Ponganis Paul J.

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Ponganis
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Paul J.
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  • Article
    Full circumpolar migration ensures evolutionary unity in the Emperor penguin
    (Nature Publishing Group, 2016-06-14) Cristofari, Robin ; Bertorelle, Giorgio ; Ancel, André ; Benazzo, Andrea ; Le Maho, Yvon ; Ponganis, Paul J. ; Stenseth, Nils Christian ; Trathan, Phil N. ; Whittington, Jason D. ; Zanetti, Enrico ; Zitterbart, Daniel ; Le Bohec, Céline ; Trucchi, Emiliano
    Defining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species’ response to global environmental change is likely to follow a shared evolutionary trajectory.
  • Article
    Stroke frequency, but not swimming speed, is related to body size in free-ranging seabirds, pinnipeds and cetaceans
    (Royal Society, 2006-12-05) Sato, Katsufumi ; Watanuki, Yutaka ; Takahashi, Akinori ; Miller, Patrick J. O. ; Tanaka, Hideji ; Kawabe, Ryo ; Ponganis, Paul J. ; Handrich, Yves ; Akamatsu, Tomonari ; Watanabe, Yuuki ; Mitani, Yoko ; Costa, Daniel P. ; Bost, Charles-Andre ; Aoki, Kagari ; Amano, Masao ; Trathan, Phil N. ; Shapiro, Ari D. ; Naito, Yasuhiko
    It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of animals ranging from 0.5kg seabirds to 30000kg sperm whales using animal-borne accelerometers. Dominant stroke cycle frequencies of swimming specialist seabirds and marine mammals were proportional to mass−0.29 (R2=0.99, n=17 groups), while propulsive swimming speeds of 1–2ms−1 were independent of body size. This scaling relationship, obtained from breath-hold divers expected to swim optimally to conserve oxygen, does not agree with recent theoretical predictions for optimal swimming. Seabirds that use their wings for both swimming and flying stroked at a lower frequency than other swimming specialists of the same size, suggesting a morphological trade-off with wing size and stroke frequency representing a compromise. In contrast, foot-propelled diving birds such as shags had similar stroke frequencies as other swimming specialists. These results suggest that muscle characteristics may constrain swimming during cruising travel, with convergence among diving specialists in the proportions and contraction rates of propulsive muscles.
  • Article
    Advances in remote sensing of emperor penguins: First multi-year time series documenting trends in the global population
    (The Royal Society, 2024-03-13) LaRue, Michelle ; Iles, David T. ; Labrousse, Sara ; Fretwell, Peter T. ; Ortega, David ; Devane, Eileen ; Horstmann, Isabella ; Viollat, Lise ; Foster-Dyer, Rose ; Le Bohec, Celine ; Zitterbart, Daniel ; Houstin, Aymeric ; Richter, Sebastian ; Winterl, Alexander ; Wienecke, Barbara ; Salas, Leo ; Nixon, Monique ; Barbraud, Christophe ; Kooyman, Gerald L. ; Ponganis, Paul J. ; Ainley, David G. ; Trathan, Philip ; Jenouvrier, Stephanie
    Like many polar animals, emperor penguin populations are challenging to monitor because of the species' life history and remoteness. Consequently, it has been difficult to establish its global status, a subject important to resolve as polar environments change. To advance our understanding of emperor penguins, we combined remote sensing, validation surveys and using Bayesian modelling, we estimated a comprehensive population trajectory over a recent 10-year period, encompassing the entirety of the species’ range. Reported as indices of abundance, our study indicates with 81% probability that there were fewer adult emperor penguins in 2018 than in 2009, with a posterior median decrease of 9.6% (95% credible interval (CI) −26.4% to +9.4%). The global population trend was −1.3% per year over this period (95% CI = −3.3% to +1.0%) and declines probably occurred in four of eight fast ice regions, irrespective of habitat conditions. Thus far, explanations have yet to be identified regarding trends, especially as we observed an apparent population uptick toward the end of time series. Our work potentially establishes a framework for monitoring other Antarctic coastal species detectable by satellite, while promoting a need for research to better understand factors driving biotic changes in the Southern Ocean ecosystem.