Callum found that newts could tolerate exceptional levels of salt - for an amphibian, at least - in their Highland habitats. "Most amphibians react very badly to saltwater," O'Brien says. When roads are salted in the winter, he points out, that poses a problem to breeding frogs if the minerals are swept into ponds.
Given their proximity to the sea, the Scottish ponds near the inlet of Loch Alsh are salty. (They're not as intense as an estuary, but they're no fresh country lakes, either.) That newts could survive unusual salinities had been noted once before, by a biologist in the Netherlands. But to hear O'Brien say it, the previous observation was a note in a paper, rather than a full inquiry. In some ways, Callum's approach is "more scientific than the scientist" was.