Investigating diverse sources of variation in the amount of time Weddell seal (Leptonychotes weddellii) pups spend in the water during the lactation period
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Date
2020
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Montana State University - Bozeman, College of Letters & Science
Abstract
The early-developmental period can have important consequences for offspring success later in life. Phenotypic differences among parents and offspring influence energy availability as well as patterns of allocation and trade-offs during development. Variation in behavioral development prior to weaning may be an important determinant of post-weaning success. Here, we use hierarchical Bayesian models and a long-term database of phenotypic characteristics to investigate sources of variation in total time spent in the water and age at first entry in Weddell seal pups from 11-30 days of age. We found that time in the water was greater for pups with higher birth mass, greater for female than for male pups, lower for pups first entering the water at older ages, had a quadratic relationship with maternal age that peaked at intermediate maternal ages, and was higher for pups born to mothers who skipped reproduction the previous year than those born to mothers that were pre-breeders or reproduced the previous year. Some mothers consistently gave birth to pups that spent more time in the water. Age at first entry was earliest for pups with higher birth mass born to mothers with above average reproductive experience. Maternal identity accounted for slight variation in age at first entry. We document that the first entry can occur as early as 4 days old, but on average occurs at age 14 days. Pups born heavier may have more stored energy to allocate to activity or mitigate costs of submergence. Male pups may spend less time in the water to compensate for higher developmental costs. We found support for proxies of maternal body condition but not maternal behavior in describing time in the water, although maternal reproductive experience was supported in our analysis of age at first entry. Our results indicate that some variation in time spent in the water can be explained by the phenotypic characteristics of mothers and pups, though unaccounted-for sources of variation could be involved. It would be useful if future studies would investigate additional sources of variation and seek to understand how time spent in the water is related to post-weaning outcomes.