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Media release
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Media Release from Science (AAAS)
In the first continent-wide population estimate of Weddell seals across Antarctica and the first study to count every female individual for a wide-ranging, wild animal species on Earth, scientists used very high resolution (VHR) satellite imagery from November 2011 and a crowd-sourcing campaign to determine an abundance of about 202,000 adult and sub-adult female seals – a smaller than expected count. Males, which spend much of this time maintaining underwater territories, were excluded from the analysis. The study also unexpectedly found that Weddell seals only inhabited 0.55% of suitable fast ice (named as such because it is “fastened” to the coastline).
The findings suggest that ocean depth and fast ice, as well as distances to penguin colonies, explain the seals’ spatial prevalence and distribution. Michelle LaRue and colleagues conclude that efforts to monitor the Southern Ocean ecosystem must account for the complexities of community ecology.
Although Weddell seals, which are found along the Antarctic coastline, are among the best-studied marine mammals in the world, scientists have known little about larger-scale patterns in the seal’s distribution, population size, or structure. However, increasingly available VHR satellite imagery has made it feasible for scientists to monitor Weddell seals and other species at appropriate spatial scales. To estimate the size of the Weddell seal population in Antarctica and to understand environmental factors that influence it, LaRue et al. gathered VHR satellite imagery with about 30- to 50-centimeter spatial resolution from November 2011. Next, LaRue et al. launched a campaign in which volunteers tagged seals in 500-meter by 500-meter sections of an original satellite image. These data were used to develop models to predict seal populations at locations across the continent. The researchers found a negative relationship between Weddell seal counts and the size of nearby emperor penguin colonies, supporting that the two species might compete for resources. This study, which takes a non-invasive approach to studying a sensitive region, highlights the potential of remote sensing, rather than fieldwork, for population monitoring.
Expert Reaction
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Dr Michelle LaRue, lead author, University of Canterbury and University of Minnesota
A special element about this project to me personally is that the two institutions I’m fortunate to be affiliated with – University of Canterbury and University of Minnesota – are both the places where the original Weddell seal work came out of in the early 1960s, back when the only way to study the seals was to travel by snow machine, or if you were lucky, a helicopter flight to get a little farther afield.
Now, anyone with internet access can count them from space. Ōtautahi Christchurch has been an Antarctic Gateway City for more than a century, and a hub for Antarctic research and discovery - so to follow in the footsteps of people like Dr. Ian Stirling, who initiated the study of the species at University of Canterbury, and Dr. Don Siniff who then continued the seal work for several decades at the University of Minnesota, is amazing to me.
The connection between these two places a world apart from each other is also emblematic of the importance of international collaboration and the idea that 'we are all in this together', as we can now move forward and use this new research to contribute to the best-available science from which to make solid policy decisions.
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