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Rarotonga, Cook Islands

Clapham P.J.,National Oceanic and Atmospheric Administration | Clapham P.J.,South Pacific Whale Research Consortium | Zerbini A.N.,National Oceanic and Atmospheric Administration | Zerbini A.N.,Cascadia Research Collective
Marine Biology

Humpback whales (Megaptera novaeangliae) in the Southern Hemisphere were heavily exploited by commercial whaling. Today, their recovery is variable: Humpbacks remain surprisingly scarce in some formerly populous areas (e.g., New Zealand, Fiji), while in other regions (such as eastern Australia), they appear to be rebounding at or even above the maximum plausible rate of annual increase. Here, we propose that this phenomenon cannot be explained solely in demographic terms. Through simulation, we test the hypothesis that reported high rates of increase represent a combination of true intrinsic growth rates and temporary immigration, driven by a strong tendency to aggregate for mating. We introduce the idea that overexploitation diminished density at major breeding grounds such that these were no longer viable; then, during subsequent population recovery, a critical mass was attained in certain areas which drew in whales that formerly bred elsewhere. The simulations show that, to maintain high increase rates, the contribution to that rate by temporary immigration from a second, “source” population would have to represent a larger and larger proportion of the source stock and would require relatively high (but quite plausible) intrinsic rates of increase for each population. In the modeling scenarios, the demand for immigrants would eventually exceed the supply and exhaust the source population, but the simulations demonstrated that high increase rates can be sustained over periods of more than 20 years. This hypothesis, if correct, would not only explain excessively high rates of increase in current “hotspots” such as eastern Australia, but also imply that formerly important areas (e.g., Fiji) host few whales today not necessarily because of a failure to recover, but because the species’ mating system leads the whales concerned to migrate to higher-density breeding grounds elsewhere. Overall, we caution that assessments of depleted animal populations that do not consider the social behavior of a species are missing a potentially vital component of the picture. © 2015, Springer-Verlag Berlin Heidelberg (outside the USA). Source

Since 1987, Japan has conducted extensive special permit whaling ("scientific whaling") in the Antarctic and North Pacific. This has been viewed by many as a way to circumvent the International Whaling Commission's (IWC) moratorium on commercial whaling, which was implemented in 1985. Recently, Australia took Japan to the International Court of Justice (ICJ) over this issue. Using various criteria, the Court ruled that Japan's whaling was not "for purposes of scientific research" as required by Article VIII of the International Convention for the Regulation of Whaling, and ordered Japan to immediately cease its JARPA II whaling program in the Antarctic. Despite optimism that the Court's ruling might spell the end of Japanese whaling in the Antarctic and even elsewhere, Japan has indicated that it will redesign its whaling programs and continue operations. Based upon Japan's history at the IWC, I argue here that this was an expected outcome; I predict the course of events over the next months, and suggest that the ICJ ruling, while satisfying as an independent vindication of Japan's critics, represents little more than a temporary setback for that nation's whaling enterprise. © 2014 Elsevier Ltd. Source

Garland E.C.,University of Queensland | Garland E.C.,South Pacific Whale Research Consortium | Goldizen A.W.,University of Queensland | Rekdahl M.L.,University of Queensland | And 11 more authors.
Current Biology

Cultural transmission, the social learning of information or behaviors from conspecifics [1-5], is believed to occur in a number of groups of animals, including primates [1, 6-9], cetaceans [4, 10, 11], and birds [3, 12, 13]. Cultural traits can be passed vertically (from parents to offspring), obliquely (from the previous generation via a nonparent model to younger individuals), or horizontally (between unrelated individuals from similar age classes or within generations) [4]. Male humpback whales (Megaptera novaeangliae) have a highly stereotyped, repetitive, and progressively evolving vocal sexual display or "song" [14-17] that functions in sexual selection (through mate attraction and/or male social sorting) [18-20]. All males within a population conform to the current version of the display (song type), and similarities may exist among the songs of populations within an ocean basin [16, 17, 21]. Here we present a striking pattern of horizontal transmission: multiple song types spread rapidly and repeatedly in a unidirectional manner, like cultural ripples, eastward through the populations in the western and central South Pacific over an 11-year period. This is the first documentation of a repeated, dynamic cultural change occurring across multiple populations at such a large geographic scale. © 2011 Elsevier Ltd. Source

Garland E.C.,University of Queensland | Garland E.C.,South Pacific Whale Research Consortium | Garland E.C.,National Oceanic and Atmospheric Administration | Garland E.C.,University of St. Andrews | And 15 more authors.
Conservation Biology

For cetaceans, population structure is traditionally determined by molecular genetics or photographically identified individuals. Acoustic data, however, has provided information on movement and population structure with less effort and cost than traditional methods in an array of taxa. Male humpback whales (Megaptera novaeangliae) produce a continually evolving vocal sexual display, or song, that is similar among all males in a population. The rapid cultural transmission (the transfer of information or behavior between conspecifics through social learning) of different versions of this display between distinct but interconnected populations in the western and central South Pacific region presents a unique way to investigate population structure based on the movement dynamics of a song (acoustic) display. Using 11 years of data, we investigated an acoustically based population structure for the region by comparing stereotyped song sequences among populations and years. We used the Levenshtein distance technique to group previously defined populations into (vocally based) clusters based on the overall similarity of their song display in space and time. We identified the following distinct vocal clusters: western cluster, 1 population off eastern Australia; central cluster, populations around New Caledonia, Tonga, and American Samoa; and eastern region, either a single cluster or 2 clusters, one around the Cook Islands and the other off French Polynesia. These results are consistent with the hypothesis that each breeding aggregation represents a distinct population (each occupied a single, terminal node) in a metapopulation, similar to the current understanding of population structure based on genetic and photo-identification studies. However, the central vocal cluster had higher levels of song-sharing among populations than the other clusters, indicating that levels of vocal connectivity varied within the region. Our results demonstrate the utility and value of using culturally transmitted vocal patterns as a way of defining connectivity to infer population structure. We suggest vocal patterns be incorporated by the International Whaling Commission in conjunction with traditional methods in the assessment of structure. © 2015, Society for Conservation Biology. Source

Garland E.C.,University of Queensland | Garland E.C.,South Pacific Whale Research Consortium | Garland E.C.,National Oceanic and Atmospheric Administration | Lilley M.S.,IBM | And 6 more authors.

Animals can communicate using visual and acoustic displays to convey information to conspecifics. In some cases, such displays are produced in highly stereotyped and repetitive sequences. Here we use a quantitative analysis technique, the Levenshtein distance, to assess similarity in sequences of displays at both the population and individual levels. We review two existing variations of the method and present two new variations that complement and extend these existing techniques. Three of the methods include the use of a median string sequence and three use a normalisation of the original equation. Humpback whale song theme sequences from multiple populations, years and song types (different variations of the display) are used as examples to illustrate the application and success of each variation. A novel outcome of this technique is that it can produce a threshold measure of similarity to assess when behavioural sequences are so dissimilar that they must be considered different, with a measure of the probability of such clusters being distinct. The Levenshtein distance is applicable to all behavioural data produced in sequences and its use should not be limited to acoustical studies. © 2012 Koninklijke Brill NV, Leiden. Source

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