Home Planet - 16/03/2010

Each year anglers await the annual salmon run. Thousands of magnificent fish forsake the bounty of the sea and head inland to their ancestral spawning grounds. But as any keen fisherman will tell you, some mature salmon are there to be caught from the spring time onwards. This week on Home Planet, you ask why a small number of salmon make the trek up river months before their fellow fish. If the advantage is so great, why don't they all do it? Then there's the mysterious black and white bird seen but not identified in Dorset; what is it and why does it have such unusual markings? Why, you ask, do chimpanzees still exist when there cousins, us humans, have clearly outstripped them in evolutionary terms? What happens underneath a frozen river as the tides ebb and flow beneath? And we continue the discussion on collecting wild plants and animals; just when is it acceptable to kill a specimen for science? Join Richard Daniel and his guests marine biologist Dr Helen Scales; conservationist Derek Moore and Professor Philip Stott, an environmental scientist from the University of London. A Pier production for BBC Radio 4.