06 March 2012

WARMING HARDER ON MIGRATORY PENGUINS

Gentoo penguin and chick. Credit: © Julia Whitty.
  
There are big changes underway in penguin colonies in the Antarctic Peninsula.
  
Why? First up, it's one of the fastest warming regions on Earth.
  
And we know that a warming climate can shift the phenology—the timing of annually recurring lifecycle events like migrations and flowering—of species. 
    
Phenological shifts can leads to "trophic mismatches." That is, where interacting species fall out of sync.
  
Caribou. Credit: NPS.
    
For instance, a study in Proceedings of the Royal Society B showed a trophic mismatch between caribou (whose seasonal migration to summer calving ranges is cued by changes in day length) and the plants they feed on in their summer ranges (whose growing season is cued by local temperatures).
  
Trophic mismatches are increasingly likely in a warming world, especially among migratory species that have no way to know the schedule is speeding up hundreds or thousands of miles away.
  
Adélie penguin and chick. Credit: © Heather Lynch.
  
A new paper in MEPS (Marine Ecology Progress Series) takes an interesting look at another aspect of phenological change—the possible effects on species that breed (and compete) together.
  
Specifically on three penguins on the Antarctic Peninsula: Adélie, chinstrap, and gentoo
  
Adélies and chinstraps migrate to their breeding colonies. The gentoo is resident year round.

Warming in Antarctica in degrees C per year between 1981-2007.Credit: NASA Earth Observatory, image by Robert Simmon, based on data from Joey Comiso, GSFC.
    
You can probably already hypothesize a dynamic among these three species competing for breeding space and to some extent food resources in a rapidly warming area.
  
The authors of the MEPS paper investigated changes in clutch initiation dates (the date the first egg is laid) of the three species in the Western Antarctic Peninsula (WAP)—that's the pointy bit at the upper left of the map, above. 

The results were striking. From the paper:
    
We found that clutch initiation was most significantly correlated with October air temperatures such that all 3 species advanced clutch initiation to varying degrees in warmer years. Gentoo penguins were able to advance [clutch initiation dates] almost twice as much (3.2 d°C−1) as Adélie (1.7 d°C−1) and chinstrap penguins (1.8 d°C−1). 

Chinstrap penguins and chicks. Credit: Hannes Grobe/AWI via Wikimedia Commons.
    
What jumps out here is that resident gentoos, who are already on the breeding ground, appear able to accurately judge the advancing spring dates and lay earlier. And this may be the reason, at least in part, as to why Adélies and chinstraps are suffering population declines and gentoos are thriving in the WAP:
   

  • Adélies declining in 18 of 24 surveyed breeding sites
  • Chinstraps declining at 16 of 29 surveyed breeding sites
  • Gentoos increasing at 32 of 45 surveyed breeding sites
    
Those numbers are forthcoming in another paper from some of this same team.
  
Heather Lynch counting gentoo penguins at Port Lockroy, Antarctica. Credit: © Julia Whitty.
  
BTW, I first wrote about two of these researchers—Heather Lynch and Ron Naveen—in my Mother Jones article March of the Tourists a while back.


The papers:

  
  • Heather J. Lynch, William F. Fagan, Ron Naveen, Susan G. Trivelpiece, Wayne Z. Trivelpiece. Differential advancement of breeding phenology in response to climate may alter staggered breeding among sympatric pygoscelid penguins. MEPS. DOI:10.3354/meps09252.09252
  • Eric Post and Mads C Forchhammer. Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch. Phil. Trans. R. Soc. B. DOI:10.1098/rstb.2007.2207

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