We used network-based diffusion analysis to reveal the cultural spread of a naturally occurring foraging innovation, lobtail feeding, through a population of humpback whales (Megaptera novaeangliae) over a period of 27 years. Support for models with a social transmission component was 6 to 23 orders of magnitude greater than for models without. The spatial and temporal distribution of sand lance, a prey species, was also important in predicting the rate of acquisition. Our results, coupled with existing knowledge about song traditions, show that this species can maintain multiple independently evolving traditions in its populations. These insights strengthen the case that cetaceans represent a peak in the evolution of nonhuman culture, independent of the primate lineage.

Hunting during the last 200 years reduced many populations of mysticete whales to near extinction. To evaluate potential genetic bottlenecks in these exploited populations, we examined mitochondrial DNA control region sequences from 90 individual humpback whales (Megaptera novaeangliae) representing six subpopulations in three ocean basins. Comparisons of relative nucleotide and nucleotype diversity reveal an abundance of genetic variation in all but one of the oceanic subpopulations. Phylogenetic reconstruction of nucleotypes and analysis of maternal gene flow show that current genetic variation is not due to postexploitation migration between oceans but is a relic of past population variability. Calibration of the rate of control region evolution across three families of whales suggests that existing humpback whale lineages are of ancient origin. Preservation of preexploitation variation in humpback whales may be attributed to their long life-span and overlapping generations and to an effective, though perhaps not timely, international prohibition against hunting.Humpback whales (Megaptera novaeangliae) once numbered >125,000 individuals distributed into three oceanic populations: the North Pacific, the North Atlantic, and the southern oceans. Within each population, observations of migratory movement by marked individuals suggest that humpback whales form relatively discrete subpopulations that are not separated by obvious geographic barriers (1). Before protection by international agreement in 1966, the world-wide population of humpback whales had been reduced by hunting to <5000, with some regional subpopulations reduced to <200 individuals (Table 1).To evaluate the possibility that commercial hunting reduced genetic variation in baleen whales, we examined nucleotide sequence variation in the mitochondrial (mt) DNA from 90 humpback whales collected from the three major oceanic basins. We chose humpback whales for this evaluation because their well-described subpopulation divisions and well-documented history of exploitation provide a historical framework within which to evaluate genetic data (Table 1). We chose mtDNA as a genetic marker because of its power in describing the genetic structure of maternal lineages within populations and its sensitivity to demographic changes in populations (20). To allow the use of small skin samples collected by biopsy darting, we applied the polymerase chain reaction (PCR) and direct "solid-phase" sequencing methodology (21) to the mtDNA control region or "D-loop," a noncoding region that is highly variable in most vertebrates (22).The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.We first verified that oceanic populations of humpback whales are independent demographic units by estimating mtDNA gene flow with a cladistic analysis of the control region sequences. We then evaluated mtDNA diversity within each o...

No abstract

Humpback whales (Megaptera novaeangliae) migrate nearly 10,000 km each year between summer feeding grounds in temperate or near-polar waters and winter breeding grounds in shallow tropical waters. Observations of marked individuals suggest that major oceanic populations of humpback whales are divided into a number of distinct seasonal subpopulations which are not separated by obvious geographic barriers. To test whether these observed patterns of distribution and migration are reflected in the genetic structure of populations, we looked for variation in the mitochondrial DNA of 84 individual humpback whales on different feeding and wintering grounds of the North Pacific and western North Atlantic oceans. On the basis of restriction-fragment analysis, we now report a marked segregation of mitochondrial DNA haplotypes among subpopulations as well as between the two oceans. We interpret this segregation to be the consequence of maternally directed fidelity to migratory destinations.

Groups of humpack whales (Megaptera novaeangliae) were observed from 1980 to 1987 on their feeding grounds in the southern Gulf of Maine. Although most groups were together for only brief periods, two types of stable association were found: 'continuous' (individual whales associated for at least 7 consecutive days; n = 30) or 'recurring' (individuals associated at least five times in a 6-week period; n = 21). Thirty-seven stable pairs and 3 stable trios involving 56 individual whales were recorded; 11 stable pairs re-associated during more than 1 year. Continuous associations lasted up to 79 days (mean 29.65). Thirty of the 40 associations (75.0%) contained only adults. Females were present in 22 adult associations (73.3%), whereas males were present in only 8 (26.6%). Females sighted with a calf the following year, and therefore pregnant, were members of 6 of the 11 (54.5%) associations that reformed. It is hypothesized that stable associations allow adult females to maximize their net energy gain through cooperative feeding, and may be comprised of closely related animals or individuals with compatible feeding styles.

