Was high grouse hag in early 20th century Norway due to a program for extermination of small game predators?

A Norwegian program for extermination of (small game) predators (NPEP) was run during 1900‐ 1914, This initiative is believed to have caused larger small game stocks and more regional synchrony in rodents. To investigate the effectiveness of the NPEP time series of predators bountied (1885–1914), rodent dynamics (1885–1914), ptarmigan hunting index (1885–1914 and 1900/1‐1914), and willow ptarmigan and berry export statistics (1885–1914) were analyzed for three different regions: south, east and central Norway. In south and east Norway there were higher ptarmigan export in the period 1907–1914 than the years before, but not in central Norway. There was not bountied higher number of red fox. eagle or goshawk in any of the three regions when comparing years a) before and after 1900. and b) when comparing the periods 1900–1906 and 1907–1914. This suggests that predator removal was not the cause of increased ptarmigan export. The ptarmigan hunting index and rodent index for south and east Norway were correlated in the period 1885 1914, while the ptarmigan export from east Norway was correlated with berry export from the year before. However, for central Norway the rodent index was not correlated with the hunting index. There were cross correlation between berry and ptarmigan export with lag from minus one to nine years for south and east Norway, The NAO (North Atlantic Oscillation) ‐ an indication of the winter weather variation ‐ had higher values during 1900–1914 than 1885–1899, indicating moister and warmer winters in the last period. This analysis indicates that NPEP generally did not increase predator removal. The results suggest, however, that it was a series of years with high rodent density, that caused the increase in ptarmigan populations In south and cast Norway, which, in turn, may have been caused by favourable weather conditions leading to among others good berry crops. Conclusions based on old data series must, however, be drawn with caution.