Factors influencing the diurnal behaviour of white rhino (Ceratotherium simum) in Matobo National Park,Zimbabwe

Activity periods and diurnal behaviour of southern white rhino (Ceratotherium simum simum) were studied in Matobo National Park, Zimbabwe, from August 2016 to July 2017 using camera trapping and focal group sampling, respectively. Camera trap data showed that diurnal and nocturnal movements of white rhino varied significantly with moon phase, with more frequent nocturnal photographic captures during full- and third-quarter moon phases than during new and crescent moon phases. Permutational MANOVA and canonical correspondence analysis of focal group observation data were used to test the effects of season, time of day, habitat type, distance to roads, moon phase, presence/absence of other mammals, age/sex category, individual identity and herd composition on daytime behaviour. Weather conditions accounted for the majority of variation in rhino behaviour, with more time spent feeding during cloudy and rainy weather than sunny weather. Time of day and moon phase also accounted for high variation in behaviour, followed by habitat attributes and age/sex category. Variance partitioning by sets of explanatory variables showed that weather conditions had the greatest explanatory power in the variation of rhino behaviour, followed by temporal attributes, habitat attributes and age/sex category. Our findings provide insights for white rhino population management strategies aimed at increasing the effectiveness of security patrols, minimising disturbance and improving sightings for tourists.     

Population dynamics of Bactrocera dorsalis (Diptera: Tephritidae) and analysis of factors influencing populations in Baoshanba, Yunnan, China

Population dynamics of the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), were monitored year‐round using methyl eugenol‐baited traps in 2003, 2004, 2005 and 2006 in Baoshanba, Yunnan Province, China. Environmental factors including air temperature, rainfall and host‐plant species were analyzed with respect to the population dynamics. This species occurred only during April–November, with one yearly peak in August. The population fluctuation patterns with respect to season were identical in all study years. Correlation analysis and stepwise regression analysis indicated that air temperature, rainfall, sunlight hours and relative humidity were the major climatic factors that correlated with changes in the size of the fly population, and that monthly mean temperature, monthly sunlight hours and monthly relative humidity were most important. The seasonal increase in population size coincided with the fruiting period of the fly's host plants, but host fruit availability influenced the population size only when temperatures were sufficiently high. Cold temperatures may explain why there was no trap capture in the winter months. We believe that air temperature is the key factor explaining the seasonal occurrence of the fly population at Baoshanba.     

云南六库桔小实蝇成虫种群数量变动及其影响因子分析

应用诱蝇谜引诱剂诱捕法于2003-2005年调查了云南六库桔小实蝇成虫种群动态,系统分析了气候因子及寄主植物对该种群变动的影响。研究结果表明：云南六库桔小实蝇种群发生呈季节性,仅出现于3-12月,成虫消长基本为单峰型,高峰出现在7月。六库桔小实蝇种群数量与气温、降雨量和月雨日数等气象因子有密切关系。决定系数和通径分析结果显示,月降雨量是影响六库桔小实蝇种群动态的主要决策因素;月平均气温和月平均最低气温是影响种群数量变动的主要限制因素,其中,月平均最低温度是间接影响种群数量变动的重要指标。主成分分析筛选出低温条件主成分,其累积方差贡献率达77.65%。逐步回归分析也证实,影响六库桔小实蝇种群月变动的主要气象因子是月平均气温和月平均最低气温。综合分析认为,低温是导致六库桔小实蝇季节性发生的关键因素。     

Rainfall influences on ungulate population abundance in the Mara-Serengeti ecosystem

