Effects of neonicotinoid insecticides on the bionomics of twospotted spider mite (Acari: Tetranychidae)

Previous reports indicate that applications of imidacloprid, a neonicotinoid insecticide, can lead to population buildups of twospotted spider mite, Tetranychus urticae Koch, in the field. Moreover, laboratory studies showed enhanced fecundity of T. urticae after an imidacloprid treatment. In this study, experiments were conducted in the greenhouse to investigate the potential effects of imidacloprid and several other neonicotinoid insecticides on fecundity, egg viability, preimaginal survivorship, and sex ratio of T. urticae (German strain WI) on French beans, Phaseolus vulgaris L. Four insecticides, i.e., imidacloprid (Confidor 200SL), thiacloprid (Calypso 480 SC), acetamiprid (Mospilan 70 WP), and thiamethoxam (Actara 25 WG), were tested at field-relevant (100, 120, 125, and 95 ppm) and sublethal doses (10, 12, 12.5, and 9.5 ppm), respectively. Both spray and drench applications were tested. At field-relevant doses, fecundity of T. urticae decreased and was lower in the treatments compared with the untreated control, whereas preimaginal survivorship and proportion of female offspring (i.e., sex ratio) were lower compared with the control. At sublethal doses, no significant differences were found among the treatments. Data on egg viability, preimaginal survivorship, and sex ratio at sublethal doses followed the same trends as at field-relevant doses. In an additional experiment, the metabolism of imidacloprid into monohydroxy-imidacloprid, olefine, guanidine, and 6-chloronicotinic acid was compared with the oviposition pattern of T. urticae. These findings are discussed with regard to previous laboratory and field observations of imidacloprid-induced fertility increases in T. urticae.     

Infrapopulation dynamics of a wild strain of Taenia crassiceps (WFU) (Cestoda: Taeniidae) in BALB/cJ mice

Taenia crassiceps cysticerci form large infrapopulations that persist in the tissues of their rodent hosts. Early infrapopulation growth appears inhibited and is followed by rapid increases that appear not to be controlled by the host immune response. This investigation was undertaken to examine the infrapopulation growth dynamics of a normally developing strain (WFU) of T. crassiceps during a 60-day primary intraperitoneal (i.p.) infection. Three, 6, 9, 14, 28, and 60 days after i.p. inoculation of 5 cysticerci, mice were killed, and the numbers of larvae, developmental stage, and buds per larva were recorded. Larval infrapopulation abundance increased exponentially beginning on day 6 postinoculation (PI), indicating an initial lag in reproduction. A stage-structured exponential growth model, assuming no mortality, fits the larval infrapopulation dynamics in terms of the numbers of larvae in reproductive and nonreproductive stages, indicating that cysticerci evade or suppress (or both) host immune mechanisms that are parasite restrictive after the first week of infection.     

The Distribution and Diversity of Bartonella Species in Rodents and Their Ectoparasites across Thailand

