Trapping Sessions Research Articles

Mechanisms of Hantavirus Transmission in Oligoryzomys longicaudatus.

The cricetid rodent Oligoryzomys longicaudatus is the species host of Andes virus (ANDV) which causes hantavirus pulmonary syndrome in southern Argentina and Chile. Population density, behavioral interactions, and spacing patterns are factors that affect viral transmission among wild rodents. We predict that the highest prevalence of hantavirus antibody positive would be found among wounded, reproductive males and that, at high population densities, wounded, reproductive males would be dispersers rather than resident individuals. The study was conducted seasonally from October (spring) 2011 to October (spring) 2013 in a shrubland habitat of Cholila, Argentina. During each trapping session, we classified captured O. longicaudatus as resident or disperser individuals, estimated population density, and recorded wounds as an indicator of aggression among individuals. We obtained blood samples from each individual for serological testing. We used generalized linear models to test the statistical significance of association between antibody prevalence, and sex, resident/dispersal status, wounds and trapping session. The highest proportion of seropositive O. longicaudatus individuals was among wounded reproductive males during periods of the greatest population density, and the characteristics of seroconverted individuals support that transmission is horizontal through male intrasexual competition. A positive association between dispersing individuals and hantavirus antibody was detected at high population density. Our study design allowed us to obtain data on a large number of individuals that are seroconverted, enabling a better understanding of the ecology and epidemiology of the ANDV host system.

Evaluation of honey-baited FTA cards in combination with different mosquito traps in an area of low arbovirus prevalence

BackgroundThe threat of mosquito-borne diseases is increasing in continental Europe as demonstrated by several autochthonous chikungunya, dengue and West Nile virus outbreaks. In Switzerland, despite the presence of competent vectors, routine surveillance of arboviruses in mosquitoes is not being carried out, mainly due to the high costs associated with the need of a constant cold chain and laborious processing of thousands of mosquitoes. An alternative approach is using honey-baited nucleic acid preserving cards (FTA cards) to collect mosquito saliva that may be analysed for arboviruses. Here, we evaluate whether FTA cards could be used to detect potentially emerging viruses in an area of low virus prevalence in combination with an effective mosquito trap.MethodsIn a field trial in southern Switzerland we measured side-by-side the efficacy of the BG-Sentinel 2, the BG-GAT and the Box gravid trap to catch Aedes and Culex mosquitoes in combination with honey-baited FTA cards during 80 trapping sessions of 48 hours. We then screened both the mosquitoes and the FTA cards for the presence of arboviruses using reverse-transcription PCR. The efficacy of the compared trap types was evaluated using generalized linear mixed models.ResultsThe Box gravid trap collected over 11 times more mosquitoes than the BG-GAT and BG-Sentinel 2 trap. On average 75.9% of the specimens fed on the honey-bait with no significant difference in feeding rates between the three trap types. From the total of 1401 collected mosquitoes, we screened 507 Aedes and 500 Culex females for the presence of arboviruses. A pool of six Cx. pipiens/Cx. torrentium mosquitoes and also the FTA card from the same Box gravid trap were positive for Usutu virus. Remarkably, only two of the six Culex mosquitoes fed on the honey-bait, emphasising the high sensitivity of the method. In addition, two Ae. albopictus collections but no FTA cards were positive for mosquito-only flaviviruses.ConclusionsBased on our results we conclude that honey-baited FTA cards, in combination with the Box gravid trap, are an effective method for arbovirus surveillance in areas of low prevalence, particularly where resources are limited for preservation and screening of individual mosquitoes.

Wildfire-induced short-term changes in a small mammal community increase prevalence of a zoonotic pathogen?

