OCCURRENCE, COMPOSITION, AND POTENTIAL FUNCTIONS OF NORTH ATLANTIC RIGHT WHALE (EUBALAENA GLACIALIS) SURFACE ACTIVE GROUPS

Marine mammal social interactions are poorly understood primarily because of the difficulty of observing these behaviors in the wild. Observations of copulations in North Atlantic right whale surface active groups (SAGs) have led to the hypothesis that the function of these groups is for conception. The occurrence and composition of SAGs sighted from 1992 to 2001 were investigated on the basis of age, sex, and reproductive status of individuals. A total of 918 SAG events were documented. SAGs were observed in all habitat areas and in all months in which right whales were sighted. Group compositions revealed both potentially conceptive groups and nonconceptive groups. Of right whales whose age was known, 93% were first sighted in SAGs as juveniles, and more than half of all observed groups contained at least one juvenile whale. The group composition and timing of occurrence of SAGs do not support the hypothesis that all groups serve a purely conceptive function. Their functional role is likely much broader. Other potential functions include play, mating practice, or maintenance of social bonds.     

RATES AND POTENTIAL CAUSES OF MORTALITY IN NORTH ATLANTIC RIGHT WHALES (EUBALAENA GLACIALIS)

North Atlantic right whale mortality rates range from 2% to 17% over the first four years of life. Sources of mortality in this population include ship collisions, entanglements, and natural causes. A combined analysis of stranding data, entanglement records, and photographic information indicates that approximately one third of all right whale mortality is caused by human activities. Anthropogenic sources of right whale mortality may be a significant factor inhibiting growth in the North Atlantic population.     

THE GUNSHOT SOUND PRODUCED BY MALE NORTH ATLANTIC RIGHT WHALES (EUBALAENA GLACIALIS) AND ITS POTENTIAL FUNCTION IN REPRODUCTIVE ADVERTISEMENT

North Atlantic right whales ( Eubalaena glacialis ) make a short, distinctive broadband sound that is produced internally called a Gunshot sound. This sound has been recorded in the Bay of Fundy, Canada from both single whales ( n = 9) and social surface active groups ( n =49). Those single whales producing Gunshot sounds whose sex could be determined ( n = 9) were all mature males. Gunshot sounds were produced as part of a stereotyped behavioral sequence by these individuals, including frequent head-lifts and flipper slapping at the surface. In surface active groups, Gunshot sounds were commonly recorded when males were present in the group. The rate of production of Gunshot sounds was weakly correlated with the total number of males present in the group. Given the behavioral context of Gunshot sound production, and production of the sound only by male whales, Gunshots may function in a reproductive context as an advertisement signal to attract females, an agonistic signal directed toward other males, or a combination of the two functions.     

GENETIC BASIS AND EVOLUTIONARY SIGNIFICANCE OF VENTRAL SKIN COLOR MARKINGS IN NORTH ATLANTIC RIGHT WHALES (EUBALAENA GLACIALIS)

Approximately one third of the North Atlantic right whale population has white ventral skin patches. Most white-marked animals have both a belly and a chin patch, and the distribution of white pigment suggests that the patches represent a single ventral marking that varies in size and location. Population frequencies and cow-calf inheritance patterns indicate that the white mark is an autosomal recessive trait. There is no evidence to suggest that ventral coloration patterns are currently under selection. White-marked and black cows appear to experience similar levels of reproductive success based on calving intervals and length of sighting histories. Also, white-marked animals were equally common among cows and nulliparous adult females and among live vs. dead animals. Male reproductive success could not be tested because calf paternity is not known; white-marked and black males exhibit similar survival rates. White-marked cows were more common among females that took some or all of their calves to the Bay of Fundy summer nursery area compared to females that did not visit Fundy. This suggests that female habitat-use patterns may influence nuclear gene flow. Increased sample sizes and additional markers are needed to further investigate gene flow.     

LONG-RANGE MOVEMENTS OF SOUTH ATLANTIC RIGHT WHALES EUBALAENA AUSTRALIS

Abstract: Movements of southern right whales between Gough Island and South Africa, and between Argentina and Tristan da Cunha, southern Brazil, and South Georgia are documented through matching of six photoidentified individuals. These include the resighting of a male in a mid-oceanic locality some 4,424 km away from (and 11 yr after) its last sighting in a coastal area where it had been seen in six of the preceding eight years, a female photographed in mid-Atlantic resighted with a calf in a coastal nursery area 2,769 km away, resightings of females with calves in different nursery areas 2,051 km apart in different years, and the first example of a link between a coastal nursery area and a feeding ground in high latitudes. The possible implications of these movements for estimates of calving interval and survival rate based on resightings in coastal waters are discussed. The potential for intermingling between populations on either side of the South Atlantic seems greater than was previously considered likely from a comparison of animals photographed in coastal waters.     

