Blasts from the past: how ice age ponds are coming back to life

Once watering holes for mammoth and elk, Herefordshire's neglected ancient ponds are being restored

Ecologist Will Watson is hunting for Britain's largest blood-sucking leech in a 14,000-year-old pond in Herefordshire. The elusive medicinal leech (Hirudo medicinalis), grows up to 20cm long and has only officially been recorded three times in the county in the past two decades. In the ice age pond in Moccas Park national nature reserve it was last found in 2000.

Watson shakes his net in the water. Most creatures shy away from such disturbance but this leech - the only one in Britain that sucks human blood - is attracted to the vibrations as they suggest the movements of large mammals trampling around the edge of the pond, which could signal a potential meal.