Our study highlights the surveillance of Bartonella species among rodents and their associated ectoparasites (ticks, fleas, lice, and mites) in several regions across Thailand. A total of 619 rodents and 554 pooled ectoparasites (287 mite pools, 62 flea pools, 35 louse pools, and 170 tick pools) were collected from 8 provinces within 4 regions of Thailand. Bandicota indica (279), Rattus rattus (163), and R. exulans (96) were the most prevalent species of rats collected in this study. Real-time PCR assay targeting Bartonella-specific ssrA gene was used for screening and each positive sample was confirmed by PCR using nuoG gene. The prevalence of Bartonella DNA in rodent (around 17%) was recorded in all regions. The highest prevalence of Bartonella species was found in B. savilei and R. rattus with the rate of 35.7% (5/14) and 32.5% (53/163), respectively. High prevalence of Bartonella-positive rodent was also found in B. indica (15.1%, 42/279), and R. norvegicus (12.5%, 5/40). In contrast, the prevalence of Bartonella species in ectoparasites collected from the rats varied significantly according to types of ectoparasites. A high prevalence of Bartonella DNA was found in louse pools (Polyplax spp. and Hoplopleura spp., 57.1%) and flea pools (Xenopsylla cheopis, 25.8%), while a low prevalence was found in pools of mites (Leptotrombidium spp. and Ascoschoengastia spp., 1.7%) and ticks (Haemaphysalis spp., 3.5%). Prevalence of Bartonella DNA in ectoparasites collected from Bartonella-positive rodents (19.4%) was significantly higher comparing to ectoparasites from Bartonella-negative rodents (8.7%). The phylogenetic analysis of 41 gltA sequences of 16 Bartonella isolates from rodent blood and 25 Bartonella-positive ectoparasites revealed a wide range of diversity among Bartonella species with a majority of sequences (61.0%) belonging to Bartonella elizabethae complex (11 rodents, 1 mite pool, and 5 louse pools), while the remaining sequences were identical to B. phoceensis (17.1%, 1 mite pool, 5 louse pools, and 1 tick pool), B. coopersplainensis (19.5%, 5 rodents, 1 louse pool, and 2 tick pools), and one previously unidentified Bartonella species (2.4%, 1 louse pool).     

长爪沙鼠的肝毛细线虫感染率与鼠类及猛禽密度的关系

为研究鼠类密度和猛禽密度对鼠类肝毛细线虫(Capillaria hepatica)感染率的影响,作者于2004年7月在内蒙古锡林郭勒盟阿巴嘎旗北部和东乌珠穆沁旗西南部典型草原草场选取了14个实验样地,采用洞口计数法(四分之一圆面积法)调查估计各实验样地内长爪沙鼠(Meriones unguiculatus)密度,同时采用夹线调查法捕获鼠类样本,进行常规解剖获取肝毛细线虫的感染数据。采用目测计数法统计猛禽的出现频次,并以其出现频次作为猛禽的相对密度指标。实验样地共捕获长爪沙鼠1 058只,观察到鹰隼类活动69只次。数据分析结果表明,长爪沙鼠肝毛细线虫感染率与鼠类密度之间存在极显著的正相关关系(P0.01,R~2=0.926),长爪沙鼠肝毛细线虫感染率与猛禽密度之间亦存在极显著的正相关关系(P0.01,R~2=0.853)。该结果说明,长爪沙鼠是肝毛细线虫的主要宿主,鼠类密度和猛禽密度的升高均会增加长爪沙鼠肝毛细线虫感染率,猛禽密度和鼠类密度之间还存在叠加效应,猛禽的捕食作用会加快肝毛细线虫病的传播周期,加重肝毛细线虫病疫情。     

Rodent louse diversity,phylogeny, and cospeciation in the Manu Biosphere Reserve,Peru

We investigated the diversity, cophylogenetic relationships, and biogeography of hoplopleurid sucking lice (Phthiraptera: Anoplura) parasitizing rodents (Muridae: Sigmodontinae) in the Manu National Park and Biosphere Reserve. Our morphological and molecular studies reveal that 15 distinct louse species parasitize 19 rodent species. Three of these louse species are new to science, and all but two of the host associations were previously unknown. We find that hoplopleurid lice in South America parasitize multiple host species across a large geographic area, and that Peru represents a new geographic locality for almost all the louse species collected in the present study. Phylogenetic analyses of mitochondrial and nuclear data reveal that the louse family Hoplopleuridae and the genera Hoplopleura and Pterophthirus are not monophyletic, and lice do not appear to group by host tribe, collecting locality, or collection elevation. The lack of monophyly for these apparently natural groups (taxonomic, locality, and elevation) indicates that host switching with or without parasite speciation may be prevalent among hoplopleurid lice. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 598–610.     