1. Rainfall is the prime climatic factor underpinning the dynamics of African savanna ungulates, but no study has analysed its influence on the abundance of these ungulates at monthly to multiannual time scales. 2. We report relationships between rainfall and changes in age- and sex-structured abundances of seven ungulate species monitored monthly for 15 years using vehicle ground counts in the Maasai Mara National Reserve, Kenya. 3. Abundance showed strong and curvilinear relationships with current and cumulative rainfall, with older topi, Damaliscus korrigum (Ogilby); warthog, Phacochoerus aethiopicus (Pallas); waterbuck, Kobus ellipsyprimnus (Ogilby); and impala, Aepyceros melampus (Lichtenstein) responding to longer lags than younger animals, portraying carryover effects of prior habitat conditions. 4. The abundances of newborn calves were best correlated with monthly rainfall averaged over the preceding 5-6 months for topi, waterbuck, warthog, and 2 months for the migratory zebra Equus burchelli (Gray), but with seasonal rainfall averaged over 2-5 years for giraffe, Giraffa camelopardalis (L.); impala; and kongoni, Alcelaphus busephalus (Pallas). The cumulative late wet-season rainfall was the best predictor of abundance for quarter- to full-grown animals for most species. Monthly rainfall exerted both negative and positive effects on the abundances of zebra, impala and waterbuck. Ignoring age, both sexes responded similarly to rainfall. 5. Births were strongly seasonal only for warthog and topi, but peaked between August and December for most species. Hence abundance was strongly seasonal for young topi and warthog and the migratory zebra. Pronounced seasonality in births for warthog and topi obliterated otherwise strong relationships between abundance and rainfall when both month and rainfall were included in the same model. Aggregated density produced relationships with rainfall similar to those for fully grown animals, emphasizing the necessity of demographic monitoring to reliably reveal rainfall influences on ungulate abundance in the Mara. 6. Strong relationships between abundance and rainfall suggest that rainfall underpins the dynamics of African savanna ungulates, and that changes in rainfall due to global warming may markedly alter the abundance and diversity of these mammals. Ungulates respond to rainfall fluctuations through movements, reproduction or survival, and the responses appear independent of breeding phenology and synchrony, dietary guild, or degree of water dependence. Newborns and adults have contrasting responses to rainfall. Males and females respond similarly to rainfall when age is ignored.     

Declining and low fecal corticoids are associated with distress, not acclimation to stress, during the translocation of African rhinoceros

Concentrations of adrenal steroid metabolites in feces are routinely used to assess the welfare of animals that are the subject of conservation efforts. The assumption that low and declining corticoid concentrations indicate the absence of stress and acclimation, respectively, is often made without experimental support or wild-animal comparisons, although intrinsic control of adrenal steroids might occur even under ongoing stress and distress. We adopted the capture and 11-week captivity of 18 black ( Diceros bicornis : 11 males, seven females) and 52 white ( Ceratotherium simum : 22 males, 30 females) rhinoceros as an experimental test of the relationship between corticoid concentrations and stress (translocation) and measured for suppressed gonad function as an indicator of distress – the biological cost of cumulative stressors. Fecal samples collected from the rectum at capture and during captivity were stored frozen and their corticoid, and androgen (in males) or progestin (in females), concentrations determined by radioimmunoassay. Corticoid profiles followed the expected pattern of being two to five times pre-capture levels (ng g⁻¹: black rhino: female 24.5±3.7, male 23.9±2.2; white rhino: female 16.3±1.6, male 12.3±2.4) for up to 17 days after capture and declined with time in captivity. Black rhinoceros and male white rhinoceros corticoids declined below pre-capture values and were associated with suppressed levels of androgens and progestins with increased time in captivity. Declining corticoids could not be interpreted as acclimation or the absence of stressors, without also measuring for distress in African rhinoceros. White rhinoceros female corticoid values remained elevated, although their gonad steroid levels were also suppressed. We discuss our findings for the management of rhinoceros in the wild and captivity.     

BLUE WHALE (BALAENOPTERA MUSCULUS)DISTRIBUTION IN THE EASTERN TROPICAL PACIFIC

The distribution of blue whales, Balaenoptera musculus , in the eastern tropical Pacific (ETP) was analyzed from 211 sightings of 355 whales recorded during research vessel sighting surveys or by biologists aboard fishing vessels. Over 90% of the sightings were made in just two areas: along Baja California, and in the vicinity of the Costa Rica Dome (a large, stationary eddy centered near 9°N, 89°W), with the rest made along the equator near the Galapagos islands, the coasts of Ecuador and northern Peru. All sightings occurred in relatively cool, upwelling-modified waters. Because these areas are the most productive parts of the ETP, and have relatively large standing stocks of euphausiids, it seems possible that blue whales select low latitude habitats which permit foraging. The waters off western Baja California were occupied seasonally, with a peak in sightings coinciding with the spring peak in upwelling and biological production. The Costa Rica Dome area was occupied year round, suggesting either a resident population, or that both northern and southern hemisphere whales visit, with temporal overlap. The modal group size was one for all areas and seasons, but the frequency of groups with two or more whales was significantly higher in sightings made near the Galapagos Islands and the coast of Ecuador and northern Peru.     

Generalized Seasonal Autoregressive Integrated Moving Average Models for Count Data with Application to Malaria Time Series with Low Case Numbers

Introduction

With the renewed drive towards malaria elimination, there is a need for improved surveillance tools. While time series analysis is an important tool for surveillance, prediction and for measuring interventions’ impact, approximations by commonly used Gaussian methods are prone to inaccuracies when case counts are low. Therefore, statistical methods appropriate for count data are required, especially during “consolidation” and “pre-elimination” phases.

