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

Abstract

Identifying factors that affect the timing of parturition among annual breeders is important to aid our understanding of how variations may adversely affect population trends over both short and long temporal scales. We investigated the effect of several parameters on the timing of parturition among individual Steller sea lions (Eumetopias jubatus (Schreber, 1776)) over 6 years between 2005 and 2016 using an information–theoretic approach. In addition to the random effect of year, birth and care of a pup in the previous year had the largest effect on parturition, causing a 2.4 day delay. Maternal age was negatively correlated with timing of parturition and male pups were born nearly a day earlier than female pups, on average. There was limited support for effects of sex and mass, with heavier pups born marginally earlier than lighter ones. This study illustrates some of the complexity of variables that can influence the timing of birth in this species and which should be considered in models that attempt to identify long-term trends in changing marine ecosystems.

Age‐specific reproduction in female Steller sea lions in Southeast Alaska

“…However, sample size of oldest females was very small ( n = 13), which also may have precluded the ability to determine whether body condition declined for the oldest females in that sample (Pitcher et al, 1998 ). However, parturition dates were later for the oldest mothers (parturition dates became earlier from ages 5 to 12 and then became later from ages 12 to 20; Hastings & Jemison, 2016 ; but see Maniscalco & Parker, 2018 ) and later parturition dates were associated with poor body condition in other species (reviewed by Hastings & Jemison, 2016 ).…”

Sex ratios of migrating southern hemisphere humpback whales: A new sentinel parameter of ecosystem health

“…Indeed, in times of nutritional stress, marine mammals may forego reproduction or restrict maternal investment. This has most frequently been evidenced in pinnipeds (Maniscalco and Parker, 2017). For example, in a study of Antarctic fur seals (Arctocephalus gazellaon), lower pup weights were found to be associated with a decline in maternal body condition, resulting in a significant percentage of pup mortalities (Lunn and Boyd, 1993).…”

The role of heterogeneity in the population ecology and resilience of marine predator species

“…The timing of the peaks and the actual length of the pupping season at these colonies were not aligned, however, which suggests that the processes influencing the length of the pupping season are not shared between colonies, despite their geographical proximity. Changes that occur in warmer years at the Skomer colony may encourage earlier, more successful weaning and greater survival probability (Bowen et al, 2015;Maniscalco and Parker, 2018;Pomeroy et al, 1999). This may also bring pups born at the Skomer colony in line with those born at the Marloes and Ramsey colonies which may already have a competitive advantage if their earlier weaning is synchronous with greater resource availability.…”

“…Changes in phenology -the cyclic timing of life-history events such as breeding -can have consequences from individual to population and community level, affecting connectivity, rates of reproduction and survival, and ecosystem function (Carson et al, 2010;Miller-Rushing et al, 2010;Thackeray et al, 2016). Phenological change has been attributed to a number of drivers, including global climate change, (Chambers et al, 2014;Poloczanska et al, 2016;Thackeray et al, 2016, although see Both, 2005 andBurthe et al, 2012 on the challenge of quantifying this) population density (Votier et al, 2009), resource availability and individual physiological status (Maniscalco and Parker, 2018), and interactions between these processes (Rotella et al, 2016). The ways in which species respond to environmental changes are complex and can vary considerably, and will largely be determined by a species' ecological and physiological characteristics (Poloczanska et al, 2016).…”

“…Alternatively, population-level shifts in demographic structure associated with climate change have been suggested as a regional driver of variation in breeding phenology (Bull et al, 2021). Births occurring after the peak pupping season (which will vary according to region) have been associated with reduced mass at weaning, and lower rates of juvenile survival (Bowen et al, 2015;Maniscalco and Parker, 2018). In long-lived iteroparous species that raise one offspring annually (i.e.…”