Natural disturbances like droughts and fires are important determinants of wildlife community structure and are suggested to have important implications for prevalence of wildlife‐borne pathogens. After a major wildfire affecting >1,600 ha of boreal forest in Sweden in 2006, we took the rare opportunity to study the short‐term response (2007–2010 and 2015) of small mammal community structure, population dynamics, and prevalence of the Puumala orthohantavirus (PUUV) hosted by bank voles (Myodes glareolus). We performed snap‐trapping in permanent trapping plots in clear‐cuts (n = 3), unburnt reference forests (n = 7), and the fire area (n = 7) and surveyed vegetation and habitat structure. Small mammal species richness was low in all habitats (at maximum three species per trapping session), and the bank vole was the only small mammal species encountered in the fire area after the first postfire year. In autumns of years of peak rodent densities, the trapping index of bank voles was lowest in the fire area, and in two of three peak‐density years, it was highest in clear‐cuts. Age structure of bank voles varied among forest types with dominance of overwintered breeders in the fire area in the first postfire spring. PUUV infection probability in bank voles was positively related to vole age. Infection probability was highest in the fire area due to low habitat complexity in burnt forests, which possibly increased encounter rate among bank voles. Our results suggest that forest fires induce cascading effects, including fast recovery/recolonization of fire areas by generalists like bank voles, impoverished species richness of small mammals, and altered prevalence of a rodent‐borne zoonotic pathogen. Our pilot study suggests high human infection risk upon encountering a bank vole in the fire area, however, with even higher overall risk in unburnt forests due to their higher vole numbers.Open Research Badges This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://osf.io/6fsy3/.

Host-feeding patterns of Aedes (Aedimorphus) vexans arabiensis, a Rift Valley Fever virus vector in the Ferlo pastoral ecosystem of Senegal.

BackgroundHost-vector contact is a key factor in vectorial capacity assessment and thus the transmission of mosquito-borne viruses such as Rift Valley Fever (RVF), an emerging zoonotic disease of interest in West Africa. The knowledge of the host-feeding patterns of vector species constitutes a key element in the assessment of their epidemiological importance in a given environment. The aim of this work was to identify the blood meal origins of the mosquito Aedes vexans arabiensis, the main vector of RVF virus in the Ferlo pastoral ecosystem of Senegal.Methodology/principal findingsEngorged female mosquitoes were collected in Younouféré in the pastoral ecosystem in the Ferlo region during the 2014 rainy season. CO2-baited CDC light traps were set at six points for two consecutive nights every month from July to November. Domestic animals present around traps were identified and counted for each trapping session. Blood meal sources of engorged mosquitoes were identified using a vertebrate-specific multiplexed primer set based on cytochrome b. Blood meal sources were successfully identified for 319 out of 416 blood-fed females (76.68%), of which 163 (51.1%) were single meals, 146 (45.77%) mixed meals from two different hosts and 10 (3.13%) mixed meals from three different hosts. Aedes vexans arabiensis fed preferentially on mammals especially on horse compared to other hosts (FR = 46.83). Proportions of single and mixed meals showed significant temporal and spatial variations according to the availability of the hosts.ConclusionAedes vexans arabiensis shows an opportunistic feeding behavior depending on the host availability. This species fed preferentially on mammals especially on horses (primary hosts) and ruminants (secondary hosts).

Bias averted: personality may not influence trappability

If bold animals are more likely to be trapped than shy animals, we take a biased sample of personalities—a problem for behavioural research. Such a bias is problematic, also, for population estimation using mark-recapture models that assume homogeneity in detection probabilities. In this study, we investigated whether differences in boldness result in differences in detection probability in a native Australian rodent, the grassland melomys (Melomys burtoni). During a mark-recapture study of this species, we used modified open field tests to assess the boldness (via emergence, and interaction with a novel object) of melomys trapped on the last night of four trapping nights in each of two trapping sessions. Despite melomys showing repeatable variation in these behavioural traits, neither boldness nor emergence latency had an effect on detection probability, and we found no evidence that detection probability varied between individuals. This result suggests that any neophobia is experienced and resolved in individuals of this species on a scale of minutes, rather than the hours across which traps are made available each night. Our work demonstrates that personality-caused sampling bias may not be inevitable, even in situations where animals are required to respond to novelty to be detected, such as in baited traps. Heterogeneity in personality does not inevitably lead to heterogeneity in detection probability. Historically, passive traps were assumed a non-biased means of sampling animal populations. Increasingly behavioural ecologists suggest that personality traits, particularly individual boldness, may influence behaviour and, as a consequence, could result in sampling bias. Here, we present a comprehensive example of when animal personality has no effect on detection probability. Despite having distinct personalities, detection probabilities of a native Australian rodent, grassland melomys Melomys burtoni, were not influenced by whether they were ‘shy’ or ‘bold’. We provide evidence that heterogeneity in personality does not inevitably lead to heterogeneity in detection probability. Given that population estimation models typically assume homogeneity in detection probability between individuals, if this is a broad phenomenon, consistently similar results may improve our confidence in this assumption.

