Differential trappability of small mammals in three habitats of Southeastern Brazil.

We compared the trappability of marked and unmarked individuals in species of marsupials and rodents of three tropical assemblages of small mammals in Brazil. Two studies used trapping grids, one in cerrado and the other in an Atlantic forest reserve, whereas the study in a rural area used transects. In the two studies using trapping grids, marked animals were frequently more trappable than unmarked ones, but in some species this difference was not significant. In the rural area, marked and unmarked animals did not differ significantly. The number of recaptures per resident animal was higher in the two studies using trapping grids than in the rural area where transects were used. Differences in trappability between the three studies might have been caused by differences not only in trapping design (grids vs. transects), but also in the type of trap used, bait, and habitat. Although differential trappability tends to be considered the rule in small mammals, these results suggest that trappability of marked and unmarked animals may be specific for the particular combination of sampling design, field methods, and habitat under study.     

The influence of trap type on evaluating population structure of the semifossorial and social rodent <Emphasis Type="Italic">Octodon degus</Emphasis>

Trap type may influence captures of individuals in different age-sex categories in small mammal studies, resulting in biased population and demographic information. We deployed 4 live trap types at burrow systems of the rodent, Octodon degus Molina, 1782, in central Chile to determine trap efficacy in capturing individuals of 6 demographic categories. We captured 2672 individuals in 17 709 trap days (15.1% trapping success). Tomahawks were the most efficient trap capturing half of individuals during both years, followed by mesh Sherman traps, large Sherman traps, and medium Sherman traps in 2005. All trap types equally sampled sexes. Large and medium Sherman traps provided similar demographic structure, where half of the individuals captured were pups; Tomahawk traps sampled more adults than pups. Relative captures of pups were similar across different trap types, suggesting that pups are equally sampled by each of the deployed trap types. Relative captures of adults were lower in Sherman traps, suggesting that this age class avoided solid-walled traps. For Octodon degus, the sole use of Tomahawk traps may produce sufficient, unbiased demographic data. Only 4 trap mortalities occurred (0.15%). Researchers may minimize trap mortality without compromising sufficient demographic sampling by trapping during peak animal activity.     

A field study of the effect of prebaiting on censusing by the capture-recapture method in a vole population

Populations of the vole, Clethrionomys rufocanus, in a lowland woodlot of Hokkaido were studied for the presence of effects of prebaiting on censusing by the capture-recapture method. A grid of 121 live-traps, spaced 5 m apart, was laid out on each of two plots, one of which alone was prebaited three days long. Owing to very high densities and great trap-efficiency, sufficient and favourable samples could be available for statistical analysis, except the trend of delayed catch for young in sampling. The population on either plot, however, proved to be markedly variable in catchability of unmarked animals in the course of trapping; while the probability of recapture was counted as invariable on the average from day to day, the recapture frequency was different between juveniles, subadults and adults. Needless to say, the catchability was distinctly greater for marked voles than for unmarked ones, whether prebaited or not, through the trapping period, except that the first-day catchability for unmarked ones on the prebaited plot seems not to be significantly lower than that for marked ones. Consequently, it turns out that the prebaiting has almost never helped to eliminate the important bias induced by differential trap-response of marked and unmarked animals; its contribution is only that the catchability for unmarked ones is slightly higher on the part of the prebaited plot on earlier days of the period. In accordance with the heterogeneous catchability, the Γ-form distribution analogous to the geometric could be applied with thorough fitness to the capture frequency in order to estimate the whole populations. The fact that the estimates are reliable, being not at any rate underestimates, was further confirmed by the result of a follow-up work conducted by means of the removal method with wider trap-spacing which brought forth distinct underestimation chiefly referable to unexposure to traps of the partial populations. The subject of unexposure was discussed by laying stress on the relation between minimum range length and trap-spacing.     

