Management of the stinging ant Myrmica rubra, using a baited granular formulation of hydramethylnon, 1997
No abstract available.
Arthropod Management Tests↗
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Arthropod prey for riparian associated birds in headwater forests of the Oregon Coast Range
Headwater riparian areas occupy a large proportion of the land base in Pacific Northwest forests, and thus are ecologically and economically important. Although a primary goal of management along small headwater streams is the protection of aquatic resources, streamside habitat also is important for many terrestrial wildlife species. However, mechanisms underlying the riparian associations of some terrestrial species have not been well studied, particularly for headwater drainages. We investigated the diets of and food availability for four bird species associated with riparian habitats in montane coastal forests of western Oregon, USA. We examined variation in the availability of arthropod prey as a function of distance from stream. Specifically, we tested the hypotheses that (1) emergent aquatic insects were a food source for insectivorous birds in headwater riparian areas, and (2) the abundances of aquatic and terrestrial arthropod prey did not differ between streamside and upland areas during the bird breeding season. We found that although adult aquatic insects were available for consumption throughout the study period, they represented a relatively small proportion of available prey abundance and biomass and were present in only 1% of the diet samples from only one of the four riparian-associated bird species. Nonetheless, arthropod prey, comprised primarily of insects of terrestrial origin, was more abundant in streamside than upland samples. We conclude that food resources for birds in headwater riparian areas are primarily associated with terrestrial vegetation, and that bird distributions along the gradient from streamside to upland may be related to variation in arthropod prey availability. Because distinct vegetation may distinguish riparian from upland habitats for riparian-associated birds and their terrestrial arthropod prey, we suggest that understory communities be considered when defining management zones for riparian habitat.
Oregon↗
Distribution of invasive ants and methods for their control in Hawai'i Volcanoes National Park
The first invasive ants were detected in Hawai`i Volcanoes National Park (HAVO) more than 80 years ago. Ecological impacts of these ants are largely unknown, but studies in Hawai`i and elsewhere increasingly show that invasive ants can reduce abundance and diversity of native arthropod communities as well as disrupt pollination and food webs. Prior to the present study, knowledge of ant distributions in HAVO has primarily been restricted to road- and trail-side surveys of the Kīlauea and Mauna Loa Strip sections of the park. Due to the risks that ants pose to HAVO resources, understanding their distributions and identifying tools to eradicate or control populations of the most aggressive species is an important objective of park managers. We mapped ant distributions in two of the most intensively managed sections of the park, Mauna Loa Strip and Kahuku. We also tested the efficacy of baits to control the Argentine ant ( Linepithema humile ) and the big-headed ant ( Pheidole megacephala ), two of the most aggressive and ecologically destructive species in Hawai`i. Efficacy testing of formicidal bait was designed to provide park managers with options for eradicating small populations or controlling populations that occur at levels beyond which they can be eradicated. Within the Mauna Loa Strip and Kahuku sections of HAVO we conducted systematic surveys of ant distributions at 1625 stations covering nearly 200 km of roads, fences, and transects between August 2008 and April 2010. Overall, 15 ant species were collected in the two areas, with 12 being found on Mauna Loa Strip and 11 at Kahuku. Cardiocondyla kagutsuchi was most widespread at both sites, ranging in elevation from 920 to 2014 m, and was the only species found above 1530 m. Argentine ants and big-headed ants were also found in both areas, but their distributions did not overlap. Surveys of Argentine ants identified areas of infestation covering 560 ha at Mauna Loa Strip and 585 ha at Kahuku. At both sites, upper boundaries of big-headed ants coincided with lower boundaries of Argentine ants. Significantly, Wasmannia auropunctata (little fire ant) was not detected during our surveys. Formicidal baits tested for controlling Argentine ants included Xstinguish TM (containing fipronil at 0.01%), Maxforce ® (hydramethylnon 1.0%), and Australian Distance ® (pyriproxyfen 0.5%). Each bait was distributed evenly