DWRC is continuing research into the feasibility of using 
immunocontraception as a method to manage some 
mammal populations. DRWC has completed 4 years of 
immunocontraceptive research on white-tailed deer, in 
cooperation with The Pennsylvania State University, to 
determine the long-term effects of immunocontraceptive 
vaccines on the fawning rate of the contracepted deer. In 
the 4-year study, the fawning rate was reduced in treated 
deer by 88 percent. No health problems developed in the 
vaccinated deer. 
DWRC is completing its second year of funding by the 
DoD’s Legacy Program to develop chemical methods for 
managing brown tree snakes. DWRC scientists have been 
working on Guam nearly continuously to conduct field 
evaluations of attractants, oral and dermal toxicants, activity 
patterns using radiotelemetry relative to implementing a 
baiting strategy, and operational trapping strategies. 
Bird and other wildlife strikes to aircraft are a serious, but 
largely unquantified, economic and safety problem for 
civilian aircraft in the United States. For the first time, 
DWRC, working through an interagency agreement with the 
Federal Aviation Administration (FAA), has completed an 
analysis of all wildlife strikes reported for an entire year. 
The analysis of 1994 revealed 2,220 nonduplicate strikes to 
civilian aircraft reported to FAA. Gulls (30 percent) and 
waterfowl (13 percent) were the most common species 
striking aircraft. Mammal strikes included 57 deer and 
9 coyotes. Damage was reported for 519 aircraft, including 
118 incidents of engine damage. 
DWRC biologists estimated that less than 20 percent of 
known strikes were reported to FAA. If this estimate is 
accurate, nationwide economic losses from strikes to civilian 
aircraft in 1994 exceeded $100 million. Losses from strikes 
to U.S. military aircraft are estimated to average $112 million 
per year. Thus, bird and other wildlife strikes are probably 
costing the U.S. military and civilian transport industry more 
than $200 million per year. 
Protection of Agricultural Resources 
Every year, birds and mammals of many species cause 
several hundred million dollars’ worth of damage to food 
crops and livestock. Blackbirds and starlings regularly 
consume grain crops in all stages of growth, from sprouting 
seeds to mature crops. Affected crops include wheat, corn, 
rice, sorghum, and sunflowers. Ducks and geese trample, 
eat, and foul swathed grain and seeds. Fish-eating birds 
cause serious losses to catfish and other fish grown at 
aquaculture facilities. Mammals such as deer, prairie dogs, 
gophers, and raccoons also cause damage to a wide variety 
of food crops. Certain predators cause significant damage 
to the livestock industry by killing or injuring sheep, goats, 
cattle, poultry, and other kinds of livestock. 
Here are some specific examples of ADC’s 
accomplishments in protecting U.S. agriculture in 1996: 
¢ During 1996, ADC personnel involved with the Cattail 
Management Project in North Dakota removed about 5,500 
acres of dense cattails in wetland areas in the State. Since 
the program began in 1991, more than 17,000 acres of 
cattails in North Dakota have been treated with an aquatic 
herbicide. This type of wetland restoration offers the 
additional benefit of providing improved habitat for waterfowl 
and other wildlife species. Historically, in North Dakota 
blackbirds have caused a considerable amount of crop 
damage because their nesting and roosting habitats have 
been located very close to sunflowers and other farm crops 
that the birds eat. Removing enough of the blackbirds’ 
nesting and roosting habitat forces them to seek suitable 
habitat in other areas. 
« An avocado farmer in San Luis Obispo County, CA, 
reported an estimated $50,000 in damage to his trees 
caused by feral hogs. Feral hogs in the area have been 
implicated in the spread of root fungus that kills the trees 
when the roots are exposed as a result of the hogs’ digging 
activities. With the help of dogs, ADC removed several hogs 
from the area and put a stop to the damage. 
ADC Program Highlights, 1996/7 
