Maternal effects on offspring growth rate and weaning mass in harbour seals

Bowen, W. D.; Ellis, Sara L.; Iverson, Sara J.; Boness, Daryl J.

doi:10.1139/z01-075

Cited by 59 publications

(31 citation statements)

References 51 publications

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“…Maternal effects are especially strong for phocid seals that fast throughout lactation (Bowen et al 2001). The strong evidence we found for a relationship between maternal age and pup weaning mass is driven by age-related variation in maternal body mass at parturition .…”

Section: Individual Heterogeneity and Age-related Variation In Weaninmentioning

confidence: 58%

Decomposing the variance in southern elephant seal weaning mass: partitioning environmental signals and maternal effects

et al. 2015

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Abstract. Predator populations are likely to respond to bottom-up processes, but there remains limited understanding of how wide-ranging marine predators respond to environmentally driven temporal variation in food availability. Widespread declines of several Southern Ocean predators, including southern elephant seals Mirounga leonina, have been attributed to decreases in food availability following environmental changes. We used linear mixed models to examine temporal process variance in weaning mass (a key fitness component) of southern elephant seals at Marion Island over a 27-year period . We quantified the contribution of within-and between-year covariates to the total phenotypic variance in weaning mass and determined whether the observed reversal of population decline was associated with a continued increase in weaning mass, suggesting improvement in per capita food availability to adult females. Weaning mass initially increased rapidly with maternal age, but reached an asymptote when females were nine years old. Longitudinal data examining between-individual maternal differences suggested latent, age-independent maternal influences on weaning mass. Between-year differences accounted for only 6% of the total phenotypic variance in weaning mass. We found no evidence for a systematic trend in weaning mass, but model predicted weaning mass was 8.70 kg (95% CI ¼ 2.14-14.73) lower during the 1980s, suggesting that food limitation may have been most severe during these years when the population was declining. Model support for a population size effect was entirely driven by the low weaning mass and comparatively high (but declining) population size from 1986 to 1988; subsequent variation in population size had no detectable influence on weaning mass. Remotely sensed chlorophyll-a concentration within the seals' foraging distribution explained 45% of the between-year variation (1998-2013, n ¼ 9) in weaning mass, with higher weaning mass in years of positive chlorophyll-a anomalies. Environmental variation associated with variability in the Southern Annular Mode poorly predicted temporal variation in weaning mass. Our long-term data on elephant seal weaning mass provides a perspective on variation in food availability in a pelagic environment which is poorly known. Examining the long-term regionally specific effects of environmental variability aids our understanding of how these predators interact with their environment.

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Section: Individual Heterogeneity and Age-related Variation In Weaninmentioning

confidence: 58%

Decomposing the variance in southern elephant seal weaning mass: partitioning environmental signals and maternal effects

et al. 2015

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“…For the longer-lived females alone, 39-57% survival from 1965 is expected. o There is growing evidence that large animals play important roles in ecosystem dynamics (53)(54)(55)(56)(57). Furthermore, retrospective analyses of numerous coastal marine systems demonstrate or suggest a pervasive influence from the historical removal of these large animals (58).…”

Section: Discussionmentioning

confidence: 99%

Sequential megafaunal collapse in the North Pacific Ocean: An ongoing legacy of industrial whaling?