Are small carnivores urban avoiders or adapters: Can they be used as indicators of well-planned green areas?

Terrestrial mammalian carnivores are generally sensitive to urbanization. Yet, some mesocarnivores have adapted to the urban and suburban environment. The response of small carnivores to urbanization is poorly studied, partly due to methodological difficulties. We assessed the impact of urbanization on a representative of small carnivores – the least weasel Mustela nivalis. Data from 254 trapping sessions of monitoring small mammals (27 810 trap-days) conducted in different urbanized and non-urbanized habitats (Poland, Central Europe) were used and analysed in a logistic regression model. The probability of occurrence of weasels was tested in relation to the land cover type, abundance of rodents (weasel’s food base), proportion of a built-up area (on the 500 m radius buffer) and trapping effort. The weasel avoided urban areas and if the percentage of a built-up area was higher than 32% the probability of occurrence of the weasel was low (P < 0.5). Within urbanized areas, least weasel were only detected on the outskirts of a city or in the valleys of large rivers. Conversely, habitat type did not predict the presence of least weasel in non-urbanized areas. The possible reasons for the lack of the weasel in urban green areas are narrow food specialization (mainly rodents as prey; no use of anthropogenic food sources), high energetic demands, and fragmentation and isolation of green areas. Despite the high ecological plasticity of this species, the strong negative response of the least weasel to urbanization causes that their occurrence can be an indicator of well-planned urban greenery. The occurrence of the least weasel indicates both the functional connectivity of green areas in the city and the abundance and availability of the prey base – ground-dwelling animals from lower trophic groups.

Changes in Abundance of the Ixodes scapularis Say (Blacklegged Tick) in Adair County, Missouri, from 2006 to 2015

Ixodes scapularis (Blacklegged Tick), vector of Lyme disease, has a broad distribution in eastern North America, but is relatively rare in Missouri. In this study, we report the change in abundance of this species in Adair County, MO, from 2006 to 2015. We collected data from 85 small-mammal trapping sessions beginning in 2006, and from 175 off-host sampling sessions using both drag and bait sampling beginning in 2007. The total number of Blacklegged Ticks collected in this study was 182; we collected <10 Blacklegged Ticks in most years. However, we collected 61.5% of specimens in 2014 and 86% in the last 3 years. Systematic, long-term monitoring has provided information about the dynamics of a tick species with low abundance.

Partial replacement of Rainbow Lorikeets Trichoglossus haematodus moluccanus by hybrid lorikeets in Hobart, Tasmania

The Eastern Rainbow Lorikeet Trichoglossus haematodus moluccanus recently became established in Tasmania. This study presents opportunistic observations of the species in Hobart from March 2007 to August 2018. During the first 6 years, flocks of more than four Rainbow Lorikeets were seldom seen. However, during the middle of 2013 larger flocks of up to 14 birds were observed repeatedly. Following this, five birds were trapped and removed in August 2013 and another four in May 2014. Thereafter, only five observations of more than a single Rainbow Lorikeet were made, suggesting that trapping may be effective at controlling their populations locally. However, following the trapping sessions, apparent hybrids between Rainbow Lorikeets and native Musk Lorikeets Glossopsitta concinna became more common and more diverse in appearance. Four morphotypes of hybrids were observed, with one of these almost certainly the result of interspecific mating in the wild. Rainbow Lorikeets and hybrids foraged predominantly from flowers of Swamp Gum Eucalyptus ovata and at bird-feeders. Hence, Rainbow Lorikeets could possibly have impacts on Musk Lorikeets through interbreeding and, if they become more common, on these and other species of birds through competition for nectar and pollen of eucalypts.

