The Denver wildlife research center : highlights report, 1993

42 Pages·1994·2.3 MB·English

by  Denver Wildlife Research Center

Historic, archived document
Do not assume content reflects current
scientific knowledge, policies, or practices.

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Animal and Research Center
Plant Health
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Miscellaneous Highlights Report, 1993
Publication No. 1521
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U.S. Department of Agriculture Mention of companies or commercial products does not
Animal and Plant Health Inspection Service imply recommendation or endorsement by USDA over
DenverWildlife Research Center others not mentioned. USDA neitherguarantees nor
P.O. Box 25266 warrants the standard of any product mentioned. Product
Building 16, Federal Center names are mentioned solely to reportfactually on available
Denver, CO 80225-0266 data and to provide specific information.
Office of the Director [phone] This publication reports research involving pesticides,
Information and Technology Transfer [phone] rodenticides, and avicides. All uses of such pesticides must
be registered by appropriate State and/or Federal agencies
The U.S. Department of Agriculture (USDA) prohibits before they can be recommended.
discrimination in its programs on the basis of race, color,
national origin, sex, religion, age, disability, political beliefs, CAUTION: Pesticides can be injurious to humans,—domestic
and marital orfamilial status. (Not all prohibited bases apply animals, desirable plants, and fish or otherwildlife if they
to all programs.) Persons with disabilities who require are not handled or applied properly. Use all pesticides
alternative means forcommunication of program information selectively and carefully. Follow recommended practices for
(braille, large print, audiotape, etc.) should contact the the disposal of surplus pesticides and pesticide containers.
USDA Office of Communications at [phone] (voice)
or [phone] (TDD).
To file a complaint, write the Secretary of Agriculture,
U.S. Department of Agriculture, Washington, DC 20250, or
call [phone] (voice) or [phone] (TDD). USDA
is an equal employment opportunity employer.
Issued August 1994
Contents Introduction
Introduction 3 The DenverWildlife Research Center (DWRC), the research
facility of the Animal and Plant Health Inspection Service's
Research Highlights 4 (APHIS) Animal Damage Control (ADC) program, continued
Agricultural Crops 4 to make advances in many areas of wildlife damage
Nuisance, Safety, and Health Concerns 10 management during fiscal year (FY) 1993. Although
Livestock 14 reregistration and registration of pesticides remained a high
Aquaculture 17 priority to the overall ADC program, alternative research
Product Development 19 efforts increased, and the Center undertook some new
DWRC
Product Chemistry 20 initiatives. scientists continued research into wildlife
Immunocontraception 23 immunocontraception and resolving bird pest problems to
row and fruit crops, aviation, and aquaculture, and mammal
International Cooperation 24 damage problems to livestock and timber production. In
Bangladesh 24 addition, Center scientists began new initiatives in rangeland
Chad 25 rodents, bird repellants and dispersal methods, and mammal
DWRC-Russian Collaboration 26 attractants.
NigerConsultancy 26
DWRC
Argentina Sabbatical 26 continued to strengthen its current cooperativeties
Mexico 26 with universities and began to plan a major initiative to
Australia 26 establish a more comprehensive, cooperative wildlife-
damage research system at universities to better address
Internationa! Visitors 27 vertebrate pest management needs within the United States.
Outreach Activities 28 DWRC also broke ground in September 1993 for a new
research facility on the campus of Colorado State University
Program Support 31 in Fort Collins, CO. These 1993 research and program
Information Transfer/Library 31 activities clearly demonstrate DWRC's commitments to the
Archives 31 present and future needs of wildlife damage management.