RIGHT WHALES (EUBALAENA GLACIALIS) ON JEFFREYS LEDGE: A HABITAT OF UNRECOGNIZED IMPORTANCE?

North Atlantic right whales ( Eubalaena glacialis ) are known to spend the majority of the year between the Great South Channel southeast of Cape Cod, and the Nova Scotian shelf. We examined sightings of right whales on and around Jeffreys Ledge, a 54-km-long glacial deposit off the coast of northern Massachusetts, New Hampshire, and Maine. Sightings on Jeffreys Ledge were extracted from three data sets: (1) a systematic survey of the entire northeastern continental shelf between 1979 and 1982, (2) whale-watch and research-cruise sighting data from 1984 to 1997, and (3) a collaborative database of sightings collected by organizations conducting right whale research and all other available sources. Each database supported two seasonal sighting peaks. During summer (especially July and August) sightings were primarily of mother-calf pairs. Several cow-calf pairs were seen over several days to weeks. Several females were resighted in more than one year, but only when calves were present. During October, November, and December, sightings included all age classes, surface-feeding behavior was frequently observed, and some animals were resighted over several weeks. Given the relatively reduced sighting effort during fall, this number of sightings is surprising. During the 20 yr of observations, 52 of 374 photo-identified North Atlantic right whales (13.9%) were seen at least once on Jeffreys Ledge. We suggest that Jeffreys Ledge may be a more important right whale habitat than previously believed, and that it may play an important role in annual movements and distribution of this population.     

SEASONAL OCCURRENCE OF NORTH ATLANTIC RIGHT WHALE (EUBALAENA GLACIALIS) VOCALIZATIONS AT TWO SITES ON THE SCOTIAN SHELF

A year-long acoustic survey for critically endangered North Atlantic right whales was conducted at two sites on the central and western Scotian Shelf. Autonomous hydrophones recorded sound continuously from July 2004 to August 2005. Right whale contact calls (upcalls) were identified using automatic recognition software, and the resulting detections were checked manually. Substantial numbers of hours with upcalls were observed at both sites, with approximately four times as many hours with calls at the western site as the central one. Calls occurred mainly from August through October, with the earliest calls in late June and the latest at the end of December at both sites. In addition to this seasonal trend, there was a significant diel pattern in calling at the central site but not at the more westerly site. Results are analyzed in light of feeding ecology and broad-scale movements of right whales.     

ESTIMATION OF PREY DENSITIES REQUIRED BY WESTERN NORTH ATLANTIC RIGHT WHALES

The apparent lack of significant recovery of western North Atlantic right whale populations may be related to the availability of prey in exploitable densities. We have attempted to estimate the concentration of zooplankton required by right whales to obtain a net energetic benefit over the long term, using estimated values for body weight, metabolic rate, assimilation efficiency, time spent feeding, mouth size and swimming speed. The estimated range of required energy densities is 7.57 to 2,394 kcal m⁻³ (3.17 × 10⁴ to 1.00 × 10⁷ joule m⁻³). These values are from one to more than three orders of magnitude greater than the densest concentration sampled in the vicinity of right whale aggregations in the Great South Channel. Right whales must seek out and exploit extremely dense patches of prey organisms in order to feed efficiently. The presence of such dense patches of zooplankton is likely to be a primary characteristic of spring, summer and fall right whale habitats.     

LOCALIZATION OF NORTH ATLANTIC RIGHT WHALE SOUNDS IN THE BAY OF FUNDY USING A SONOBUOY ARRAY

A free-drifting 14-sonobuoy array was used to localize North Atlantic right whales ( Eubalaena glacialis ) in the Grand Manan Basin area of the Bay of Fundy. This area is a primary summer/autumn right whale habitat and overlaps an international shipping lane. The three-hour deployment on a single day provided two-dimensional localization of 94 right whale sounds based on arrival time differences determined from spectrogram cross-correlation analysis. The sounds were of two distinct types: tonal and gunshot. Maximum detection distances were about 30 km for both types of sound. The mean RMS location error was 1.8 km for tonal-type sounds and 2.5 km for gunshot-type sounds. The average RMS error was 20% of the average distance from the receiving hydrophones, the primary source of error being uncertainty in the sonobuoy positions.     