Springer

Estes

Vliet

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

421

375

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Populations of seals, sea lions, and sea otters have sequentially collapsed over large areas of the northern North Pacific Ocean and southern Bering Sea during the last several decades. A bottom-up nutritional limitation mechanism induced by physical oceanographic change or competition with fisheries was long thought to be largely responsible for these declines. The current weight of evidence is more consistent with top-down forcing. Increased predation by killer whales probably drove the sea otter collapse and may have been responsible for the earlier pinniped declines as well. We propose that decimation of the great whales by postWorld War II industrial whaling caused the great whales' foremost natural predators, killer whales, to begin feeding more intensively on the smaller marine mammals, thus ''fishing-down'' this element of the marine food web. The timing of these events, information on the abundance, diet, and foraging behavior of both predators and prey, and feasibility analyses based on demographic and energetic modeling are all consistent with this hypothesis.T he abrupt decline of the western stock of Steller sea lions (Eumetopias jubatus) h across most of the northern North Pacific Ocean and southern Bering Sea is one of the world's most well known yet poorly understood marine conservation problems. For years, scientists attributed this decline to nutritional limitation, the presumed consequence of a climate regime shift and͞or competition with regional fisheries (1). Although fisheries and regime shifts undoubtedly influenced both the fishes and their associated food webs (2-5), several recent reviews of the available information on sea lions and their environment, including an assessment by the National Research Council, cast doubt on the nutritional limitation hypothesis (6, 7), notwithstanding evidence from field and laboratory studies that diet quality is a factor in sea lion energetics (8). The doubt stems from three main findings. First, most measures of behavior, physiology, and morphology from surviving adult sea lions and pups in the western Gulf of Alaska and Aleutian Islands are inconsistent with nutritional limitation. These animals have better body condition, reduced foraging effort, and reduced field metabolic rates relative to similar measures from the increasing sea lion population in southeast Alaska (7). Second, sea lion prey is abundant in most areas of the decline (9). Known changes in prey availability and other features of the oceanic ecosystem are particularly incongruous with the most precipitous phase of the decline, which occurred during the mid-to late 1980s, and can be accounted for only by greatly increased adult mortality (6). Third, populations of piscivorous sea birds, many of which feed on earlier life stages of the same fish species consumed by sea lions, have remained stable or increased in the same area and over the same period that the sea lions have declined (10). Top-down forcing now appears to have been an important contributor to declines of Steller sea lion...

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“…, 1994], more than doubling their natal weight before weaning [Bowen et al . , 1992, 2001]. Harbor seal milk consists of approximately 40% fat at parturition and increases to approximately 50% by day 7 where it remains until pups are weaned.…”

Section: Discussionmentioning

confidence: 99%

The effect of diet and feeding level on survival and weight gain of hand‐raised harbor seal pups (Phoca vitulina)

2010

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Hundreds of stranded harbor seals pups (Phoca vitulina) are brought to wildlife rescue centers every year. Typical hand-rearing diets include artificial milk-replacers and diets based on macerated fish fed via gavage, but weight gains are often low and mortality rates can be high. This study compared survival and weight gain of orphaned seal pups fed either artificial milk-replacer or fish-formula. Pups admitted to the facility in summer 2007 (n=145) and 2008 (n=98) were randomly assigned to one of two diets and fed by gavage until weaning. In 2007, pups fed milk-replacer gained more (43 ± 12 g/d) than those fed fish-formula (loss of 13 ± 6 g/d; P<0.002). In 2008, when intake was increased from 8 to 11% of body weight daily, weight gain improved for both diets but remained higher in pups fed milk-replacer (123 ± 12 g/d, vs. loss of 6 ± 8 g/day; P<0.001). Pup survival to weaning was significantly higher in 2008 than 2007 (P<0.001) and was higher for pups on milk-replacer compared with those on fish-formula (P<0.05). Survival was also correlated with body weight at admittance (P<0.001). Although neither diet achieved the weight gains recorded in mother-raised pups (400-800 g/d), the artificial milk-replacer was clearly more successful, and pups fared better in the second year of the study when intake was higher.

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Maternal effects on offspring growth rate and weaning mass in harbour seals

Cited by 59 publications

References 51 publications

Decomposing the variance in southern elephant seal weaning mass: partitioning environmental signals and maternal effects

Decomposing the variance in southern elephant seal weaning mass: partitioning environmental signals and maternal effects

Sequential megafaunal collapse in the North Pacific Ocean: An ongoing legacy of industrial whaling?

The effect of diet and feeding level on survival and weight gain of hand‐raised harbor seal pups (Phoca vitulina)

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