over four 2500 m 2 replicate plots. Applications were repeated approximately four weeks after the initial treatment. Plots were subdivided into 25 subplots and ants monitored within each subplot using paper cards containing tuna bait at approximately one week intervals for about 14 weeks. All treatments reduced ant numbers, but none eradicated ants on any of the plots. Xstinguish TM produced a strong and lasting effect, depressing ant abundance below 1% of control plot levels within the first week and for about eight weeks afterward. Maxforce ® was slower to attain maximum effectiveness, reducing ants to 8% of control levels after one week and 3% after six weeks. Australian Distance ® was least effective, decreasing ant abundance to 19% of control levels after one week with numbers subsequently rebounding to 40% of controls at four weeks and 72% at 10 weeks. In measurements of the proportion of bait cards at which ants were detected, Xstinguish TM clearly out-performed Maxforce ® , reaching a minimum detection rate of 3% of bait cards at one week compared to a low of 19% for Maxforce ® two weeks following the second treatment. Although ant abundances were dramatically reduced on Xstinguish TM plots, it is not currently registered for use in the USA. Our results suggest that ant abundance can be greatly reduced using registered baits, but further research is needed before even small-scale eradication of Argentine ants can be achieved. Formicidal baits tested to control big-headed ants included Amdro ® (hydramethylnon 0.75%), Xstinguish TM (fipronil 0.01%), Extinguish ® Plus (a blend of hydramethylnon 0.365% and S- methoprene 0.25%), and Australian Distance ® Plus (hydramethylnon 0.365% and pyriproxyfen 0.25%). Application methods were the same as used for Argentine ants, with baits being applied on two occasions (approximately four weeks apart) on four 2500 m 2 replicate plots. All four baits reduced populations to below 2% of control plot levels within one week of treatment. Amdro ® was particularly effective as no ants were detected on two of the four Amdro ® plots immediately following treatment. Suppression was long-lived in three of the treatments; Amdro ® , Australian Distance ® Plus, and Extinguish ® Plus all maintained ant abundances at levels less than 1% of control plots over 12 weeks of study. In contrast, ant abundances in Xstinguish TM plots rose to 7% of control plots after four weeks and 20% after 10 weeks. Our results corroborate other recent studies indicating that small populations of big-headed ants can be controlled in natural areas using products registered in the USA.
Hawaii↗
Comparative demographics of a Hawaiian forest bird community
Estimates of demographic parameters such as survival and reproductive success are critical for guiding management efforts focused on species of conservation concern. Unfortunately, reliable demographic parameters are difficult to obtain for any species, but especially for rare or endangered species. Here we derived estimates of adult survival and recruitment in a community of Hawaiian forest birds, including eight native species (of which three are endangered) and two introduced species at Hakalau Forest National Wildlife Refuge, Hawaiʻi. Integrated population models (IPM) were used to link mark–recapture data (1994–1999) with long-term population surveys (1987–2008). To our knowledge, this is the first time that IPM have been used to characterize demographic parameters of a whole avian community, and provides important insights into the life history strategies of the community. The demographic data were used to test two hypotheses: 1) arthropod specialists, such as the ‘Akiapōlā‘au Hemignathus munroi , are ‘slower’ species characterized by a greater relative contribution of adult survival to population growth, i.e. lower fecundity and increased adult survival; and 2) a species’ susceptibility to environmental change, as reflected by its conservation status, can be predicted by its life history traits. We found that all species were characterized by a similar population growth rate around one, independently of conservation status, origin (native vs non-native), feeding guild, or life history strategy (as measured by ‘slowness’), which suggested that the community had reached an equilibrium. However, such stable dynamics were achieved differently across feeding guilds, as demonstrated by a significant increase of adult survival and a significant decrease of recruitment along a gradient of increased insectivory, in support of hypothesis 1. Supporting our second hypothesis, we found that slower species were more vulnerable species at the global scale than faster ones. The possible causes and conservation implications of these patterns are discussed.
