Ultrasound measurements of subcutaneous fat at 18 body sites on each of 23 southern elephant seals
Mirounga leonina (Linn.), together with circumference and length measurements, were used to estimate
the total subcutaneous blubber weight on each animal. Twelve cows (including animals that were pregnant
and others at early, mid-, late and post-lactation), 10 males and one male pup were anaesthetised for
these measurements, made at Heard I. (53�01'S.,73�23'E.) on various dates in October and November
1985. Comparison of the estimates of blubber weight from cows at various stages of lactation allowed
a mean blubber loss of 62.8 kg per cow per lactation to be calculated. It is suggested that measuring
variations in the subcutaneous fat reserves of cows coming ashore to pup at Heard I. may be one
relevant approach in any future research that attempts to explain the 60% drop in pup production at
that island between 1949 and 1985. The use of ultrasound to estimate the subcutaneous fat reserves of
seals was shown to be a safe, non-invasive and logistically practical technique.
Reproductive skipping as an optimal life history strategy in the southern elephant seal, Mirounga leonina
