Browsing by Author "Oliver,Matthew J."
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Item Projected asymmetric response of Adelie penguins to Antarctic climate change(Nature Publishing Group, 6/29/16) Cimino,Megan A.; Lynch,Heather J.; Saba,Vincent S.; Oliver,Matthew J.; Megan A. Cimino, Heather J. Lynch, Vincent S. Saba and Matthew J. Oliver; Oliver, Matthew JohnThe contribution of climate change to shifts in a species' geographic distribution is a critical and often unresolved ecological question. Climate change in Antarctica is asymmetric, with cooling in parts of the continent and warming along the West Antarctic Peninsula (WAP). The Adelie penguin (Pygoscelis adeliae) is a circumpolar meso-predator exposed to the full range of Antarctic climate and is undergoing dramatic population shifts coincident with climate change. We used true presence-absence data on Adelie penguin breeding colonies to estimate past and future changes in habitat suitability during the chick-rearing period based on historic satellite observations and future climate model projections. During the contemporary period, declining Adelie penguin populations experienced more years with warm sea surface temperature compared to populations that are increasing. Based on this relationship, we project that one-third of current Adelie penguin colonies, representing similar to 20% of their current population, may be in decline by 2060. However, climate model projections suggest refugia may exist in continental Antarctica beyond 2099, buffering species-wide declines. Climate change impacts on penguins in the Antarctic will likely be highly site specific based on regional climate trends, and a southward contraction in the range of Adelie penguins is likely over the next century.Item Social Network Analysis Reveals Potential Fission-Fusion Behavior in a Shark(Nature Publishing Group, 9/30/16) Haulsee,Danielle E.; Fox,Dewayne A.; Breece,Matthew W.; Brown,Lori M.; Kneebone,Jeff; Skomal,Gregory B.; Oliver,Matthew J.; Danielle E. Haulsee, Dewayne A. Fox, Matthew W. Breece, Lori M. Brown, Jeff Kneebone, Gregory B. Skomal and Matthew J. Oliver; Oliver, Matthew JohnComplex social networks and behaviors are difficult to observe for free-living marine species, especially those that move great distances. Using implanted acoustic transceivers to study the inter-and intraspecific interactions of sand tiger sharks Carcharias taurus, we observed group behavior that has historically been associated with higher order mammals. We found evidence strongly suggestive of fission-fusion behavior, or changes in group size and composition of sand tigers, related to five behavioral modes (summering, south migration, community bottleneck, dispersal, north migration). Our study shows sexually dimorphic behavior during migration, in addition to presenting evidence of a potential solitary phase for these typically gregarious sharks. Sand tigers spent up to 95 consecutive and 335 cumulative hours together, with the strongest relationships occurring between males. Species that exhibit fission-fusion group dynamics pose a particularly challenging issue for conservation and management because changes in group size and composition affect population estimates and amplify anthropogenic impacts.