Hawaii↗
The Haleakala Argentine ant project: A synthesis of past research and prospects for the future
1. The Haleakala Argentine Ant Project is an ongoing effort to study the ecology of the invasive Argentine ant in the park, and if possible to develop a strategy to control this destructive species. 2. Past research has demonstrated that the Argentine ant causes very significant impacts on native arthropods where it invades, threatening a large portion of the park’s biodiversity in subalpine shrubland and alpine aeolian ecosystems. 3. Patterns of spread over the past 30+ years indicate that the invasion process is influenced to a substantial degree by abiotic factors such as elevation, rainfall and temperature, and that the ant has not reached its potential range. Predictions of total range in the park suggest that it has only invaded a small fraction of available suitable habitat, confirming that this species is one of most serious threats to the park’s natural resources. 4. Numerous experiments have been conducted since 1994 in an attempt to develop a method for eradicating the Argentine ant at Haleakala using pesticidal ant baits. Thirty baits have been screened for attractiveness to ants in the park, and ten of these were tested for effectiveness of control in field plots. While some of these baits have been very effective in reducing numbers of ants, none has been able to eliminate all nests in experimental plots. 5. Research into a secondary management goal of ant population containment was initiated in 1996. By treating only expanding margins of the park’s two ant populations with an ant pesticide, rates of outward spread were substantially reduced in some areas. While this strategy was implemented from 1997 to 2004, it was ultimately discontinued after 2004 because of the difficulty and insufficient effectiveness of the technique. 6. In order to achieve the types of results necessary for eradication, the project would probably need to explore the possibility of developing a specialized bait, rather than relying on a commercially produced bait. An alternative would be to pursue approval to use Xstinguish bait, a commercial bait manufactured in New Zealand and not registered for use in the US, which has yielded good results against Argentine ants. Either route would involve significant regulatory hurdles. Because the baits ultimately used would likely be liquid or paste in form, there would also be major logistical challenges in devising methods to successfully apply the baits across the two large ant populations at Haleakala.
Technical Report↗
Limiting spread of a unicolonial invasive insect and characterization of seasonal patterns of range expansion
Limiting dispersal is a fundamental strategy in the control of invasive species, and in certain situations containment of incipient populations may be an important management technique. To test the feasibility of slowing the rapid spread of two Argentine ant ( Linepithema humile ) supercolonies in Haleakala National Park, Hawaii, we applied ant bait and toxicant within an experimental plot situated along a supercolony boundary. The 120×260 m plot simulated a small section of what could potentially be a 120 m wide treatment encompassing the entire expanding boundaries of both supercolonies. Foraging ant numbers at baited monitoring stations decreased sharply within two weeks after treatment, and ant spread was completely halted within the plot for at least one year. In contrast, an adjacent untreated colony boundary advanced an average of 65.2 m over the course of 1 year. Most of this spread took place in the summer and fall, at the time of highest ant abundance at bait monitoring stations, while no outward dispersal occurred during the spring and early summer. These patterns are consistent with the hypothesis that local budding dispersal in this unicolonial species stems from density dependent pressure rather than inherent founding behavior associated with mating. Based on results from this experiment, we are investigating the effectiveness of annual boundary treatments in slowing the Argentine ant invasion at Haleakala National Park. The goals of this program are to protect populations of native arthropods and to keep options open for eventual attempts at eradication.
