Capital Expenditure and Income (Foraging) during Pinniped Lactation: The Example of the Weddell Seal (Leptonychotes weddellii)

Eisert, Regina; Oftedal, Olav T.

doi:10.5479/si.097884601x.25

Cited by 10 publications

(8 citation statements)

References 94 publications

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“…Lactation is a feature unique to mammalian reproduction with complex selective pressures operating at the family unit level (Dall & Boyd, ; Hayssen, ). Evolutionarily, lactation across different mammalian species is in a constant mode of flux as energy needs must be synchronized with resource availability, and these needs consequently influence reproductive timing, as well as other behavior and physiological attributes (Eisert & Oftedal, ; Hayssen, ; Pond, ). A key determinant of reproductive success is body condition, which is dependent on foraging behavior (Hamel & Côté, ).…”

Section: Discussionmentioning

confidence: 99%

To feed or not to feed? Bioenergetic impacts of fear‐driven behaviors in lactating dolphins

Srinivasan

Swannack

Grant³

et al. 2017

Ecology and Evolution

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In mammals, lactation can be the most energetically expensive part of the reproductive cycle. Thus, when energy needs are compromised due to predation risk, environmental disturbance, or resource scarcity, future reproductive success can be impacted. In marine and terrestrial environments, foraging behavior is inextricably linked to predation risk. But quantification of foraging energetics for lactating animals under predation risk is less understood. In this study, we used a spatially explicit individual‐based model to study how changes in physiology (lactating or not) and the environment (predation risk) affect optimal behavior in dolphins. Specifically, we predicted that an adult dolphin without calf would incur lower relative energetic costs compared to a lactating dolphin with calf regardless of predation risk severity, antipredator behavior, or prey quality consumed. Under this state‐dependent analysis of risk approach, we found predation risk to be a stronger driver in affecting total energetic costs (foraging plus locomotor costs) than food quality for both dolphin types. Further, contrary to our hypothesis, after accounting for raised energy demands, a lactating dolphin with calf does not necessarily have higher relative‐to‐baseline costs than a dolphin without calf. Our results indicate that both a lactating (with calf) and non‐lactating dolphin incur lowered energetic costs under a risk‐averse behavioral scheme, but consequently suffer from lost foraging calories. A lactating dolphin with calf could be particularly worse off in lost foraging calories under elevated predation risk, heightened vigilance, and increased hiding time relative to an adult dolphin without calf. Further, hiding time in refuge could be more consequential than detection distance for both dolphin types in estimated costs and losses incurred. In conclusion, our study found that reproductive status is an important consideration in analyzing risk effects in mammals, especially in animals with lengthy lactation periods and those exposed to both biological and nonbiological stressors.

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Section: Discussionmentioning

confidence: 99%

To feed or not to feed? Bioenergetic impacts of fear‐driven behaviors in lactating dolphins

Srinivasan

Swannack

Grant³

et al. 2017

Ecology and Evolution

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“…Lactating Weddell seals lose a large proportion-40% or more-of their postpartum body mass and for this reason were long believed to fast during lactation, but it is now clear that most if not all females feed after an initial fast of 1-3 wk (Eisert et al 2005;Eisert and Oftedal 2009). This transition from fasting lactation to lactation while feeding provides an interesting model in which the relative importance of maternal versus neonatal factors may be changing.…”

Section: Introductionmentioning

confidence: 98%

Milk Composition in the Weddell SealLeptonychotes weddellii: Evidence for a Functional Role of Milk Carbohydrates in Pinnipeds