Comparison of sex pheromone traps for monitoring pink hibiscus mealybug (Hemiptera: Pseudococcidae)

The pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae), is a highly polyphagous pest that invaded Florida in 2002 and has recently been reported from several locations in Louisiana. Although identification of its sex pheromone in 2004 improved monitoring capabilities tremendously, the effectiveness and efficiency of different pheromone trap designs for capturing males has not been evaluated. We deployed green Delta, Pherocon IlB, Pherocon V, Jackson, and Storgard Thinline traps in Homestead, FL, and compared the number of male M. hirsutus captured per trap, the number captured per unit of trapping surface area, the amount of extraneous material captured, and the time taken to count trapped mealybugs. Pheromone-baited traps with larger trapping surfaces (green Delta, Pherocon IIB, and Pherocon V) captured more males per trap than those with smaller surfaces (Jackson and Storgard Thinline), and fewest males were captured by Storgard Thinline traps. However, Jackson traps captured as many or more males per square centimeter of trapping surface as those with larger surfaces, and the time required to count males in Jackson traps was significantly less than in green Delta, Pherocon IIB, and Pherocon V traps. Although all trap designs accumulated some debris and nontarget insects, it was rated as light to moderate for all designs. Based on our measures of effectiveness and efficiency, the Jackson trap is most suitable for monitoring M. hirsutus populations. Additionally, unlike the other traps evaluated, which must be replaced entirely or inspected in the field and then redeployed, only the sticky liners of Jackson traps require replacement, enhancing the efficiency of trap servicing.     

Field evaluation of Medfly (Dipt., Tephritidae) female attractants in a Mediterranean agrosystem (Balearic Islands, Spain)

Field evaluation of female-targeted trapping systems for the Mediterranean fruit fly Ceratitis capitata (Wied.) was carried out in a Citrus orchard in Majorca (Spain). Traps and lures included: IPMT and Tephri traps, both baited with a three-component food-based synthetic attractant 3FA (composed of putrescine, ammonium acetate and Trimethylamine) as well as IPMT-baited with Nu-Lure, and Delta traps baited with Trimedlure. The 3FA food-based synthetic attractant was set up either wet (containing water) or dry (without water) in IPMT and Tephri traps. Two experiments were conducted, the first during autumn/winter conditions and high Medfly population levels, and the second during spring conditions and low population levels. The results obtained show that the 3FA was very effective at capturing females at high and low population levels. In the first experiment the best performance was shown by the Tephri trap baited with 3FA in combination with water, and in the second the best was also the Tephri trap but with dry treatment. The high number of non-targeted insects captured by the first treatment together with servicing difficulties would indicate that the 3FA/dry-baited Tephri trap is the best choice in the area of the study. On the other hand the 3FA captured a percentage of mated females equivalent to those obtained with Nu-Lure. The Trimedlure proved to be an adequate tool to detect the earliest Medfly males in increasing spring population. The implications and advantages of using the 3FA female attractants in sterile insect technique programmes and mass trapping approaches, are discussed.     

Effectiveness of mass trapping in the reduction of Monochamus galloprovincialis Olivier (Col.: Cerambycidae) populations

Monochamus galloprovincialis Olivier beetles vector the causal agent of pine wilt disease (PWD), nematode Bursaphelenchus xylophilus (Steiner and Bührer) Nickle, in Europe. Traps and attractants have been optimized for the capture of M. galloprovincialis, increasing the possibility of developing methods of lowering its population in PWD‐affected areas with the aim of either eradicating the disease or containing the spread of it. To evaluate the effectiveness of such mass‐trapping campaigns, two sets of experiments were carried out in 2010 and 2013. The release of 353 laboratory‐reared beetles in the experimental area of 2010 facilitated the evaluation of capture–mark–recapture (CMR) procedures in the calculation of population abundance estimates using the POPAN formulation of the Jolly–Seber model, a prerequisite for the assessment of mass trapping. Abundance estimates derived from best‐fitting parameters fell within one standard error of the real figures, proving the method appropriate. In 2013, four trap densities were tested in six 36 ha plots. To evaluate the removed proportions, the local beetle population was estimated in a contiguous 260 ha study area. A superpopulation of 21 319 individuals could be calculated from the CMR data, corresponding to a rough density of 82 individuals per hectare. Evaluated trapping densities removed 4.66%, 20.50%, 33.33% and 59.80% of M. galloprovincialis population at 0.02, 0.11, 0.25 and 0.44 traps/ha, respectively, thus the estimated 95% removal would occur at 0.82 traps/ha. These results suggest that substantial reduction of M. galloprovincialis abundances might be achieved via mass trapping and that this represents a very promising management method for the containment or eventual eradication of B. xylophilus at the areas affected by the PWD.     

