Hedge fund managers are increasingly positioning themselves for a further correction in the global economy and equity markets, by taking safe-haven bets that will earn them much less than their traditional "two-and-twenty" trades.

For the first time in 20 months, hedge fund managers have become buyers of US Treasurys, one of the most easily traded and safest investment instruments in the world, according to Bank of America Merrill Lynch's weekly hedge fund monitor.