• California condors and DDT: Examining the effects of endocrine disrupting chemicals in a critically endangered species

      Tubbs, Christopher W. (2016)
      In 1987, the last free-flying California condor (Gymnogyps californianus) was captured and brought into captivity, rendering the species extinct in the wild. At the time, only 27 condors remained. Today, the population numbers approximately 430 individuals and though condors continue their remarkable recovery, they still face numerous challenges. One challenge, specific to condors inhabiting coastal regions, is exposure to the endocrine disrupting chemical (EDC) p,p'-DDE, through the scavenging of marine mammal carcasses. The exposure levels these birds currently experience appears to be causing eggshell thinning, reminiscent of the phenomenon that nearly collapsed populations of several avian species decades ago. We were interested in further exploring the potential effects of EDCs on California condors. Investigating EDC effects on a critically endangered species like the condor can be difficult, with limited options for studies that can be feasibly conducted. Therefore, we conducted non-invasive, in vitro estrogen receptor (ESR) activation assays to characterize activation by EDCs that coastal condors encounter. Here, I give a brief history of EDCs effects on birds, and in particular the California condor. Additionally, our ESR data are summarized and mechanisms of eggshell thinning are reviewed, highlighting the potential implications of EDC exposure on the continued recovery of the California condor.
    • Chelonian perivitelline membrane-bound sperm detection: A new breeding management tool

      Croyle, Kaitlin E.; Gibbons, Paul; Light, Christine; Goode, Eric; Durrant, Barbara S.; Jensen, Thomas (2016)
      Perivitelline membrane (PVM)-bound sperm detection has recently been incorporated into avian breeding programs to assess egg fertility, confirm successful copulation, and to evaluate male reproductive status and pair compatibility. Due to the similarities between avian and chelonian egg structure and development, and because fertility determination in chelonian eggs lacking embryonic growth is equally challenging, PVM-bound sperm detection may also be a promising tool for the reproductive management of turtles and tortoises....
    • Detection of oocyte perivitelline membrane-bound sperm: A tool for avian collection management

      Croyle, Kaitlin E.; Durrant, Barbara S.; Jensen, Thomas (2015)
      The success and sustainability of an avian breeding programme depend on managing productive and unproductive pairs. Given that each breeding season can be of immeasurable importance, it is critical to resolve pair fertility issues quickly. Such problems are traditionally diagnosed through behavioural observations, egg lay history and hatch rates, with a decision to re-pair generally taking one or more breeding seasons. In pairs producing incubated eggs that show little or no signs of embryonic development, determining fertility is difficult. Incorporating a technique to assess sperm presence on the oocyte could, in conjunction with behaviour and other data, facilitate a more timely re-pair decision. Detection of perivitelline membrane-bound (PVMbound) sperm verifies successful copulation, sperm production and sperm functionality. Alternatively, a lack of detectable sperm, at least in freshly laid eggs, suggests no mating, lack of sperm production/function or sperm–oviduct incompatibility. This study demonstrated PVM-bound sperm detection by Hoechst staining in fresh to 24-day-incubated exotic eggs from 39 species representing 13 orders. However, a rapid and significant time-dependent loss of detectable PVM-bound sperm was observed following incubation of chicken eggs. The PCR detection of sperm in seven species, including two bacterially infected eggs, demonstrated that this method was not as reliable as visual detection using Hoechst staining. The absence of amplicons in visually positive PVMs was presumably due to large PVM size and low sperm count, resulting in DNA concentrations too low for standard PCR detection. In summary, this study demonstrated the feasibility and limitations of using PVM-bound sperm detection as a management tool for exotic avian species. We verified that sperm presence or absence on fluorescence microscopy can aid in the differentiation of fertile from infertile eggs to assist breeding managers in making prompt decisions for pair rearrangements. This protocol is currently used to manage several breeding pairs in San Diego Zoo global avian conservation programmes.
    • Identification of California condor (Gymnogyps californianus) estrogen receptor variants and their activation by xenoestrogens

      Felton, Rachel G.; Owen, Corie M.; Cossaboon, Jennifer M.; Steiner, Cynthia C.; Tubbs, Christopher W. (2020)
      California condors released in costal sites are exposed to high levels of xenoestrogens, particularly p,p'-DDE, through scavenging of marine mammal carcasses. As a result, coastal condors carry a higher contaminant loads and experience eggshell thinning when compared to their inland counterparts....
    • Identification of California condor estrogen receptors 1 and 2 and their activation by endocrine disrupting chemicals

      Felton, Rachel G.; Steiner, Cynthia C.; Durrant, Barbara S.; Keisler, Duane H.; Milnes, Matthew R.; Tubbs, Christopher W. (2015)
      ...There is evidence that coastal-dwelling condors experience reproductive issues, such as eggshell thinning, likely resulting from exposure to endocrine-disrupting chemicals (EDCs). To address this problem, we have identified and cloned condor estrogen receptors (ESRs) 1 and 2 and characterized their activation by EDCs present in the coastal habitats where condors reside....
    • Inter-aviary distance and visual access influence conservation breeding outcomes in a territorial, endangered bird

      Flanagan, Alison M.; Rutz, Christian; Farabaugh, Susan M.; Greggor, Alison L.; Masuda, Bryce M.; Swaisgood, Ronald R. (2020)
      Species extinctions are becoming a global crisis, affecting biodiversity and ecosystem services, with island populations being particularly vulnerable. In response, conservation managers are increasingly turning to ex situ conservation breeding programs to establish assurance populations and provide a source for release and re-establishment of wild populations. The 'Alalā (Hawaiian crow, Corvus hawaiiensis) is a critically endangered and territorial island corvid that became extinct in the wild in 2002, following a severe and prolonged population decline during the late 20th century....