The scientific, financial and ethical implications of three common wildlife-trapping designs

Abstract ContextTrapping design influences information collected about wildlife populations and biodiversity. Trapping is also resource-intensive and has animal welfare implications. AimsThe scientific, financial and ethical performances of three trap designs were compared for estimating diversity and sampling small vertebrates. MethodsSmall vertebrates were trapped over 16 trapping sessions, from April 2009 to May 2011, with aluminium box-style (Elliott) traps and two pitfall trap designs (shallow–wide and deep–narrow), in an arid environment. Key resultsShallow pitfalls recorded highest overall species richness (S=22) and diversity (qD=10.622), reptile diversity (qD=8.112) and reptile capture rates (13.600 individuals per 100 trap nights). Shallow and deep pitfalls sampled ~79.0% and 85.0% (respectively) more small mammals than did Elliott traps. Deep pitfalls sampled the greatest diversity (qD=6.017) and number (29.700 individuals per 100 trap nights) of small mammals, and captured the greatest number of small mammal species (0.003) and individuals (0.106) per dollar. Shallow pitfalls were the most cost-efficient trap type for sampling reptile species (0.003) and individuals (0.044) per dollar. Between-session recapture rates were greatest in Elliott traps, indicating an increased likelihood of biased capture rates for certain small mammal species over time. Elliott traps were the least efficient traps on most scientific and cost measures, and recorded the greatest overall recapture rates, particularly for Sminthopsis crassicaudata and S. macroura. Body size of one species only, the nationally threatened Pseudomys australis, influenced its capture rate, with larger individuals more likely to be caught in deep pitfalls. Mortality was highest in pitfalls and mostly related to interactions between animals caught in the same trap. Key conclusionsShallow pitfalls are suitable for studies focused on estimating species richness, and reptile diversity and abundance. Deep pitfalls are cost-effective for sampling small mammals. Ethical issues associated with pitfalls could be managed by checking traps more often at night, and/or including materials that provide increased protection from predators caught in the same trap, particularly during periods of high abundance. ImplicationsTrap design profoundly influences cost-effectiveness and welfare outcomes of wildlife research. We provide a tool to assist cost-benefit related decisions.

Orthohantavirus genotype Lechiguanas in Oligoryzomys nigripes (Rodentia: Cricetidae): New evidence of host-switching

To identify and predict situations of increased risk of orthohantavirus infection in humans, it is necessary to study the relationships between the virus and its rodent hosts. The present study investigated orthohantavirus infection in an assemblage of wild Sigmodontinae rodents of the Paraná Delta, Argentina, and providing new evidence of host-switching events. Rodents belonging to the species Oxymycterus rufus (n = 187), Akodon azarae (n = 82), Oligoryzomys flavescens (n = 80), Oligoryzomys nigripes (n = 47), Scapteromys aquaticus (n = 38), Deltamys kempi (n = 7) and Holochilus brasiliensis (n = 2) were captured at 4 sampling sites during 20 trapping sessions. Blood samples were analyzed by IgG ELISA and livers by a nested reverse transcription PCR for the diagnosis of orthohantavirus infection. The amplified products of the S and M orthohantavirus genomes were sequenced and analyzed to determine similarities with species of the Orthohantavirus genus. The species of the Oligoryzomys positive to the virus were confirmed by amplifying and sequencing the complete cyt b gene. Of the 443 serum samples analyzed by IgG ELISA, A. azarae presented the highest host-specific prevalence value (10/82, 12.2%) followed by Ol. nigripes (4/47, 8.5%) and Ox. rufus (1/187, 0.5%). All the sero-positive Ol. nigripes (n = 4) were positive to the amplification of the S and M segments of the Lechiguanas genotype (98% nucleotide identity for both segments). This is surprising given that Ol. nigripes has been previously associated with Juquitiba genotype, not Lechiguanas. The latter is generally associated with Ol. flavescens, which in our study were all sero-negative. In addition, the association Ox. rufus – Pergamino genotype found here is, to our knowledge, novel and another potential evidence of host-switching considering that Pergamino has been originally associated with A. azarae. These findings contribute to the building evidence that contradicts the one-genotype-one-reservoir species premise in the association between rodent reservoirs and orthohantaviruses, and supports the hypothesis that the community structure of sympatric host species may contribute to orthohantavirus dynamics.

