Observations on the composition and behaviour of groups of female sperm whales near the Galapagos Islands

1989 ◽  
Vol 67 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Tom Arnbom ◽  
Hal Whitehead
Keyword(s):  
Significant Variation ◽  
Galapagos Islands ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales ◽  
Acoustic Tracking ◽  
Dorsal Fin ◽  
Significant Difference ◽  
High Incidence ◽  
Mixed Groups

During visual and acoustic tracking of sperm whales, Physeter macrocephalus, off the Galapagos Islands, observations were made on the composition and behaviour of the 13 photographically identified groups being followed. Observations of calves and the high incidence of animals with dorsal fin calluses suggested that the groups could be categorized as mixed groups, which contain females and their offspring. Animals recorded to be escorting calves were probably females. Individual calves were escorted by different individuals at different times, and known individuals were observed to escort more than one calf on different occasions. There was a significant difference in the proportion of open and closed fluke notches between groups, suggesting some relatedness of individuals within a group. Twenty-one percent of the identified individuals had tooth mark scars on their flukes, but there was no significant variation in this proportion between groups.

Population Structure of Female and Immature Sperm Whales (Physeter macrocephalus) off the Galápagos Islands

1992 ◽  
Vol 49 (1) ◽  
pp. 78-84 ◽  
Author(s):  
Hal Whitehead ◽  
Susan Waters ◽  
Thomas Lyrholm
Keyword(s):  
Monte Carlo ◽  
Population Structure ◽  
Maximum Likelihood ◽  
Confidence Interval ◽  
Galapagos Islands ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Population Parameters ◽  
Sperm Whales ◽  
Population Simulation

The structure of the population of female and immature sperm whales (Physeter macrocephalus) in the region of the Galápagos Islands was studied using individual photographic identifications of 1285 animals collected between 1985 and 1989. Population parameters were estimated using a maximum-likelihood mark–recapture estimate permitting emigration from the study area in which identifications are collected and then reimmigration back into it. Because permanent associations among whales violated assumptions of independence, confidence intervals for the estimates were constructed using Monte-Carlo population simulation. The analysis suggested that there is a population of very approximately 200 whales in the study area around the islands at any time. These were part of a larger population numbering between 2600 and 5300 individuals (95% confidence interval). An average of 39–94% (95% confidence interval) of the whales left the study area in any month, with a similar number immigrating.

Coda communication by sperm whales (Physeter macrocephalus) off the Galápagos Islands

1993 ◽  
Vol 71 (4) ◽  
pp. 744-752 ◽  
Author(s):  
Linda Weilgart ◽  
Hal Whitehead
Keyword(s):  
Social Cohesion ◽  
Temporal Pattern ◽  
Sequential Analysis ◽  
Sperm Whale ◽  
Galapagos Islands ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales ◽  
Insight Into

To gain insight into the function of sperm whale vocalizations known as codas (short, patterned series of clicks), sperm whales (Physeter macrocephalus) were tracked continuously for periods of days totalling months off the Galápagos Islands, Ecuador, and vocalizations were tape recorded systematically. In total, 1333 codas were classified according to their temporal pattern and the number of clicks they contained. Codas were found to be temporally very clustered, and could be categorized into 23 fairly discrete types. Sequential analysis of codas revealed that they overlapped one another according to type in a nonrandom way, and that type 5 tended to initiate coda exchanges. "Regular" coda types (with evenly spaced clicks) tended to occur with other regular coda types and "irregular" coda types (with one or two delayed final clicks) were heard with other irregular coda types. Codas may function principally as a means of communication, to maintain social cohesion within stable groups of females following periods of dispersion during foraging.