Hawaii↗
Effects of climate change on plague exposure pathways and resulting disease dynamics
Introduction and Objectives: Sylvatic plague, a zoonotic flea-borne disease, caused by the bacterium Yersinia pestis , is relevant to the Department of Defense (DOD), because prairie dogs and other susceptible rodents are present on military installations in several western states. Arthropod-borne diseases, like plague, are thought to be particularly sensitive to local climate conditions. Expected changes in temperature and humidity over the next several decades will likely increase the geographical expansion of plague outbreaks in wildlife. Through a combination of field and laboratory work, along with data-driven modeling, we evaluated the potential effects of climate change on plague exposure pathways in prairie dogs and associated rodents to provide guidance to DOD partners regarding the potential for future outbreaks. Briefly, our specific objectives were to determine the relation between local climate conditions and the prevalence of plague and other pathogens while assessing the ecological roles of specific rodent hosts and vector species in plague dynamics, evaluate flea intensity on rodent hosts and in burrows in relation to local climate conditions, and develop models to predict the effects of climate change on plague dynamics. Technical Approach: Using data and samples collected during a large field study on the effectiveness of vaccination to manage plague in prairie dogs, we assessed rodent/flea assemblages, pathogen prevalence in fleas, and determined how local climate conditions influence flea development rates and relative abundance. Live animals (prairie dogs and some small rodents) were trapped to collect fleas and other samples on 46 prairie dog plots in 6 western states, many sites near DOD lands. At seven additional locations on a latitudinal gradient, fleas were collected from burrows several times per year to assess seasonality and effects of local climate conditions on flea abundance. These data were then used to develop predictive models that could be used to test specific hypotheses. Results: We determined that flea developmental rates, on-host flea abundance, species composition of the flea community, and burrow temperatures varied across a latitudinal gradient. Rodent and flea community composition and abundance differed geographically and were highly specialized. Flea-switching between prairie dogs and short-lived rodents was rare. Flea development rates, on-host flea abundance, and burrow temperatures increased with increasing ambient temperature. Although relative humidity can affect flea development, burrow humidity was uniformly high (~85%) across sampling sites and seasons. A large increase in the number of fleas found on a prairie dog colony, coupled with a greater number of infested burrows, could have substantial effects on plague dynamics in the western United States as the climate warms. In addition to affecting flea load, climate change may also influence body condition of prairie dogs by reducing the amount of forage. This may result in animals being more tolerant of high flea loads (less engaged in grooming behavior) and more vulnerable to disease.
Arizona, Montana, South Dakota, Texas, Utah, Wyomi↗
BLM Density Management and Riparian Buffer Study: Establishment Report and Study Plan
The Bureau of Land Management (BLM), Pacific Northwest Research Station (PNW), U.S. Geological Survey (USGS), and Oregon State University (OSU) established the BLM Density Management and Riparian Buffer Study (DMS) in 1994 to demonstrate and test options for young stand management to meet Northwest Forest Plan objectives in western Oregon. The primary objectives of the DMS are to evaluate the effects of alternative forest density management treatments in young stands on the development of important late-successional forest habitat attributes and to assess the combined effects of density management and alternative riparian buffer widths on aquatic and riparian ecosystems. The DMS consists of three integrated studies: initial thinning, rethinning, and riparian buffer widths. The initial thinning study was installed in 50- to 80-year-old stands that had never been commercially thinned. Four stand treatments of 30-60 acres each were established at each of seven study sites: (1) unthinned control, (2) high density retention [120 trees per acre (TPA)], (3) moderate density retention (80 TPA), and (4) variable density retention (40-120 TPA). Small (1/4 to 1 acre in size) leave islands were included in all treatments except the control, and small patch cuts (1/4 to 1 acre in size) were included in the moderate and variable density treatments. An eighth site, Callahan Creek, contains a partial implementation of the study design. The rethinning study was installed in four 70- to 90-year-old stands that previously had been commercially thinned. Each study stand was split into two parts: one part as an untreated control and the other part as a rethinning (30-60 TPA). The riparian buffer study was nested within the moderate density retention treatment at each of the eight initial thinning study sites and two rethinning sites. Alternative riparian buffer widths included: (1) streamside retention (one tree canopy width, or 20-25 feet), (2) variable width (follows topographic and vegetative breaks, 50 feet slope distance minimum), (3) one full site-potential tree height (approximately 220 feet), and (4) two full tree heights (approximately 440 feet). A second round of density management manipulations are now being planned for implementation beginning in 2009. Stem density will be reduced in the high, moderate, and variable density treatments and most existing riparian buffers, leave islands, and patch cuts will remain in place. Remeasurement, data management, and analysis are ongoing for three long-term, core components of the DMS: vegetation, microclimate, and aquatic vertebrates. In addition, several short-term collaborative studies have been completed on these sites, including leave island effectiveness as refugia, treatment response of terrestrial and aquatic arthropods, and smaller-scale studies of fungal, lichen, and bryophyte community response. Additional collaborative studies are encouraged on DMS sites.
Scientific Investigations Report↗