Dear marmamers, My coauthors and I are pleased to announce our recent publication in the Journal of Experimental Biology. The objective in the present study was to provide novel data about metabolic demands on the Pacific walrus, which could help understand the potential impacts of environmental change. In this study we report measured metabolic rates in adult female Pacific walruses while floating in water and during stationary dives and subsurface swimming. The data show that the underwater activities did not increase metabolic costs above those while floating in water. Citation: Alicia Borque-Espinosa, Karyn D. Rode, Diana Ferrero-Fernández, Anabel Forte, Romana Capaccioni-Azzati, Andreas Fahlman; Subsurface swimming and stationary diving are metabolically cheap in adult Pacific walruses (Odobenus rosmarus divergens). J Exp Biol 1 December 2021; 224 (23): jeb242993. doi: https://doi.org/10.1242/jeb.242993 Abstract: Walruses rely on sea-ice to efficiently forage and rest between diving bouts while maintaining proximity to prime foraging habitat. Recent declines in summer sea ice have resulted in walruses hauling out on land where they have to travel farther to access productive benthic habitat while potentially increasing energetic costs. Despite the need to better understand the impact of sea ice loss on energy expenditure, knowledge about metabolic demands of specific behaviours in walruses is scarce. In the present study, 3 adult female Pacific walruses (Odobenus rosmarus divergens) housed in professional care participated in flow-through respirometry trials to measure metabolic rates while floating inactive at the water surface during a minimum of 5 min, during a 180 s stationary dive, and while swimming ∼90 m horizontally underwater. Metabolic rates during stationary dives (3.82±0.56 l O2 min−1) were lower than those measured at the water surface (4.64±1.04 l O2 min−1), which did not differ from rates measured during subsurface swimming (4.91±0.77 l O2 min−1). Thus, neither stationary diving nor subsurface swimming resulted in metabolic rates above those exhibited by walruses at the water surface. These results suggest that walruses minimize their energetic investment during underwater behaviours as reported for other marine mammals. Although environmental factors experienced by free-ranging walruses (e.g. winds or currents) likely affect metabolic rates, our results provide important information for understanding how behavioural changes affect energetic costs and can be used to improve bioenergetics models aimed at predicting the metabolic consequences of climate change on walruses. The journal provided open limited downloads by using the following link: https://journals.biologists.com/jeb/article/doi/10.1242/jeb.242993/273684/Subsurface-swimming-and-stationary-diving-are?guestAccessKey=a9080811-7e8a-4a63-b785-63a83d25b59f<http://track.smtpsendmail.com/9032119/c?p=-tLZF4Pb8qHY6qLA1I3v_gYajtTZrEr_ErHU424cQ_AX3JsLvdwm0lx3HxBEsMLARmjKk5e1Edxy1PD1BHTfzhOgzYcW-7JYy67o-w1eXtDnI1GHDPIJ4VUgtnMOkW59bxzRYKo_B0k0jWLrcnTY-A9cJpEyMVSZBsOAStuTOiBRNW9ELqi-4FV6cnc8YbvWo-4912bUlL57_srcbkFe2r5rCMXr9ZmwPa16t7mvxn04nu0ooAKWPanvkS70sDpXgJq3GxYFAJkxn3vb0wb7hx1IY0WAVcRaMR5gqtpK_lWJB8g-MUnGh34DG_C901RO9S4M2gqxa7HpGkZHk_y_Pw==> Please, feel free to contact (ali_bor@hotmail.com<mailto:ali_bor@hotmail.com>) for any comment, question or for a PDF copy of the manuscript. Kind regards, Alicia Borque Espinosa PhD Candidate, Universitat de València & Fundación Oceanogràfic de la Comunitat Valenciana.