2.3.1 Insurance Population Establishment
The Tasmanian Devil Insurance Population (TDIP) was established predominately through three intakes of wild born Tasmanian devils, supplemented by a few Australasian Species Management Program (ASMP) devils deemed appropriate for inclusion and wild devils brought into captivity opportunistically (typically pouch young hand-reared due to the euthanasia of the mother due to DFTD). The areas in which devils were captured were sites considered DFTD free at the time of the trapping to reduce the risk that the devils may have been exposed to DFTD prior to capture. The first group of wild Tasmanian devils (year of birth 2004) were removed from Narawntapu National Park or Southport (Eastern Provenance; trapped February – March 2005; n = 13) or Temma West, Arthur River, and Granville Harbour (Western Provenance; April – May 2005; n = 10) as 1 year old juveniles (just after dispersal) with no clinical signs of DFTD. The offspring (n = 6) from three litters of females with DFTD captured in August 2004 from Woolnorth (Western Provenance), initially held as part of a vertical transmission study, were also added to the TDIP in 2005 upon receiving a clean bill of health. All of these animals were held and bred in quarantine facilities during their first breeding season (2006) before being transferred to mainland facilities to establish the TDIP.
The second group of wild Tasmanian devils (year of birth 2006) were captured from north-western Tasmania at the beginning of 2007 as yearling juveniles (n = 31). The third and final major intake of wild devils occurred in early 2008 with the intake of yearling juveniles (n = 62) from north-western Tasmania. Of these, some were sent to
50 intensively managed facilities on the mainland (n = 30) and the remainder (n = 32) were used to establish Free Ranged Enclosures (FRE) or Managed Environmental Enclosures (MEE).
Until 2011, the TDIP included only mainland Australian facilities but this was expanded to include two Tasmanian DPIPWE facilities in 2011 and two privately owned Tasmanian wildlife parks in 2012 (both historically holding and breeding non-TDIP devils).
2.3.2 Insurance Population Breeding Success 2006-2012
To evaluate the success of the TDIP during the first 7 years of the program, data regarding annual breeding recommendations and outcomes were gathered from the Annual Report and Recommendations published between 2006 and 2012 by ZAA for all 14 institutions and the three purpose built quarantine facilities (first year of the program) participating in the TDIP during those years. Data evaluation was restricted to intensely managed facilities as data on Free Ranged Enclosures (FRE) or Managed Environmental Enclosures (MEE) was limited and paternities (and sometimes maternities) of a large number of offspring are currently unknown. Information recorded and evaluated included the devil’s studbook number, name, sex, breeding recommendations, breeding success, litter size, litter sex ratio, and institution. The Tasmanian devil studbook was used to provide dates of birth for breeding animals and to confirm information provided in the annual reports.
To assess the potential for male fertility to influence female devil reproductive success we determined whether or not unsuccessful females were paired with proven or
51 unproven males. A proven male was defined as one that had previously successfully sired viable pouch young. An unproven male was one that was offered mating opportunities but produced no confirmed pregnancies (i.e. no viable pouch young). In cases where records indicated that more than one male could be paired with the female and there was no confirmation whether all suggested males were trialled, these were designated as proven (if both males had produced viable young), unproven (if neither male had produced viable young) or unknown (if there was both a proven and unproven male breeding recommendation and no confirmation if one or both were tried).
2.3.3 Founder Evaluation
All records of wild caught Tasmanian devils (brought into captivity 2005 – 2010) that were listed in the studbook (Carla Srb, Zoos Victoria, 2015) for the species were databased and analysed to examine founder lines. In this study, we defined a “founder” as an individual that is wild born, with unknown wild parents, that either was brought into captivity with pouch young or had at least one opportunity to breed in captivity between the ages of two and four for females or two and six for males. Devils that were brought into captivity but never had an opportunity to be paired for mating were excluded as a founder. The number of litters per female, the male sire, the number of young and the sex of all offspring were recorded. Founder lines were traced for both males and females to determine how many were still active or had terminated. To be considered “active” a founder line had to have descendants that would be under the age of four for a female or six for a male, with the potential for breeding recommendations for subsequent years.
The Tasmanian devil studbook lists a large number of devils that never had the chance to contribute to the captive breeding program. Some of these animals were brought into
52 captivity for the purposes of breeding as part of the insurance population. Others are wild caught females, likely DFTD positive, with pouch young, none of which survived to contribute to the captive population, or males which died within a couple of months of capture. These animals were not included in the analysis. Females and males that died before having an opportunity to breed in captivity were also removed as potential founders for the analysis. Potential female and male founders that were housed in unmanaged FREs were excluded from the analysis due to the difficulty of ascertaining whether or not they had bred.
2.3.4 Studbook Evaluation
The studbook evaluation is limited by the accuracy of the record and the nature and amount of information made available to the studbook keeper over time. As such it is recognised that there may be a degree of inaccuracy within the records that cannot be accounted for. Initially, the Tasmanian Devil Insurance Population (TDIP) consisted of zoological institutions on the mainland of Australia. The devils housed in two of the Tasmanian managed enclosures were not included in the breeding recommendations until 2011 and two further facilities were included in the breeding recommendations in 2012. In both 2008 and 2009 a female devil with a breeding recommendation died before being paired with a male, therefore these two animals were excluded from the dataset.
By the end of 2012, the TDIP population had grown to 515 devils (75% in intensively managed facilities) (Hogg et al. 2012). With the growth of the TDIP, and limitations on space, breeding recommendations were no longer provided to all adult female devils and an increase in multiple males paired with females meant paternity was not always known.
53 2.3.5 Housing
After the breeding results for the most recent season were completed, a voluntary survey was sent to all nine mainland Australian institutions that were active participants in the captive breeding program (i.e. all mainland institutions with breeding recommendations throughout the survey period). The survey requested information from each institution on the layout, size (area, height of walls), construction material and composition of inclusions (e.g. den boxes, climbing structures) of enclosures used to house breeding Tasmanian devils for captive breeding. The survey requested information regarding the location of occupancy of breeding females and all other devils (e.g. males, juveniles) at that institution during the 2011 breeding season with a request for additional years (2008 to 2010) if available.
2.3.6 Statistical Analysis
All statistical analyses were performed using GenStat 16th Edition (VSN International Ltd., UK). A linear mixed model was used to test the effects of origin of birth (wild- caught or captive born) and age of the dam on the number of pouch young produced. A liner mixed model was also used to test the effects of female age and the age difference between the male and female on reproductive success (confirmation of pouch young vs no pouch young). Data from individual female devils provided breeding opportunities for more than one year were assumed to be random variables for each year. A P value < 0.05 was considered to be significant. Data are presented as ± SEM, unless otherwise noted.
A two-tailed t-test was performed on the sex of pouch young born to wild caught females and a chi squared test on among year effect of breeding success over the seven year period.
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