Tree seed rain and seed removal, but not the seed bank, impede forest recovery in bracken (Pteridium aquilinum (L.) Kuhn)-dominated clearings in the African highlands.

Considerable areas dominated by bracken Pteridium aquilinum (L.) Kuhn occur worldwide and are associated with arrested forest recovery. How forest recovery is impeded in these areas remains poorly understood, especially in the African highlands. The component processes that can lead to recruitment limitation—including low seed arrival, availability and persistence—are important determinants of plant communities and offer a potential explanation for bracken persistence. We investigated key processes that can contribute to recruitment limitation in bracken‐dominated clearings in the Bwindi Impenetrable National Park, Uganda. We examined if differences in seed rain (dispersal limitation), soil seed bank, or seed removal (seed viability and persistence) can, individually or in combination, explain the differences in tree regeneration found between bracken‐dominated areas and the neighboring forest. These processes were assessed along ten 50‐m transects crossing the forest–bracken boundary. When compared to the neighboring forest, bracken clearings had fewer seedlings (bracken 11,557 ± 5482 vs. forest 34,515 ± 6066 seedlings/ha), lower seed rain (949 ± 582 vs. 1605 ± 335 tree seeds m−2 year−1), comparable but sparse soil seed bank (304 ± 236 vs. 264 ± 99 viable tree seeds/m2), higher seed removal (70.1% ± 2.4% vs. 40.6% ± 2.4% over a 3‐day interval), and markedly higher rodent densities (25.7 ± 5.4 vs. 5.0 ± 1.6 rodents per 100 trapping sessions). Camera traps revealed that rodents were the dominant animals visiting the seeds in our seed removal study. Synthesis: Recruitment limitation contributes to both the slow recovery of forest in bracken‐dominated areas, and to the composition of the tree species that occur. Low seed arrival and low persistence of unburied seeds can both explain the reduced density of seedlings found in bracken versus neighboring forest. Seed removal, likely due to rodents, in particular appears sufficient to constrain forest recovery and impacts some species more severely than others.

First report on Leptospira interrogans in the sigmodontine rodent Scapteromys aquaticusPrimeiro relato da presença de Leptospira interrogans em roedores sigmodontíneos Scapteromys aquaticus

RESUMENLa leptospirosis es una enfermedad zoonótica de distribución mundial que puede transmitirse por contacto directo o indirecto con orina o tejidos de animales infectados. En Argentina, la leptospirosis es endémica en la provincia de Santa Fe y presenta brotes epidémicos durante las inundaciones. Sin embargo, se sabe muy poco sobre el papel que cumplen los roedores silvestres en la diseminación de la enfermedad en el país. El objetivo de este estudio fue identificar las especies hospederas de leptospiras patógenas entre los roedores presentes en un asentamiento ribereño de la provincia de Santa Fe.Se realizó un muestreo de roedores durante octubre de 2015. Los riñones de los animales capturados se analizaron por real-time PCR para el gen LipL32 de leptospiras patógenas. En los animales que resultaron positivos, se realizó test de microaglutinación (MAT) y tipificación molecular por amplificación del gen 16S rRNA y dos esquemas de MLST.Se capturaron 37 roedores de las especies Akodon azarae, Cavia aperea, Oligoryzomys flavescens, Rattus rattus y Scapteromys aquaticus. En el análisis por real-time PCR resultó positivo un macho de Scapteromys aquaticus. El suero de este individuo y del resto de los S. aquaticus capturados (n = 18) se analizaron por test de microaglutinación (MAT), y fueron no reactivos para los 10 serovares probados. La amplificación del gen 16S rRNA identificó la especie infectante como Leptospira interrogans, mientras que no se obtuvo amplificación para los dos esquemas de MLST.El hallazgo de este estudio aporta nueva información acerca de presencia de leptospiras patógenas en roedores silvestres, que es relevante para la zona por tratarse de una especie ampliamente distribuida en ambientes pantanosos e inundables de América del Sur.