Efficacy of Fluon conditioning for capturing cerambycid beetles in different trap designs and persistence on panel traps over time

Fluon PTFE is a fluoropolymer dispersion applied as a surface conditioner to cross-vane panel traps to enhance trap efficiency for cerambycid beetles. We describe the results of three experiments to further optimize cerambycid traps of different designs and to test the effect of Fluon over time. We tested Fluon with Lindgren funnel and panel traps fitted with either wet or dry collection cups on catches of cerambycid beetles and how the effect of Fluon on panel traps persisted. Fluon-treated funnel traps with wet collection cups captured approximately 6x more beetles than the untreated funnel traps with wet collection cups. Untreated funnel traps with dry collection cups did not capture any beetles; however, Fluon-treated funnel traps with dry collection cups captured an average of four beetles per trap. Fluon-treated panel traps with wet collection cups captured approximately 9x more beetles than untreated panel traps with wet collection cups. Fluon-treated panel traps with dry collection cups captured approximately 11x more beetles than untreated panel traps with dry collection cups. The effect of Fluon on capturing cerambycid beetles did not decline after use in one or two field seasons. There was no significant difference in the number of beetles captured in freshly treated panel traps compared with traps that had been used for 1 or 2 yr. Fluon-treated traps captured nine species that were not captured in untreated traps. Conditioning both Lindgren funnel and panel traps with Fluon enhances the efficacy and sensitivity of traps deployed to detect exotic cerambycid species, or for monitoring threatened species at low population densities.     

Toward reliable population density estimates of partially marked populations using spatially explicit mark–resight methods

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Determination of an Optimal Pitfall Trap Size for Sampling Spiders in a Western Australian Jarrah Forest

Pitfall trapping is a sampling technique extensively used to sample surface foraging invertebrates for biological diversity studies and ecological monitoring. To date, very few invertebrate studies have considered what trap size is optimal for sampling spiders. This study presents preliminary findings from a single short sampling period on the role of trap size in sampling spiders in a Western Australian Jarrah forest. Four different trap diameters (4.3, 7.0, 11.1 and 17.4 cm) were examined (4 trap sizes × 15 replicates = 60 traps). Two-way ANOVAs revealed no significant interaction effects between trap size or the spatial positioning of transects within the study site along which the pitfall traps were arranged. Post-hoc tests revealed abundance, family richness and species richness increased with increasing trap sizes for traps 7.0 cm. No significant differences in these dependent variables occurred between 4.3 and 7.0 cm traps, or for species richness between 11.1 and 17.4 cm traps. Determination of an optimal trap size was undertaken by bootstrapping and calculating species accumulation curves for increasing numbers of traps used. Three different criteria were considered: equivalent number of traps (15), standardized sampling intensity (cumulative trap circumference, approximately 207 cm) and standardized cumulative handling time (approximately 1 hour 17 minutes). The largest trap size (17.4 cm) was most efficient in terms of number of traps and trap circumference. For the same number of traps, it caught 19 species whereas all other trap sizes caught ten species. At the standardized circumference, it caught seven species whereas all other trap sizes caught five. For handling time, however, the two largest trap sizes (17.4 and 11.1 cm) were optimal. Both caught nine species whereas all other traps caught 相似文献   

