Establishment of the Hilo, HI,
current NWRC Hilo, HI, field station was initially established as a
DWRC (Denver Wildlife Research Center) Wildlife Damage Research Station,
within the U.S. Dept. of the Interior, Bureau of Sport Fisheries &
Wildlife, Animal Damage Control Program.
The station was funded by a congressional appropriation in response
to concerns raised by the Hawaiian agricultural industry concerning
rat damage losses. For example, at the time the station was established,
it was estimated that rat damage to sugarcane resulted in the loss of
45,000 tons per year, an amount worth $5 million. The macadamia nut
crop was also impacted by rats, with losses estimated at more than $400,000
The field station's mission, then, at the time of establishment, was
to research and develop methods to alleviate rat damage to agricultural
crops. Field station personnel often worked closely with members of
the Hawaiian Sugar Planters’ Association (HSPA).
Rat Damage- Sugarcane Research: 1967-1972
Early work at the field station centered on ways to reduce rat damage
to sugarcane. Protocols were established to test standard, and possible
new, lethal agents. Scientists evaluated the acceptance and efficacy
of treated baits and carriers. Studies on basic rodent biology and sugarcane
damage characteristics were also undertaken.
Expanding Research: 1973-1983
Zinc phosphide and modeling.
In cooperation with the HSPA, scientists initiated studies to evaluate
the use of zinc phosphide oat baits to reduce rat damage in sugarcane
fields. Zinc phosphide was the first rodenticide (1970) registered in
the United States for in-crop use. The baiting program was eventually
operationally adopted by both Hawaiian and Floridian sugarcane growers.
Also, during this period, sampling protocols and models were developed
to quantify damage distribution and yield losses.
Nonlethal control approaches evaluated.
Nonlethal approaches to rat control were also evaluated. Techniques
tested included manipulation or modification of non-crop habitats to
reduce rodent population reservoirs; incorporation of “rat-resistant”
traits into HSPA’s sugarcane varieties; and early cropping to
reduce damage at harvest time.
Additional emerging vertebrate pest problems.
New wildlife damage problems were also emerging in Hawaii at this time:
- Feral pigs, goats, and sheep were damaging forest regeneration efforts
- Rats were impacting native forest bird survival and watershed quality
- Cattle egrets foraging at the Hilo Airport began to pose hazards
Rodent control research was also initiated to assist the rapidly expanding
macadamia nut industry in reducing crop losses to rats.
Congressional action closed the Hilo, HI, field station in
Research Efforts, 1984-1989
The Denver Wildlife Research Center maintained a small presence at
the field station facilities and initiated research to reduce mongoose
depredation on native Hawaiian ground-nesting birds. The U.S. Environmental
Protection Agency approved a diphacinone hamburger bait for control
of mongooses in 1989.
Research in a Changing Economy: 1989-2001
The Hawaii field station was re-established through congressional funding
in 1989 as part of the U.S. Dept. of Agriculture, Animal & Plant
Health Inspection Service, Wildlife Services, Denver (later renamed
National) Wildlife Research Center.
Studies again evaluated new, and refined old, methods to alleviate
rodent losses in sugarcane, macadamia nuts, and other emerging agricultural
Due to falling sugar prices, stiffer environmental requirements, and
rising land, labor, and operational costs, the Hawaiian sugar industry
was faced with major belt-tightening decisions, and many plantations
closed. By 1998, only 4 plantations remained. Vacant sugarcane fields
were gradually replaced with a variety of other agricultural crops.
Additionally, the field station, in coordination with state and other
federal agencies, conservationists, and private landowners, worked to
develop control strategies for reducing rat depredations in native conservation
areas. Studies were also initiated to support registration of diphacinone
rodenticide baits in Hawaiian forests.
Current and Future Research Challenges
The Hawaii field station continues to have a major role in research
to address existing and emerging invasive vertebrate problems in the
region. For example, extensive screening of lethal agents (as well as
other control research) is being conducted to reduce the rapid spread
of and island colonization by recently introduced Caribbean tree frogs
Also, ongoing studies in Guam aim to develop control strategies for
the brown treesnake to reduce its population on the island and prevents
its spread elsewhere.
Future challenges for NWRC scientists in Hawaii include bird problems
at airports, new vertebrate pest problems in in diverse agricultural
crops, and impacts of mesopredators (i.e., mongoose, feral cats) on
native threatened and endangered species.
Current Field Station