Response of Lizards to High-Severity Wildfires in a Southern United States Mixed Pine/Hardwood Forest

High-severity forest fires are increasing in large areas of the southern and western United States as the climate becomes warmer and drier. Natural resource managers need a better understanding of the short- and long-term effects of wildfires on lizard populations, but there is a paucity of studies focused on lizard-wildfire relationships. We used a before-after, control-impact (BACI) sample design to assess the response of three lizard species—Six-lined Racerunner (Aspidoscelis sexlineata), Prairie Lizard (Sceloporus consobrinus), and Little Brown Skink (Scincella lateralis)—to high-severity wildfires that occurred in the Lost Pines Ecoregion, Texas, USA. Specifically, we analyzed monitoring data collected across 17 trapping sessions from spring 2008 to spring 2013 using stratified N-mixture models to estimate trends in lizard abundances, while accounting for environmental parameters that might influence lizard detectability. We found no evidence of a fire-induced change in abundance for any of the lizar...

Boreal small mammals show evidence of density-dependent patterns with area-sensitivity

In recent years, habitat amount in fragmented landscapes has been shown to positively influence population size, species occurrence, and species diversity. Quantifying how sensitive bioindicator species respond to the amount of habitat in disturbed landscapes (i.e. area-sensitivity) has become a growing research focus to provide robust guidelines for ecosystem-based management. In this study, we modelled the occurrence of North American boreal small mammals in relation with the total amount of forest surrounding remnant forest patches in disturbed landscapes while controlling for local habitat associations. Over the summers of 2013 and 2014, we conducted four trapping sessions in 60 sites located in old forest remnant patches of old forests in both wildfires and aggregated clearcuts, and in continuous old forest blocks within the black spruce forest of northwestern Quebec, Canada. American red squirrels (Tamiasciurus hudsonicus), southern red-backed voles (Myodes gapperi) and masked shrews (Sorex cinereus) represented 85.5% of our total captures. We measured the amount of habitat (percentage of forest cover) within 100 concentric buffers around each capture grid using digital forest cover maps. Buffers varied in radii from 50m to 5km. We quantified area-sensitivity using dynamic models of single-species occupancy to estimate the probabilities of initial site occupancy, site extinction and site colonisation of each species according to both local habitat variables and surrounding habitat amount. We found no associations between initial site occupancy, site colonisation, or site extinction with local habitat features, possibly in response to habitat structure similarity of our three site types. Species studied had different life histories in terms of population dynamics' and timing of juvenile dispersal, possibly explaining why each species had its individual response to the amount of habitat in the surrounding landscape. For the American red squirrel, we found no evidence of within-year area-sensitivity on initial site occupancy patterns, whereas negative area sensitivity on initial site occupancy between-years was observed for the southern red-backed vole. In contrast, we found positive area-sensitivity on between-years site colonisation for this latter species at small spatial scales. For masked shrews, we detected negative area-sensitivity on initial site occupancy within-year. As populations were sampled at low density, we suspect that the sparse distribution of individuals may influence area-sensitivity patterns. Future studies should consider area-sensitivity with regards to both spatial and temporal scales. We encourage long-term monitoring of animal populations at multiple spatial scales to investigate the underlying ecological mechanisms of positive and negative area-sensitivity.