Some factors affecting the efficiency of water-traps for capturing cabbage root flies

Several factors influencing the efficiency of water-traps in capturing cabbage root flies were studied at Wellesbourne in 1971 and 1972. In both the laboratory and field, approximately twice as many flies were caught in fluorescent as in non-fluorescent yellow traps. Depending upon trap density, addition of a source of the attractant allylisothiocyanate (ANCS) increased the numbers of females captured by approximately twofold in fluorescent traps and from two- to sevenfold in non-fluorescent traps. Traps were equally efficient irrespective of whether the ANCS was renewed every 2, 3, 4 or 5 days. On the first day of trapping, the number of flies caught per unit area was linearly related to the square root of the number of traps in that area. On the following days the rate was probably in equilibrium with the combined effect of immigration and the rate of development of responsive flies in the trapping zone. Most males were caught 30 cm above the soil surface and most females at soil level. Traps 120 cm above the soil surface caught few flies. Populations of marked flies were released into large field cages containing both a section of hedgerow and a plot of cauliflowers. Even after a week, only 81 % of the males and 55 % of the females had been recaptured from the most responsive of these captive populations. Furthermore, only 30 % of females were recaptured when they were more than 8 days old, the age at which most probably enter the new host-crop.     

Evaluation of trap types and food attractants for Rhagoletis cerasi (Diptera: Tephritidae)

Trapping experiments were conducted during the period of flight activity of the cherry fruit fly Rhagoletis cerasi L. in the area of Thessaloniki, northern Greece, during the years 1993-1997 to test several traps alone and in combination with different food attractants. Yellow sticky-coated visual traps were more effective than McPhail-type traps baited with different food attractants. Of the visual traps, the most effective was the yellow Rebell trap. The Rebell trap, provided with a dispenser containing a slow release formulation of ammonium acetate attached to the lower part of the trap, was found to be the most effective of all treatments tested, capturing approximately 50% more R. cerasi flies than the Rebell trap without any attractant. Ammonium carbonate dispensers did not increase the performance of Rebell traps. More mature females were captured in Rebell traps baited with or without ammonium acetate than in McPhail-type traps baited with ammonium acetate. This study demonstrates that Rebell traps baited with an ammonium acetate dispenser can provide a more effective tool for monitoring and mass trapping of R. cerasi than the currently used unbaited Rebell traps.     

Pheromone trapping of the sugarcane weevil borer, Rhabdoscelus obscurus (Boisduval) (Coleoptera: Curculionidae): an evaluation of trap design and placement in the field

Abstract  The sugarcane weevil borer ( Rhabdoscelus obscurus ) is a pest of sugarcane and palm plantations in high rainfall areas of far north Queensland. Pheromone mass trapping of adult borers is an effective method of monitoring and may also impact on their population densities. Trials to evaluate different designs of pheromone trap showed the 'water trap' to be the most effective in capturing the highest number of adult borers. The water trap is a 20 cm-diameter pot with a plastic bag inserted to hold water with pheromone lures and cane pieces held together in a plastic container suspended over the water from a square of wire mesh. Results also showed that adult borers in adjacent fields are able to sense the lures and migrate into treated fields. The sex ratio of captured borers in split-cane traps (which is a standard population monitoring tool) was male biased from February to April but was more balanced later in the year. However, the pheromone traps mainly attracted female borers all year round, except during May. Thus, we recommend pheromone traps to be deployed early in the season (November to early December) to attract the maximum number of adult females at a critical time for the population as it starts to build up. In addition, placing pheromone traps inside cane paddocks did not improve the total catch in most cases. Therefore, placing pheromone traps under the shade of trees outside the paddock or at the edge of the paddock under sugarcane can be a feasible mass trapping method that can easily be implemented by cane growers.     

