Flightless Giant Canada Goose Depredation Abatement and Disgestibility of Selected Crops in South Dakota

Crop depredation by flightless giant Canada geese (Branta Canadensis maxima) has become a common occurrence across the upper Midwest. Due to numerous landowner complaints, South Dakota Department of Game, Fish and Parks (SDGFP) is evaluating several methods to solve this problem. One method is the use of vegetation visual barriers in conjunction with a food plot. A study site was chosen along an open shoreline on the Whitewood Slough Game Production Area, Kingsbury County, South Dakota. The existing alfalfa field was manipulated to form an alfalfa barrier and adjacent food plot. The objectives in 1997 were to determine the minimum width of barrier required to deter geese from breaking through and to determine a preference for either barley or a barley and clover mix as a food plot forage. A supplemental food plot was also established to evaluate the response of the food plot forages to the stress of goose grazing. Food plot forage preference was determined by the cage comparison technique. The alfalfa visual barrier was evaluated by establishing a height-density index and comparing breakthrough points to the barrier as a whole. Observation was also used to evaluate alfalfa visual barrier effectiveness. Activity budgets and feeding rates for goose family groups were also recorded opportunistically. In 1998, a larger barley food plot was established on the same site and the alfalfa visual barrier eliminated to determine if this would deter geese from feeding in a soybean field immediately upland from it. Separately, feeding trials were conducted on 9 captive giant Canada goose goslings to determine the nutritional and digestible qualities of 4 possible food plot forages. Carrying capacity for goose food plots was determined. Alfalfa visual barrier breakthrough sites had significantly lesser height-density characteristics than the barrier as a whole with both Robel pole (P=O.0001) and coverboard (P=O.0009) data. Mean width of the alfalfa visual barrier at breakthrough sites was 5.8 m (SE=O.6959), with a maximum width of 12.2 m. The alfalfa used in this project was ultimately not tall or dense enough to constitute a substantial barrier, although it repelled geese early in the season. The alfalfa barrier was only effective when used in conjunction with a food plot containing forage that was short and palatable. Geese showed no preference for food plot forages as there are no significant differences (P=O.9049) between amounts of forage consumed by vegetation type. Also, the food plot had to be mowed to keep weeds from invading and rendering it unpalatable. A larger food plot without a barrier appeared to be ineffective as geese fed freely in the soybean field upland from the food plot. No significant difference (P=0.2386) was seen between adult and gosling feeding rates. Activity budgets showed significant differences between subject groups in both 1997 (P=0.0001) and 1998 (P=0.0001). Adults with goslings spent significantly more time in alert behaviors than did their goslings, while goslings spent more time feeding. Feeding trial results showed barley and soybeans to possibly be superior to wheat and bluegrass in digestibility. Soybeans were lowest in non-digestible constituents and highest in nitrogen later in the season at a time when the graminoid species were maturing and becoming unpalatable to geese. Individual giant Canada geese had a daily dry matter intake of 0.3744 kg. The animal unit equivalent for giant Canada geese is 0.04, meaning it would take 25 geese to equal one animal unit. Further research is needed to evaluate the proper use of alfalfa visual barriers. Managers should consider the time and energy needed to establish and maintain food plots. Simply keeping the wetland edge mowed or grazed may be a better alternative