Age‐specific variation in timing of parturition in Steller sea lions at Forrester Island Complex, Alaska

Maternal and offspring effects on the timing of parturition in western Steller sea lions (Eumetopias jubatus)

“…Therefore, we may not necessarily expect the same influences on the timing of parturition between the two populations. Nevertheless, our findings are broadly comparable to results from similar studies with eastern SSLs (Hastings and Jemison 2016), other pinnipeds (Lunn and Boyd 1993;Rotella et al 2016) and terrestrial mammals (e.g., Solberg et al 2007;Wolcott et al 2015), with maternal age and year commonly found to have meaningful effects on the timing of parturition. General scientific consensus suggests that these and other factors affect parturition through physiological constraints such that energetic deficiencies can cause reproductive delays (Boyd 1991;Gaillard et al 2000).…”

“…It is, however, difficult to assess variation in the onset of active gestation among wild pinnipeds (Pomeroy 2011), though not impossible (Testa et al 2010). Variation in the timing of full-term parturition is easier to observe and in SSL, it is already known to be associated with maternal age, parity (Maniscalco et al 2006;Hastings and Jemison 2016), and rookery location (Pitcher et al 2001), with little data previously available to test for additional influencing parameters. Yet, several additional factors have been shown to be associated with variation in the timing of parturition in several other pinniped species (e.g., Lunn and Boyd 1993;Boltnev and York 2001;Rotella et al 2016).…”

A re-examination of the timing of pupping for Steller sea lions Eumetopias jubatus breeding on two islands in Alaska

“…If female sea lions from MB4 or other beaches moved their pup to MB7 during the count period, this would result in an increase in daily pup counts unrelated to births at that beach, which would push the estimated MPD later. Similar small-scale movements by mother-pup sea lions pairs during the breeding season have been described for Steller sea lions at the Forrester Island Complex, Alaska (Hastings & Jemison 2015).…”

“…For some pinniped species, older or prime-aged females give birth earlier in the season than younger females (Lunn & Boyd 1993, Gentry 1998, Boltnev & York 2001, Maniscalco et al 2006, Hastings & Jemison 2015. This was reported for Steller sea lions that breed on Chiswell Island, Alaska, and the Forrester Island Complex, Alaska (Maniscalco et al 2006, Hastings & Jemison 2015. For Antarctic fur seals it was suggested that, by returning earlier, older females could select the most suitable pupping sites (Lunn & Boyd 1993).…”

Estimating dispersal rates of Steller sea lion (Eumetopias jubatus) mother-pup pairs from a natal rookery using mark-resight data

“…Movements of Steller sea lion mother-pup pairs have been previously reported during the pupping season [ 24 , 35 ]; however, the amount of dispersal has not been quantified. By using observations of marked sea lions collected from a long-term study site, we were able to estimate the extent of these movements.…”