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Exploring habitat use and movement patterns of humpback whales in a reoccupation area off Brazil: A comparison with the Abrolhos Bank

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Abstract

After the worldwide moratorium on whaling, humpback whale populations began to recover, reoccupying former areas of use, as also observed on the Brazilian coast. Abrolhos Bank represents the area of greatest humpback whale concentration but the number of individuals to the north has increased, as has happened in the region of Serra Grande. To compare relative abundance, habitat use, and movement patterns between a well-established breeding and a reoccupation area, visual monitoring from land-based stations was performed: 160 days in the Abrolhos Archipelago located on the Abrolhos Bank and 133 days in Serra Grande in 2014, 2015, 2018, and 2019. While relative abundance varied annually in the Abrolhos Archipelago, it gradually increased in Serra Grande, surpassing the number registered in Abrolhos in 2019. Group composition frequency was similar between areas except for mother and calf accompanied by one or more escorts, which were more frequent in Abrolhos. Despite similar movement speed and linearity values, whales in Serra Grande had a higher reorientation rate. Monitoring different areas occupied by this population supports decisions about spatial management of the Brazilian coast in relation to the implementation of anthropogenic activities, especially in areas where whales have recently returned to occupy.

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Between 5 October and 19 November 1993, 62 sightings of 155 humpback whales were made from the lighthouse at Cape Columbine, South Africa, in 3 episodes about 9 d apart. For 59 groups tracked by theodolite, the average distance offshore peaked at 2 to 2.5 km. Independent information on offshore distribution was obtained from 1112 km searched by a ski-boat in the vicinity of Cape Columbine, from which the proportions of humpback whale groups in 2 strata (0 to 5 and > 5 km) from the shore as seen from the lighthouse did not differ from those expected from the boat data. Net directions of movement for 51 groups were distributed equally to all 4 quadrants of the compass, and those groups showing a concerted directionality of movement were headed equally to the north and to the south. Of the same 51 groups, 70% travelled at net speeds of less than 1.5 km h(-1). Migratory indices for individual groups (average speed/net speed) ranged as high as 82, and those with the lowest indices (corresponding to those most likely to be migrating) were distributed equally between northerly and southerly directions. Individual identification photographs taken of 27 humpback whales over 20 d revealed only 10 individuals, 5 of which were resighted on more than 1 occasion and up to 20 d apart. Apparent feeding behaviour by humpback whales was seen on 10 occasions over 38 d, and the production of reddish particulate faeces indicative of recent feeding was seen on 7 occasions, at a defecation rate of 0.22 whale(-1) h(-1). Faecal samples collected contained euphausiid remains (possibly Euphausia lucens) on 2 occasions and amphipods on another. Overall the data indicated that the southward migration of humpback whales expected at this time of year on the west coast of South Africa had been suspended, probably in response to locally abundant prey.
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The Abrolhos Bank off Brazil is considered the main breeding ground for the humpback whale (Megaptera novaeangliae) in the Southwest Atlantic. However, owing to an increase in the occurrence of the species along the north coast of the State of Bahia, it has been suggested that the species is reoccupying that region, which was probably utilized by the whales before commercial whaling. Information is presented on the occurrence and distribution of humpback whales along the north coast of the State of Bahia, with a comparative overview, for the period 2000-2006. Daily research cruises were conducted from July to October, departing from Praia do Forte (13°40′S 38°10′W) and lasting ∼9 h. Data on sampling and sighting effort, and geographical position and composition of groups of humpback whales, were collected on standardized field sheets. In all, 230 surveys were performed, covering some 9740 nautical miles in 1645 h of sampling effort, during which 1626 humpback whales were sighted, including 118 calves. Humpback whales were sighted throughout the study area. Solitary individuals and pairs were the most frequent group composition, 26% and 37% of the observed groups (n = 723), respectively. Depth of water varied from 15 to 1657 m (mean = 62.4; s.d. = 99). The sightings values were grouped into depth classes to ascertain the highest frequencies (∼30%) for the two classes, i.e. between 35.1 and 55 m of water. There was an increase in the encounter rates of humpback whales on the north coast of the State of Bahia between 2000 and 2006, identifying a difference in SPUE [sightings per unit (h) of effort] among years (Kruskal-Wallis H = 30.155, d.f. = 6, p < 0.05). The results support the hypothesis that humpback whales are reoccupying former breeding areas along the Brazilian coast. © 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.