Effects of host age and host availability on developmental period,adult size,sex ratio,longevity and fecundity inLariophagus distinguendus Förster (Hymenoptera: Pteromalidae)

The effects of host age on parasitoid reproductive capacity are studied using the pteromalid parasitoid Lariophagus distinguendusFörster and its bruchid hosts, Callosobruchus chinensis (L.) and C. maculatus (F.). A series of experiments were performed to investigate relationships between age and size of host parasitized and the developmental period of pre-imaginal progeny, sex ratio, female size, longevity, fecundity and oviposition rate. There was no effect of host size on preimaginal parasitoid developmental period. Sex ratio varied from less than 5% females from young (small) hosts to 60% females from mature (large) hosts. Adult size, female longevity, fecundity, and oviposition rate were also positively related to host age. Females provided mature hosts lived longer than those provided either young hosts or no hosts, possibly because of an increased ability to host-feed from the larger hosts. The implications of these findings to parasitoid population reproductive capacity and host-parasitoid synchrony are discussed.     

The spiny rat louse, Polyplax spinulosa, as a parasite of the rice rat, Oryzomys palustris, in North America

The spiny rat louse, Polyplax spinulosa, was collected, as adults and embryonated ova from the rice rat, Oryzomys palustris, a cricetid rodent, in Davidson Co., Tennessee. This sucking louse is typically parasitic on domestic rats, which are murid rodents. Because most sucking lice are normally host specific, such cross-familial host infestation is noteworthy.     

A comparative study on effects of normal versus elevated temperatures during preimaginal and young adult period on body weight and fat body content of mature Coccinella septempunctata and Harmonia axyridis (Coleoptera: Coccinellidae)

Two climate chamber experiments were performed to simulate the effects of global warming on life table parameters of coccinellids. We investigated the effects of two daily temperature profiles during preimaginal development (larval and pupal) and the young adult period (first 10 d) on body weight and fat body content of adult Coccinella septempunctata L. and Harmonia axyridis (Pallas) fed English grain aphids [Sitobion avenae (F.)] ad libitum: 1) normal, i.e., current daily temperatures in central Europe (T0: mean, 17.8°C; maximum, 21.8°C; minimum, 13.4°C) and 2) increased by 3K (T3: mean, 20.8°C; maximum, 25.5°C; minimum, 15.7°C). The first experiment was performed at the same temperatures (T0 or T3) during both periods to establish the responses of the two species to temperature. The second was conducted to identify the period (preimaginal or adult) in which the responses occurred and to confirm the results of the first experiment. Compared with normal temperatures (T0), elevated temperatures (T3) resulted in significant decreases in preimaginal development time and increases in aphid consumption rates in both species. C. septempunctata (10-d-old adults) had the highest weights when reared at T3, H. axyridis at T0. C. septempunctata was significantly heavier than H. axyridis in most cases, particularly in females. The body fat content of C. septempunctata was higher than that of H. axyridis at T0 and T3 temperatures. At T3 temperatures, fat accumulation in C. septempunctata increased, whereas that in H. axyridis remained relatively low. Body weight and fat body content of 10-d-old adults of both species seemed to be determined by temperature conditions during preimaginal development.     

新疆卡拉麦里山有蹄类野生动物自然保护区啮齿动物群落多样性及其与环境因子的关系

啮齿动物的群落结构受生态环境特征影响,并能反映环境变化规律。为探讨啮齿动物群落多样性及其与环境因子间的关系,利用铗捕法获得了新疆卡拉麦里山有蹄类野生动物自然保护区9种生境类型的环境因子及啮齿动物群落结构数据。2019-2020年春、夏季,共布设样地291块,有效铗日55269个,调查总面积176.875 km²,记录了啮齿类分布的12个环境因子。捕获啮齿动物419只,分属1目4科10属12种,优势种为三趾跳鼠（Dipus sagitta）和五趾跳鼠（Allactaga sibirica）,分别占捕获总个体数的34.13%和27.68%。分析结果显示,卡山自然保护区啮齿类捕获率最高的生境类型为沙漠（2.18%）;捕获鼠种的主要分布型为耐旱型（98.09%）。12个环境因子在9个生境类型中均呈极显著差异（P<0.01）,说明该保护区啮齿动物分布的生境异质性高。冗余分析表明,海拔高度、植被种类、灌木盖度和灌木高度是决定啮齿动物群落结构最主要的4个环境因子,其中植被种数与啮齿类群落多样性呈正相关,随着植被种数数值的增加,除优势度指数外,其它多样性指数随之增加。     

