Individual photographic identification : a key to the social organization of sperm whales

Sperm whales were tracked visually and acoustically in the waters west of the Galapagos between February and April 1985. A method for photographically identifying individual sperm whales is described. Measures of the photograph quality were compared with the certainty with which individuals were identified. A total of 210 females or immatures, 7 large adult males and 6 calves were recognized with certainty and individually identified. A simple model suggested that up to 9% of the females/immatures could not be identified using this method of photographic identification, despite high quality photographs. It was shown that these individuals have a lower number of unique marks on their flukes than the 210 identified females/immatures. The assumption of random sampling when taking photographs of individual sperm whales is discussed. The time and geographical positions of the re-sightings of known individuals suggest that the sperm whales preferred a rich upwelling area. -- The identified females/immatures were clustered into 23 discrete groups. Thirteen of these groups contained more than six associated members. Observations of calves and the high frequency of dorsal fins with a callus suggested that the groups of sperm whales off the Galapagos fell into the category of "mixed groups". Whales recorded as escorting a calf were most probably females. Different females/immatures were observed to escort the same calf, and identified females/immatures were observed with several different calves. -- Large males were observed either as singles, pairs or a set of three. In the observations of identified individuals there was no indication that particular pairs of large males, or large males of a similar size, were preferred companions. No fresh wounds or agonistic behaviour between large males was observed. The lack of sightings of medium-sized males suggest that they do not take part in reproduction in this area. The proportion of large males to mature females suggests that all large males do not migrate to the breeding grounds and do not participate in breeding every year. Identified large males were observed with different mixed groups and, further, different large males were associated with particular mixed groups. There was no indication that some mixed groups associated more with large males, than others. Large males seemed to follow a strategy of searching for mixed groups, instead of holding harems. -- During an attack by killer whales on sperm whales a high degree of coordination of the sperm whales' behaviour was noted. Twenty-one percent of the sperm whale flukes had tooth mark scars of which a majority were probably derived from shark attacks. A difference in the number of unique marks on the flukes between different geographical areas suggests that the method of individual photographic identification relying on uniquely marked flukes may be less successful in other areas

Postweaning behaviour in pups of the southern elephant seal (Mirounga leonina) on South Georgia

After weaning, southern elephant seal pups (Mirounga leonina) fast for 3 – 8 weeks, for largely unknown reasons. During the postweaning fast we observed daytime behaviour and movements of pups on South Georgia in relation to mass, sex, and tooth eruption. There was variation in behaviour, with the lowest levels of activity from about 09:00 to 15:00. When ashore, weaned pups spent 97% of the time resting. There was no difference in activity between the sexes, except that only male pups were observed fighting. There was a significant difference in tooth eruption between the sexes. In female pups, 87.9% had teeth at weaning, while only 28.7% of male pups had. There was no correlation between mass at weaning and activity in either sex. Weaned pups tended to gather in groups (median group size 3, range 2 – 67). Several factors may affect the behaviour of pups during the postweaning fast: the resting behaviour required to save energy favours spending time ashore during the day (which also enhances vitamin D synthesis), and foraging is more effectively practiced at night because their prey is more active at night

Water flux, body composition, and metabolic rate during molt in female southern elephant seals (Mirounga leonina)

Tritiated water dilution was used to measure changes in the proximate body composition of adult female southern elephant seals at the end of lactation and at the beginning and end of molt. During the 72 ± 0.9 d foraging phase between lactation and molt, seals gained 1.50 ± 0.16 kg·d⁻¹. Of the total mass gain (1065 ± 10.5 kg) 49% was water, 39% was fat, and 11% was protein. This represented an increase in total body gross energy of 2,111 ± 283 MJ throughout the foraging period. The rate of mass lost during molt was 4.70 ± 0.21 kg· d⁻¹ comprising 49% water, 33% fat and 16% protein. Although it was impossible to measure accurately the duration of fasting during the molt, the minimum cost of molt was 1,631 ± 146 MJ, which was not significantly different from the energy gained between lactation and molt. Females invested half as much in molt as in the growth of their pups. The metabolic rate during molt was 2.15 ± 17 W·kg1⁻¹, which was 2.8 ± 0.2 times the predicted resting metabolic rate. Water influx was greater than expected from metabolic water production, and seals had an additional water influx of 1. 75 ± 0.31 L·d⁻¹. This additional influx was negatively related to metabolic water production. There was some evidence from measurements of water influx that seals fed during molt, but this accounted for only 11.5% of the daily energy expenditure

