What do Soay sheep have to do with global warming and climate change?

Apparently a lot, but you sure couldn’t prove it by looking out in our fields.  As near as I can tell, the only impact weather has on our flock is that when it gets cold, the sheep tuck their feet under and hunker down in the pasture.  In the summer, the sheep drink a lot more water and hang out under whatever shade they can find.  But global warming?  Until this week I would have said anyone talking about Soay sheep and climate change in the same breath needs a weekend in the city to clear her head. 

Not so, according to the media in London, both an article in the London Times (kindly brought to my attention by my new friend Anne in Yorkshire) and on the BBC website.  On first reading, the media seemed to be saying our sheep should be getting smaller because more small animals should survive the warmer winters and that means they should all get smaller.  Are you with me?  Researchers in the U.K. have been out on the St. Kilda archipelago off the northwest coast of Scotland observing the wild Soay sheep flock on Hirta island, annually collecting data since long before global warming was recognized. Little did they know how useful all that fundamental data would turn out to be! If you have kept up with your Soay sheep history, you will recall the Soay on Hirta are a closed flock subject to awful winters, making them ideal subjects for studying climate change. Their little island is a natural laboratory where the combination of animal size and comparative level of available grass (which of course varies with the weather) can be used to make predictions about flock and individual sheep size. Every August the ecologists visit, measure, tag, and count as many of the Soay sheep as they can catch, usually about half the flock. They do not have to account for predators; there are none on Hirta. Nor are there humans to affect the animals’ health. They do not migrate, unlike their distant relatives the deer. Their existence boils down to how much grass the climate allows to grow on Hirta.   

Despite my natural wariness of all things scientific, curiosity took over.  I read the article in the London Times and I read the material from the BBC and immediately concluded in my “what good will it do” manner that smaller animals would mean less hay would mean less expense. Not exactly. You also will recall I am married to a scientist, and bless his heart if he didn’t look up the new research article in the journal Science that provoked the media coverage to see if they got it right. Turns out the researchers have done a nice job of taking data over many years and they are in fact in a position to study trends in the Soay sheep population on Hirta, but they were very circumspect in the article and did not make the bold pronouncements about shrinking size that were suggested in the press. To be sure, once the researchers got outside their meticulous and rather cautious conclusions in the Science article about what size has to do with ability to reproduce, they gave the media interviewers a little more to chew on, namely the business about smaller sizes and who breeds better and survives better.

All of which sounds just ducky if you are both able to and interested in translating the complexities of research articles, and if you are, I urge you to look up the article in the March 16 [2007] issue of Science. You will be a more informed person and you almost certainly will have a new conversation-stopper for your next cocktail party. But you will not learn much about how to care for your own flock. The data from the wild Hirta Soay sheep has nothing to do with domestic “kept” Soay sheep.  The Soay in our pastures are not getting smaller or larger due to climate change and neither are yours. Why? Because we feed them. Nobody brings hay for Hirta Soay sheep. 

Don’t get me wrong. I am simply delighted to see Soay sheep getting this much press. That our flock’s cousins on their tiny island may be contributing to a better understanding of a pretty scary scenario for our planet should make all of us who own Soay sheep mighty proud. If nothing else, next time your friends scoff at the little rascals in your field, you might ask them when they last saw their angus bull or cocker spaniel featured in the media as the breed of choice for studying anything, much less the hottest environmental issue of the day.

For now …