A conceptual model of the variation in parental attendance in response to environmental fluctuation: foraging energetics of lactating sea lions and fur seals

Abstract

ABSTRACT1. A conceptual model is described and tested using empirical data that predicts how air-breathing marine vertebrates that are tied to shore for reproduction, but feed at sea, should respond to changes in prey availability.2. The model examines the trade-off between changes in trip duration and foraging intensity as measured by field metabolic rate. It predicts that parents should increase the intensity of effort, and hence metabolic rate, prior to increasing the duration of foraging trips to maintain nutrient delivery to the young.3. The model was tested with data on the foraging energetics and trip duration of four species, northern and Antarctic fur seals and California and Australian sea lions, each studied over two contrasting seasons.4. The response of these marine predators to changes in prey availability due to climate driven environmental perturbation was found to support the conceptual model.

Dynamic Influence of Maternal and Pup Traits on Maternal Care during Lactation in an Income Breeder, the Antarctic Fur Seal

“…In capital breeders, size and condition are strongly correlated to reproductive effort and success (Festa-Bianchet et al 1998;Côte and Festa-Bianchet 2001;Crocker et al 2001); however, most mammals are income breeders, animals that provision offspring from current food intake. Although size and condition have been shown to be weakly correlated with reproductive effort in income breeders (Andersen et al 2000;Boyd 2000), maternal traits, provisioning strategy, and offspring traits may have a different influence on energy allocation to offspring in income breeders (Costa 1993). For example, a study of European roe deer, an income breeder, found that maternal body weight did not have a pervasive effect on maternal care, contrary to authors' predictions (Andersen et al 2000).…”

“…Additionally, some of the females were recaptured to collect milk samples approximately 5 d ( ), 1 mo ( ), or 2 mo postpartum ( ). n p 11 n p 10 n p 21 Milk-consumption measurements were collected from the pups of captured females at three developmental stages-perinatal (newborn, ), premolt (1 mo, ), and molt n p 48 n p 45 (2 mo, )-using the doubly labeled water (DLW) techn p 31 nique (Costa 1987b;Donohue et al 2002). Sample size decreased with pup age because some pups were lost to predation (17 pups died because of suspected leopard seal predation; one pup died of starvation).…”

“…One important factor that may affect the predicted relationship between maternal traits and reproductive effort is foraging behavior or pattern (Stearns 1992;Testa 2004). Animals that provision their offspring from distant food sources must balance the time needed to look for food before returning to their offspring with the time and energy provided to their offspring before returning to search for more food Costa 2008).…”

“…[3]), because singlepool equations are best for small animals and the Nagy equation allows for change in mass that is appropriate in growing pups (Speakman 1997). Daily energy expenditure was calculated from CO 2 production, using a conversion factor of 27.44 kJ/L CO 2 (Costa 1987a) and assuming a respiration quotient of 0.7 for a milk-based diet (Schmidt-Nielsen 1979; Costa 1987a). Metabolic water production was calculated from the metabolic rate assuming a conversion factor of 0.0263 g H 2 O/kJ (SchmidtNielsen 1979).…”

Investigating foraging utilization distribution of female New Zealand sea lions, Auckland Islands

“…For mammal predators, lactation is the most energydemanding period for a female. Therefore, during this time, they must optimize their foraging behaviour to maximize energy intake to rear their offspring successfully (Gittleman and Thompson 1988;Arnould 1997;Trillmich and Weissing 2006;Costa 2007). Pinnipeds (seals and sea lions) are marine mammal predators who are often central place foraging colonial breeders which restrict their foraging range during breeding and can heighten impacts with fisheries activities as they have no alternative foraging locations.…”