SEXUAL COMPOSITION and ANALYSIS OF REPRODUCTIVE FEMALES IN THE NORTH ATLANTIC RIGHT WHALE, EUBALAENA GLACIALIS, POPULATION

To test hypotheses involving reproduction and demographics, the sex of individuals must be established, but many species of Cetacea are not obviously dimorphic. In the North Atlantic right whale, Eubalaena glacialis , population, the sex of 61 males and 55 females had been determined previously by observation of the urogenital region, and the sex of 43 more females had been inferred from repeated sightings with a calf. To confirm the sex of some of these animals and to identify the sex of mote animals, genomic DNA was isolated from skin samples of 95 individual right whales (54 from among those described above and 41 additional recognizable individuals). The DNA was surveyed using the human Y-chromosome probe pDP1007. With Eco RI-digested DNA, a clear, sex-discriminating banding pattern was apparent. This method verified the sex of all 54 animals whose sex was previously known or inferred and identified the sex of an additional 41 recognizable individuals. A total of 89 male and 111 female right whales was identified in the population. The most unbiased estimate of sex ratio available is the 36 male and 34 female calves identified by genital morphology and DNA techniques. The sex ratio of this sample does not differ significantly from unity (P = 0.811). Only 38% (58/152) of the females in the North Atlantic population are known to have been reproductively successful compared with 54% in the population of right whales in the western South Atlantic. The population growth rate reported for the North Atlantic population is only 33% of that reported for right whales in the South Atlantic. Thirteen adult North Atlantic females have been identified that have not been known to calve during the past 11 yr. These data suggest that the absence of measurable recovery may be due to a combination of fewer actively reproducing females and lower reproductive rates of some females.     

ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA II: WITHIN BAY DISTRIBUTION

Environmental factors are thought to strongly influence the distribution and predictability of the coastal distribution of southern right whales ( Eubalaena australis ) off South Africa. Preferred habitat had generally shallow sloping sedimentary floors and was characteristically protected from open ocean swell and prevalent seasonal winds. This study investigated whether habitat choices at smaller scales (within bays) were similar. Fine scale distribution patterns (GPS) from three years' surveys (1997, 1999, 2000) were analyzed separately within the three main concentration areas St Sebastian Bay, De Hoop, and Walker Bay (containing ∼73% of cow-calf pairs and ∼49% of unaccompanied adults in the whole survey region). Whale density at this scale of within particular bays did not correlate well with predicted variables, but Chi-squared analysis strongly supported results at broader scales, in all bays. Post-hoc "choice" tests between similar areas differing in only one variable revealed that cow-calves preferred (presumed) sandy substrates and especially protection from swell. The strength and predictability of preferences shown at fine scale (where individual movement and weather variability could have great influence) provide strong support for findings at larger scales and emphasize the importance of environmental factors in the habitat choice of wintering right whales.     

NORTH ATLANTIC RIGHT WHALE DISTRIBUTION IN RELATION TO SEA-SURFACE TEMPERATURE IN THE SOUTHEASTERN UNITED STATES CALVING GROUNDS

Standardized aerial surveys were used to document the winter (December–March) distribution of North Atlantic right whales in their calving area off the coasts of Georgia and northeastern Florida (1991–1998). Survey data were collected within four survey zones in and adjacent to federally designated critical habitat. These data, including whale‐sighting locations and sampling effort, were used to describe right whale distribution in relation to sea‐surface temperature (SST) from satellite‐derived images. Locations where whales were sighted (n= 609) had an overall mean SST of 14.3°C ± 2.1° (range 8°–22°C). Data from two survey zones having sufficient data (including the “early warning system” (EWS) zone and the Florida nearshore) were pooled by season and stratified by month to investigate changes in monthly ambient SST and fine‐scale distribution patterns of right whales in relation to SST within spatially explicit search areas. Using Monte Carlo techniques, SSTs and latitudes (means and standard deviations) of locations where whales were sighted were compared to a sampling distribution of each variable derived from daily‐search areas. Overall, results support a nonrandom distribution of right whales in relation to SST: during resident months (January and February), whales exhibited low variability in observed SST and a suggested southward shift in whale distribution toward warmer SSTs in the EWS zone; while in the relatively warmer and southernmost survey zone (Florida nearshore), right whales were concentrated in the northern, cooler portion. Our results support that warm Gulf Stream waters, generally found south and east of delineated critical habitat, represent a thermal limit for right whales and play an important role in their distribution within the calving grounds. These results affirm the inclusion of SST in a multivariate predictive model for right whale distribution in their southeastern habitat.     

ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA I: BROAD SCALE PATTERNS

Aerial surveys over the last 32 yr have shown that the distribution of southern right whales Eubalaena australis along the south coast of South Africa is markedly discontinuous, but highly predictable. A GIS was used at a variety of scales to investigate whether this pattern was related to environmental characteristics. Whale distribution was analyzed as density per 20-min bin of longitude over two temporal and spatial scales, namely 15 bins for 32 yr, and a wider scale but shorter time period, 23 bins for 19 yr, as well as using three years of GPS accuracy data (15 bins) for finer scale analysis. Environmental factors tested were depth, distance from shore, sea floor slope, protection from swell, protection from wind, and shore type. The majority of whales were concentrated in areas that provided reasonable protection from open ocean swell and seasonal winds, and had sedimentary floors with gentle slopes. They generally avoided exposed rocky shorelines. Cow-calf pairs were found significantly closer to shore and in shallower water than unaccompanied whales, particularly off sandy beaches. Habitat choice at this time of year may be related both to energy conservation for calves and lactating females (calm sea conditions) and to protection of the new-born.     

FISHING GEAR INVOLVED IN ENTANGLEMENTS OF RIGHT AND HUMPBACK WHALES

Interactions between marine mammals and fishing gear are an issue of global concern. Entanglements in the western North Atlantic are a major source of injury and mortality for endangered large whales. In this study, entanglements of 31 right whales ( Eubalaena glacialis ) and 30 humpback whales ( Megaptera novaeangliae ) were analyzed to determine the types and parts of gear involved. When gear was identified, 89% ( n = 32) of the entanglements were attributed to pot and gill net gear; however, a wide range of specific gear types were implicated. Despite gear recovery, gear type was not identified in 20% ( n = 9) of the cases. Although pot gear was recovered from both species equally, gill net gear was less frequently retrieved from right whales ( n = 2) than humpback whales ( n = 11). When gear part was identified, 81% ( n = 21) involved entanglements in buoy line and/or groundline. For right whales, the most common point of gear attachment was the mouth (77.4%); for humpback whales, the tail (53%) and the mouth (43%) were common attachment sites. Four right and three humpback whales in this sample were known to have died subsequent to entanglement. However, when identified, the gear types and parts involved in lethal cases were not substantially different from entanglements with non-lethal outcomes. Large whales can become entangled in a wide variety of fishing gear types and parts, and additional insight will depend on continued efforts to document entanglements and recover associated gear.     

ESTIMATING BODY LENGTH OF PYGMY RIGHT WHALES (CAPEREA MARGINATA) FROM MEASUREMENTS OF THE SKELETON AND BALEEN

Various parts of the skeleton and/or the longest baleen plate of 46 specimens of Caperea marginata from Australia and New Zealand were measured and related to body length. Of the 32 skull, postcranial and baleen-plate measurements available, eight were analysed and seven found to be good predictors of body length, by using a curvilinear model describing their relationship with body length. Greatest skull width, supraoccipital length and mandible length had the smallest prediction limits (± 0.28-0.33 m in small animals, ±0.44-0.58 m in large animals) when compared with postcranial measurements (scapula length, vertebra 7 centrum width). Baleen-plate length was also a useful predictor of body length (±0.32-0.77 m). There was a substantial increase in the arch of the skull as body length increased. Bulla length was not a good predictor of body length, because measurements were highly variable and because the bulla grew little during postnatal life. Physical maturity occurred at body lengths of at least 5.9 m, also the shortest length at which both epiphyses of the humerus and proximal epiphyses of the radius and ulna were fused. Weaning appears to occur at about 3-3.5 m. The following approximate relative age/length classes were erected: dependent calves, <3.6 m; subadults, 3.6-5.5 m; adults, >5.5 m. Females were significantly longer than males in the sample of 22 animals greater than 5.9 m, length of the smallest recorded physically mature animal.     

