Pinniped censuses at Año Nuevo, California, 1967-2017

Regular pinniped censuses at Año Nuevo Island, California, were initiated by our research group in 1967 to support studies of reproductive behavior of male elephant seals, Mirounga angustirostris.
Research on elephant seals at the colony has continued since, expanding to cover female behavior, reproductive success, physiology and energetics, migrations and foraging, and more. The other species of pinnipeds, Steller sea lion (Eumetopias jubata), California sea lion (Zalophus californianus), and harbor seal (Phoca vitulina), have been the focus of additional studies.
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Censuses were collected to support the wide range of research, but population size of has been an important topic as the elephant seal population expanded. We described the initial expansion to the mainland in 1975, and in 2011 described details of long-term growth and then stabilization of the breeding elephant seal population over the entire colony.
Año Nuevo has also been central to understanding the entire northern elephant seal population, which has recovered from a remnant population in Mexico after overhunting and continues to grow.
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The field notebooks in which censuses were recorded from 1967-2005 were saved. They are now archived at the University of California Santa Cruz library:
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UCSC Elephant Seal and other Pinniped Research records. UA 132. Special Collections and Archives, University Library, University of California, Santa Cruz.

Methods
Field counts of pinnipeds from high ground near the colony. Data were originally written into small notebooks, one census per day. These were transcribed into digital format and organized into a MySQL database over 2004-2006. After 2005, data were entered directly into this database via a web interface, and any paper notes used by observers were not stored. The data archived here was extracted from the MySQL database after the census of 25 May 2017.

1967年，本研究团队为支持北象海豹（Mirounga angustirostris）雄性繁殖行为相关研究，在加利福尼亚州阿诺新岛（Año Nuevo Island）启动了常规鳍足类（Pinniped）动物普查工作。此后，该繁殖地的象海豹研究持续推进，研究范畴逐步拓展至雌性行为、繁殖成功率、生理学与能量学、迁徙与觅食等多个领域。此外，其他鳍足类物种——斯泰勒海狮（Steller sea lion, Eumetopias jubata）、加州海狮（California sea lion, Zalophus californianus）以及港海豹（harbor seal, Phoca vitulina）——也成为了后续专项研究的重点。
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本次普查工作的开展旨在支撑上述多维度研究，但随着象海豹种群的扩张，种群规模始终是核心研究议题之一。本团队曾于1975年首次记录了象海豹向大陆扩散的现象，并在2011年详述了整个繁殖地象海豹种群长期增长后趋于稳定的细节。阿诺新岛同时也是解析整个北象海豹种群的核心基地：该种群曾因过度捕猎在墨西哥仅剩残余种群，如今已实现全面恢复并持续增长。
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1967年至2005年期间用于记录普查数据的野外记录本已得到妥善留存，现归档于加利福尼亚大学圣克鲁兹分校图书馆：加利福尼亚大学圣克鲁兹分校图书馆特藏与档案部，馆藏编号UA 132，馆藏名称为“UCSC象海豹及其他鳍足类研究记录”（UCSC Elephant Seal and other Pinniped Research records）。

**研究方法**
研究人员在繁殖地附近的高地开展鳍足类动物野外计数。原始数据最初被记录于小型每日普查记录本中，2004年至2006年间，这些纸质记录被转录为数字化格式并整理至MySQL数据库。2005年之后，研究人员通过网页界面直接将数据录入该数据库，且未留存后续使用的纸质观测记录。本次公开的存档数据提取自2017年5月25日普查完成后的MySQL数据库。