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Results of studies of the structure and dynamics of two humpback whale stocks of the southern hemisphere (group IV, 70º E.-130°E.; group V, 130º E.-170º W.) are drawn together. Estimates are made of recruitment and mortality rates, and an assessment is made of the yields to be taken from these stocks under various conditions. The two stocks are shown to be, in the main, independent of one another although there is a negligible sporadic exchange between them. The group V stock is shown to fragment, but probably randomly, in its northern migration. Reproduction, nutrition, and growth are described. Birth rate of females is estimated to be 0.186, and since the sex ratio is approximately 1, the total birth rate is about 0.37. Parameters (von Bertalanffy) for growth are L∞ 42.58 ft for males, 45.21 ft for females; k(male) = 0.266, k(female): = 0.205. The history of exploitation is reported. Population structure is described from evidence drawn from examination of commercial catches; substantial changes in recent years (reduction of the numbers in older groups) are described. Measurement of effort, and an analysis of variations in selectivity of the killings are reported in detail. Decline in the abundance of these groups, group IV steadily since 1954 and group V sharply since 1959, is described. Total mortality, natural mortality, fishing mortality, and recruitment rates are estimated and are used in estimating stock numbers and sustainable yields. The group IV stock probably consisted of 12,000-17,000 individuals in its unfished state, of about 10,000 individuals in 1949, and no more than 800 in 1962. The group V stock probably contained about 10,000 individuals in its unfished state, but only 500 or less in 1962. In its present state, group IV could give a sustainable yield of 18 (range 4-32) whales, and group V of 12 (range 3-21) whales. The maximum yields these stocks could sustain in completely regenerated state are: group IV, 390 whales per year; group V, 330 whales per year. Group IV would require 28-49 years to reach that state, group V would require 36-63 years.
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The humpback whale (Megaptera novaeangliae) population that uses Abrolhos Bank, off the east coast of Brazil as a breeding ground is increasing. To describe temporal changes in the relative abundance of humpback whales around Abrolhos, seven years (1998–2004) of whale count data were collected during July through to November. During one-hour-scans, observers determined group size within 9.3 km (5 n.m.) of a land-based observing station. A total of 930 scans, comprising 7996 sightings of adults and 2044 calves were analysed using generalized linear models that included variables for time of day, day of the season, years and two-way interactions as possible predictors. The pattern observed was the gradual build-up and decline in whale counts within seasons. Patterns and peaks of adult and calf counts varied among years. Although fluctuation was observed, there was generally an increasing trend in adult counts among years. Calf counts increased only in 2004. These fluctuations may have been caused by some environmental conditions in humpback whales' summering grounds and also by changes in spatial–temporal concentrations in Abrolhos Bank. The general pattern observed within the study area mirrored what was observed in the whole Abrolhos Bank. Knowledge of the consistency with which humpback whales use this important nursing area should prove beneficial for designing future monitoring programmes especially related to whale watching activities around Abrolhos Archipelago.
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The Brazilian coast is recognised as a Southern Hemisphere humpback whale ( Megaptera novaeangliae ) wintering ground (IWC breeding stock 'A'). The northeastern coast of Brazil was an important whaling ground in the 20 th century. Shipboard sighting surveys were conducted in this area to evaluate large whales' distribution and density in 1999 and 2000. Humpback whale sightings (n = 81, 153 individuals) were recorded using line transect methodology. Data from the 2000 survey were used to estimate abundance over the continental shelf from 5 to 12°S (20,040km 2). A total of 872.1km were surveyed on effort. Humpback whales were distributed from nearshore to the 800m isobath, but 93.5% of sightings were recorded shoreward of the 300m isobath. The relatively high density off northeastern Brazil suggests that the species is reoccupying historical areas of distribution and the presence of newborn indiv iduals indicates that calving and nursing occur in the area. The hazard rate model best fit perpendicular distance data. Abundance was estimated at 628 individuals (CV = 0.335, 95% CI = 327-1,157). This estimate probably corresponds to only a portion of the breeding population. Ther efore, additional studies must be conducted to estimate the total size of the humpback whale population wintering off Brazil.
