Eradication of Norway Rats for Recovery of Seabird Habitat on Langara Island, British Columbia

Introduced Rattus norvegicus (Norway rats) caused the decline of Synthliboramphus antiquus (ancient murrelets) and other seabirds breeding on Langara Island (approximately 3,100 ha), British Columbia. Using funds from the litigation settlement following the Nestucca oil spill, Environment Canada eradicated Norway rats using a technique developed in New Zealand which involved dispensing wax baits containing the anticoagulant brodifacoum at 50 ppm from fixed bait stations. Bait stations were placed every 75 to 100 m on a grid over the entire island (1 station/ha). Rats removed bait for 26 days, after which crews placed baits in protective plastic bags in each bait station. Stations loaded with baits were left on the island and rechecked four times over 2 years, after which bait stations and remaining bait were removed. The eradication succeeded. No signs of rats have been detected on Langara Island and its associated islands since January 1996. No rats were trapped during 1,700 trap‐nights following the poison campaign. Incisor marks of rats were not found on apples or oil‐dipped chew‐sticks. Corvus corax (common ravens) likely suffered greater than 50% mortality from the eradication after apparently gaining access to the poison directly from bait stations and from scavenging rat carcasses. A monitoring and response system is being developed in conjunction with current users of the islands. The success on Langara Island demonstrates how the technique proven on small New Zealand islands of less than 300 ha can be effectively extrapolated to much larger islands.     

Toxicity of cholecalciferol to rats in a multi-species bait

The effectiveness of Feracol?, a possum control paste bait containing 0.8% cholecalciferol, as a rodenticide has been assessed in cage and field trials. Caged rats were provided with toxic bait in choice and no-choice tests. Feracol? was readily eaten when presented as the sole food source or with other food, and was effective at killing rats in both situations. Wild-caught and laboratory rats (n =?35), comprising both ship (Rattus rattus) and Norway rats (R.?norvegicus), were presented with 30 g of Feracol? alone or with an equivalent toxic bait over 48 h. Thirty-four rats died in an average of 4.0 days. Having established that the paste, originally designed for possum control, is also an effective rodenticide for rat control, field trials were initiated with the paste delivered in the field in Philproof? and Striker? bait stations. Monitoring of rat numbers before and after application of toxic bait was undertaken at three trial sites, Lions Hut, Mangaone and Pakoakoa, in Te Urewera National Park in the North Island of New?Zealand. Rat population density was assessed using tracking tunnels. Philproof? bait stations containing 200 g of Feracol? were placed 50 m apart on grids at Lions Hut and monitoring was undertaken at one location per hectare using tracking tunnels. At Mangaone and Pakoakoa, two Striker? bait stations containing 18 g of Feracol? were sited at 25-m intervals on lines 150 m apart, and monitoring was undertaken with five lines of 10 tunnels at 50-m intervals. At Lions Hut, rat tracking decreased from 78% to 3% of tunnels tracked; at Mangaone the reduction was 51% to 0%; and at Pakoakoa from 36% to 0%. These trials demonstrate that Feracol? is effective at reducing both moderate and high concentrations of ship rats in the Philproof? and Striker? bait station delivery systems.     

The home range of ship rats (Rattus rattus) in beech forest in the Eglinton Valley,Fiordland, New Zealand: A pilot study

Abstract

Three male and two female ship rats (Rattus rattus) were radio‐tagged and tracked in beech (Nothofagus) forest in the Eglinton Valley, Fiordland, New Zealand over two field periods in 1996 and 2000. The home range of each animal was calculated using the minimum convex polygon method. Ranges of three male rats were 7.5, 9.1, and 11.4 ha whereas those of the female rats were 0.89 and 0.27 ha. The home ranges recorded for male rats were considerably larger than those reported from other studies in non‐beech forest. Ship rats are important predators of forest birds, and home range information could be used to provide a guide for trap or bait station spacing in beech forests. To carry out rat control in beech forests effectively, further studies are needed to determine if the results of this pilot study are typical, and if home ranges of ship rats change with season, or at various stages of the beech mast cycle.     

Fatty acid composition of the depot fats of the Polynesian rat,Rattus exulans,Tokelau Islands

The fatty acid composition of the stomach contents, adipose tissue, and perinephric fat of Polynesian rats (Rattus exulans Peale), from the Tokelau Is indicated that the dietary fat consisted mainly, if not exclusively, of coconut oil. Lower ratios of lauric : myristic acids were found in the depot fats of the Polynesian rats than in the dietary coconut oil. These results were consistent with chain elongation of lauric to myristic acid after ingestion, as previously reported in rats and other mammals.     