Social organization of sperm whales off the Galapagos Islands, February–April 1985

1987 ◽  
Vol 65 (4) ◽  
pp. 913-919 ◽  
Author(s):  
Hal Whitehead ◽  
Tom Arnbom
Keyword(s):  
Simple Model ◽  
Social Organization ◽  
Galapagos Islands ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales ◽  
Searching Strategy ◽  
Breeding Grounds ◽  
Statistical Criteria

Between February and April 1985 sperm whales (Physeter macrocephalus) were tracked visually and acoustically in the waters west of the Galapagos Islands. Individuals were identified and measured photographically. Using statistical criteria the female and immature whales encountered were clustered into 13 groups with closed membership during the study period. These groups had a median estimated population of 19.5 animals each, and associated with one another at different times. The groups showed no significant immigration into or emigration from the study area during the study. Seven large males were identified. These associated with each other and the groups of females and immatures for periods lasting approximately 6 h. Individual males were found with different groups of females and immatures at different times. A simple model suggests that a male employing a "searching" strategy should encounter more oestrous females than the traditionally accepted "harem" holder when the interval between encountering groups of females is less than the duration of the females' oestrus. Neither the groups of females nor the mature males appeared to possess territories or preferred ranges within the study area. The number of large males encountered was considerably less than that expected if all large males were present on the breeding grounds, suggesting that males may not breed every year.

The behaviour of mature male sperm whales on the Galápagos Islands breeding grounds

1993 ◽  
Vol 71 (4) ◽  
pp. 689-699 ◽  
Author(s):  
Hal Whitehead
Keyword(s):  
Reproductive Success ◽  
Galapagos Islands ◽  
Mature Male ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales ◽  
Male Sperm ◽  
Breeding Grounds

The behaviour of mature male sperm whales (Physeter macrocephalus) was observed off the Galápagos Islands between 1985 and 1991. The abundance of males peaked in April and May at 3% of the population. Only 1 of the 18 photographically identified males was sighted off the Galápagos in two different years. In their residency periods off the Galápagos and their lack of preferred ranges, and in many aspects of their behaviour, males were similar to females. However, unlike females, males were sometimes seen alone and never performed any aerial behaviour. Although they were occasionally seen or heard together, there are indications that males avoided one another, perhaps by listening for the "slow click" vocalizations made by males approximately 75% of the time. One incidence of possible aggression between males was observed, and many males possessed parallel scars on their heads, presumably made during aggressive encounters. Males moved between groups of females, spending very approximately 8 h with each group. Groups of females were often revisited by particular males over periods of a few days but never over more than 1 week. Males showed no obvious preference for particular groups, although a few close associations between individual males and individual females were noticed over intervals of a few days. When males were present, females showed increased rates of making spyhops and sideflukes (indicating manoeuvring) and codas (a communicative vocalization). Copulation was not observed. The evidence is consistent with males' maximizing their expected reproductive success by roving between groups of females.

Diving behaviour of the sperm whale, Physeter macrocephalus, off the Galapagos Islands

1989 ◽  
Vol 67 (4) ◽  
pp. 839-846 ◽  
Author(s):  
Vassili Papastavrou ◽  
Sean C. Smith ◽  
Hal Whitehead
Keyword(s):  
Diurnal Variation ◽  
Sperm Whale ◽  
Galapagos Islands ◽  
Diving Behaviour ◽  
Ocean Floor ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales ◽  
Direct Information ◽  
Oxygen Minimum

Sperm whales, Physeter macrocephalus, were tracked by means of a recording depth sounder in the waters off the Galapagos Islands. At depths of less than 300 m the whales generally dived nearly vertically at 60–100 m/min. At greater depths their descents were usually slower. Between February and April 1985, they dived to about 420 m, which is approximately the depth of the oxygen minimum. In 1987, a year of warmer water temperatures, they usually dived about 70 m shallower. There was no apparent diurnal variation in dive depths. None of the whales tracked dived to the ocean floor. Whales dived for about 40 min, followed by 10 min at the surface. Sperm whales usually started to make regular clicks when 150–300 m deep. Young calves appeared not to make prolonged deep dives. Our results are generally consistent with other direct information on the diving behaviour of relatively undisturbed sperm whales, but often conflict with results obtained using sonar for sperm whales being chased by whale catchers.