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Humpback whales (Megaptera novaeangliae) were tracked from shore to determine habitat-use patterns in an area relatively undisturbed by human activity near the "Big Island" of Hawaii during the winter 1988 and 1989 calving seasons. The temporal and spatial distributions of whales differed with group size and composition. During afternoon hours, groups containing a calf occurred in water significantly shallower and nearer to shore than did groups without a calf. Late in the breeding season, the same segregation pattern occurred throughout the day. Between-groups distances were significantly greater for groups with a calf than distances between all other groups. The number of whales observed per hour peaked during mid-February, although the relative sighting rates for various group sizes and compositions varied across the breeding season. Adults without a calf may use deep water to facilitate breeding behavior, while maternal females may use shallower water to avoid harassment and injury to calves from sexually active males, turbulent offshore or deep sea conditions, or predators. The predominance of cows with a calf in coastal habitat increases their exposure to expanding human-related development and aquatic activities that could injure, disturb, or displace them.
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Behavior of humpback whales was observed during the reproductive period off the northern coast of the state of Bahia (NB, n = 378 groups) and at the Abrolhos Bank (AB, n = 919) to compare patterns and group composition between the two locations. Alone individuals and dyads were most often encountered in both areas, although mother-calf pairs were more common in AB. While these two regions comprise distinct concentrations of humpback whales, with intrinsic environmental differences, behavior patterns were quite similar. The only behavioral differences found where for "tail up" and "resting". The patterns found here may reflect differences in the protection status of the areas or intrinsic environmental differences.
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The population of humpback whales (Megaptera novaeangliae) wintering off the eastern coast of South America is referred to by the International Whaling Commission as ‘Breeding Stock A’ (BSA). This population was heavily exploited in 20th century modern commercial whaling operations. After more than 30 years of protection, its present status remains unknown. A deterministic sex and age-aggregated population dynamics model was used to estimate the pre-exploitation population size (K), the maximum net recruitment rate (rmax), the maximum depletion level (Nmin/K), and other quantities of interest of BSA. Input data included modern whaling catch series, absolute estimates of abundance, observed growth rates and indices of relative abundance. A Bayesian statistical method was used to calculate probability distributions for the model parameters. Prior distributions were set on rmax – an uninformative (Uniform [0, 0.106]) and an informative (Normal [0.067, 0.042]) – and on the population size in 2005 – N2005 (Uniform [500, 22,000]). A total of 10,000 samples were used to compute the joint posterior distribution of the model parameters using the Sampling-Importance-Resampling algorithm. Sensitivity of model outputs to the priors on rmax, a genetic constraint, data inclusion and catch allocation scenarios was investigated. Medians of the posterior probability distributions of quantities of interest for the base case scenario were: rmax = 0.069 (95% probability intervals [PI] = 0.013–0.104), K = 24,558 (95% PI = 22,791–31,118), Nmin/K = 2% (PI = 0.31%–12.5%), N2006/K = 27.4% (PI = 18.3%–39.5%), N2020/K = 61.8% (PI = 23.8%–88.6%), and N2040/K = 97.3% (PI = 31.6%–99.9%). Despite apparent recovery in the past three decades, the western South Atlantic humpback whale population is still low relative to its pre-exploitation size and requires continued conservation efforts.
