Inferring Variation in Southern Elephant Seal At-Sea Mortality by Modelling Tag Failure
Inferring Variation in Southern Elephant Seal At-Sea Mortality by Modelling Tag Failure
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DOI：
10.3389/fmars.2020.517901
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发表时间：
2020-09-24
影响因子：
3.7
通讯作者：
Hindell, Mark A.
中科院分区：
文献类型：
--
作者：
Henderson, Angus F.;McMahon, Clive R.;Hindell, Mark A.
确定影响生存的因素是理解种群持久性的关键。虽然卫星遥测是研究偏远动物生态和行为的有力工具，但很少用于人口统计学研究，因为很难区分动物死亡(个体死亡率)和标签失效(机械标签失效)。南部象海豹提供了一个机会，将标记失败与动物死亡率分开，这要归功于大型跟踪数据集的可用，对人口统计学比率的广泛了解，以及因为对这些大型动物来说，众所周知卫星标记不会影响死亡率。与使用传统的捕获-标记-重新捕获方法相比，研究卫星遥测以估计死亡率的一个关键理由是有可能获得空间和时间上的具体信息，特别是在动物在海上且基本上看不到的情况下。我们使用了2004至2018年间部署在科尔盖伦岛的182只海豹的卫星标签数据。在这些标签中，76个(42%)是为整个换羽后觅食旅程(最大雌性和最长为265天。305天)，其余107个标签(58%)停止在海上传播。我们发现，与预期相反，行为选择似乎不会通过机械手段影响标签失败率，相反，我们检测到的信号似乎与先前描述的不同组之间的死亡率差异一致。尽管证据有限，但有证据表明，在南方环状模式为负的年份(南大洋生产力较低)，成年女性的标签失败率会增加。我们推测，这种失败的增加可能意味着这些年更高的死亡率。此外，使用科尔盖伦高原的男性比在海冰区的男性有更高的标签失败率，这可能表明死亡率更高。我们怀疑，不同种群之间标签失败率的差异反映了捕食者暴露和觅食成功率的差异。这表明卫星遥测可以用来推断南方象海豹在海上的死亡事件。
Identifying factors influencing survivorship is key to understanding population persistence. Although satellite telemetry is a powerful tool for studying remote animal ecology and behaviour it is rarely used for demographic studies because distinguishing the death of the animal (individual mortality) from failure of the tag (mechanical tag failure) has proven difficult. Southern elephant seals present an opportunity to separate tag failure from animal mortality thanks to the availability of large tracking datasets, broad knowledge of demographic rates, and because for these large animals, satellite tags are known not to influence mortality rates. A key rationale for investigating satellite telemetry to estimate mortality as compared to using traditional Capture-Mark-Recapture methods is the potential for obtaining spatially and temporally specific information, particularly while the animals are at sea and largely unobservable. We used satellite tag data from 182 seals from Isles Kerguelen, deployed between 2004 and 2018. Of these, 76 (42%) tags transmitted for the full post-moult foraging trip (max. 265 days for females and max. 305 days for sub-adult males) with the remaining 107 tags (58%) ceasing transmission at sea. We found that contrary to expectations, behavioural choices seem not to influence tag failure rates by mechanical means, rather the signals we detected seemed to align with previously described variation in mortality between groups. There was evidence, albeit limited, for an increase in tag failure for adult females in years with negative Southern Annular Mode (lower Southern Ocean productivity). We speculate that this increase in failure may suggest higher mortality in these years. Also, males using the Kerguelen Plateau had higher tag failure rates than those in the sea-ice zone, perhaps indicative of higher mortality. We suspect that these differences in tag failure rates between groups reflect variation in predator exposure and foraging success. This suggests satellite telemetry could be used to infer mortality events for southern elephant seals while they are at sea.