Importance of Nest Predation by Alien Rodents and Avian Poxvirus in Conservation of Oahu Elepaio

ABSTRACT The Oahu elepaio (Chasiempis sandwichensis ibidis) is an endangered forest bird endemic to the Hawaiian island of Oahu (USA) and is threatened by nest predation from alien rodents and mosquito-borne diseases. I investigated importance of these threats and evaluated success of conservation efforts from 1995 to 2008. I controlled rodents with snap-traps and bait stations in 3 valleys and switched sites from non-treatment to treatment over time. I mist-netted and color-banded 91 elepaio, inspected them for symptoms of avian poxvirus (Poxvirus avium), and estimated survival using multistate mark-recapture models. I determined annual fecundity of each breeding pair and monitored success of 212 nests. The oldest known Oahu elepaio was ≥15 years old. Survival of females was higher with rodent control (0.82 ± 0.05) than without (0.55 ± 0.12), but survival of males was not affected by rodent control (0.86 ± 0.02 with vs. 0.84 ± 0.04 without). Survival of elepaio with active or inactive pox-like lesions was 4–10% lower than survival of elepaio with no pox symptoms. Rodent control resulted in higher annual fecundity (0.69 ± 0.05 vs. 0.33 ± 0.06 fledglings/pair) and nest success (62% vs. 33%). Female site-fidelity, mate fidelity, and female encounter probability were lower in the absence of rodent control because more females switched territories and mates after nest failure. Population growth calculated from survival and fecundity estimates was stable with rodent control (1.07 ± 0.04) but declining without rodent control (0.69 ± 0.05). Elepaio numbers have continued to decline despite rodent control, probably because some young birds disperse into adjacent unmanaged areas that act as sinks. The best immediate management strategy for Oahu elepaio is to conduct rodent control over larger areas. Restoration of native forest would benefit elepaio by providing nest sites that are less attractive to rodents. Construction of predator-proof fences and eradication of predators would provide the best long-term protection for elepaio.     

The parasitism of immature stages of Ixodes loricatus (Acari: Ixodidae) on wild rodents in Argentina

Ixodes loricatus has long been considered with strict-total specificity to New World Marsupials. However, frequent findings of its immature stages on rodents suggest that these vertebrates play an important role in the tick’s life cycle. Aspects dealing with the ecology of Sigmodontinae rodents infestation by I. loricatus are unknown. To contribute to the knowledge of the ecology of this tick species, environmental factors, as well as host species, sex and age, were evaluated to find associations of immature I. loricatus infestation of the most abundant wild rodent species from riparian locations of Buenos Aires province (Argentina). A total of 290 hosts belonging to the subfamily Sigmodontinae were captured and examined for ticks at six locations. The data analysis showed that there was a preference of I. loricatus towards Akodon azarae, but only for those hosts captured in lands not prone to flooding. The results suggest that the host preference of I. loricatus is mainly related to factors such as habitat type and host density.     

