The good news: in Europe, once-declining gray wolf populations are rebounding, thanks in part to protection laws in many countries. Unfortunately, some wolves are celebrating their recovery by indulging in mutton—sheep attacks are on the rise. How can we keep the sheep safe without killing the wolves? Just wire up the flocks to let them call for help—literally.
The snowy, wind-blown Scottish archipelago of St. Kilda may be inhospitable, but because it is inhospitable, it is an ideal natural laboratory. The last people left this place behind nearly a century ago, but the sheep stayed. And the in absence of human interference in their breeding, the sheep of St. Kilda have shown scientists something peculiar.
It has to do with the relationship between the immune system and reproduction. Andrea Graham and colleagues have studied the islands’ Soay sheep for years and years, and found the average lifespan of the ewes to be about 6 years. However, there’s great variation in there: Some lived just a few years, and some as many as 15.
The short-lived ewes had lower concentrations of antibodies than the longer-lived ones, which suggested why their lives were so short. But why was natural selection not weeding them out? Dr. Graham said the researchers found this to be a puzzle: “What are all these sheep doing with low antibody concentrations?” [The New York Times]
Don’t be alarmed, but on a remote island in Scotland the sheep are shrinking.
Instead of gradually increasing in size as expected due to evolution, the average weight of the wild sheep has decreased as average temperatures heat up. The discovery shows that a species’ response to global warming can be unpredictable, and can be based on multiple factors. According to a study published in Science, warmer and wetter winters have made it easier for smaller sheep to survive the hard months and go on to bear offspring, thus passing these “small” genes onto the next generation of sheep.
Since 1985, the average weight of the wild Soay sheep living on the island of Hirta has decreased by about 5 percent. Due to global warming, the winters on the Scottish isles are becoming becoming shorter and milder. That makes food more abundant and allows some of the smaller, more vulnerable and younger sheep to survive. Then they go on to have offspring that tend to be small themselves — and have a better chance of survival because of the increasingly mild winters. “The environmental and evolutionary processes are intertwined. There’s still natural selection, but it’s not leaving as big a signature as it used to. There’s still a disadvantage to being small, but not as much” [Time], says lead researcher Tim Coulson.