging of the normal nasal cavity and paranasal sinuses of the koala (Phascolarctos cinereus)

      Bercier, Marjorie; Alexander, Kate; Gorow, April; Pye, Geoffrey W. (2014)
      The objective of this study is to describe computed tomography (CT) and magnetic resonance (MR) for the cross-sectional imaging of the normal anatomy of the nasal cavity and paranasal sinuses of the koala (Phascolarctos cinereus), to provide reference figures for gross anatomy with corresponding CT and MR images, and to compare the features of the nasal cavity and paranasal sinuses of the normal koala with that reported in other domestic species. Advanced imaging can be used to aid in diagnosis, to plan surgical intervention, and to monitor therapeutic responses to diseases of the nasal passages in koalas....
    • Demographic, environmental and genetic determinants of mating success in captive koalas (Phascolarctos cinereus)

      Abts, Kendra C.; Ivy, Jamie A.; DeWoody, J. Andrew (2018)
      Many factors have been shown to affect mating behavior. For instance, genes of the major histocompatibility complex (MHC) are known to influence mate choice in a wide variety of vertebrate species....
    • Dietary specialization and Eucalyptus species preferences in Queensland koalas (Phascolarctos cinereus)

      Higgins, Alexis L.; Bercovitch, Fred B.; Tobey, Jennifer R.; Andrus, Chris Hamlin (2011)
      Koalas specialize on�Eucalyptus�leaves, but also feed selectively. Food choice is not random, but depends on various factors that are not well understood, although most research has focused on the role of secondary plant compounds. We studied the feeding choices of four adult male koalas housed at the San Diego Zoo....
    • Dietary specialization and Eucalyptus species preferences in Queensland koalas (Phascolarctos cinereus)

      Higgins, Alexis L.; Bercovitch, Fred B.; Tobey, Jennifer R.; Andrus, Chris Hamlin (2011)
      ...We studied the feeding choices of four adult male koalas housed at the San Diego Zoo. All subjects had a choice of nine types of Eucalyptus leaves over the eight‐week study....
    • Disentangling the mechanisms of mate choice in a captive koala population

      Brandies, Parice A.; Grueber, Catherine E.; Ivy, Jamie A.; Hogg, Carolyn J.; Belov, Katherine (2018)
      Successful captive breeding programs are crucial to the long-term survival of many threatened species. However, pair incompatibility (breeding failure) limits sustainability of many captive populations. Understanding whether the drivers of this incompatibility are behavioral, genetic, or a combination of both, is crucial to improving breeding programs. We used 28 years of pairing data from the San Diego Zoo koala colony, plus genetic analyses using both major histocompatibility complex (MHC)-linked and non-MHC-linked microsatellite markers, to show that both genetic and non-genetic factors can influence mating success. Male age was reconfirmed to be a contributing factor to the likelihood of a koala pair copulating. This trend could also be related to a pair’s age difference, which was highly correlated with male age in our dataset. Familiarity was reconfirmed to increase the probability of a successful copulation. Our data provided evidence that females select mates based on MHC and genome-wide similarity. Male heterozygosity at MHC class II loci was associated with both pre- and post-copulatory female choice. Genome-wide similarity, and similarity at the MHC class II DAB locus, were also associated with female choice at the post-copulatory level. Finally, certain MHC-linked alleles were associated with either increased or decreased mating success. We predict that utilizing a variety of behavioral and MHC-dependent mate choice mechanisms improves female fitness through increased reproductive success. This study highlights the complexity of mate choice mechanisms in a species, and the importance of ascertaining mate choice mechanisms to improve the success of captive breeding programs.
    • Disseminated coccidoidomycosis in a koala (Phascolarctos cinereus)

      Burgdorf-Moisuk, Anne; Stalis, Ilse H.; Pye, Geoffrey W. (2012)
      A16-yr-old male koala (Phascolarctos cinereus) presented for nonspecific signs of illness and weight loss. Despite 2 mo of diagnostics and supportive care, the koala's health declined and euthanasia was elected....
    • Fat-soluble vitamin and mineral comparisons between zoo-based and free-ranging koalas (phascolarctos cinereus)

