Relationship between the female attendance pattern and pup growth rate in the South American sea lion (Carnivora)

Massimiliano Drago,Valentina Franco-Trecu,Pablo Inchausti,Federico G Riet-Sapriza,Luis Cardona,Néstor García,Enrique A Crespo

doi:10.3989/scimar.05128.008

Abstract

Changes in the duration and frequency of foraging trips by female otariids may result in changes in the duration and frequency of lactation bouts and hence influence pup growth rate, unless females modify milk energy density and/or the total amount of milk delivered depending on the trip duration. To test this hypothesis on South American sea lions, we measured two attendance pattern components (foraging trip and haul-out duration) and three diving behaviour components of nursing females (dive time, bottom time and number of dives per h) at two different rookeries in Uruguay and Argentina, the composition and energy density of their milk, and the growth rate of their pups. Female foraging trip and haul-out durations depended on pup sex and weight, whereas milk energy density depended on female body mass and foraging trip durations. By contrast, the three dive variables were independent of female body mass or pup sex. Pup growth was also independent of the foraging trip and haul-out duration, with pup sex as the only significant variable. This suggests that individual differences in female foraging behaviour play a minor role in determining pup growth rates during the first three weeks after birth.

Highlights

Parental care is the main component of the reproductive cost in birds and female mammals, and offspring survival is expected to be more strongly influenced by parent foraging efficiency than breeding periodicity or clutch/litter size (Clutton-Brock 1991, Davies et al 2012)
Summary: Changes in the duration and frequency of foraging trips by female otariids may result in changes in the duration and frequency of lactation bouts and influence pup growth rate, unless females modify milk energy density and/or the total amount of milk delivered depending on the trip duration
Female foraging trip and haul-out durations depended on pup sex and weight, whereas milk energy density depended on female body mass and foraging trip durations

Summary

Introduction

Parental care is the main component of the reproductive cost in birds and female mammals, and offspring survival is expected to be more strongly influenced by parent foraging efficiency than breeding periodicity or clutch/litter size (Clutton-Brock 1991, Davies et al 2012). The growth rate of otariid pups depends largely on three major maternal care components: the balance between the length of the foraging trips and that of the suckling haul-outs (i.e. the maternal attendance pattern), the amount of milk delivered to the pup, and the quality of the milk delivered (Gentry et al 1986, Georges et al 2001, Georges and Guinet 2000). Females involved in long foraging trips targeting richer foraging grounds may balance a lower attendance frequency by increasing milk fat content or total milk delivery (Arnould and Boyd 1995, Arnould and Hindell 1999), which may explain the positive correlation between the length of foraging trips and the pup absolute mass gain reported in some studies (Guinet et al 1999)

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