Ectoparasites of rodents of the urban region of Belo Horizonte, MG. I. Interaction between ectoparasites and hosts

A rodent ectoparasite survey was made in the city of Belo Horizonte, Minas Gerais, Brazil, from June 1980 to September 1982. The species of ectoparasites captured from 950 Rattus norvegicus norvegicus were: Xenopsylla cheopis, Ctenocephalides felis felis, Polyplax spinulosa, Laelaps nuttalli, Echinolaelaps echidninus and Atricholaelaps glasgowi, the last species only represented by three specimens interchanged with wild rodent. P. spinulosa and L. nuttalli, although cosmopolitan, are recorded for the first time in State of Minas Gerais. The sex ratio of the ectoparasites, as well as the prevalence of fleas, mites and lice on the separate sexes of rodents are presented. 66.9% of the rats were infested by mites, almost twice more than infestations by fleas and louse jointly (39%). L. nuttalli was found in great numbers and presented the highest index of infestation: 55.1%. Single infestations are as common as associated ones. P. spinulosa, contrary to L. nuttalli, rarely occurs in single infestation. Data on the distribution of the ectoparasites on the rodents are also reported. The infestation observed in Belo Horizonte is confronted with those obtained by other authors in different places.     

Host behaviour drives parasite genetics at multiple geographic scales: population genetics of the chewing louse,Thomomydoecus minor

Pocket gophers and their symbiotic chewing lice form a host–parasite assemblage known for a high degree of cophylogeny, thought to be driven by life history parameters of both host and parasite that make host switching difficult. However, little work to date has focused on determining whether these life histories actually impact louse populations at the very fine scale of louse infrapopulations (individuals on a single host) at the same or at nearby host localities. We used microsatellite and mtDNA sequence data to make comparisons of chewing‐louse (Thomomydoecus minor) population subdivision over time and over geographic space where there are different potential amounts of host interaction surrounding a zone of contact between two hybridizing pocket‐gopher subspecies. We found that chewing lice had high levels of population isolation consistent with a paucity of horizontal transmission even at the very fine geographic scale of a single alfalfa field. We also found marked genetic discontinuity in louse populations corresponding with host subspecies and little, if any, admixture in the louse genetic groups even though the lice are closely related. The correlation of louse infrapopulation differentiation with host interaction at multiple scales, including across a discontinuity in pocket‐gopher habitat, suggests that host behaviour is the primary driver of parasite genetics. This observation makes sense in light of the life histories of both chewing lice and pocket gophers and provides a powerful explanation for the well‐documented pattern of parallel cladogenesis in pocket gophers and chewing lice.     

Three‐year surveillance (2016–2018) of chigger mites vector for tsutsugamushi disease in the Hwaseong‐Si area of Gyeonggi‐Do,Republic of Korea

Owing to climate change, the global resurgence of vector‐borne infectious diseases has emerged as a critical public health issue. Orientia tsutsugamushi is the etiological agent of tsutsugamushi disease (scrub typhus) a mite‐borne acute febrile disease occurring in the Asia‐Pacific region. We investigated the prevalence of tsutsugamushi disease transmitted by chigger mite vectors living on rodents. Using sticky‐type chigger traps for three months during 2016–2018, 1,057 chigger mites were collected (chigger mite index, 1.31) from four locations in the Hwaseong‐si area of Gyeonggi‐do, Republic of Korea. Five species distributed among three genera were identified. In addition, 94 rodents were captured (collection rate: 7.83%) using Sherman live traps over the course of three months (April, October, and November) during 2016–2017. Three rodent species were captured and identified and the striped field mouse (Apodemus agrarius) was the dominant rodent host species in the surveyed area. A total of 10,469 ectoparasitic chigger mites were recovered from the 94 rodents, from which 13 species distributed among four genera were identified. Of the 5,250 chigger mites examined, Leptotrombidium pallidum was most abundant (n = 2,558), followed by L. orientale, L. scutellare, L. zetum, Euschoengastia koreaensis, L. subintermedium, and Neotrombicula tamiyai. Of the examined chigger mites, no groups recovered from rodent hosts tested positive for O. tsutsugamushi. This study provides fundamental regional information on vector‐borne disease data collection in the Hwaseong‐si area, Gyeonggi‐do, and will further contribute to formulating disease control and prevention strategies.     