Eisert¹,

Oftedal²,

Barrell³

2013

Physiological and Biochemical Zoology

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We propose that secretion of milk sugar has important consequences for the metabolic economies of lactating phocid seals and their pups. Milk was collected from 21 Weddell seals Leptonychotes weddellii in McMurdo Sound, Antarctica, and assayed by standard methods. Milk composition changed over the course of lactation, but at mid- to late lactation (16-40 d postpartum), Weddell seal milk composition was relatively constant at 33.8% +/- 0.82% water, 54.0% +/- 0.80% fat, 10.1% +/- 0.16% crude protein, 0.84% +/- 0.03% sugar, 0.75% +/- 0.02% ash, and 23.3 +/- 0.3 kJ g−1 whole milk (WM). At this stage, milk composition varied among individual seals in all assayed constituents except ash. The concentration of sugar in the aqueous phase of Weddell seal milk ( 24.9 +/- 0.6g sugar L−1 water) was ca. 44%-77% of levels found in terrestrial carnivores, indicating that the low sugar concentration of WM is primarily due to its high fat content, not alteration of the aqueous phase. In early lactation, fasting Weddell seals were estimated to devote 39 g d(-1) glucose to milk sugar synthesis, an amount similar to the estimated demand of the maternal brain. This additional glucose demand must be covered by gluconeogenesis in fasting animals and represents a considerable additional drain on maternal resources. However, provision of sugar to offspring at rates sufficient to meet neonatal substrate requirements appears to be essential for efficient fat and protein deposition and thus may be an important component of the phocid reproductive strategy of rapid growth and early weaning.

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“…); the difference is presumably mainly due to costs stemming from the enormous mass loss that occurs during lactation (Wheatley et al. , Eisert and Oftedal , Shero et al. ).…”

Section: Introductionmentioning

confidence: 99%

Coping with the loss of large, energy‐dense prey: a potential bottleneck for Weddell Seals in the Ross Sea

Salas

Nur

Ainley

et al. 2017

Ecological Applications

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Abstract. Extraction of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea began in 1997, following a management plan that targets the largest fish with a goal of reducing the spawning biomass by 50% over 35 yr. We investigate the potential long-term consequences of the reduced availability of this prey for Weddell seals (Leptonychotes weddellii). Energy demands in seals are acute, especially immediately following lactation, when females must recover substantial mass and cope with molting costs. We tested the hypothesis that toothfish are critically important for adult female seals during this period. Toothfish body mass is three orders of magnitude greater, and its energy density nearly double that of the most common seal prey, Antarctic silverfish (Pleuragramma antarcticum). Reduction or elimination of toothfish consumption could impair a female's ability to sufficiently recover and successfully produce a pup in the following pupping season. Our goals are to (1) illustrate mechanisms and conditions whereby toothfish depletion might plausibly affect seal population trends; (2) identify measurable parameters of the seals' ecology that may help better understand the potential negative impact of toothfish depletion on seal populations; and (3) promote a precautionary management approach for the fishery that includes monitoring of seal populations We constructed a set of inter-linked models of seal diving behavior, physiological condition, and demography based on existing information. We evaluate the effect of the following factors on seal mass recovery and intrinsic population growth rates: fishery depletion rate, daily diving limits, probability of a successful dive, and body mass recovery target. We show that loss of toothfish has the greatest potential impact on seal populations' growth rate. Under some scenarios, populations may decrease at >10% per year. Critical parameters to better understand fishery impacts include prevalence and size of toothfish in the seals' diet; the relationship between diet and the rate of mass recovery; and female breeding propensity in relation to body condition at the end of the molting period. Our results lend support to concerns about the potential negative impact of toothfish extraction in the Ross Sea; and to advocate for a precautionary management approach by the fishery.

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Capital Expenditure and Income (Foraging) during Pinniped Lactation: The Example of the Weddell Seal (Leptonychotes weddellii)

Cited by 10 publications

References 94 publications

To feed or not to feed? Bioenergetic impacts of fear‐driven behaviors in lactating dolphins

To feed or not to feed? Bioenergetic impacts of fear‐driven behaviors in lactating dolphins

Milk Composition in the Weddell SealLeptonychotes weddellii: Evidence for a Functional Role of Milk Carbohydrates in Pinnipeds

Coping with the loss of large, energy‐dense prey: a potential bottleneck for Weddell Seals in the Ross Sea

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