The relative efficiency of two commercial live-traps for small mammals

Data obtained from live-trapping a population of field voles, Microtus agrestis, over a seven-month period was used to compare the trapping efficiencies of the Longworth and the Ugglan Mouse Special traps. The Ugglan Mouse Special is a cheaper alternative that is widely used in Scandinavia. Biases in the sex or age of captured animals were the same for both types of trap and the total numbers of captures were similar. There was no evidence that individual animals were more likely to be captured in the same type of trap at each capture session. We conclude that the Ugglan Mouse Special trap is a practical alternative to the Longworth trap for studies of small mammals by capture-mark-recapture techniques.     

Influence of pitfall versus Longworth livetraps, bait addition, and drift fences on trap success and mortality of shrews

Pitfall trapping is believed to be the most efficient method for capturing shrews (Sorex spp.); however, Longworth live-traps have been used successfully in North America and Great Britain. Due to high metabolic rates, previous attempts to livetrap shrews have been faced with very high (exceeding 95 % in some circumstances) mortality rates. Here we report the results of two experiments attempting to integrate successful livetrapping of shrews into standard rodent trapping protocols. In Experiment 1 we compared efficiency of pitfall and Longworth live-traps operated with drift fences on 1-ha trapping grids for capturing vagrant shrews (Sorex vagrans) on agricultural set-asides in Delta, British Columbia, Canada. A total of 100 trap stations, on each of three trapping grids, were equipped with a 3-m-long drift fence and randomly assigned either one pitfall at the centre of each fence, or two Longworth traps, one at each end of the fence. In addition, we randomly selected 50 % of trap stations and provided 6 g of mealworms (Tenebrio molitor) larvae as bait. In response to high mortality rates, we varied the frequency of trap checks, with intervals of 12–14 h (long), 6–9 h (medium) and 3–4 h (short). Contrary to our predictions, Longworth traps captured significantly more shrews than pitfall traps. We observed the highest mean mortality rates in traps without mealworms, checked at long intervals. Shrews in mealworm-baited traps checked at short intervals experienced no mortality. Mortality rates in mealworm-baited traps checked at short and medium intervals were similar (t?=??1.33, P?=?0.20, Bonferroni-corrected alpha?=?0.004). In Experiment 2, we attempted to determine the relative gains in efficiency when using drift fences in conjunction with Longworth and pitfall traps. However, due to small sample size, we were unable to detect significant differences. A trapping protocol using Longworth traps in conjunction with drift fences, provided with mealworms as food, and checked at a maximum interval of 8 h should be sufficient to effectively include shrews in rodent livetrapping studies.     

Impact of trap design, windbreaks, and weather on captures of European corn borer (Lepidoptera: Crambidae) in pheromone-baited traps

Pheromone-baited traps are often used in ecological studies of the European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae). However, differences in trap captures may be confounded by trap design, trap location relative to a windbreak, and changes in local weather. The objectives of this experiment were, first, to examine differences in 0. nubilalis adult (moth) captures among the Intercept wing trap, the Intercept bucket/funnel UNI trap, and the Hartstack wire-mesh, 75-cm-diameter cone trap (large metal cone trap) as well as among three cone trap designs. Second, we examined the influence of the location of the large metal cone trap relative to a windbreak on the number of moths captured. Third, we examined the relationship between nightly mean air temperature, relative humidity, wind speed, precipitation, and the number of moths captured in large metal cone traps. The number of moths captured was significantly influenced by trap design, with large metal cone traps capturing the most moths. Wing and bucket traps were ineffective. Differences among trap captures were significant among trap locations relative to a windbreak. Under strong (>14 kph) or moderate (7 <14 kph) wind speeds, traps located leeward of the windbreak captured the most moths, but when wind speeds were light (<7 kph), traps not associated with windbreaks captured the most moths. The multiple regression model fitted to the relationship between number of moths captured per Julian date and nightly weather patterns was significant. Nightly mean air temperature was the most influential parameter in the model, and its relationship with moth capture was positive.     