Managed parks as a refuge for the threatened red squirrel (Sciurus vulgaris) in light of human disturbance

As the invasive grey squirrel continues to spread, red squirrels are dying out. The result may be isolated populations in managed parks, where access can be controlled. However, recreation can often have a negative effect on wildlife, reducing the conservation potential of parks. Fota Wildlife Park receives over 300,000 visitors each year and is located on an island that is currently free of grey squirrels. We examined the effect of visitors on the existing red squirrel population. Sampling was conducted in the presence and absence of the public. Ten trapping sessions took place from March 2013 to 2014 and faeces were collected to examine stress levels. Squirrels were observed to concentrate their activity in non-public areas and move into public areas when the park was closed. Radio tracked squirrels, from the adjacent gardens (intermediate disturbance), also used habitats in the wildlife park (high disturbance) when it was closed but returned when the park had opened. When squirrels were observed in public areas, visitors were only visible on 15% of occasions. Levels of faecal cortisol metabolites (FCM) were highest in areas where human disturbance was greatest. However, there was no correlation between visitor numbers and the stress levels of squirrels. FCM levels were however, positively correlated with density of squirrels. The fact that high numbers of squirrels continued to utilise the wildlife park demonstrates that managed parks could provide an important reserve for the maintenance of the species, as long as non-public areas are accessible.

Where do Norway rats live? Movement patterns and habitat selection in livestock farms in Argentina

Context The Norway rat (Rattus norvegicus) is recognised as one of the most harmful invasive mammal species in natural, urban and rural environments worldwide. Prevention and control of pest species in livestock farms is necessary to protect animal and human health, but control practices usually do not take into account the biology and ecology of the species to be controlled. The understanding of the biological requirements of Norway rats is necessary for the implementation of efficient management actions. Aims The aim of this research was to study movement patterns and habitat selection of Norway rats on livestock farms in central Argentina. We hypothesised that rats select specific areas within the farms according to the farm’s structure and to the availability of resources. Methods We conducted live-trapping of rats in a pig farm and a dairy farm, during each of four seasons over 1 year. Traps were active for three consecutive days at each trapping session. Movements and habitat selection were assessed by spool-and-line technique combined with environmental surveys and GIS tools. Key results We captured a total of 133 Norway rats and evaluated the movements of 47 individuals. The mean length travelled, registered for one night, was 84.28 ± 38.21 m. They did not travel great linear distances within the farms, but instead performed tortuous trajectories around specific sites. Norway rats selected sites containing food, water and refuges; and avoided travelling across areas with short vegetation. Sites containing food sources were most preferred. Conclusions Because food sources for rats were present ad libitum in farms, our findings strongly support the idea that management strategies of prevention and control of this species must include adequate rodent-proof food storage. Also, because rats are found close to livestock, improvement in preventing rats’ access to animal sheds is necessary to prevent contamination of livestock feeders with pathogens carried by rats. Implications The present study provides novel information about the ecology of Norway rats on livestock farms. We encourage farmers to follow our recommendations in order to improve rodent-control strategies.

Additional Evidence Against Radio-handicapping of Northern Bobwhites

The validity of radio-telemetry to produce reliable information (e.g., survival estimates) has recently been challenged. Radio-telemetry is a widely used technique in studies of numerous species, therefore, concerns regarding potential bias in these estimates warrant further investigation. As such, and as part of a larger study, we investigated 3 aspects of potential radio-bias: 1) variation in survival distributions among treatment (newly radio-tagged) and control (previously radio-tagged) groups; 2) proportion of trapped animals censored during the traditional 7-day censor period; and 3) ramifications to cause-specific mortality through estimation of harvest rate. Kaplan-Meier survival, based on 30-day post trapping, was similar between treatment (n = 901) and control (n = 293) bobwhites for all but 1 of 8 trapping sessions during 2000-2004. In this case, treatment bobwhites (0.970, SE = 0.015) had higher survival than control birds (0.878, SE = 0.042). We determined the effect of censoring relative to sample size was inconsequential for our analysis because the proportion of bobwhites (18 out of 1,350; 0.013) meeting the criteria for censoring, i.e., dying during the first 7 days, was minimal. Censoring of these data influenced survival estimates by an average of only 0.016 (SE = 0.004; range: 0.00 - 0.04). We evaluated harvest rate by comparing first year recovery rates of banded verses radio-tagged birds during thirteen hunting seasons occurring between 1992 and 2005. Annual recovery rate was not different (P < 0.05) for banded birds and radio-tagged birds where harvest averaged 6.68% (range 3.3 - 11.7) and 6.65% (range 3.4 - 11.1), respectively. These findings are consistent with previous research demonstrating that radio-telemetry can provide reliable demographic information. However, we recommend that future researchers test for these potential effects among their data before making biological inferences.

