Northern Prairie Wildlife Research Center
JOHN T. LOKEMOEN AND ROBERT O. WOODWARD
U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research
Route 1, Box 96C, Jamestown, ND 58401-9736
Electric fences were built across the base of peninsulas using 1-inch poultry netting (18 gauge). Fences were 5.5 feet high, 1 foot below ground level, and extended 50 to 150 feet into the adjoining wetland. Two energized wires were placed on the outside of the fence, one was 4 feet high and one was set at the top of the poultry netting. Moats built at the base of the peninsulas were 100 yards wide and were filled with water 1.5 to 3 feet deep.
On peninsulas with electric fences there were 1,119 nests which experienced 59% nest success compared to 116 nests with 13% nest success on the controls. During the 5 years of study 6,587 ducklings hatched on the treated peninsulas and only 325 hatched on the control areas. On peninsulas with moats there were 936 nests with 70% nest success compared to 234 nests and 12% nest success on control areas. During the study, 6,226 ducklings hatched on the peninsulas with moats but only 473 hatched on control areas. On the fenced peninsulas, gadwalls (Anas Strepera) composed 44% of the nesting population, blue-winged teal (Anas discors) 17%, and mallards (Anas platyrhynchos) 15%.
The electric fences and moats enhanced nest hatching success but did not halt all predation on the peninsulas. Some incubating hens were killed by raptors and eggs were destroyed by such predators as American crows (Corvus brachyrhynchos), mink (Mustela vison), and raccoon (Procyon lotor). From 1986 through 1989 a total of 108 small mammals were removed from inside the treated peninsulas. Raccoon and striped skunk (Mephitis mephitis) made up 91% of the total animals captured.
The average capital cost of each fence was $5,965. This cost amortized over 20 years plus maintenance fees results in an annual average cost of $918 or $5.02 per duckling hatched. The annual average capital cost plus maintenance expenses for moats was, $14,216 or a cost of $20.54 per duckling hatched.
Results of this study indicate that electric fences and moats can be highly effective in reducing mammalian predation on peninsulas. The response of nesting ducks to the protected areas was rapid with the number of hatched young increasing from 572 in 1985 to 3,857 in 1987. The productivity of peninsulas could be further increased with more effective methods of predator removal.