Hair type,intake, and detection method influence Rhodamine B detectability

Rhodamine B (RB) is a popular bait-marking tool in wildlife research, although its use has required many assumptions about marking reliability. These assumptions have limited dosage ranges and detection methods in research applications. Identification of alternate detection methods, hair types, and dosage rates could create new opportunities for RB use and potentially reduce adverse effects on target animals. We examined the relationship between hair types, dosage rate, and detection method for RB applications using black rats (Rattus rattus) in laboratory settings. We gave study animals varying doses of RB, and examined vibrissae and guard hairs for the detection of RB bands using ambient light, ultraviolet (UV) light, and fluorescence microscopy techniques. Fluorescence microscopy detected more RB marked hairs than UV light or ambient light. Fluorescence microscopy was more sensitive to RB dose rate detection; with receiver operating characteristic curves suggesting that the minimum dose rates at which RB intake can be correctly detected are 3.9 and 33 mg/kg for vibrissae and guard hairs, respectively. Guard hair RB detection was less reliable under ambient light and UV lamps, but equally detectable as vibrissae under fluorescence microscopy. Our results confirmed the interrelationship between dosage and detection methods in the efficacy of bait markers. We demonstrated that guard hairs can be a reliable hair type for the detection of RB. This application is less invasive than sampling animal tissues to detect bait uptake. © 2012 The Wildlife Society.     

Palatability and toxicity of fipronil as a systemic insecticide in a bromadiolone rodenticide bait for rat and flea control

Vector control in plague-infested areas requires a simultaneous killing of rodents and their fleas. We investigated the efficacy of a combination of a systemic insecticide, fipronil, in a rodenticide bait formulation under laboratory conditions. Four different concentrations of fipronil (0.05%, 0.005%, 0.0005% with acetone as a solvent, and 0.05% with propylene glycol as a solvent) and two controls (solvents only) were combined with the rodenticide bait (crushed organically grown wheat with 0.005% bromadiolone). Each concentration was offered together with an untreated non-poisonous challenge bait to 10 singly caged Rattus rattus L., each with 100 rat fleas Xenopsylla cheopis Rothschild (Siphonaptera: Pulicidae) in the nest. Treated bait consumption was relatively low and an unsatisfactory rat mortality of around 50% only was obtained in all tests. The palatability of the bait, however, was not affected by the fipronil concentration. Even at the lowest fipronil concentration, average flea mortality was still above 95%, and doses of more than I mg fipronil per kg rat body weight gave a nearly complete kill of fleas. Fipronil can be highly effective as a systemic insecticide to for flea control, provided that a more attractive bait base for roof rats is used.     

Barrier spraying to control the malaria vector Anopheles albimanus: laboratory and field evaluation in the Dominican Republic

Abstract. To develop a new strategy for control of exophilic/exophagic malaria vectors which rest on peridomestic foliage, Anopheles albimanus was used for laboratory bioassays of mosquito adulticides applied to various vegetation types. Of the three classes of insecticide tested, the pyrethroid (permethrin at 112 g/ha) showed greater foliar persistence than either the carbamate (bendiocarb at 340g/ha) or the organophosphorus compound (malathion at 277g/ha). Field evaluation of barrier spraying against An.albimanus was evaluated in rural villages of southwest Dominican Republic during 1989. The pyrethroid deltamethrin was sprayed aerially for ultra-low volume application at treatment rates of 17-19ga.i./ha in a radius of 500m around two villages. An.albimanus were monitored by light-traps and human bait collections at both treated villages, compared with two similar untreated villages, up to 9 nights post-treatment. Densities of female An.albimanus were significantly reduced in the sprayed villages for at least 8 or 9 nights. Further evaluation of barrier spraying is recommended to determine optimal pyrethroid formulations and applications rates, their impact on non-target fauna and efficacy against malaria transmission.     

Efficacy of triapenthenol as a safener against metribuzin injury in soybean (Glycine max) cultivars

Triapenthenol or RSW 0411 (B(-cyclohexalmethylene)-gamma-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol), a triazole plant growth regulator, applied preemergence as a separate broadcast application, protected tolerant and midtolerant soybean cultivars from metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one)-induced necrotic injury, and stabilized seedling fresh weight and dry weight loss to herbicide treatment. Soybean yields were not significantly reduced by triapenthenol treatment alone, but 1.12 kg ai/ha metribuzin and a 0.56 kg ai/ha triapenthenol plus 1.12 kg ai/ha metribuzin combination reduced crop yield averaged across cultivars.     

