Culturally transmitted song exchange between humpback whales (Megaptera novaeangliae) in the southeast Atlantic and southwest Indian Ocean basins

Funding: E.C.G. was funded by a Royal Society Newton International Fellowship and Royal Society University Research Fellowship.In migratory marine species, investigating population connectivity and structure can be challenging given barriers to dispersal are less evident and multiple factors may influence individual movement patterns. Male humpback whales sing a song display that can provide insights into contemporary connectivity patterns, as there can be a cultural exchange of a single, population-wide shared song type with neighbouring populations in acoustic contact. Here, we investigated song exchange between populations located on the east and west coasts of Africa using 5 years of concurrent data (2001–2005). Songs were qualitatively and quantitatively transcribed by measuring acoustic features of all song units and then compared using both Dice’s similarity index and the Levenshtein distance similarity index (LSI) to quantitatively calculate song similarity. Song similarity varied among individuals and potentially between populations depending on the year (Dice: 36–100%, LSI: 21–100%), suggesting varying levels of population connectivity and/or interchange among years. The high degree of song sharing indicated in this study further supports genetic studies that demonstrate interchange between these two populations and reinforces the emerging picture of broad-scale connectivity in Southern Hemisphere populations. Further research incorporating additional populations and years would be invaluable for better understanding of fine-scale, song interchange patterns between Southern Hemisphere male humpback whales.Publisher PDFPeer reviewe

Population Structure of Humpback Whales from Their Breeding Grounds in the South Atlantic and Indian Oceans

Although humpback whales are among the best-studied of the large whales, population boundaries in the Southern Hemisphere (SH) have remained largely untested. We assess population structure of SH humpback whales using 1,527 samples collected from whales at fourteen sampling sites within the Southwestern and Southeastern Atlantic, the Southwestern Indian Ocean, and Northern Indian Ocean (Breeding Stocks A, B, C and X, respectively). Evaluation of mtDNA population structure and migration rates was carried out under different statistical frameworks. Using all genetic evidence, the results suggest significant degrees of population structure between all ocean basins, with the Southwestern and Northern Indian Ocean most differentiated from each other. Effective migration rates were highest between the Southeastern Atlantic and the Southwestern Indian Ocean, followed by rates within the Southeastern Atlantic, and the lowest between the Southwestern and Northern Indian Ocean. At finer scales, very low gene flow was detected between the two neighbouring sub-regions in the Southeastern Atlantic, compared to high gene flow for whales within the Southwestern Indian Ocean. Our genetic results support the current management designations proposed by the International Whaling Commission of Breeding Stocks A, B, C, and X as four strongly structured populations. The population structure patterns found in this study are likely to have been influenced by a combination of long-term maternally directed fidelity of migratory destinations, along with other ecological and oceanographic features in the region

Minimal similarity in songs suggests limited exchange between humpback whales (Megaptera novaeangliae) in the southern Indian Ocean

Comparing humpback whale song from different breeding assemblages can reveal similarities in song due to acoustically interacting males, and therefore indirectly test whether males from different breeding sites are mixing. Northern Hemisphere song comparisons illustrated that whales within ocean basins share similar songs and are subpopulations within a larger population, whereas whales in different ocean basins are isolated populations and therefore do not share songs. During the 2006 breeding season, recordings were collected in Madagascar and Western Australia, and were compared visually plus aurally. Both regions shared one theme, whereas each region had four and six private themes, respectively. This study had a substantially low number of shared themes. The co-occurrence of one theme was interpreted as an indication of limited exchange between these breeding assemblages, and we speculate that limited song similarity is due to inter-oceanic interactions. Male(s) from an Indian Ocean breeding group could be exposed to novel song when they geographically overlap, and acoustically interact, with males from a different ocean basin. Novel song could induce rapid temporal changes as new song content is incorporated, thereby minimizing song similarities between that breeding group and other Indian Ocean breeding groups that were not exposed to the novel song

Breeding ecology and nestling growth of the Madagascar Pond Heron Ardeola idae in a monospecific colony at Sofia Lake, northern Madagascar