The effect of manual removal on movement distances in populations of signal crayfish (Pacifastacus leniusculus)

1. Crayfish are amongst the most frequently introduced non‐native aquatic organisms, with well‐documented negative effects on a large number of freshwater taxa. Many crayfish‐control strategies make use of manual removal by trapping, a method known preferentially to remove the largest individuals, leaving the juvenile population almost entirely untrapped. 2. Removal by trapping may be used in an attempt to delay colonisation of new stretches by invasive crayfish. It is, however, unclear what effects trapping may have on movement distances of crayfish in wild populations. We examine the impacts of removal by trapping on the movements of American signal crayfish in two UK rivers. 3. We studied four 100 m stretches of two rivers, the Evenlode and Thame, comprising two removal and two non‐removal stretches. Each river supported both treatments. Half of the crayfish captured from the removal sections were removed and humanely destroyed by freezing, and half were marked with their trap location and released there. All crayfish captured from the non‐removal sections were marked and returned at the point of capture. 4. Mean movement distances were smaller in the removal stretches than the non‐removal stretches, both within capture sessions (10.8 and 16.0 m, respectively) and between sessions (14.5 and 24.6 m, respectively), suggesting that removal trapping resulted in the remaining crayfish making smaller movements. Larger crayfish under both treatments made substantially larger movements than those with smaller carapace lengths, both within capture sessions (range 7.6–19.6 m) and between range capture sessions (range 8.9–32.6 m). 5. The results of this study are consistent with expectations if removal by trapping lowered population densities, which we speculate may have affected movement distances directly or indirectly through increasing the availability of food and shelter. 6. This study suggests that trapping at the margins of a population may be sufficient to delay colonisation of new stretches by: (i) maintaining low densities and therefore reducing movements, and (ii) preferentially reducing the population of large individuals, which make the largest movements. However, it remains unlikely that any trapping programme can entirely prevent emigration /dispersal, and therefore colonisation, by signal crayfish.     

Mark-Recapture and Mark-Resight Methods for Estimating Abundance with Remote Cameras: A Carnivore Case Study

Abundance estimation of carnivore populations is difficult and has prompted the use of non-invasive detection methods, such as remotely-triggered cameras, to collect data. To analyze photo data, studies focusing on carnivores with unique pelage patterns have utilized a mark-recapture framework and studies of carnivores without unique pelage patterns have used a mark-resight framework. We compared mark-resight and mark-recapture estimation methods to estimate bobcat (Lynx rufus) population sizes, which motivated the development of a new "hybrid" mark-resight model as an alternative to traditional methods. We deployed a sampling grid of 30 cameras throughout the urban southern California study area. Additionally, we physically captured and marked a subset of the bobcat population with GPS telemetry collars. Since we could identify individual bobcats with photos of unique pelage patterns and a subset of the population was physically marked, we were able to use traditional mark-recapture and mark-resight methods, as well as the new “hybrid” mark-resight model we developed to estimate bobcat abundance. We recorded 109 bobcat photos during 4,669 camera nights and physically marked 27 bobcats with GPS telemetry collars. Abundance estimates produced by the traditional mark-recapture, traditional mark-resight, and “hybrid” mark-resight methods were similar, however precision differed depending on the models used. Traditional mark-recapture and mark-resight estimates were relatively imprecise with percent confidence interval lengths exceeding 100% of point estimates. Hybrid mark-resight models produced better precision with percent confidence intervals not exceeding 57%. The increased precision of the hybrid mark-resight method stems from utilizing the complete encounter histories of physically marked individuals (including those never detected by a camera trap) and the encounter histories of naturally marked individuals detected at camera traps. This new estimator may be particularly useful for estimating abundance of uniquely identifiable species that are difficult to sample using camera traps alone.     