Suitability of Aerially Sown Artificial Baits as a Technique for Poisoning Feral Goats

The preferences of a captive herd of goats with feral ancestry were evaluated for 11 artificial pest control baits and commercial stock feed pellets. A commercial stock food pellet (based on barley, bran, and oats) was the most preferred basic bait. A mixture of 2% diced Griselinia littoralis (broadleaf) leaves (a preferred natural food plant) and 2% molasses (per weight of basic bait) increased palatability of this basic bait. The best lured bait was aerially sown at I kg ha(-1) in a 380 ha area with about 50 feral goats. Only 25% of the goats were shown by the biological tracer iophenoxic acid to have eaten baits after 8 days. We conclude that one-hit aerial poisoning of goats is unlikely to be effective as a control method because most goats are unlikely to eat food from off the ground.     

Road and topography effects on invasion: edge effects in rat foraging patterns in two oceanic island forests (Tenerife, Canary Islands)

We studied the effect of road edges on foraging activity by introduced ship or roof rats Rattus rattus in road-fragmented laurel and pine forests on Tenerife (Canary Islands), By using selective baited stations enabling only foraging by rats we assessed bait removal rates along a road-interior gradient and different topographic locations. We recorded higher removal rates in the laurel than in the pine forest regardless of the distance to road. We detected an edge effect of paved roads on introduced rat foraging. Removal rates were significantly greater along road edges than in forest interior in the laurel forest but not In the pine forest. Rats were more active along road habitats in forest ridges and slopes than in ravine beds in the laurel forest. There was no difference between topographic locations in rat activity at any distance from the road in the pine forest. It is suggested that variation in foraging intensity by introduced rats in road-fragmented forests on these islands may depend, among other factors, on forest type, road edge effects and topographic pattern of the landscape.     

Efficacy of broadcast and perimeter applications of S-methoprene bait on the red imported fire ant in grazed pastures

The red imported fire ant, Solenopsis invicta (Buren), is a major pest in the United States because of its painful sting. Toxic bait has been an important management tool against fire ants, but site registrations prohibit applications of most baits on grazed pastures. Extinguish, containing the insect growth regulator methoprene, was selected for this study because it has a broad site registration that includes grazed pastures. The primary objective of this research was to evaluate the efficacy for control of red imported fire ants by using broadcast applications of methoprene bait at a label rate of 1,121 g/ha versus applications around the perimeter of a target area at the reduced rate of 280 g/ha. Grazed pastures in Lee County, Alabama, and Chambers County, Alabama, were selected for this study, with broadcast treatments, perimeter treatments, and controls replicated three times at each site. All mounds were counted and rated using the USDA population index before applications and then at 8 and 16 wk posttreatment. Perimeter applications did not significantly reduce S. invicta mound abundance, but bait treatments significantly reduced mound abundance at 16 wk posttreatment at site 1 where applications were conducted in early evening. However, broadcast applications were not effective at site 2 where treatments were conducted in early morning with warmer temperatures. Emergence of winged alates was observed at 12 wk posttreatment, followed by a high density of incipient mounds that may have masked the full treatment effect of methoprene applications at site 2. Methoprene bait was effective in reducing abundance of S. invicta only when full label rates were applied.     

The effectiveness of poison bait stations at reducing ship rat abundance during an irruption in a Nothofagus forest

Abstract

Ship rats exhibit large increases in abundance (irruptions) following heavy beech seedfall in New Zealand's Nothofagus forests. Predation by rats at high density severely damages native fauna populations. In 2006 the Department of Conservation undertook a management experiment in the Eg‐linton Valley to see if they could protect endangered species during a rat irruption. Poison (0.15% 1080, followed by 0.0375% coumatetralyl, or Racumin®) was laid in bait stations, and the consequences for rat abundance and survival were estimated. All 10 radio‐tagged rats died, suggesting that 1080 had a high impact on the rat population. The two rats that made the smallest daily movements survived longer than the others. Live trapping documented a reduced abundance of rats within the poison area (450 ha) after 1 month of poisoning. However, after 4 months of poisoning, the abundance of rats had begun to recover. Further investigation is needed on acceptance of Racumin® to rats, optimum spacing of bait stations for rats, and bait competition between rats and mice when densities of both species are high.     

