Department of Biology, Western Washington University, Bellingham, Washington, USA.
PLoS One. 2012;7(6):e39046. doi: 10.1371/journal.pone.0039046. Epub 2012 Jun 18.
Worldwide, adult harbor seals (Phoca vitulina) typically limit their movements and activity to <50 km from their primary haul-out site. As a result, the ecological impact of harbor seals is viewed as limited to relatively small spatial scales. Harbor seals in the Pacific Northwest are believed to remain <30 km from their primary haul-out site, one of several contributing factors to the current stock designation. However, movement patterns within the region are not well understood because previous studies have used radio-telemetry, which has range limitations. Our objective was to use satellite-telemetry to determine the regional spatial scale of movements.
METHODOLOGY/PRINCIPAL FINDINGS: Satellite tags were deployed on 20 adult seals (n=16 males and 4 females) from two rocky reefs and a mudflat-bay during April-May 2007. Standard filtering algorithms were used to remove outliers, resulting in an average (± SD) of 693 (± 377) locations per seal over 110 (± 32) days. A particle filter was implemented to interpolate locations temporally and decrease erroneous locations on land. Minimum over-water distances were calculated between filtered locations and each seal's capture site to show movement of seals over time relative to their capture site, and we estimated utilization distributions from kernel density analysis to reflect spatial use. Eight males moved >100 km from their capture site at least once, two of which traveled round trip to and from the Pacific coast, a total distance >400 km. Disjunct spatial use patterns observed provide new insight into general harbor seal behavior.
CONCLUSIONS/SIGNIFICANCE: Long-distance movements and disjunct spatial use of adult harbor seals have not been reported for the study region and are rare worldwide in such a large proportion of tagged individuals. Thus, the ecological influence of individual seals may reach farther than previously assumed.
在全球范围内，成年斑海豹（Phoca vitulina）通常将其活动范围限制在距其主要上岸点<50 公里以内。因此，人们认为斑海豹的生态影响仅限于相对较小的空间尺度。人们认为，太平洋西北地区的斑海豹仍保持在距其主要上岸点<30 公里的范围内，这是当前种群指定的几个促成因素之一。然而，由于先前的研究使用了范围有限的无线电遥测技术，因此该地区内的运动模式尚不清楚。我们的目标是使用卫星遥测技术来确定区域运动的空间尺度。
方法/主要发现：2007 年 4 月至 5 月，在两个岩石礁和一个泥滩海湾，用卫星标签对 20 只成年海豹（n=16 只雄性和 4 只雌性）进行了标记。使用标准滤波算法去除异常值，结果每只海豹在 110 天（±32 天）内平均有 693（±377）个位置。采用粒子滤波器对位置进行时间内插并减少陆地位置的错误。计算了过滤位置与每个海豹的捕获位置之间的最小水上距离，以显示海豹随时间相对于其捕获位置的运动，并使用核密度分析的密度分析来估计利用度分布，以反映空间利用情况。8 只雄性海豹至少有一次移动了>100 公里，其中 2 只往返于太平洋海岸，总距离超过 400 公里。观察到的不连续空间使用模式为一般斑海豹行为提供了新的见解。
结论/意义：在研究区域，成年斑海豹的远距离运动和不连续的空间使用尚未报道，在如此多的标记个体中，在世界范围内也很少见。因此，单个海豹的生态影响可能比以前认为的更远。
