Population research on small rodents (Rodentia) and shrews (Soricidae) in Lierne Municipality – Norway; 2018-2021 based on systematic catches with ordinary mouse traps in traplines

Study Extent

The study was conducted from 1988 through 2021 and will continue for another year with collection of more detailed data. The approximate coordinates for the trapsites is: N64.24.20 - E13.49.00 in Lierne municipality, Trondelag county, Norway. Habitat is Northern Boreal Spruce forest. One trapline is placed in natural old-growth blueberry-dominated forest. The second trapline is placed in younger succsession cultural spruce forest, edging a richer vegetation and wet, rich minerogen mire. The traplines are located approx. 540 m.a.s.l..

Sampling

Ordinary mouse traps (for killing mouse) have been put out with 5 m. distance through the two traplines, each with 50 traps, bated with raw potatoes. Traps are with few exceptions out for 2 nights and 3 times a year: Mid June, late July/early August and September/October. The same traplines and trap spots have been used all years.

Quality Control

Mouse and shrew species are visually determined on spot, aged as adult, subadult and juveniles, weighed and sexed whenever possible.

Method steps

1. The results give a total and species specific, population index calculated as Number/100 Catch-Nights. The results will give an comparable index for population cycles over a 35 years period for this area.

The catches are aimed on small rodents (Rodentia) and shrews (Soricidae). Main species will be: The Bank Vole (Myodes/Chletrionomys glareolus), The Grey-sided Vole, (M. rufocanus), The Field Vole (Microtus agrestis), The Wood Lemming (Myodes schisticolor), The Lemming (Lemmus lemmus), The Common Shrew (Sorex araneus), The Pygmy Shrew (S. minutus) and The Water Shrew (Neomys fodiens).

1. Rodentia
   common name: Rodents rank: order
2. Soricidae
   common name: Shrews rank: family

Lierne Municipality, Norway. The trap-lines are placed in North-boreal spruce dominated forest - one line in an oldgrowth, natural blueberry spruce forest - mixed with birch. The other line in a young, planted spruceforest after clearcutting, partly at the egde of minerotrofe herb-dominated bogs. Altitude approx. 540 masl.