Influence of visual and olfactory cues on field trapping of the pollen beetle, Astylus atromaculatus (Col.: Melyridae)

Field trapping experiments investigated the response of the pollen beetle Astylus atromaculatus to visual and olfactory cues during a 3-year period, 1999–2001. The visual preference of the pollen beetle was determined using yellow, white, blue, green and red water traps. The yellow trap was most attractive, capturing 56% of the total beetles trapped, with 30% caught by the blue and white traps, while 14% was caught by the red and green traps. The response of the beetle to olfactory cues was then evaluated by using the yellow water trap with three antennally active components identified in the volatiles of sorghum panicles by coupled gas chromatography (GC)–electroantennographic detection and GC–mass spectrometry. These components were 2-phenylethanol, benzyl alcohol and linalool. There were no significant colour × chemical compound interactions and traps baited with 2-phenylethanol captured significantly more beetles than unbaited traps, irrespective of trap colour, demonstrating the effectiveness of olfactory cues in trapping the pollen beetle. Traps baited with 2-phenylethanol were more attractive than and caught more beetles than traps baited with linalool. 2-Phenylethanol had the greatest effect on the relatively unattractive blue trap, confirming the importance of olfactory cues mediating A. atromaculatus attraction .     

Estimating population size by spatially explicit capture–recapture

The number of animals in a population is conventionally estimated by capture–recapture without modelling the spatial relationships between animals and detectors. Problems arise with non‐spatial estimators when individuals differ in their exposure to traps or the target population is poorly defined. Spatially explicit capture–recapture (SECR) methods devised recently to estimate population density largely avoid these problems. Some applications require estimates of population size rather than density, and population size in a defined area may be obtained as a derived parameter from SECR models. While this use of SECR has potential benefits over conventional capture–recapture, including reduced bias, it is unfamiliar to field biologists and no study has examined the precision and robustness of the estimates. We used simulation to compare the performance of SECR and conventional estimators of population size with respect to bias and confidence interval coverage for several spatial scenarios. Three possible estimators for the sampling variance of realised population size all performed well. The precision of SECR estimates was nearly the same as that of the null‐model conventional population estimator. SECR estimates of population size were nearly unbiased (relative bias 0–10%) in all scenarios, including surveys in randomly generated patchy landscapes. Confidence interval coverage was near the nominal level. We used SECR to estimate the population of a species of skink Oligosoma infrapunctatum from pitfall trapping. The estimated number in the area bounded by the outermost traps differed little between a homogeneous density model and models with a quadratic trend in density or a habitat effect on density, despite evidence that the latter models fitted better. Extrapolation of trend models to a larger plot may be misleading. To avoid extrapolation, a large region of interest should be sampled throughout, either with one continuous trapping grid or with clusters of traps dispersed widely according to a probability‐based and spatially representative sampling design.     

Evaluation of traps used to monitor southern pine beetle aerial populations and sex ratios

1 Various kinds of traps have been employed to monitor and forecast population trends of the southern pine beetle (Dendroctonus frontalis Zimmermann; Coleoptera: Scolytidae), but their accuracy in assessing pine‐beetle abundance and sex ratio in the field has not been evaluated directly. 2 In this study, we used fluorescent powder to mark pine beetles emerging from six isolated infestations. We then compared estimates of total abundances and proportions of males emerging from within each infestation to the estimates from three types of traps: passive sticky traps (2, 5, 10 and 20 m away from the source of beetles), multi‐funnel traps baited with pine beetle attractants (100 m away) and pine trees baited with attractants (also 100 m away). 3 We found that the proportion of males captured in traps was significantly affected by the type of trap used. 4 Within an infestation, equal proportions of males and females were marked (0.53 ± 0.02 males; mean ± SE), but the proportions captured in trap trees and passive traps were more female biased (0.42 ± 0.03 and 0.46 ± 0.01 males, respectively). On the other hand, funnel traps provided an estimate of the proportion of males that was nearly identical to the proportion from within infestations (0.51 ± 0.03). 5 Numbers of marked beetles captured in traps were uncorrelated with the numbers of marked beetles emerging from the focal infestations. This suggests that traps positioned around an infestation may not be effective at estimating relative abundances of beetles within the infestation.