Sources of variability in aggregation and sex ratios of Crataerina melbae (Diptera: Hippoboscidae) among adult colonial alpine swifts

Aggregation of Crataerina melbae flies on breeding adult alpine swifts (Apus melba) was low when compared with other host-parasite systems and varied with sampling date, year, and sex of the flies. Generalized linear models were performed to ascertain which factors, extrinsic and/or intrinsic to the host, explained variability in the number of louse flies present on a single host, i.e., abundance. Overall abundance was unrelated to any host characteristic but varied slightly among years. Abundance of female flies varied among years, but also with date of sampling, the number of females increasing as the breeding season advanced. In contrast, abundance of males decreased as the season progressed, independently of host characteristics. Despite these different patterns, the number of flies of each sex on a given host was strongly intercorrelated. These results suggest that mate attraction may explain aggregation patterns in this louse fly species. Overall sex ratio of louse flies did not differ from unity. However, the proportion of males decreased during the breeding season, as a consequence of the opposite sex-related seasonal patterns in parasite abundance. Sex-ratio variability was not related to host characteristics or to infrapopulation sizes.     

Effects of voltinism, interspecific competition and parasitism on the population dynamics of the hemlock scales, Fiorinia externa and Tsugaspidiotus tsugae (Homoptera: Diaspididae)

Abstract.

• 1 Life tables were constructed for solitary and coexisting populations of univoltine Fiorinia externa Ferris and bivoltine Tsugaspidiotus tsugae (Marlatt) (Homoptera: Diaspididae), two exotic scale pests of eastern hemlock, Tsuga canadensis Carriere, in the northeastern United States.
• 2 Solitary and coexisting populations of F. externa had similar survivorship and population growth rates resulting in an annual increase in density of 7–16%. Survivorship of solitary and coexisting populations of T. tsugae also was similar, but growth rates differed substantially. While solitary populations increased their density by 68% annually, populations coexisting with F. extema were reduced 74% each year.
• 3 The annual reduction in T. tsugae density where it coexists with F. externa was due in part to interspecific competition which resulted in higher mortality to nymphs from dispersal and starvation and in lower fecundity of adult females relative to solitary populations. A host shift by the parasitoid, Aspidiotiphagus citrinus (Crawford) (Hymenoptera: Aphenlinidae) from F. externa to T. tsugae in autumn also accounted for 71% of the annual decrease in T. tsugae numbers. Therefore, F. externa adversely affects the growth of T. tsugae populations not only because of its superior competitive ability but also because adult para-sitoids which emerge from it subsequently attack nymphs of T. tsugae in autumn.
• 4 Parasitism and starvation of nymphs resulting from competition were the key mortality factors in the population dynamics of these exotic hemlock scales.

     

The parasitism of immature stages of <Emphasis Type="Italic">Ixodes loricatus</Emphasis> (Acari: Ixodidae) on wild rodents in Argentina

Ixodes loricatus has long been considered with strict-total specificity to New World Marsupials. However, frequent findings of its immature stages on rodents suggest that these vertebrates play an important role in the tick’s life cycle. Aspects dealing with the ecology of Sigmodontinae rodents infestation by I. loricatus are unknown. To contribute to the knowledge of the ecology of this tick species, environmental factors, as well as host species, sex and age, were evaluated to find associations of immature I. loricatus infestation of the most abundant wild rodent species from riparian locations of Buenos Aires province (Argentina). A total of 290 hosts belonging to the subfamily Sigmodontinae were captured and examined for ticks at six locations. The data analysis showed that there was a preference of I. loricatus towards Akodon azarae, but only for those hosts captured in lands not prone to flooding. The results suggest that the host preference of I. loricatus is mainly related to factors such as habitat type and host density.     