INCREASED HARASSMENT OF RIGHT WHALES (EUBALAENA AUSTRALIS) BY KELP GULLS (LARUS DOMINICANUS) AT PENÍNSULA VALDÉS, ARGENTINA

Kelp gulls at Península Valdés, Argentina, have recently developed the habit of feeding on pieces of skin and blubber that they gouge from the backs of southern right whales. In response, the whales flinch violently, submerge, and swim rapidly away underwater. The level of harassment in 1995 was almost five times higher than when first studied in 1984 by Thomas (1988). In 1995, 67% of attacks were aimed at large white lesions on the whales' backs. The proportion of whales with lesions increased from 0.01 in 1974 to 0.32 in 1990. Mother-calf pairs that were attacked traveled at medium and fast speeds for 3.1 h per day, compared to 0.8 h for undisturbed pairs. Mother-calf pairs are estimated to spend approximately 24% of their daylight hours in states of gullinduced disturbance. Little food is available at Península Valdés, so mothers must rely on blubber reserves to support their calves' growth, behavioral development, and migration to the feeding grounds. Even when undisturbed by gulls, mothers often curtail their calves' play and nursing bouts, suggesting that their energy reserves are limited. Increasingly intense harassment by gulls may therefore compromise calf development and might even induce right whales to abandon Península Valdés for other calving grounds.     

HISTORICAL OBSERVATIONS OF HUMPBACK AND BLUE WHALES IN THE NORTH ATLANTIC OCEAN: CLUES TO MIGRATORY ROUTES AND POSSIBLY ADDITIONAL FEEDING GROUNDS

The seasonal distributions of humpback and blue whales ( Megaptera novaeangliae and Balaenoptera musculus , respectively) in the North Atlantic Ocean are not fully understood. Although humpbacks have been studied intensively in nearshore or coastal feeding and breeding areas, their migratory movements between these areas have been largely inferred. Blue whales have only been studied intensively along the north shore of the Gulf of St. Lawrence, and their seasonal occurrence and movements elsewhere in the North Atlantic are poorly known. We investigated the historical seasonal distributions of these two species using sighting and catch data extracted from American 18th and 19th century whaling logbooks. These data suggest that humpback whales migrated seasonally from low-latitude calving/ breeding grounds over a protracted period, and that some of them traveled far offshore rather than following coastal routes. Also, at least some humpbacks apparently fed early in the summer west of the Mid-Atlantic Ridge, well south of their known present-day feeding grounds. In assessing the present status of the North Atlantic humpback population, it will be important to determine whether such offshore feeding does in fact occur. Blue whales were present across the southern half of the North Atlantic during the autumn and winter months, and farther north in spring and summer, but we had too few data points to support inferences about these whales' migratory timing and routes.     

UNEXPECTED RESPONSE TO VITAMIN B12 OF DOMINANT CENTRIC DIATOMS FROM THE SPRING BLOOM IN THE GULF OF MAINE (NORTHEAST ATLANTIC OCEAN)1,2

Twelve clones (seven species) representative of centric diatoms dominant in the spring phytoplankton bloom in the Gulf of Maine were isolated and rendered axenic. Genera included were Thalassiosira, Porosira and Chaetoceros. Unlike most centric diatoms studied previously, none of these has an absolute requirement for vitamin B_12. However, B₁₂ (5 ng.l^-1) stimulated growth of most clones by eliminating or reducing the lag phase and increasing the growth rate. Bloom population densities developed 4–54 days earlier with B₁₂ present. Several clones grown with B₁₂ removed more than 80% of the vitamin from the medium. When grown in vitamin-free medium the cells put 0.01–0.7 ng.l^-1 B₁₂ into the medium. We conclude that vitamin B₁₂ is of ecological significance even though the requirement for it is not absolute.     

SPATIOTEMPORAL PREDICTION MODELS OF CETACEAN HABITATS IN THE MID-WESTERN NORTH ATLANTIC OCEAN (FROM CAPE HATTERAS, NORTH CAROLINA, U.S.A. TO NOVA SCOTIA, CANADA)

Habitat prediction models were developed for 13 cetacean species of the mid-western North Atlantic Ocean: beaked whale, fin whale, humpback whale, minke whale, pilot whale, sperm whale, bottlenose dolphin, common dolphin, Risso's dolphin, spotted dolphin, whitesided dolphin, and harbor porpoise. Using the multiple logistic regression, sightings of cetaceans during the 1990–1996 summer (June-September) surveys were modeled with oceanographic (sea surface temperature, monthly probability of front occurrence) and topographic (depth, slope) variables for the same period. Predicted habitat maps for June and August were created for each species using a Geographical Information System. The predicted habitat locations matched with current and historic cetacean sighting locations. The model also predicted habitat shifts for some species associated with oceanographic changes. The correct classification rate of the prediction models with 1997–1998 summer survey data ranged from 44% to 70%, of which most of the misclassifications were caused by false positives ( i.e. , absence of sightings at locations where the models predicted).