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Age specific survival rates of Steller sea lions at rookeries with divergent population trends in the Russian Far East.

Altukhov AV, Andrews RD, Calkins DG, Gelatt TS, Gurarie ED, Loughlin TR, Mamaev EG, Nikulin VS, Permyakov PA, Ryazanov SD, Vertyankin VV, Burkanov VN - PLoS ONE (2015)

Bottom Line: The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there.However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends.High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas.

View Article: PubMed Central - PubMed

Affiliation: University of Alaska Fairbanks, Fairbanks, Alaska, USA; Kamchatka Branch of the Pacific Geographical Institute FEB RAS, Petropavlovsk-Kamchatsky, Kamchatsky Kray, Russia.

ABSTRACT
After a dramatic population decline, Steller sea lions have begun to recover throughout most of their range. However, Steller sea lions in the Western Aleutians and Commander Islands are continuing to decline. Comparing survival rates between regions with different population trends may provide insights into the factors driving the dynamics, but published data on vital rates have been extremely scarce, especially in regions where the populations are still declining. Fortunately, an unprecedented dataset of marked Steller sea lions at rookeries in the Russian Far East is available, allowing us to determine age and sex specific survival in sea lions up to 22 years old. We focused on survival rates in three areas in the Russian range with differing population trends: the Commander Islands (Medny Island rookery), Eastern Kamchatka (Kozlov Cape rookery) and the Kuril Islands (four rookeries). Survival rates differed between these three regions, though not necessarily as predicted by population trends. Pup survival was higher where the populations were declining (Medny Island) or not recovering (Kozlov Cape) than in all Kuril Island rookeries. The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there. However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends. High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas.

No MeSH data available.


Average age specific resight probabilities of females (red circles) and males (blue squares).Error bars = 95% confidence intervals. Medny Island (MY), Kozlov Cape (KC), Antisferov Island (AI), Lovushki Islands (LI), Raykoke Island (RI), Brat Chirpoev Island (BI).
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pone.0127292.g002: Average age specific resight probabilities of females (red circles) and males (blue squares).Error bars = 95% confidence intervals. Medny Island (MY), Kozlov Cape (KC), Antisferov Island (AI), Lovushki Islands (LI), Raykoke Island (RI), Brat Chirpoev Island (BI).

Mentions: Although age specific resight patterns differed between all sites, resight probability generally increased with age, with the exception that on Medny Island and Kozlov Cape the male resight probability for pups was higher than in the second year (Fig 2). Resighting rates were higher on Medny Island and Kozlov Cape than on all Kuril Islands rookeries.


Age specific survival rates of Steller sea lions at rookeries with divergent population trends in the Russian Far East.

Altukhov AV, Andrews RD, Calkins DG, Gelatt TS, Gurarie ED, Loughlin TR, Mamaev EG, Nikulin VS, Permyakov PA, Ryazanov SD, Vertyankin VV, Burkanov VN - PLoS ONE (2015)

Average age specific resight probabilities of females (red circles) and males (blue squares).Error bars = 95% confidence intervals. Medny Island (MY), Kozlov Cape (KC), Antisferov Island (AI), Lovushki Islands (LI), Raykoke Island (RI), Brat Chirpoev Island (BI).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4446299&req=5

pone.0127292.g002: Average age specific resight probabilities of females (red circles) and males (blue squares).Error bars = 95% confidence intervals. Medny Island (MY), Kozlov Cape (KC), Antisferov Island (AI), Lovushki Islands (LI), Raykoke Island (RI), Brat Chirpoev Island (BI).
Mentions: Although age specific resight patterns differed between all sites, resight probability generally increased with age, with the exception that on Medny Island and Kozlov Cape the male resight probability for pups was higher than in the second year (Fig 2). Resighting rates were higher on Medny Island and Kozlov Cape than on all Kuril Islands rookeries.

Bottom Line: The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there.However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends.High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas.

View Article: PubMed Central - PubMed

Affiliation: University of Alaska Fairbanks, Fairbanks, Alaska, USA; Kamchatka Branch of the Pacific Geographical Institute FEB RAS, Petropavlovsk-Kamchatsky, Kamchatsky Kray, Russia.

ABSTRACT
After a dramatic population decline, Steller sea lions have begun to recover throughout most of their range. However, Steller sea lions in the Western Aleutians and Commander Islands are continuing to decline. Comparing survival rates between regions with different population trends may provide insights into the factors driving the dynamics, but published data on vital rates have been extremely scarce, especially in regions where the populations are still declining. Fortunately, an unprecedented dataset of marked Steller sea lions at rookeries in the Russian Far East is available, allowing us to determine age and sex specific survival in sea lions up to 22 years old. We focused on survival rates in three areas in the Russian range with differing population trends: the Commander Islands (Medny Island rookery), Eastern Kamchatka (Kozlov Cape rookery) and the Kuril Islands (four rookeries). Survival rates differed between these three regions, though not necessarily as predicted by population trends. Pup survival was higher where the populations were declining (Medny Island) or not recovering (Kozlov Cape) than in all Kuril Island rookeries. The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there. However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends. High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas.

No MeSH data available.