Palatability and efficacy to possums and rats of pest control baits containing bird repellents

Repellents used to reduce by-kill of birds during pest control must not compromise acceptance by target species. Two repellents combined, anthraquinone (AQ; 0.4 g kg^?1) and d-pulegone (DP; 1.0) did not reduce the palatability of blue-coloured carrot baits to laboratory rats (Rattus norvegicus); nor did DP (2.0). Green-coloured carrot baits coated with AQ, DP or AQ + DP were taken from bait stations by wild possums (Trichosurus vulpecula) and rats. Toxic (1080) bait coated with AQ (0.4) and peanut oil (0.1) had reduced palatability but was accepted by laboratory rats. However, laboratory rats did not consume enough baits coated with AQ and bacon, peanut butter, cinnamon or DP to be killed. Anthraquinone (0.4 or 0.8) plus cinnamon and DP (0.5) did not affect palatability or lethality to captive ship rats (R. rattus) or possums. Anthraquinone and DP as surface coatings on baits are therefore acceptable to possums and possibly rats, at concentrations that deter some bird species.     

Ultrasonic vocalizations and social learning of food preferences by female Norway rats

We examined whether ultrasonic vocalizations facilitate social learning of food preferences in female Norway rats, Rattus norvegicus. Females produced ultrasonic vocalizations at higher rates when they were reunited with a familiar conspecific if one member of the reunited pair had eaten an unfamiliar food while the pair members were separated. However, the influence of demonstrator rats on food choices of their observers was as great in pairs of rats that had been devocalized surgically as it was in sham-operated controls. The latter result is not consistent with the hypothesis that ultrasonic vocalizations facilitate social learning of food preferences in Norway rats.     

Residual Mn and associated soybean yield response from MnSO4 application on a sandy loam soil

Summary A field experiment was initiated in 1977 to evaluate soybean (Glycine max (L.) Merr.) response to rates of broadcast Mn and was continued in 1978 to determine the residual effects of applied Mn. This study was conducted on a Dragston fine sandy loam soil with an initial pH of 6.0 and 2.5% organic matter. In 1977 the 40kg Mn/ha rate increased seed yields by 900 kg/ha and raised leaf tissue Mn concentration from 10.3 to 16.1 g Mn/g. Residual Mn increased seed yield and leaf Mn concentration. Reapplied Mn produced higher yields and tissue Mn levels than the residual Mn. The Mitscherlich plant growth model r=0.67^**, fit the relationship between yield and leaf Mn concentration. Double acid extractable Mn in soil sampled in 1978 was linearly related to broadcast Mn and soybean yields. Applied Mn increased Mn concentrations of soybean seed parts by 97%, 182% and 109% in the cotyledon, embryo and seedcoat, respectively.     

The impacts of rats on the endangered native flora of French Polynesia (Pacific Islands): drivers of plant extinction or coup de grâce species?

Although rats have clearly contributed to bird extinctions on islands, their role in plant extinctions is not as clear. Paleoenvironmental studies suggest rats were responsible for the demise of several island palm species. French Polynesia’s islands provide an opportunity to evaluate “modern” impacts of rats on native flora. Our study shows that 15 threatened taxa (nine families) are damaged by rats. All 12 subjected to seed predation are woody plants with large-seeded drupes. Three experience severe predation and recruitment depression (Santalum insulare, Ochrosia tahitensis, Nesoluma nadeaudii). Three-year monitoring of Polynesian sandalwood (Santalum insulare) populations in Tahiti during rat control suggested that over 99% of fruits were eaten before ripening. Seed predation on sandalwood appeared to be lower on islands without black rats Rattus rattus. Studies from Indo-Pacific islands document rat impact on at least 56 taxa (28 families). Certain families (Arecaceae, Elaeocarpaceae, Rubiaceae, Santalaceae, and Sapotaceae) are particularly vulnerable to seed predation. Other soft-barked trees (Araliaceae, Euphorbiaceae, and Malvaceae) suffer from stem or bark damages, especially during dry seasons. Although rats depress seedling recruitment and alter vegetation dynamics, no evidence demonstrates that they are solely responsible for current plant extinctions. Most of French Polynesia’s endangered species impacted by rats occur in severely degraded habitats. We therefore suggest that rats can be viewed more as coup de grace species (i.e., that give the final stroke of death), rather than as main drivers of plant extinctions. More research is needed to clarify the impacts of rat species and their importance in plant population decline or demise.     