      Schmidt, Debra A.; Pye, Geoffrey W.; Hamlin-Andrus, Chris C.; Ellis, William A.; Ellersieck, Mark R.; Chen, Tai C.; Holick, Michael F. (2013)
      As part of a health investigation on koalas at San Diego Zoo, serum samples were analyzed from 18 free-ranging and 22 zoo-based koalas, Phascolarctos cinereus. Serum concentrations of calcium, chloride, cobalt, copper, iron, magnesium, manganese, molybdenum, phosphorus, potassium, selenium, sodium, zinc, and vitamins A, E, and 25(OH)D3 were quantified....
    • Gastrointestinal torsions and intussusception in Northern koalas (Phascolarctos cinereus) at San Diego Zoo (1976–2012)

      Joyce-Zuniga, Nicole M.; Roesler, Jennifer; Andrus, Chris Hamlin; Sutherland-Smith, Meg; Rideout, Bruce; Pye, Geoffrey W. (2014)
      The recent classification as threatened status of the northern koala (Phascolarctos cinereus) by the Australian Government highlights the importance of the conservation and health management of this iconic Australian marsupial. This case series describes gastrointestinal torsion and intussusception in six northern koalas (three males, three females, 2–11 yr old) at the San Diego Zoo from 1976 to 2012….
    • Immunomics of the koala (Phascolarctos cinereus)

      Abts, Kendra C.; Ivy, Jamie A.; DeWoody, J. Andrew (2015)
      The study of the koala transcriptome has the potential to advance our understanding of its immunome—immunological reaction of a given host to foreign antigens—and to help combat infectious diseases (e.g., chlamydiosis) that impede ongoing conservation efforts….. Our efforts have produced full-length sequences for potentially important immune genes in koala, which should serve as targets for future investigations that aim to conserve koala populations.
    • Koala bellows and their association with the spatial dynamics of free-ranging koalas

      Ellis, William A.; Bercovitch, Fred B.; FitzGibbon, S.; Roe, P.; Wimmer, J.; Melzer, A.; Wilson, R. (2011)
      Acoustic communication mediates sociality in a variety of animals. One of the more ubiquitous vocal signals to have evolved is the sexual advertisement call of males. Koala (Phascolarctos cinereus) males emit a sonorous bellow call during the breeding season, but no detailed studies of the calling context appear to have been published. We used a novel remote sound detection network to monitor koala bellowing while simultaneously collecting koala behavioral data using collar-mounted GPS units. Our approach enabled us to examine fine scale temporal variation in vocalization and spatial movements of free-ranging koalas without direct behavioral observations. Bellow occurrence was susceptible to weather conditions, with fewer calls occurring when wind speed and temperatures were high. The number of bellow vocalizations recorded during an annual period mirrored breeding activity, with nearly all male bellows recorded during peak mating season. The distance traveled by koalas and the occurrence of koala bellows both peaked around midnight, but only female travel distance during the breeding season was temporally correlated with bellow occurrence. We conclude that environmental factors might trigger male bellowing to launch the breeding season and that these male vocal signals function more to attract females than to repel males. Female mate selection is probably an important component of male reproductive success in koalas, which is partly mediated by male bellow characteristics.
    • Koala birth seasonality and sex ratios across multiple sites in Queensland, Australia

      Ellis, William A.H.; Bercovitch, Fred B.; FitzGibbon, S.; Melzer, A.; de Villers, D.; Dique, D.; (2010)
      ...he annual pattern of births was identical for males and females within locations, but overall annual patterns of births differed between the southern and northern sites. We conclude that koalas can bear offspring in every month of the year, but breed seasonally across Australia, and that a sex bias in the timing of births is absent from most regions.
    • Koala retrovirus diversity, transmissibility, and disease associations