Analytical Methods Development 31
Animal Care 32
Quality Assurance 32
Statistics 32
Research and Support Staff by Area of Expertise 33
Birds 33
International Programs 33
Mammals 34
Chemistry/Registration of Pesticides 34
Information Transfer 35
Program Support 35
Publications 36
DWRCHighlights Report: 1993/3
Research Highlights
Agricultural Crops
—
Bird-Exclusion Netting for Commercial Vineyards Few
control measures are available for reducing bird damage in
vineyards. The expectation of extensive damage in
vineyards with high-value grapes may warrant the
implementation of moderately costly protection measures
such as protective netting. DWRC personnel developed two
types of tractor-mounted, hydraulically powered unitsfor
applying and removing bird-exclusion netting from
grapevines. The netting system provided cost-effective
protection where high levels of damage (>6 percent on
yields of 6,804 kg/ha) were anticipated but may not be
practical in small vineyards or where low levels of damage
are expected. Controlled experiments are needed to
quantify the effectiveness ofthis netting system. Vegetative
growth afterthe onset of grape ripening and the resulting
entanglement of vine shoots in the netting may preclude
cost-effective use of bird-protective netting with vigorous
varieties (e.g.. Cabernet Sauvignon) growing on rich soils.
Entanglement in nets is a potential source of bird mortality.
Reducing Blackbird Damageto Sunflower in the repellants, mechanical scare devices, avicides, and altered
—
Northern Great Plains In Minnesota, North Dakota, and cultural practices have been tested to reduce these losses.
South Dakota, millions of common grackles and red-winged Each was found to have limitations because of excessive
and yellow-headed blackbirds begin congregating in dense cost in relation to benefits, logistical considerations, limited
cattail marshes in midsummer and concurrently initiate effectiveness, oradverse environmental effects. Hence,
feeding on early ripening sunflowers. Annual sunflower new management techniques are needed for reducing
losses to blackbirds amount to millions of dollars. Chemical blackbird damage to sunflowers.
4/DWRCHighlights Report: 1993
Currently, scientists from DWRC's North Dakota field Altering Sugar Composition To Control Fruit-Eating
—
station, in cooperation with North Dakota State University, Birds Recent discoveries regarding bird feeding behaviors
North Dakota ADC, and the U.S. Department of the Interior's and digestive physiology suggest that conditioned aversions
(USDI) Fish and Wildlife Service (FWS), are testing a new may develop in response to fruit chemistry. Majorfruit-
method of lessening blackbird damage to sunflower. The eating pests (e.g., European starlings and American robins)
process involves dispersing blackbirds by reducing their cannot digest sucrose, a minorcomponent of blueberries,
preferred roosting habitat in cattail marshes. To accomplish cherries, and othersmall fruits, because these birds do not
thistaskefficiently, the aquatic herbicideglyphosate (Rodeo®) have sucrase, the necessary digestive enzyme that splits
is applied aerially to the cattails from a fixed-wing aircraft. the sucrose molecule. Developing techniques that would
substitute sucrose for the simpler, digestible sugars naturally
Research on the amount of habitat that must be altered to more prevalent in fruit (glucose and fructose) could reduce
disperse blackbirds was completed in 1993. The benefits of bird damage. This avenue was explored on two fronts in
fragmenting wetlands for other birds, especially waterfowl, 1993: biochemical alterations of fruit chemistry and
were assessed. Data collection on the effects of cattail repellancy investigations.
management on aquatic invertebrates, an essential food
source forwaterfowl, was completed. Additionally, the first Feeding trials were conducted to evaluate the responses of
year of a 3-year study designed to assess the effects of avian fruit pests with and without the ability to digest
cattail management on ring-necked pheasant populations sucrose. Cedarwaxwings can digest sucrose but do so
was completed. inefficiently. Starlings cannot digest sucrose. Both species
are majorfruit-crop pests throughout the country.
Preliminary analyses of the data indicate that herbicide Researchers at DWRC's Florida field station presented
reduction of cattails leads to increased use of treated captive waxwings and starlings with artificial fruit made of
marshes by waterfowl while invertebrate populations either agar, water, sugar, and food coloring. Both species were
remain stable or are enhanced by the treatments. The able to distinguish between berries containing sucrose and
numbers of roosting blackbirds using the treated marshes those made with the fructose and glucose. When only fruits
appear to be significantly reduced. Sunflower damage data containing sucrose were offered, however, interspecific
will be analyzed to quantifythe effectiveness of cattail differences were apparent. To compensate for digestive
management for reducing sunflower damage. Experiments inefficiency, waxwings increased theirconsumption of
begun in 1990 on the effect of various herbicide application artificial berries. In contrast, consumption by starlings
rates and timing of sprays on cattails were continued in dropped to nearzero because of postingestional distress.
