Hart Tom

No Thumbnail Available
Last Name
First Name

Search Results

Now showing 1 - 3 of 3
  • Preprint
    Stable isotope analyses of feather amino acids identify penguin migration strategies at ocean basin scales
    ( 2017-07) Polito, Michael J. ; Hinke, Jefferson T. ; Hart, Tom ; Santos, Mercedes ; Houghton, Leah A. ; Thorrold, Simon R.
    Identifying the at-sea distribution of wide ranging 20 marine predators is critical to understanding their ecology. Advances in electronic tracking devices and intrinsic biogeochemical markers have greatly improved our ability to track animal movements on ocean-wide scales. Here we show that, in combination with direct tracking, stable carbon isotope analysis of essential amino acids in tail feathers provides the ability to track the movement patterns of two, wide-ranging penguin species over ocean basin scales. In addition, we use this isotopic approach across multiple breeding colonies in the Scotia Arc to evaluate migration trends at a regional scale that would be logistically challenging using direct tracking alone.
  • Article
    A reversal of fortunes : climate change ‘winners’ and ‘losers’ in Antarctic Peninsula penguins
    (Nature Publishing Group, 2014-06-12) Clucas, Gemma V. ; Dunn, Michael J. ; Dyke, Gareth ; Emslie, Steven D. ; Levy, Hila ; Naveen, Ron ; Polito, Michael J. ; Pybus, Oliver G. ; Rogers, Alex D. ; Hart, Tom
    Climate change is a major threat to global biodiversity. Antarctic ecosystems are no exception. Investigating past species responses to climatic events can distinguish natural from anthropogenic impacts. Climate change produces ‘winners’, species that benefit from these events and ‘losers’, species that decline or become extinct. Using molecular techniques, we assess the demographic history and population structure of Pygoscelis penguins in the Scotia Arc related to climate warming after the Last Glacial Maximum (LGM). All three pygoscelid penguins responded positively to post-LGM warming by expanding from glacial refugia, with those breeding at higher latitudes expanding most. Northern (Pygoscelis papua papua) and Southern (Pygoscelis papua ellsworthii) gentoo sub-species likely diverged during the LGM. Comparing historical responses with the literature on current trends, we see Southern gentoo penguins are responding to current warming as they did during post-LGM warming, expanding their range southwards. Conversely, Adélie and chinstrap penguins are experiencing a ‘reversal of fortunes’ as they are now declining in the Antarctic Peninsula, the opposite of their response to post-LGM warming. This suggests current climate warming has decoupled historic population responses in the Antarctic Peninsula, favoring generalist gentoo penguins as climate change ‘winners’, while Adélie and chinstrap penguins have become climate change ‘losers’.
  • Article
    Multi-modal survey of Adélie penguin mega-colonies reveals the Danger Islands as a seabird hotspot
    (Nature Publishing Group, 2018-03-02) Borowicz, Alex ; McDowall, Philip ; Youngflesh, Casey ; Sayre-McCord, Thomas ; Clucas, Gemma V. ; Herman, Rachael ; Forrest, Steven ; Rider, Melissa ; Schwaller, Mathew ; Hart, Tom ; Jenouvrier, Stephanie ; Polito, Michael J. ; Singh, Hanumant ; Lynch, Heather J.
    Despite concerted international effort to track and interpret shifts in the abundance and distribution of Adélie penguins, large populations continue to be identified. Here we report on a major hotspot of Adélie penguin abundance identified in the Danger Islands off the northern tip of the Antarctic Peninsula (AP). We present the first complete census of Pygoscelis spp. penguins in the Danger Islands, estimated from a multi-modal survey consisting of direct ground counts and computer-automated counts of unmanned aerial vehicle (UAV) imagery. Our survey reveals that the Danger Islands host 751,527 pairs of Adélie penguins, more than the rest of AP region combined, and include the third and fourth largest Adélie penguin colonies in the world. Our results validate the use of Landsat medium-resolution satellite imagery for the detection of new or unknown penguin colonies and highlight the utility of combining satellite imagery with ground and UAV surveys. The Danger Islands appear to have avoided recent declines documented on the Western AP and, because they are large and likely to remain an important hotspot for avian abundance under projected climate change, deserve special consideration in the negotiation and design of Marine Protected Areas in the region.