      Zheng, HaoQiang; Pan, Yi; Tang, Shaohua; Pye, Geoffrey W.; Stadler, Cynthia K; Vogelnest, Larry; Herrin, Kimberly Vinette; Rideout, Bruce; Switzer, William M. (2020)
      Background Koalas are infected with the koala retrovirus (KoRV) that exists as exogenous or endogenous viruses. KoRV is genetically diverse with co-infection with up to ten envelope subtypes (A-J) possible; KoRV-A is the prototype endogenous form. KoRV-B, first found in a small number of koalas with an increased leukemia prevalence at one US zoo, has been associated with other cancers and increased chlamydial disease. To better understand the molecular epidemiology of KoRV variants and the effect of increased viral loads (VLs) on transmissibility and pathogenicity we developed subtype-specific quantitative PCR (qPCR) assays and tested blood and tissue samples from koalas at US zoos (n=78), two Australian zoos (n=27) and wild-caught (n=21) in Australia. We analyzed PCR results with available clinical, demographic, and pedigree data. Results All koalas were KoRV-A-infected. A small number of koalas (10.3%) at one US zoo were also infected with non-A subtypes, while a higher non-A subtype prevalence (59.3%) was found in koalas at Australian zoos. Wild koalas from one location were only infected with KoRV-A. We observed a significant association of infection and plasma VLs of non-A subtypes in koalas that died of leukemia/lymphoma and other neoplasias and report cancer diagnoses in KoRV-A-positive animals. Infection and VLs of non-A subtypes was not associated with age or sex. Transmission of non-A subtypes occurred from dam-to-offspring and likely following adult-to-adult contact, but associations with contact type were not evaluated. Brief antiretroviral treatment of one leukemic koala infected with high plasma levels of KoRV-A, -B, and -F did not affect VL or disease progression. Conclusions Our results show a significant association of non-A KoRV infection and plasma VLs with leukemia and other
    • Metabolic bone disease in juvenile koalas (phascolartcos cinereus)

      Pye, Geoffrey W.; Gait, Sarah Catherine; Mulot, Baptiste; de Asua, Maria Delclaux Real; Martinez-Nevado, Eva; Bonar, Christopher J.; Baines, Stephen J.; Baines, Elizabeth A. (2013)
      Due to climate restrictions in parts of North America and Europe, koalas (Phascolarctos cinereus) are housed indoors. Koala young (joeys) raised indoors are susceptible to the development of metabolic bone disease (MBD) due to a lack of exposure to natural ultraviolet light to themselves and their female paren....
    • Serum protein electrophoresis values for free-ranging and zoo-based koalas (Phascolarctos cinereus)

      Pye, Geoffrey W.; Ellis, William A.; FitzGibbon, Sean; Opitz, Brian; Keener, Laura; Arheart, Kristopher L.; Cray, Carolyn (2012)
      In a clinical setting, especially with species of special interest, it is important to use all clinical pathology testing options for general health monitoring and diagnosis. Protein electrophoresis (EPH) has previously been shown to be an important adjunct tool in veterinary medicine. Serum samples from 18 free-ranging and 12 zoo-based koalas (Phascolarctos cinereus) were subject to EPH analysis….
    • The role of bioacoustic signals in koala sexual selection: Insights from seasonal patterns of associations revealed with GPS-proximity units

      Ellis, William A.; FitzGibbon, Sean; Pye, Geoffrey W.; Whipple, Bill; Barth, Ben; Johnston, Stephen; Seddon, Jenny; Melzer, Alistair; Higgins, Damien; Bercovitch, Fred B. (2015)
      Despite being a charismatic and well-known species, the social system of the koala (Phascolarctos cinereus—the only extant member of the family Phascolarctidae) is poorly known and much of the koala’s sociality and mating behaviors remain un-quantified. We evaluated these using proximity logging-GPS enabled tracking collars on wild koalas and discuss their implications for the mating system of this species. The frequency and duration of male-female encounters increased during the breeding season, with male-male encounters quite uncommon, suggesting little direct mating competition. By comparison, female-female interactions were very common across both seasons. Body mass of males was not correlated with their interactions with females during the breeding season, although male size is associated with a variety of acoustic parameters indicating individuality. We hypothesise that vocal advertising reduces the likelihood of male-male encounters in the breeding season while increasing the rate of male-female encounters. We suggest that male mating-season bellows function to reduce physical confrontations with other males allowing them to space themselves apart, while, at the same time, attracting females. We conclude that indirect male-male competition, female mate choice, and possibly female competition, mediate sexual selection in koalas.