1993. Preliminary data indicate that glyphosate applied These results suggest that development of high-sucrose
once at 2 to 2.25 quarts/acre may provide sufficient cattail cultivars may be useful in the integrated management of
control at a manageable cost. some fruit-eating species but not others.
—
Field Testing of Potential Bird Repellents on Fruit In Potential Use of New Ins—ecticide To Reduce Bird
Florida, researchers evaluated the effectiveness of two Damage to Seeded Rice In a series of cage tests and
potential repellants for reducing bird damage to blueberries. flight-pen trials, researchers at the Florida field station
First, a half-acre plot was sprayed with phosmet (Imidan®), evaluated the responses of male red-winged blackbirdsto
an insecticide registered for use on blueberries, according to rice seed treated with imidacloprid, a newly developed
instructions on the product label. Then, for 10 days systemic insecticide. In two-cup tests, when both the
afterwards, field crews counted the number of berries on treated and untreated seed was either dyed or undyed,
tagged branches in the treatment plot and in a comparable individually caged redwings consistently avoided rice seed
control plot. Results showed that phosmet had little effect treated with imidacloprid at 833 and 2,500 p/m.
on bird-caused damage: losses in the control plot averaged Consumption of imidacloprid-treated seed at 278 p/m did not
71 percent compared to 66 percent in the treated plot. differfrom that of untreated rice. When birds had a choice
between undyed, untreated rice and dyed, imidacloprid-
In a second trial, methyl anthranilate (MA) (formulated as treated rice, consumption of treated seed was suppressed at
ReJeX-iT®AG-36, PMC Specialties Group, Cincinnati, OH) all levels. In a two-cup trial, rice consumption during the
was applied to a half-acre of blueberries at about 24 lb/ 4-day treatment phase was reduced relative to that during
acre. When captive cedarwaxwings were offered berries the 4-day pretreatment period in the 833 and 2,500 p/m
sprayed with MA and an equal number of unsprayed berries, groups but not at and 278 p/m.
they consumed 87 percent of the untreated berries and
73 percent of the MA-treated berries. Rapid degradation
through microbial activity was probably at least partially
responsible forthe ineffectiveness of the MA treatment.
DWRC Highlights Report: 1993/5
During 4-day trials in a 0.2-ha flight pen, 6 different 10-bird Chemical Repellants—DWRC scientists based atthe
flocks removed an average of 41 percent of the untreated Monell Chemical Senses Center in Philadelphia, PA,
rice seed on sample quadrats compared to 9 percent lost continue to collaborate with PMC Specialties Group and with
from plots having 2,500 p/m imidacloprid-treated seed. Low other DWRC field stations to develop MA as a practical bird
mean temperatures as well as the presence of avian repellant. During 1993, progress was made toward the
predators outside the flight pen appeared to increase the development and registration of a turf formulation (to repel
birds' consumption of treated rice in some of the flight-pen grazing geese) and a rice seed treatment (to repel
trials. Feeding rates were reduced in treated plots blackbirds). In addition, MA was successfully added to a
compared to those in control plots, but the redwings granular pesticide formulation to reduce nontarget hazards
displayed no adverse effects. Researchers estimated that that the pesticide presents to birds.
redwings ingested 13-16 percent of the imidacloprid initially
present on the seed. Thus, even at 2,500 p/m, red-winged Besides MA, a variety of other repellent materials were
blackbirds feeding normally acquired only a fraction ofthe identified and tested (e.g., turpentine, activated charcoal). A
imidacloprid calculated to be a lethal dose. patent describing the use of activated charcoal as a bird
repellant was submitted to the APHIS patent committee.
Methyl Anthranilate as a Bird-Repellent Rice Seed
—
Treatment In a series of two-cup feeding trials, red-winged DWRC-Monell scientists also collaborated with other Monell
blackbirds were given rice seed treated with MA (formulated scientists. University of Pennsylvania faculty members, and
as ReJeX-iTAG-36) at ratesof0, 0.1, 0.5, 1, and2.5 percent DWRC personnel to develop and test new, nonlethal rodent
by weight. When the birds' alternate food was untreated rice and deer repellants. The data indicate that any substance
seed, repellancywas evident at the 0.5-percent treatment containing sulfur may repel herbivores (and, incidentally,
rate. When the birds received a commercial bird chow as attract carnivores). Also, experiments suggest that
the alternate food, repellancy was obtained at the acetophenone derivativesthat repel birds may repel rodents
2.5-percent treatment rate. Thus, the type of alternative as well.
food can drastically affect expressions of a repellent effect.