Methods

Generalized autoregressive moving average (GARMA) models were extended to generalized seasonal autoregressive integrated moving average (GSARIMA) models for parsimonious observation-driven modelling of non Gaussian, non stationary and/or seasonal time series of count data. The models were applied to monthly malaria case time series in a district in Sri Lanka, where malaria has decreased dramatically in recent years.

Results

The malaria series showed long-term changes in the mean, unstable variance and seasonality. After fitting negative-binomial Bayesian models, both a GSARIMA and a GARIMA deterministic seasonality model were selected based on different criteria. Posterior predictive distributions indicated that negative-binomial models provided better predictions than Gaussian models, especially when counts were low. The G(S)ARIMA models were able to capture the autocorrelation in the series.

Conclusions

G(S)ARIMA models may be particularly useful in the drive towards malaria elimination, since episode count series are often seasonal and non-stationary, especially when control is increased. Although building and fitting GSARIMA models is laborious, they may provide more realistic prediction distributions than do Gaussian methods and may be more suitable when counts are low.     

The long-term trends and seasonal variation of the aeroallergen Alternaria in Derby, UK

Very little is known in the UK about long term trends of theAlternaria spore although it is known to trigger asthma. It hasrecently become apparent that Alternaria spore levels areincreasing in Derby and a detailed study of Alternaria wasundertaken to investigate the increase in numbers, seasonal variationand diurnal periodicity. The seasonal (June—October)Alternaria spore concentrations show a distinct upward trendand there is evidence of an earlier seasonal start and an increase inthe seasonal duration. There has been a dramatic rise in the number ofdays with an Alternaria spore count above 50 spores per cubicmetre, with the peak daily count usually occurring in August butoccasionally in late July or early September. August generally has thehighest monthly total and for 1991–1998 there was a positivecorrelation with monthly rainfall and average temperature. Day to dayspore levels show a positive correlation between Alternariaspore concentrations and maximum temperature but a slight negativecorrelation with daily rainfall. The peak time for spore capture is14.00–22.00, and more than half the daily Alternariacatch is caught between 18.00 and 24.00 hours. The upward trend inAlternaria spore concentrations may be responsible forincreasing levels of respiratory disease, especially during harvesttime.     

Anthropogenic Influences on Conservation Values of White Rhinoceros

White rhinoceros (rhinos) is a keystone conservation species and also provides revenue for protection agencies. Restoring or mimicking the outcomes of impeded ecological processes allows reconciliation of biodiversity and financial objectives. We evaluate the consequences of white rhino management removal, and in recent times, poaching, on population persistence, regional conservation outcomes and opportunities for revenue generation. In Kruger National Park, white rhinos increased from 1998 to 2008. Since then the population may vary non-directionally. In 2010, we estimated 10,621 (95% CI: 8,767–12,682) white rhinos using three different population estimation methods. The desired management effect of a varying population was detectable after 2008. Age and sex structures in sink areas (focal rhino capture areas) were different from elsewhere. This comes from relatively more sub-adults being removed by managers than what the standing age distribution defined. Poachers in turn focused on more adults in 2011. Although the effect of poaching was not detectable at the population level given the confidence intervals of estimates, managers accommodated expected poaching annually and adapted management removals. The present poaching trend predicts that 432 white rhinos may be poached in Kruger during 2012. The white rhino management model mimicking outcomes of impeded ecological processes predicts 397 rhino management removals are required. At present poachers may be doing “management removals,” but conservationists have no opportunity left to contribute to regional rhino conservation strategies or generate revenue through white rhino sales. In addition, continued trends in poaching predict detectable white rhino declines in Kruger National Park by 2016. Our results suggest that conservationists need innovative approaches that reduce financial incentives to curb the threats that poaching poses to several conservation values of natural resources such as white rhinos.     

Reproductive strategy of Psectrogaster rhomboides Eigenmann & Eigenmann, 1889, a freshwater fish from Northeastern Brazil