The relation between the size of southern elephant seal mothers, the growth of their pups, and the use of maternal energy, fat, and protein during lactation

Pregnant female southern elephant seals vary in size by more than a factor of three when they come ashore to give birth and nurse their pups. Pups are fed exclusively from the mother's body reserves, which vary in proportion to her mass at parturition. We measured the use of body materials and energy over the course of lactation using a combination of isotope dilution and mass change during four breeding seasons on South Georgia. On average, mothers lost 35% of their mass at parturition during lactation. This included approximately 52% of the energy, 61% of the fat, and 24% of the protein in the mother's body. The relative amount that mothers expend on their pups is highly variable and shows little consistent trend with the mother's mass. Some large mothers used approximately 30% of their stored energy, (comprising around 40% of stored fat and 20% of body protein) to produce medium-or large-sized pups. Whereas some smaller mothers produced only small pups, others used all of or more than the reserves estimated to be available without incurring deleterious effects (68% of energy, 80% of fat, and 27% of protein). These small animals may be at risk of compromising their future reproduction. The production of small pups by these smaller females may reflect a compromise between the survival of the pup and the future success of the mother. While we expected that the largest females might show a reduced efficiency of mass transfer during lactation (because of high metabolic overheads), their ability to reduce the duration of lactation seems to compensate for this, and no such reduction could be shown

Expenditure, investment, and acquisition of energy in southern elephant seals

Information on the expenditure and investment of energy in southern elephant seals, Mirounga leonina, was collected during breeding and molt over four field seasons at South Georgia. Weight and body composition changes of mothers, pups, and breeding males were monitored during the breeding season. These changes were also measured in adult females, before and after the 70-day period when animals fed at sea between breeding and molt. During this period, information on foraging movements and behavior was gathered using purpose-built satellite-relay data loggers. Body composition changes were measured using isotope dilution techniques. Breeding energetics information is discussed in relation to the evidence for differential investment in male and female pups. Large females produce larger pups, both at birth and weaning. Male pups are born larger than female pups. However, there is no evidence that mothers invest more energy (either relative or absolute) in male pups after birth once female size and birth weight are taken into account. Foraging movements and diving behavior are discussed in terms of the oceanography of the foraging area and possible constraints placed by prey consumption on the seals’ dive behavior. We suggest that the long-distance travel of females to distant feeding locations may be advantageous in providing for the requirements for reliable food sources in a long-lived, uniparous mammal. Dive characteristics changed during the different phases of activity in foraging animals in relation to the average daily velocity of the animal, water depth, and undersea topography

Expenditure, investment, and acquisition of energy in southern elephant seals

Information on the expenditure and investment of energy in southern elephant seals, Mirounga leonina , was collected during breeding and molt over four field seasons at South Georgia. Weight and body composition changes of mothers, pups, and breeding males were monitored during the breeding season. These changes were also measured in adult females, before and after the 70-day period when animals fed at sea between breeding and molt. During this period, information on foraging movements and behavior was gathered using purpose-built satellite-relay data loggers. Body composition changes were measured using isotope dilution techniques. Breeding energetics information is discussed in relation to the evidence for differential investment in male and female pups. Large females produce larger pups, both at birth and weaning. Male pups are born larger than female pups. However, there is no evidence that mothers invest more energy (either relative or absolute) in male pups after birth once female size and birth weight are taken into account. Foraging movements and diving behavior are discussed in terms of the oceanography of the foraging area and possible constraints placed by prey consumption on the seals' dive behavior. We suggest that the long distance travel of females to distant feeding locations may be advantageous in providing for the requirements for reliable food sources in a long-lived, uniparous mammal. Dive characteristics changed during the different phases of activity in foraging animals in relation to the average daily velocity of the animal, water depth, and undersea topography