In a paper published this week in Journal of Mammalogy<\/a>, we analyzed aerial and ground survey data on pup counts from 3 islands (South Farallon, San Miguel, and Bogoslof) (re)colonized by northern fur seals using classical and Bayesian state-space modeling approaches to describe population growth rates during their initial 21 years, with particular focus on the South Farallon Islands. We also used information from tagged animals that immigrated to the South Farallon Islands from San Miguel Island to describe the age and sex structure of the founding recolonizers of the South Farallon Islands. We found the 3 colonies had different annual population growth rates (South Farallon = 34%, San Miguel = 45%, Bogoslof = 59%), but all were growing at rates among the fastest observed for fur seals worldwide. Immigrants from San Miguel to the South Farallon Islands were younger and female-biased relative to the tagged population at San Miguel Island.<\/p>\n Northern fur seals rarely colonize new sites, or recolonize abandoned breeding sites. Of 46 known breeding colonies on North Pacific and Bering Sea islands, 18 were permanently extirpated since 1742 with only 2 recolonized, and 2 new colonies formed. Likewise, abandoned or new islands are rarely (re)colonized. Northern fur seals were extirpated from the South Farallon Islands by sealers during the 1800s, but fur seals recolonized, with the first observed birth of a pup in 1996. Bogoslof Island arose from volcanic activity in 1796 and was colonized by northern fur seals in 1980. San Miguel Island was observed to be recolonized in 1968, after a 100- to 500-year period of absence of fur seals. These (re)colonization events are few in relation to the hundreds of similar islands available for (re)colonization across the North Pacific and Bering Sea.<\/p>\n We also examined the evidence for the generality of Roux\u2019s (1987) description of fur seal population recovery using a literature review of published fur seal population growth rates. Population recovery is a continuous phenomenon, but Roux (1987)<\/a> identified 4 phases in the recovery of fur seal populations defined by changes in population growth rate, spatial distribution, and density: 1) \u201csurvival\u201d from the cessation of exploitation to the initiation of breeding; 2) \u201cestablishment,\u201d when breeding is restricted to a few founding colonies; 3) \u201crecolonization,\u201d when numbers increase and new or renewed colonies arise rapidly; and 4) \u201cmaturity,\u201d indicated by a decline in the rate of increase due to density-dependent factors.The general framework described by Roux was an effective description of observed fur seal population recovery. Our results inform our understanding of the initiation and growth of pinniped breeding colonies.<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/scienceblog.com\/wp-content\/uploads\/sites\/6\/2018\/10\/Figure.jpg?ssl=1\")
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