The breeding ecology of the endangered Madagascar Pond Heron Ardeola idae was studied at Sofia Lake, northern Madagascar, during two  consecutive breeding seasons (October 2017–April 2018 and October 2018– April 2019). Altogether 158 nests were documented at a monospecific breeding colony for both seasons combined. The breeding season occurred between November and April. Nest construction started from the middle of November and it took 8.2 ± 2.5 d on average to complete a nest (n = 158 nests, range = 5–13 d). All the nests were build inside clusters of Papyrus Cyperus madagascariensis. The nest density was 0.31 nests m−2 and 0.20 nests m−2 for Season 1 and Season 2, respectively. Egg laying took place between November and January, but it continued throughout February for renesting attempts (second clutches laid). Mean clutch sizewas 2.9 ± 0.68 eggs (n = 158, range = 2–4). Incubation started with the laying of the first egg, producing an asynchronous hatching. The incubation period averaged 20.6 ± 0.9 d (n = 158, range = 20–22 d). Of the 461 eggs laid in 158 nests, 399 (86.6%) hatched, and 326 (70.7%) of those hatchlings fledged, a reproductive success of 2.06 fledglings per nesting attempt. Data obtained from 34 measured nestlings showed a rapid growth of all measured biometric parameters, except for tarsus length. The mean daily growth rate was 9.02 g for body mass, 9.64 mm for body size length, 10.66 mm for wing length and 2.35 mm for tarsus length. Significant differences were recorded in growth rates between nestlings in the same brood in relation to their hatching sequence. The last nestlings to hatch had lower growth rates for all measured parameters than their older siblings. French title: Ecologie de reproduction et croissance des jeunes du Héron crabier blanc Ardeola idae dans la colonie monospécique au Lac Sofia, partie nord de Madagascar L’étude de l’écologie de la reproduction du Héron crabier blanc Ardeola idae a été réalisée dans une colonie monospécifique, localisée au Lac Sofia dans la partie nord de Madagascar, durant deux saisons de reproduction consécutives (octobre 2017–avril 2018 et octobre 2018–avril 2019). Un total de 158 nids a fait l’objet de suivis durant les deux saisons d’étude. La période de reproduction de l’espèce étudiée a eu lieu entre novembre et avril. La construction des nids a commencé à la mi-novembre et a duré en moyenne 8.2 ± 2.5 jours (n = 158 nids). Tous les nids sont placés dans des  touffes de Papyrus Cyperus madagascariensis. La densité des nids est de 0.31 nid m−2 et 0.20 nid m−2 respectivement durant la première et deuxième saison d’étude. La période de ponte de la première couvée se situe entre novembre et janvier et une deuxième couvée a été enregistrée entre mi-janvier et mi-février. La taille de ponte a varié de 2 à 4, avec une moyenne de 2.9 ± 0.68 œufs (n = 158 nids). L’incubation commence dès la ponte du premier œuf et dure en moyenne 20.6 ± 0.9 jours (n = 158 nids, rang: 20–22 jours). Sur les 461 œufs pondus dans les 158 nids suivis, 399 (86.6%) ont éclos, et 326 (70.7%) de poussins éclos ont pris leur envol, soit un succès de reproduction de 2.06 jeunes nids−1. Les données obtenues à partir de 34 poussins échantillonnés ont montré une croissance rapide de tous les paramètres mesurés, à l’exception du tarse. Le taux moyen de croissance journalière des poussins est de 9.02 g pour le poids, 9.64 mm pour la longueur du corps, 10.66 mm pour la longueur de l’aile et 2.35 mm pour la longueur du tarse. Nos résultats ont également montré une différence significative entre les moyennes des taux de croissances des poussins d’une même couvée en relation avec leur rang d’éclosion. Les derniers poussins éclos présentent toujours un taux de croissance les plus faibles pour tous les paramètres considérées par rapport à leurs congénères plus âgés. Keywords: asynchronous hatching, breeding season, clutch size, endangered, reproductive succes

Data from: Multiple processes drive genetic structure of humpback whale (Megaptera novaeangliae) populations across spatial scales

Elucidating patterns of population structure for species with complex life histories, and disentangling the processes driving such patterns, remains a significant analytical challenge. Humpback whale (Megaptera novaeangliae) populations display complex genetic structures that have not been fully resolved at all spatial scales. We generated a data set of nuclear markers for 3,575 samples spanning the seven breeding stocks and substocks found in the South Atlantic and western and northern Indian Oceans. For the total sample, and males and females separately, we assessed genetic diversity, tested for genetic differentiation between putative populations and isolation by distance, estimated the number of genetic clusters without a priori population information, and estimated rates of gene flow using maximum likelihood and Bayesian approaches. At the ocean basin scale, structure is governed by geographic distance (IBD p<0.05) and female fidelity to breeding areas, in line with current understanding of the drivers of broad-scale population structure. Consistent with previous studies, the Arabian Sea breeding stock was highly genetically differentiated (FST 0.034-0.161; p<0.01 for all comparisons). However, the breeding stock boundary between west South Africa and east Africa was more porous than expected based on genetic differentiation, cluster, and gene flow analyses. Instances of male-fidelity to breeding areas and relatively high rates of dispersal for females were also observed between the three substocks in the western Indian Ocean. This mismatch between demographic units and current management boundaries may have ramifications for assessments of the status and continued protections of populations still in recovery from commercial whaling

Usatdata

Humpback whale microsatellite data set (9 loci

Pairwise measures of genetic divergence in various populations of Southern Hemisphere humpback whales, using all samples (Table 4), males + females (Table 5), females only (Table 6) and males only (Table 7).

<p>Pairwise Φst and Fst values are above and below the diagonal, respectively. Significant values are highlighted in bold.</p

Pairwise measures of genetic divergence in various populations of Southern Hemisphere humpback whales, using all samples (Table 4), males + females (Table 5), females only (Table 6) and males only (Table 7).

<p>Pairwise Φst and Fst values are above and below the diagonal, respectively. Significant values are highlighted in bold.</p