Temporal and geographic variation in the social structure of female sperm whales

1992 ◽  
Vol 70 (11) ◽  
pp. 2145-2149 ◽  
Author(s):  
Hal Whitehead ◽  
Benjamin Kahn
Keyword(s):  
Social Structure ◽  
Galapagos Islands ◽  
General Area ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales ◽  
The Social ◽  
Seychelles Islands ◽  
Mean Size ◽  
Geographic Differences

The social structure of female sperm whales (Physeter macrocephalus) was examined from data collected during studies of identified individuals off the Galápagos Islands in 1985, 1987, and 1989, off the Seychelles Islands in 1990, and off mainland Ecuador in 1991. Three levels of social organization were examined in the Galápagos Islands studies. "Units," permanent associations between individuals, showed no significant deviation from a mean size of 13 individuals. "Groups," temporary associations between units lasting a few days, had a mean size of 24 individuals. Group size was lower in 1987 (an "El Niño" year) than in 1985 or 1989, but this difference was not statistically significant. "Aggregations" of groups in the same general area lasting periods of hours were significantly larger in 1985 (mean of 77 individuals) than in 1987 (mean of 47 individuals). There are significant differences between areas in aggregation sizes but not in group sizes. Groups appear to aggregate frequently off the Galápagos Islands, occasionally off mainland Ecuador, and very rarely off the Seychelles Islands. These temporal and geographic differences in sizes of groups and aggregations in sperm whales are probably caused by variations in the distribution and abundance of their food, but responses to recent exploitation may also be a factor.

Formations of foraging sperm whales, Physeter macrocephalus, off the Galápagos Islands

1989 ◽  
Vol 67 (9) ◽  
pp. 2131-2139 ◽  
Author(s):  
Hal Whitehead
Keyword(s):  
Galapagos Islands ◽  
Mutual Interference ◽  
First Year ◽  
Physeter Macrocephalus ◽  
Galápagos Islands ◽  
Sperm Whales

Groups of sperm whales, composed mostly of females and their offspring, which were tracked in the waters off the Galápagos Islands during 1985 and 1987, generally foraged in ranks about 550 m long aligned perpendicular to the direction of travel. While at the surface, they swam in clusters containing a mean of 1.7 whales, and these clusters were spaced out along the rank. When feeding at depth the whales were estimated to be about 40 m apart. The ranks travelled at approximately 2 kn (3.7 km/h) and maintained their headings for periods of several hours. Individuals showed some coordination in the timing of their dives. There were no indications that individual whales, mature males, or first-year calves were more likely to be found in particular positions along the rank. The major benefits for individuals of foraging in a rank are probably gathering information about prey densities, avoiding mutual interference, and possibly catching prey that elude other members of the formation.

Variations in the feeding success and behaviour of Galápagos sperm whales (Physeter macrocephalus) as they relate to oceanographie conditions

1993 ◽  
Vol 71 (10) ◽  
pp. 1991-1996 ◽  
Author(s):  
Sean C. Smith ◽  
Hal Whitehead
Keyword(s):  
Surface Temperature ◽  
Significant Variation ◽  
Foraging Behaviour ◽  
Geographic Area ◽  
Sea Surface ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Feeding Success ◽  
Galapagos Archipelago ◽  
Oceanographic Conditions

The feeding success of sperm whales off the Galápagos Islands, Ecuador, was examined over 5 study years; 1985, 1987, 1988, 1989, and 1991. A total of 160 days were spent following sperm whales at sea. The defaecation rates of sperm whales were used as an indication of feeding success. The recorded acoustic click rates of sperm whales were used as an indication of aggregative and foraging behaviour. Significant variation in feeding success occurred temporally over periods of days, months, and years. Feeding success also varied spatially with geographic area. Feeding success was inversely related to sea surface temperature (SST). The foraging and associative behaviour of sperm whales also varied with feeding success, SST, and by year. Variations in the feeding success and behaviour of Galápagos sperm whales can likely be attributed to changing oceanographic conditions in the waters surrounding the Galápagos archipelago.

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