—
Visual Repellants DWRC-Monell scientists evaluated the
In controlled small-plot field evaluations in Louisiana and relative effectiveness of white flags, black flags, and Mylar™
Texas, researchers tested red-winged blackbird responses streamers as snow-goose grazing deterrents. The results
to rice seed treated with MA at rates of 0.7, 1.7, and showed that white or black flags diminish grazing. Mylar
6.7 percent by weight. Results indicated a deterrent effect streamers were no more repellent that bare stakes in control
at the two higher levels but not at 0.7 percent. The repellent fields.
effect persisted for about 1 week afterseeding. —
Improvements in the formulation to retard degradation and Reducing Great-Tailed Grackle Damage to Citrus In
lengthen the period of MA activity on the seed should make recentyears, increased great-tailed grackle populations and
this a more effective bird deterrent. decreased citrus production inflicted by freeze damage have
combined to cause locally severe damage to citrus by
Methyl Anthranilate as a Bird Repellant on Ripening grackles in the lower Rio Grande Valley of Texas. In 1987,
—
Rice Researchers from the Florida field station conducted grackle damage to grapefruit alone was estimated to exceed
a small-plot field test in Vermillion Parish, LA, to evaluate $2.2 million. Grackles appear responsible for most of the
MA (formulated as ReJeX-iT) as a potential deterrent to damage that occurs to immature fruit in the spring and
blackbirds feeding on ripening rice. Fourtreatment groups ripening fruit in the fall and winter. Resident birds and their
of 10 plots each were used. Treatments were single MA offspring cause most of the damage that occurs in the late
applications of 16 and 32 kg/ha and a double application summerfrom July through September.
(1 week apart) of 16 kg/ha each. One group of plots served
as an unsprayed control. Bird activity on the plots was Although grackle frightening techniques appeareffective for
monitored daily for 3 weeks, and yields from the plots were reducing citrus damage during the fall and winter, no cost-
compared to evaluate treatment effectiveness. Although bird effective methods are available for reducing the bulk ofthe
activity in the unsprayed plots tended to exceed that in the damage that occurs in late summer. In cooperation with
sprayed plots, yield data indicated that the treatments had Texas Citrus Mutual and Texas ADC, DWRC scientists are
no effect. Additional evaluations employing largertest plots investigating population management strategies to reduce
should permit more definitive evaluation of this use of MA. localized summer resident populations responsible for
damage. Initial investigations have focused primarily on the
use of large (8-x8-x5-ft) walk-in live traps that could be used
to remove grackle populations humanely without affecting
nontarget wildlife.
DWRC
SI Highlights Report: 1993
Fourwalk-in trap designs including the modified Australian Fecundity and Diet of Roof Rats in a Macadamia
—
crow trap (MAC), a modified blackbird decoy trap, a bob Orchard Roof rats were snap-trapped in a macadamia
trap, and a ground entrance funnel trap designed by DWRC orchard fortwo crop seasons to determine seasonal
and Texas ADC were initially compared in field trials in changes in fecundity and diet. Captures included
South Texas. In the initial trial comparing MAC, decoy, and 903 males, 756 females, and 16 rats of unidentified sex;
bob traps, the bob trap was found to be ineffective and was males outnumbered females during all months of the study.
replaced with the funnel entrance trap. In two additional Immature and subadult rats were present in the orchard
trials, the funnel entrance trap captured between 1.6 and throughout the study and comprised 31 percent of captures.