Factors affecting trapping success of northern bobwhites in the rolling plains of Texas

ABSTRACTTrapping of northern bobwhites (Colinus virginianus) is commonly conducted for research purposes. We investigated the influence of weather, lunar phase, time of day, and season on bobwhite trapping success in the Rolling Plains ecoregion of Texas, USA, from 2009 to 2011. We trapped bobwhites in autumn (Oct–Nov) and spring (Feb–Mar) using walk‐in funnel traps baited with sorghum. We used a negative binomial regression to examine effects of temperature, humidity, wind speed, lunar phase, time of day, season, the number of traps set, and year on the number of bobwhites captured per trapping session. More bobwhites were trapped during the spring, in the evenings, and when temperatures were cooler. There was also some evidence for an influence of lunar phase on the number of bobwhites captured with greater counts during the new moon and third quarter. These variables may be important to consider for maximizing catch‐per‐unit‐effort, when using trapping data to estimate relative abundance, or when conducting mark–recapture studies. © 2016 The Wildlife Society.

Seasonal variations and population parameters explaining the use of space of neotropical rodents

Space use by animals has been studied for decades; however, gaps still exist in the understanding of how it is affected by biological and environmental factors. The aim of this study was to determine how biological traits, population parameters and seasonal variations affect the use of space by rodents in a tropical savannah environment. This study was performed in two grids in a grassland area at Aguas Emendadas Ecological Station between January 2004 and December 2013. The trapping sessions lasted six consecutive days and were performed monthly. Sherman traps, which were baited and reset daily, were used to capture the animals. The movement area was estimated using the minimum convex polygon method, and the mean movement distance was used to investigate the factors that affect the movement of the rodents. The hypothesis that a significant difference exists in the movement area size among species was corroborated; however, this difference was not related to body weight. As a general pattern for these rodents, males displayed larger movement areas than females. Movement area size showed an inverse relationship to population density. The understanding of the factors that affect the space use by rodents are complex and the interactions of these factors may also modulate space use by rodents. Our results suggest that space use is also affected by climatic variations.

Evaluation of statistical methods and sampling designs for the assessment of microhabitat selection based on point data

Summary Information on resource selection by a species is essential for understanding the species’ ecology, distribution and requirements for survival. Research on habitat selection frequently relies on animal detection at point locations to determine which resource units are used. A variety of approaches and statistical tools can be employed for assessing selection based on habitat variables measured in those units. The aim of this work was to evaluate the reliability of common sampling designs and statistical methods in detecting habitat selection at fine scales based on point data We reviewed literature on microhabitat selection to determine characteristics of typical studies and analysed simulated small‐mammal live‐trapping data as a case study. We considered various scenarios differing in the number of sampled units and sampling duration. For each scenario, a set of simulated surveys was analysed through two univariate tests (Welch's t‐ and Mann–Whitney U‐test), generalized linear models (GLMs), mixed‐effect models (GLMMs) and occupancy models (OMs). Analysis of simulated data revealed that overall performance of all statistical methods improved with increased trapping effort. Univariate tests were especially sensitive to the number of sampling units, while modelling methods took also advantage of longer trapping sessions. Univariate tests and GLMs provided partially correct information in most cases, whereas GLMMs and OMs offered higher probabilities of fully describing simulated habitat preferences. With typical sampling efforts, appropriate statistical analysis of point data is able to provide a moderately accurate description of habitat selection at small scales, in spite of the violation of closure and independence assumptions of applied models. Modelling approaches are proliferating; we encourage using models that can deal with multiple sources of variability, such as GLMMs and OMs, when data are hierarchically structured. There is no a priori best survey design; it should be chosen according to the scope and goals of the study, environment heterogeneity, species characteristics and practical constraints. Researchers should realize that sampling design and statistical methods likely affect conclusions regarding habitat selection.