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The Brazilian coral reefs form structures that are significantly different from the well known coral reef models. The Brazilian coral reefs are different because they have a characteristic initial growth form of mushroom shaped coral pinnacles called "chapeiröes" they are built by a very low diversity coral fauna rich in endemic species, which are relic forms, remnant of an ancient coral fauna dating back in the Tertiary; incrusting coralline algae have an important role in the construction of the reef structure; and the nearshore bank reefs are surrounded and even filled with muddy siliciclastic sediments. The chapeiröes fuse together at their tops forming large compound reef structures of varied sizes with horizontal tops, and somewhat irregular shape. They can be completely exposed during low tides. These reef structures are distributed into three major sectors along the tropical coast of Brazil: the northern, the northeastern and the eastern coasts. There are different types of bank reefs, fringing reefs and atolls. Corals, milleporids and coralline algae build the rigid flame of the reefs. The coral fauna comprises less than 18 species, some of them being endemic to the Brazilian waters. The major human impacts to the reef ecosystem are mostly associated with agricultural activities (sugarcane and timber), mineral and chemical industries and oil exploration. Increased sedimentation due to removal of the Atlantic rainforest and the disposal of industrial and urban effluents are additional stresses to the coastal marine environment in Brazil.
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Shore-based surveys of migrating humpback whales Megaptera novaeangliae were undertaken from Cape Vidal, northern KwaZulu-Natal, South Africa, each year between 1988 and 1991, and in 2002. Daily observations of migrating whale groups were carried out from an approx. 60 m-high platform during all surveys. Whale groups were tracked by position-fixing on surfacing bouts using survey theodolites, to determine swimming speeds and headings and distance offshore, while group size estimation was carried out at each theodolite measurement. Numbers of whales observed or projected (at tracked speeds) to cross the midline of the survey area within the observation period each day were tallied in each of three distance bins. These counts were adjusted to account for daily sighting effort and for proportions that were likely to have been missed on account of their distance offshore or poor sighting conditions to produce daily sighting rates. Such daily tallies were summed over the survey period to estimate the number of whales passing Cape Vidal each year, with counts from days of <2.5 h of observation effort (due to weather or sighting condition restraints) replaced by the mean of the previous and following days. The numbers passing to the north of Cape Vidal during coincident periods of 17 days over the 1988–2002 surveys (6–22 July) and 25 days over the 1990, 1991 and 2002 surveys (6–30 July) provide statistically significant increase rates of 11.5% (SE 2.8) and 9.0% (SE 2.7) per annum respectively.
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The Gold Coast bay in eastern Australia has been hypothesised to be an important habitat, primarily for humpback whale (Megaptera novaeangliae) mother-calf pairs. Here we investigated relative distribution , and temporal patterns from 2,305 humpback whales between 2011 to 2017. The data were collected from whale-watching vessels using citizen science. We analysed seasonal presence of mother-calf pairs, dive times, direction of movement and location to determine habitat use of the bay as aresting area. In average aquarter of all sighted whales were mother-calf pairs with peaks of sightings each October. The recorded average dive time of 3.20 minutes was short compared to that in migratory corridors. Mother-calf pairs were sighted more often closer to shore relative to other pods. We compared our results to recognised breeding and resting grounds and found similar results, indicating that the Gold Coast bay may serve as an important stopover for humpback whale mother-calf pairs. ARTICLE HISTORY
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Long‐distance migration is a demanding physical activity, and how well animals manage the associated costs will have important implications for their fitness. The Oceania humpback whale ( Megaptera novaeangliae ) population is recovering from past exploitation markedly slower than the neighbouring east Australian whales. The reasons for this are unknown, although higher energetic costs of longer migratory distances could be a possible explanation. Due to their fully aquatic lives, studying the energy expenditure of these large animals requires methods that do not rely on capturing the animal, such as bioenergetic models. A state‐space model was fitted to satellite data to infer behavioural states for southern migrating whales. Travel speeds and behavioural states were used in a bioenergetic model to estimate the energetic cost of the migration phase. Relative differences in average duration, distance, and energetic costs were compared between migratory routes and distances. Total energy used during migration was a trade‐off between cost of transport (determined by travel speed) and daily maintenance (determined by daily basal metabolic costs). Oceania whales migrating to the Amundsen and Bellingshausen Seas travelled fastest and furthest, 15 and 21% further than whales migrating to the d'Urville Sea (east Australian whales) and Ross Sea, respectively. Therefore, they had the highest cost of transport, 25 and 85% higher than for d'Urville Sea and Ross Sea whales, respectively. However, energy saved in terms of daily maintenance by using fewer days to complete a longer migration resulted in only a 6–7% increase in total energetic cost. The results highlight that travelling further does not necessarily translate into an increase in total energy expenditure for migratory whales, since they can compensate for longer distance by travelling faster. Further research on the energetics of different whale populations could provide insight into the productivity of Southern Ocean feeding regions and help understand the environmental and anthropogenic effects on the whales' energy budgets.