8.4 grackles pertrapping day, which was more than 5 times The monthly percentage of adult females that were pregnant
the trapping rate of eitherthe MAC or decoy trap. The averaged 19 and varied from about 8 in June to almost 54 in
funnel trap was later evaluated in the summerfor reducing April. A monthly average of 3.9 embryos was detected per
grackle damage to citrus in South Texas. Grackles utilizing pregnant female. Fragments of macadamia nuts were
citrus groves were not readily attracted to these traps present in all 199 stomachs inspected and on average
positioned outside groves: only 24 and 16 grackles were represented 85 percent of the stomach contents (mean
caught in 2 groves, respectively, during 1 month of trapping. relative frequency). Insect fragments occurred in almost
At two other groves receiving less grackle use, trap capture two-thirds of the stomachs, with a mean relative frequency
rate was zero overthe same period. Further research is of 8 percent. Lepidopteran larvae were the most commonly
now proposed to investigate ways of enhancing trapping identified insect matter. Moss was found in 48 percent of
success at citrus groves and to examine alternative means the stomachs, with a mean relative frequency of 4 percent.
of reducing localized grackle populations associated with Grass seeds, fruit seeds, and noninsect animal material
citrus damage. were present in small amounts. These results suggest that
growers may need to apply control measures throughout the
Evaluation of Bait Markers for Monitoring Consumption crop cycle to keep rat damage at acceptable levels.
—
by Wild Rats The most commonly used method for
applying rodenticides in macadamia orchards may not be Effects ofTrapping on Rat Populations—and Subsequent
effective for reducing rat populations in some orchards. Damage and Yields of Macadamia Nuts The effects of
Growers typically broadcasttoxic baits on the orchard floor. snap trapping on rat populations in a Hawaiian macadamia
However, recent trapping and telemetry studies have orchard and subsequent damage and yields of nuts were
indicated that rats spend little time on the surface of the evaluated during two cycles. During the first cycle,
ground; most spend their days in burrows and their nights in 1,681 roof rats, 22 Polynesian rats, and 1 Norway rat were
the tree canopy. A better understanding of rodent feeding captured; 360 rats of undetermined species were captured
behavior in orchards could help identify locations most likely during the second crop cycle. Cumulative rat damage for
to be effective for baiting rats in macadamia orchards. the entire season varied from 0.4 to 1.3 percent of total
annual production in the trapped sections, and from 1.7 to
In orderto develop techniques to identify ratsthat consume 3.6 percent oftotal annual production in the control sections.
bait, DWRC researchers conducted a laboratory studyto However, trapping had no effect on yields: number of nuts,
determine the suitability of three nontoxic markers for mass per nut, and total mass of undamaged nuts did not
monitoring feeding by rats in macadamia orchards. A differ between the trapped and control sections. The results
markerwas mixed with nontoxic food and placed in various suggest the need to examine crop yield more closely in
locations in orchards to determine where rats are most likely assessing methods for managing rodent infestations in
to find and consume bait. The markers were metallic flake macadamia orchards. The commonly used indices based
particles that line the gastrointestinal tract, a fat-soluble dye on rodent activity and proportion of nuts damaged may
that marks subcutaneous fat, and an antibiotic that stains overestimate the impact of rodent depredations and
growing bones and teeth. Each markerwas added to exaggerate the effectiveness of control measures in
nontoxic baits and fed to captive rats, which were examined macadamia orchards. A large incidental take of birds points
at various intervals afterthe trial for evidence of feeding. to the need for more selective techniques beforetrapping is
The antibiotic was the most persistent of the markers and utilized as a damage control measure in Hawaiian
was selected for use in a field study to compare macadamia orchards.
consumption by rats of food placed in trees, on the ground,
or in burrows. The results should indicate the most effective
location forplacing rodenticide baits in macadamia orchards.
DWRCHighlights Report: 1993/7
—
Protection of Western Redcedar Western redcedar is a Translocation of the tableted denatonium benzoate into
majorcommercial tree species of the Pacific Nortliwest ponderosa pine and Douglas-firseedlings in pocket-gopher
utilized in construction for its decay-resistant properties and field tests was not detectable, and all tree seedlings
natural beauty as an exterior and interiorwood. surviving drought conditions were killed by pocket gophers.
