Sea Otter Range - CWHR M164 [ds1946]

CWHR species range datasets represent the maximum current geographic extent of each species within California. Ranges were originally delineated at a scale of 1:5,000,000 by species-level experts more than 30 years ago and have gradually been revised at a scale of 1:1,000,000. Species occurrence data are used in defining species ranges, but range polygons may extend beyond the limits of extant occurrence data for a particular species. When drawing range boundaries, CDFW seeks to err on the side of commission rather than omission. This means that CDFW may include areas within a range based on expert knowledge or other available information, despite an absence of confirmed occurrences, which may be due to a lack of survey effort. The degree to which a range polygon is extended beyond occurrence data will vary among species, depending upon each species’ vagility, dispersal patterns, and other ecological and life history factors. The boundary line of a range polygon is drawn with consideration of these factors and is aligned with standardized boundaries including watersheds (NHD), ecoregions (USDA), or other ecologically meaningful delineations such as elevation contour lines. While CWHR ranges are meant to represent the current range, once an area has been designated as part of a species’ range in CWHR, it will remain part of the range even if there have been no documented occurrences within recent decades. An area is not removed from the range polygon unless experts indicate that it has not been occupied for a number of years after repeated surveys or is deemed no longer suitable and unlikely to be recolonized. It is important to note that range polygons typically contain areas in which a species is not expected to be found due to the patchy configuration of suitable habitat within a species’ range. In this regard, range polygons are coarse generalizations of where a species may be found. This data is available for download from the CDFW website: https://www.wildlife.ca.gov/Data/CWHR. This sea otter range was constructed from the Annual California Sea Otter Census: 2019 Range Extent Shapefile: https://www.sciencebase.gov/catalog/item/5d85427ce4b0c4f70d086f23加州野生动物栖息地关系（CWHR）物种分布范围数据集呈现了加利福尼亚州内各物种当前的最大地理分布范围。该分布范围最初由物种级专家在30余年前以1:500万比例尺划定，后续逐步以1:100万比例尺完成修订完善。 物种出现记录数据被用于界定物种分布范围，但分布范围多边形可能会超出某一特定物种的现存出现数据边界。在绘制分布边界时，加州鱼类与野生动物部（CDFW）倾向于宁可过度纳入而非遗漏。也就是说，即便某一区域因缺乏调查工作而未获得确认的物种出现记录，CDFW也可基于专家知识或其他可用信息将其纳入物种分布范围。 分布范围多边形超出出现数据的程度因物种而异，取决于各物种的扩散能力、扩散模式以及其他生态与生活史特征。分布范围多边形的边界线绘制会综合考量上述因素，并与标准化边界对齐，包括流域（NHD）、生态区（USDA）或其他具有生态意义的划定界线如海拔等高线（elevation contour lines）。 尽管CWHR分布范围旨在呈现物种当前的分布情况，但一旦某一区域被纳入CWHR的物种分布范围，即便近数十年内未出现相关记录，该区域仍会保留在分布范围中。除非专家指出，某区域经多次调查后多年未被发现，或被认定不再适宜物种生存且不太可能再次被定居，否则该区域不会从分布范围多边形中移除。 需要特别说明的是，由于物种分布范围内适宜栖息地呈斑块状分布格局，分布范围多边形通常包含一些理论上不会有该物种出现的区域。就此而言，分布范围多边形是对物种潜在分布区域的粗略概括性描述。 该数据集可从CDFW官网下载：https://www.wildlife.ca.gov/Data/CWHR。 本海獭分布范围基于《2019年加州海獭年度普查范围Shapefile》构建，其下载链接为：https://www.sciencebase.gov/catalog/item/5d85427ce4b0c4f70d086f23