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This paper reports on aerial surveys conducted to estimate the relative abundance and trend in growth of the southern right whale (Eubalaena australis) population from Península Valdés. The number of whales counted tripled from 1999 to 2016. We modeled the number of whales, the number of calves, the number of solitary individuals and the number of individuals in breeding groups using as predictive variables the year, Julian day, and Julian day² by means of generalized linear models. The rate of increase decreased from near 7% in 2007 to 0.06% and 2.30% for total number of whales and number of calves, respectively for 2016. Trends in the rates of increase for total number of whales and number of calves were negative (−0.732% and −0.376%, respectively). The habitat use of the whales changed along the years, with mothers and calves using more heavily the near‐shore strip, resulting in a decreasing trend for solitary individuals and breeding groups in near‐shore waters. We conclude that whales are still increasing their abundance, while the rate of increase is decreasing. Differences in the rates of increase of the group types and changes in habitat use are thought to be the consequence of a density‐dependence process.
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Humpback whales congregate annually in low-latitude winter breeding and calving grounds. While on these grounds, females with a dependent calf ('maternal females') are sometimes closely at-tended by one or more male escorts. Using data collected from a shore-based observation platform in the Hawaiian Islands, we tested the hypothesis that the spatial distribution of maternal females is driven primarily by avoidance of males. As predicted, we found that (1) pods containing a calf oc-curred in significantly shallower water than pods that did not contain a calf, (2) unescorted maternal females occurred in significantly shallower water than escorted maternal females, (3) the number of males escorting a female decreased significantly with decreasing water depth, and (4) the swim-ming speed of maternal females increased as a function of male presence, with escorted females travelling significantly more rapidly than unescorted females and a significant positive correlation between swimming speed and number of escorts. We suggest that maternal females incur increased energetic costs when escorted by males and consequently position themselves in shallow waters to reduce the likelihood of unwanted male attention.
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Ship strikes are one of the major threats to large whales worldwide. The potential impact from increasing vessel traffic therefore is a concern for the future of the Brazilian humpback whale ( Megaptera novaeangliae ) population. In order to evaluate the risk of collision between large vessels and humpback whales along coastal shipping routes in the region of the Abrolhos Bank – the most important breeding ground for the species in the south‐western Atlantic Ocean – commercial vessels were used as platforms of opportunity to monitor the coastal shipping routes. Humpback whale density along coastal routes was estimated through multiple covariate line‐transect ‘distance sampling’. The number of potential collisions per year was estimated using a model based on vessel size and speed, track lengths, population density and the surfacing behaviour of whales. During the peak of the 2011 breeding season, whale density on the coastal route between Belmonte and Caravelas was estimated to be 0.085 whales km ‐2 and between Caravelas and Barra do Riacho, 0.023 whales km ‐2 . The three commercial vessels operating in coastal waters between Belmonte and Barra do Riacho had the potential to collide with 25 humpback whales in total, and kill 17 of these, during the 2011 breeding season. As vessel traffic increases in the Abrolhos Bank region and humpback whale population grows, the likelihood of a vessel collision will increase. A simple and effective framework to study how changes in whale density will affect their vulnerability to ship strikes, and ensure the suitability of alternative shipping routes is presented, while evaluating whether additional mitigation measures are necessary, such as speed limits in areas or periods with higher densities of whales. Copyright © 2014 John Wiley & Sons, Ltd.