The timing of seed dispersal in Viooa nuttallii: attraction of dispersers and avoidance of predators

Summary Elaiosomes attract rodent predators, as well as ant dispersers (Myrmica discontinua and Formica podzolica), to Viola nuttallii seeds. Seed removal by ants and rodents was studied over 24 h and over two separate 4-h periods. Experimental treatments included i) ants and rodents having access to seeds, ii) only ants having access, iii) only rodents having access, and iv) neither ants nor rodents having access. Seed dehiscence was monitored for 3 days. A simple model is used to determine the relative importance of ants and rodents in removing seeds, and these frequencies are related to the time when most seeds were released. The data show that most seeds are shed from capsules between 9 AM and 1 PM and are immediately removed by ants. Ants, on the average, remove 88% of the seeds. The timing of seed dehiscence increases the probability of seeds being dispersed by ants. The results are discussed with respect to the hypothesis that a sychrony of the time of seed dispersal and the period when most ants (mutualists) and least rodents (predators) are active would be advantageous to the plant species.     

Production and export of the parasitoid Tachardiaephagus somervilli (Chalcidoidea: Encyrtidae), a biological control agent for the yellow lac scale,Tachardina aurantiaca (Hemiptera: Coccoidea: Kerriidae)

Development and reproduction of the hymenopteran parasitoid Tachardiaephagus somervilli Mahdihassan (Chalcidoidea: Encyrtidae) were studied in its native range in Malaysia as part of a classical biological control program on Christmas Island (Indian Ocean). Tachardiaephagus somervilli was reared in the laboratory on its target host, the yellow lac scale, Tachardina aurantiaca Cockerell (Coccoidea: Kerriidae). The developmental time, survival, and sex ratio of F1 offspring from two different sources of F0 adults (field-collected F0 adults [=‘wild-caught’] and F0 adults that emerged from parasitized hosts in the laboratory [=‘laboratory-emerged’]) were compared. Sources of F0 adults did not affect the developmental time of either male or female offspring, which ranged from 23 to 25 days. Furthermore, per capita fecundity of laboratory-emerged F0 females was three times greater than wild-caught F0 females. The number of emerged F1 adults was positively related to host size. Tachardiaephagus somervilli has a short generation time relative to its female Tachardina hosts (~23 vs ~90 days), high fecundity (~16 emerged offspring per laboratory-emerged female) and can potentially complete 12–15 generations per year. This rearing protocol produced sufficient quantities of adult T. somervilli for the export and successful introduction to Christmas Island (Indian Ocean) for the biological control of invasive T. aurantiaca, with near 100% survival rates for both sexes during transit.     

Nest loss in capercaillie and black grouse in relation to the small rodent cycle in southeast Norway

Summary The relationship between nest loss in boreal forest grouse and the fluctuations in small rodents was studied at Varaldskogen in southeast Norway during 1979–1986, covering two complete rodent cycles. Nest loss in capercaillie (N=174) and black grouse (N=81) was calculated according to Mayfield (1975) based on nests from radio-equipped hens (N=77) and nests found by other methods (N=178). Small rodent density was measured by snap trapping during spring and autumn. Losses varied as predicted by the classical alternative prey hypothesis (Hagen 1952 and Lack 1954, as elaborated by Angelstam et al. 1984): high losses during rodent crash years (85.5% capercaillie, 51% black grouse), and smaller losses during peak years (54.5% capercaillie, 32.5% black grouse). Losses were inversely related to autumn abundance of rodents in capercaillie (P<0.05), but the correlation was not significant for black grouse (0.10<P<0.20). In capercaillie, the only species with an adequate sample for analysis, no relationship was detected between spring density of rodents and nest loss. Losses during the prepeak years were nearly as high as during crash years, a result inconsistent with the model. We conclude that the numerical response of predators to their cyclic main prey (i.e. small rodents) probably play a main role during the low phase and prepeak year, whereas the dietary shift is most important during the peak and crash year of the cycle.