Dear MARMAM community, On behalf of my co-authors, I am pleased to share with you our new publication in *Advances in Marine Biology*: Stephanie Plön, Peter B. Best, Pádraig Duignan, Shane D. Lavery, Ric T.F. Bernard, Koen Van Waerebeek, and C. Scott Baker (2023). Population structure of pygmy (*Kogia breviceps*) and dwarf (*Kogia sima*) sperm whales in the Southern Hemisphere may reflect foraging ecology and dispersal patterns. Advances in Marine Biology 96, 85-114. Abstract Little is known about the biology of pygmy (*Kogia breviceps*) and dwarf (*K. sima*) sperm whales as these animals are difficult to observe in the wild. However, both species strand frequently along the South African, Australian and New Zealand coastlines, providing samples for these otherwise inaccessible species. The use of DNA samples from tissue and DNA extracted from historical material, such as teeth and bone, allowed a first analysis of the population structure of both species in the Southern Hemisphere. A 279 base pair consensus region of the mitochondrial cytochrome b gene was sequenced for 96 K. breviceps (53 tissue and 43 teeth or bone samples) and 29 *K. sima* (3 tissue and 26 teeth or bone samples), and 26 and 12 unique haplotypes were identified, respectively. *K. breviceps* showed a higher nucleotide diversity of 0.82% compared to 0.40% in K. sima. Significant genetic differentiation was detected in the Southern Hemisphere between K. breviceps from South Africa and New Zealand (ФST = 0.042, p < 0.05). Mitochondrial control region sequences (505 bp) were available for 44 individuals (41 *K. breviceps* and 3 *K. sima*) for comparative purposes. A comprehensive global phylogenetic analysis (maternal lineage) of our sequences together with all available *Kogia* mtDNA sequences largely supported previously published phylogenetic findings, but highlighted some changed inferences about oceanic divergences within both species. The higher nucleotide diversity and low population differentiation observed in *K. breviceps* may result from its broad foraging ecology and wide distribution, which may indicate a more opportunistic feeding behaviour and tolerance towards a larger range of water temperatures than *K. sima*. If you are interested in a pdf copy please e-mail me at: stephanie.ploen@gmail.com Kind regards, Stephanie Plön