Data from: Density trends and demographic signals uncover the long-term impact of transmissible cancer in Tasmanian Devils

Monitoring the response of wild mammal populations to threatening processes is fundamental to effective conservation management. This is especially true for infectious diseases, which may have dynamic and therefore unpredictable interactions with their host. We investigate the long-term impact of a transmissible cancer, devil facial tumour disease (DFTD), on the endemic Tasmanian devil. We analyse trends in devil spotlight counts and density across the area impacted by the disease. We investigate the demographic parameters which might be driving these trends, and use spatial capture-recapture models to examine whether DFTD has affected home range size. We found that devils have declined by an average of 77% in areas affected by DFTD, and that there is a congruent trend of ongoing small decline in spotlight counts and density estimates. Despite this, devils have persisted to date within each of nine monitoring sites. One site is showing as yet unexplained small increases in density 8–10 years after the emergence of DFTD. We also found the prevalence of DFTD has not abated despite large declines in density and that diseased sites continue to be dominated by young devils. The long-term impact of the disease has been partially offset by increased fecundity in the form of precocial breeding in 1-year-old females, and more pouch young per female in diseased sites. The lower densities resulting from DFTD did not affect home range size. Synthesis and applications. Transmission of devil facial tumour disease continues despite large declines in devil density over multiple generations. Plasticity in life history traits has ameliorated the impact of devil facial tumour disease, however broad-scale trends in density show ongoing decline. In light of this, devil facial tumour disease and the impact of stochastic events on the reduced densities wrought by the disease, continue to threaten devils. In the absence of methods to manage disease in wild populations, we advocate managing the low population densities resulting from disease rather than disease per se.监测野生哺乳动物种群对各类威胁因子的响应，是开展有效保护管理的核心前提。对于传染性疾病而言，这一点尤为关键——这类疾病与宿主间存在动态互作关系，其影响往往难以预判。 本研究针对传染性肿瘤——袋獾面部肿瘤病（devil facial tumour disease, DFTD）对特有物种袋獾（Tasmanian devil）的长期影响展开调查。我们分析了该疫病影响区域内袋獾的夜间聚光灯调查计数（spotlight counts）与种群密度变化趋势；探究了驱动这些变化的种群统计参数，并借助空间捕获-再捕获模型（spatial capture-recapture models），检验DFTD是否对袋獾的家域面积（home range size）产生了影响。 研究结果显示，受DFTD影响的区域内，袋獾种群平均下降了77%；夜间聚光灯调查计数与种群密度估算值均呈现出持续小幅下降的一致趋势。尽管如此，截至目前，九个监测样地中均仍有袋獾种群存续。其中一个样地的种群密度在DFTD暴发8至10年后，出现了迄今尚无合理解释的小幅上升。 同时我们发现，尽管种群密度大幅下降，DFTD的患病率并未出现缓解，患病区域的种群仍以年轻个体为主体。该疾病的长期影响已得到部分抵消：患病区域内，1龄雌性个体通过早熟繁殖（precocial breeding）提前进入繁殖期，且单只雌性抚育的育儿袋幼崽数量有所增加，二者共同提升了种群繁殖力。此外，DFTD导致的种群密度降低，并未对袋獾的家域面积产生影响。 研究总结与应用启示：尽管历经多代种群衰退，袋獾面部肿瘤病的传播仍在持续。生活史特征的可塑性缓解了该疫病对袋獾种群的冲击，但大范围的种群密度仍呈现持续下降趋势。鉴于此，袋獾面部肿瘤病，以及随机事件对该疾病导致的低种群密度的进一步影响，仍对袋獾构成生存威胁。在尚未找到野生种群疫病管理方法的前提下，我们建议应针对疾病引发的低种群密度开展管理，而非直接针对疫病本身。