The control of re-invasion by rats of part of a sewer network

Re-infestation by rats (Rattus norvegicus Berk.) of a section of a sewer network was studied by recording bait consumption in the manhole chambers for periods up to 18 weeks after each of three attempts to rid the section of rats. The mean rate of increase of the rat population was of the order of 20 % per week both when the section was surrounded by a permanently poison-baited zone as a barrier against re-invasion from the connected, still heavily-infested sewers, and when this barrier was absent. When, however, infestation in the connected sewers was reduced by poisoning, and the poison-bait barrier was maintained, the mean weekly rate of increase in the section declined to 4·4% and could be attributed substantially to breeding. It is concluded that the type of poison-bait barrier used in the present trials is insufficient to prevent invasion of one part of a sewer network from another if the population density in the latter is high.     

Effects of alpha-chlorohydrin on the male reproductive tissues of the Polynesian rat,Rattus exulans

Abstract

Doses of α-chlorohydrin (‘Epibloc’) were administered by gavage to mature male Polynesian rats (Rattus exulans) at 100, 200, and 300 mg per kg body weight. Animals that survived were sacrificed either 1 day or 7 days later for assessment of epididymal and testicular cytology and sperm viability. Two of 10 animals died 6 days after treatment with 100 mg/kg; 1/6 died within 24 h of treatment with 200 mg/kg, though 6/10 died when left for 7 days; 300 mg/kg was lethal to all 3 rats tested. After 1 day, microscopic lesions were observed in the Initial Segment of the epididymis of 4/6 rats dosed with 100 mg/kg and in all 5 of the 200 mg/kg group; however, in only one animal at the higher dose level was the damage severe enough to cause epithelial exfoliation and potential blockage of the lumen. In all the animals that survived for 7 days testicular and epididymal cytology were normal, and viable spermatozoa were present at all levels of the tract. Autopsies revealed no evidence of gross epididymal lesions in any of the animals that died from the drug. We conclude that although α-chlorohydrin causes minor lesions in the epididymis of this feral species, the damage appears to be reversible in animals that survive an acute dose, and the drug cannot be considered an effective chemosterilant, as distinct from a poison.     

The Effect of Nitrogen Fertilization on Fusarium Head Blight Development and Deoxynivalenol Contamination in Wheat

The impact of nitrogen (N) fertilization on the development of Fusarium head blight (FHB) in wheat and the resulting deoxynivalenol (DON) contamination in the kernels was studied. In a first experiment, the disease was assessed on two locations under natural infection pressure. Five different types of nitrogen fertilizer (both organic and mineral) were investigated, each applied at five input rates from 0 to 160 kg N/ha. With all fertilizers, a significant increase of disease intensity was observed with increasing N input, while the type of N fertilizer had poor or no effects on FHB. Depending on the fertilizer used, the percentage of diseased spikelets increased from 2.2% at zero N rate up to 6.6% at 160 kg N input per hectare. In a second series of trials, three spring wheat varieties including one Durum wheat line were artificially inoculated with a Fusarium graminearum and a F. culmorum strain, known producers of DON. A mineral N fertilizer was applied at five input levels from 0 to 160 kg N/ha. A significant increase in FHB intensity and DON contamination in the grain was observed with increasing N from 0 to 80 kg/ha. At higher input rates, relevant in contemporary crop husbandry, disease intensity and toxin contamination remained at constant levels. It is concluded that adaptation of N fertilization represents no relevant tool in managing FHB in practical wheat cultivation.     

Bait Stations for Detection and Control of Alien Rats in Galapagos

ABSTRACT Alien rats have impacted native systems worldwide, yet wildlife managers lack techniques to efficiently monitor for rodent invasions where native rodents are present and to control alien rodents sympatric with native rodents. We tested the ability of vertical bait stations to exclude native rodents in the Galapagos Islands, Ecuador. Norway rats (Rattus norvegicus) appeared able to enter all station sizes, whereas black rats (R. rattus) were excluded from larger stations. The endemic rodents Oryzomys bauri and Nesoryzomys narboroughi were unable to enter bait stations of any size, but N. swarthi entered the smallest station. Differences in climbing technique contributed to the advantage of alien rodents over endemic species. Our technique provides wildlife managers in the Galapagos, and potentially other islands with native rodents, a means for early detection and control of alien rats.