Reproductive energetics and female attendance patterns of cape fur seals (Arctocephalus pusillus pusillus) during early lactation
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abstract
The Cape fur seal (Arctocephalus pusillus pusillus) is a common pinniped species along the southern African coastline. While much information is available about this species, little is known concerning its reproductive energetics. With radio telemetry, we monitored attendance patterns for 1 to 4 mo from 1996-1999. Attendance of 29 nursing females averaged 1.86 0.77 d on shore and 5.23 2.87 d at sea. Mean cycle time was 7.09 4.33 d, of which 29.6% was spent on shore and 70.4% at sea. A significant increase in length of time at sea was observed during the first 4 mo of lactation. Reproductive condition was quantified using measures of body condition and milk composition. Milk ingestion and field metabolic rates established a baseline for the energetics of 1 mo old pups. Body composition averaged 11.05 2.31% lipid and 19.15 2.60% protein. Milk from 17 individuals was composed of 58.07 6.79% water, 2.02 0.58% ash, 10.76 1.23% protein and 23.16 8.24% lipid. Milk energy content averaged 11.02 3.10 kJ ml-1. Thirteen pups consumed milk at a rate of 136.58 29.11 ml kg-1 d-1. Mean energy intake was 1505.10 320.80 kJ kg-1 d-1, with 37.16 8.04% going to body maintenance and 62.84 8.04% to growth. Fat and protein tissue was deposited at a rate of 16.10 34.93 g d-1 and 21.40 59.20 g d-1, respectively. Pup mass gain averaged 99.30 3154.10 g d-1. Male and female pups differed significantly in body mass and field metabolic rate.