Unfortunately, its foliage is preferred by deer, elk, mountain
beavers, and other animals. In making theirtree-planting At the translocation levels achieved so far, denatonium
decisions, foresters have long known that animal damage is benzoate has not damaged the plant species tested, but
a significant potential problem with western redcedarand furthertrials to obtain higher uptake will require examination
have planted little of it as a result. Now, with majorsupplies for phytotoxicity and anycorresponding repellancy. Further
of mature western redcedar inaccessible in national forests pen and field trials with deer, elk, mountain beaver, and
because of the need to protect endangered wildlife, pocket gophers are needed along with controlled
replanting this species on other sites has become a primary greenhouse or growth-chambertests using forestsoils.
forestry goal for providing products, creating forest diversity,
using a root-rot-resistant species where Douglas-fircannot Alternative Damage Control Methodsfor Pocket
—
establish, and protecting riparian zonesforanadromous fish. Gophers A numberof studies were conducted at DWRC's
formerfield station in Bend, OR, on nonlethal approaches
DWRC's Olympia field station began cooperative studies for reducing damage to seedlings by pocket gophers. These
with the U.S. Department of Agriculture's (USDA) Forest studies provided long-term longitudinal data on seedling
Service and MacFarlane-Smith, Inc. (Scotland) to examine survival and gopher activity. The alternative methods
potential foliar and systemic repellants to protect western addressed by these studies include the use of herbicides to
redcedar and determine the growth and damage periods reduce preferred gopherfood sources, grass planting to
when protection is needed in the Pacific Northwest. Initial reduce gopherfood sources, the use of barriers around
results on the Gifford Pinchot National Forest have shown seedlings, and double stocking seedlings. However, with
damage during the fall and winter by deer and elk with the closure of the Bend field station in 1984 and the transfer
partial protection being provided mainly by application of of the study participants to the Alaska Fish and Wildlife
powdered starling experimental repellant and a registered Research Center, the large, complex datasets had never
powdered-egg repellant (BGR®). An experimental coyote been analyzed.
urine formulation provided some protection. In some trials,
the addition of treated flagging suspended over previously In 1993, DWRC's statisticians had these data sets
heavilybrowsedtreeseedlingsenhanced redcedarprotection. keybatched and analyzed. Due to the size and complexity
of the data sets, the final interpretations remain incomplete,
Evaluation of Candidate Systemic Repellent but preliminary results indicate some promising alternatives
—
Formulations To Protect Conifers Pen and field trials to lethal control. One study, currently being prepared for
were conducted in Washington and Oregon in cooperation scientific publication, compared a control plot with a plot
with USDA's Forest Service, MacFarlane-Smith, Inc., and treated with the herbicide atrazine to reduce the forbs and
the Monell Chemical Senses Centerto evaluate formulations grasses that pocket gophers preferto eat. Seedling
of denatonium benzoate as a systemic repellant for conifers. survival, damage rates, and gopher activity were monitored
This material is used primarily as a bittering agent to on both plots for 5 years. The atrazine-treated plot showed
safeguard household products but has shown some promise a substantial reduction in gopher damage rates and greatly
in Canada, Great Britain, and Scandinavian countries as a increased survival of seedlings.
systemic animal repellant.
Control of Mountain Beaver Populations and —
In a variety oftrials by DWRC field station staff, denatonium Precommercial Thinning Affect Douglas-fir Growth
benzoate has been found to translocate into Douglas-fir and Established Douglas-fir plantations are often stem- and root-
western redcedarfoliage from root-zone applications. Initial girdled by mountain beaver at about the time of canopy
field and pen trials showed high variability in uptake of closure. Foresters frequently find that the crop trees left
denatonium benzoate in compositefoliage sample collections afterthinning are later killed or injured by mountain beavers.
taken at the time tree seedlings were offered to animals. Partially girdled or root-damaged trees are subject to
disease and windthrow. Both thinned and unthinned stands
Bitterproducts are not necessarily repellentto wildlife. Penned may therefore have poorly spaced trees and large, vacant
deer, for example, strongly preferred benzoate-treated areas caused by mountain beaverdamage.
western redcedar overtreated Douglas-fir. They ate all the
offered redcedar in 1 night but took a whole month to
consumethe same amount of Douglas-firseedlings. Mountain
beaver showed a similar preference forwestern redcedar.
8/DWRC Highlights Report: 1993