Demographic attributes of southern bog lemmings colonizing two removal grids were compared with those of residents on neighboring control grids over a two year period in eastern Kansas. There was a positive association between the number of lemmings colonizing the removal grids and density of the control grids. Overall, 41% of the losses from the two control grids was accounted for by dispersal. The following differences were observed comparing residents with dispersers: 1) a greater proportion of males colonized the removal grids, 2) a lower percentage of adult females colonizing the removal grids were in breeding condition, whereas the reverse was true for subadult females, and 3) a greater proportion of subadults colonized the removal grids. These results are consistent with those obtained for other microtine species."I don't understand", said the scientist, "why you lemmings all rush down to the sea and drown yourselves". "How curious", said the lemming. "The one thing I don't understand is why you human beings don't" - from Intervie with a Lemming by James Thurber.