The genetic structure of humpback whale populations and subpopulation divisions is described by restriction fragment length analysis of the mitochondrial (mt) DNA from samples of 230 whales collected by biopsy darting in 11 seasonal habitats representing six subpopulations, or 'stocks', world-wide. The hierarchical structure of mtDNA haplotype diversity among population subdivisions is described using the analysis of molecular variance (AMOVA) procedure, the analysis of gene identity, and the genealogical relationship of haplotypes as constructed by parsimony analysis and distance clustering. These analyses revealed: (i) significant partitioning of world-wide genetic variation among oceanic populations, among subpopulations or 'stocks' within oceanic populations and among seasonal habitats within stocks; (ii) fixed categorical segregation of haplotypes on the south-eastern Alaska and central California feeding grounds of the North Pacific; (iii) support for the division of the North Pacific population into a central stock which feeds in Alaska and winters in Hawaii, and an eastern or 'American' stock which feeds along the coast of California and winters near Mexico; (iv) evidence of genetic heterogeneity within the Gulf of Maine feeding grounds and among the sampled feeding and breeding grounds of the western North Atlantic; and (v) support for the historical division between the Group IV (Western Australia) and Group V (eastern Australia, New Zealand and Tonga) stocks in the Southern Oceans. Overall, our results demonstrate a striking degree of genetic structure both within and between oceanic populations of humpback whales, despite the nearly unlimited migratory potential of this species. We suggest that the humpback whale is a suitable demographic and genetic model for the management of less tractable species of baleen whales and for the general study of gene flow among long-lived, mobile vertebrates in the marine ecosystem.

Analyses of the foraging behavior of large cetaceans have generally focused on either correlations with environmental conditions at regional scales or observations of surface behavior. We employed a novel approach combining multi-scale analyses of simultaneous environmental conditions, surface and subsurface humpback whale Megaptera novaeangliae movements, and sand lance Ammodytes spp. prey aggregations in the Gulf of Maine, USA. At the fine scale (<1 km), digital tags recorded whale movement and behavior in 3 dimensions. Concurrent synoptic prey data were collected using EK60 echosounders with simultaneous surface measurements of temperature and relative fluorescence within 1 km of the tagged whale. A geospatial analysis of environmental features and foraging patterns was conducted at the regional, seascape scale (~10 km). At the seascape scale, we found: (1) a negative relationship between relative fluorescence and sand lance density; (2) a positive relationship between predator surface feeding, presumed sand lance density, and sand bottom types near high-slope edges; (3) a cyclical relationship for predator surface-feeding likelihood and prey density with tidal height; and (4) an observed temporal lag between peak prey density and predator surface-feeding likelihood. At the fine scale, we found that: (1) time of day was the most important factor in predicting whether a whale was feeding when it surfaced; and (2) surface feeding occurred more often around more dense, vertically distributed schools of prey. Multiscale and multitrophic level studies are an important component in understanding the foraging ecology of top predators in marine systems.

Humpback whales Megaptera novaeangliae have adopted unique feeding strategies to take advantage of behavioral changes in their prey. However, logistical constraints have largely limited ecological analyses of these interactions. Our objectives were to (1) link humpback whale feeding behaviors to concurrent measurements of prey using scientific echo-sounders, and (2) quantify how sand lance behavior influences the feeding behaviors and foraging ecology of humpback whales. To measure, in fine detail, the 3-dimensional orientation and movement patterns of humpback whales underwater, we used a multi-sensor tag attached via suction cups (DTAG). We tested the specific hypothesis that the diel movement patterns of sand lance between bottom substrate and the water column correlates to changes between surface and bottom feeding strategies of humpback whales on Stellwagen Bank, MA. We collected over 96 h of both day-and nighttime data from 15 whales in 2006, and recorded 393 surface and 230 bottom feeding events. Individual whales exhibit both surface and bottom feeding behaviors, switching from one to the other in relation to changing light and prey conditions. Surface feeding behaviors were individually variable in their constitution but ubiquitously biased towards daylight hours, when prey was most abundant in the upper portion of the water column. Bottom feeding behavior occurred largely at night, coincident with when sand lance descend to seek refuge in the substrate. Our data provide novel insights into the behavioral ecology of humpback whales and their prey, indicating significant diel patterns in foraging behaviors concurrent with changes in prey behavior.