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Abstract Limited data exist on swimming speeds of humpback whales (Megaptera novaeangliae) and none on swimming speeds of singing whales during migration. We tracked humpback whales visually and acoustically during migration from the breeding grounds past our study site on the east coast of Australia (latitude 26°28′S). The mean swimming speed for whales while singing was 2.5 km/h, significantly less than for non-singing whales with a mean of 4.0 km/h but significantly greater than the mean of 1.6 km/h observed for singing whales on the Hawaiian breeding grounds. Between song sessions, there was no significant difference in speeds between whales that had been singing and other whales. Migration speeds were less for whales while singing but increased during the season. Although humpback whales can swim rapidly while singing (maximum observed 15.6 km/h), they generally do not do so, even during migration. Slower migration by singers would delay their return to the polar feeding areas and may be costly, but may be a strategy to provide access to more females.
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Fast moving groups containing three or more adult humpback whales are found in the winter on Silver Bank in the West Indies, and off Hawaii. Many of these groups have a definite structure: a central Nuclear Animal, with or without a calf, is surrounded by escorts who compete, sometimes violently, for proximity to the Nuclear Animal. This competition involves fluke thrashes, the blowing of bubblestreams, and physical contact, some of which appears designed to hurt an opponent: bleeding wounds are seen on the competing escorts. Escorts sometimes leave these groups and start singing, and singers sometimes stop to join large groups. The pattern of interactions strongly suggests that the escorts are males competing for access to a central female. Off Hawaii singers respond to such groups at ranges of up to approximately 7.5 km. On Silver Bank, Principal Escorts maintained a position of closest proximity to the Nuclear Animal for an average of 7.5 hours before replacement.
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Aerial observations of humpback whales in the region of Point Cloates, Western Australia, during 1952 are recorded. The first southward-moving humpback whale was sighted on July 21, while decreasing numbers were seen moving northwards until early October. In 1952 the change from a predominantly northward migration of humpback whales to a southward migration occurred close to August 24. The speed of migration of a number of these whales is recorded, the mean value being 4.3 kt. A few humpback whale calves were sighted early in July and a peak in their occurrence in August suggests maximum frequency of parturition early in August. A very great increase in the occurrence of calves in the area late in the season suggests that female humpback whales rearing calves move southwards later than other individuals. Some evidence is presented that Exmouth Gulf is a nursery area. The presence of some killer, fin, blue, and minke whales in the area is noted.
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Through compilation of historical whaling data, to- gether with recent aerial and boat-based survey data, a general framework for the overall peaks of migration has been estimated for the temporal and spatial movements of Group IV humpback whales along the Western Austra- lian coast. The migratory paths of humpback whales along the Western Australian coast lie within the continental shelf boundary or 200 m bathymetry. Major resting areas along the migratory path have been identified at Exmouth Gulf (southern migration only) and at Shark Bay. The northern endpoint of migration and resting area for reproductively active whales in the population appears to be Camden Sound in the Kimberley. A 6,750 square km 2 area of the Kimberley region, inclusive of Camden Sound, has also been identified as a major calving ground. The northern and southern migratory paths have been shown to be divergent at the Perth Basin, Dampier Archipelago and Kimberley regions. In all cases the northern migratory route is further off-shore.
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Humpback whales off Newfoundland in summer formed groupings containing from 1 to over 10 animals. The size of feeding groups was closely related to the horizontal size of the prey school, whereas nonfeeding humpbacks were generally found in pairs. Small groups were considerably more stable than larger ones. Apart from mothers and their 1st-year calves, there were no indications of preferred companionships over more than 1 day, although during a day particular pairings would maintain their identities when within a larger group. The humpbacks often stayed in groups while at depth. Individuals in larger groups produced faeces more frequently. Other displays (side flukes, flipperings, and lunges) were associated with group instability.