Several environmental parameters related to the spawning season of the freshwater fish, Psectrogaster rhomboides were identified. The hypothesis predicts synchrony of the spawning season with the rainy period, presenting a seasonal reproductive strategy. This study investigated the total body length and body mass, sex ratio, body size at first sexual maturity, gonadosomatic index, condition factor, fecundity and reproductive period of P. rhomboides in the natural environment. Twelve monthly samplings (mean n = 20) were carried out from March 2009 to February 2010. Fish were captured using 4 cm diameter cast nets and environmental parameters such as rainfall, temperature, dissolved oxygen concentration, pH and electrical conductivity of the water were registered. The sampled population of P. rhomboides (n = 444) showed a sex ratio of 1 : 1. Females attained first sexual maturity at 15 cm total length and males at 15.3 cm total length. Spawning occurred from March to May, with high gonadosomatic index values during the rainy season. This species is a total spawner, with a mean fecundity of 6188 (±367) mature oocytes. P. rhomboides presents a seasonal reproductive strategy, providing a population increase and exploitation of the environmental resources during the rainy period. Rainfall (196.5 ± 4.9 mm) and the concentration of dissolved oxygen (7.82 ± 0.7018 mg L^?1) were influential factors during the spawning season. Gonadosomatic index and the condition factor were negatively correlated during the gonadal development cycle of this species. The monthly gonadosomatic index values show that spawning begins when the rainy season is at its maximum and ends synchronously (females r = 0.9171; males r = 0.889) with the end of the rainy season.     

Reproductive strategy of Leporinus piau (Fowler, 1941), a neotropical freshwater fish from the semi‐arid region of Brazil

This study concerns the reproductive strategy of the freshwater fish, Leporinus piau, native to the Brazilian semi‐arid region. The hypothesis of this work predicts that the species would spawn during the rainy season, presenting a seasonal reproductive strategy. The study investigated the structure of total body length and body mass, sex ratio, body size at first sexual maturity, developmental stages of gonads, fecundity, gonadosomatic index (GSI), condition factor (K) and the spawning season of L. piau. Twelve monthly samplings (mean n = 18) were carried out in 2009 and environmental parameters such as rainfall, temperature, pH, electrical conductivity and concentration of dissolved oxygen of water were registered. The sampled population of L. piau (n = 211) showed a slight predominance of males (55%), but with larger and heavier females. First sexual maturation in males occurred earlier (16.5 cm total length) than in females (20.5 cm total length). The species is a total spawner with an average fecundity of 55 000 mature oocytes. Rainfall (225 ± 7.2 mm) and concentration of dissolved oxygen (8.5 ± 0.2 mg L^?1) acted as influential factors during the spawning season. The monthly GSI shows that spawning starts when the rainy season is at its maximum and ends synchronously (females r = 0.91; males r = 0.89) with the end of the rainy season. L. piau presents a seasonal reproductive strategy with high reproductive output, providing a population increase and exploitation of the environmental resources.     

Demography and population dynamics of the mouse opossum (Thylamys elegans) in semi-arid Chile: seasonality, feedback structure and climate

Here we present, to the authors' knowledge for the very first time for a small marsupial, a thorough analysis of the demography and population dynamics of the mouse opossum (Thylamys elegans) in western South America. We test the relative importance of feedback structure and climatic factors (rainfall and the Southern Oscillation Index) in explaining the temporal variation in the demography of the mouse opossum. The demographic information was incorporated into a stage-structured population dynamics model and the model's predictions were compared with observed patterns. The mouse opossum's capture rates showed seasonal (within-year) and between-year variability, with individuals having higher capture rates during late summer and autumn and lower capture rates during winter and spring. There was also a strong between-year effect on capture probabilities. The reproductive (the fraction of reproductively active individuals) and recruitment rates showed a clear seasonal and a between-year pattern of variation with the peak of reproductive activity occuring during winter and early spring. In addition, the fraction of reproductive individuals was positively related to annual rainfall, while population density and annual rainfall positively influenced the recruitment rate. The survival rates were negatively related to annual rainfall. The average finite population growth rate during the study period was estimated to be 1.011 +/- 0.0019 from capture-recapture estimates. While the annual growth rate estimated from the seasonal linear matrix models was 1.026, the subadult and adult survival and maturation rates represent between 54% (winter) and 81% (summer) of the impact on the annual growth rate.     

内蒙古农牧交错带长爪沙鼠种群存活的季节格局及其动态机制

了解动物种群存活特征以及相关环境因子对其变化的独立或整合作用过程,有助于阐明动物种群动态的生态学机制。长爪沙鼠（Meriones unguiculatus）是分布于我国北方典型草原、荒漠草原及其毗邻的农牧交错带的优势鼠种之一。2000年10月至2004年10月通过标志重捕法研究了栖息于内蒙古农牧交错区草地生境的种群动态。本文通过MARK软件包中的CJS和MS模型分析了长爪沙鼠半自然围栏种群表观存活率（Φ,简称存活率）的性别（g）差异和年龄（as）特征表现及其季节变化格局,并对种群存活变化的密度和气候效应加以分析,旨在检验长爪沙鼠种群存活显示季节变化特征,并受密度制约和气候条件反馈调节的假设。结果发现,长爪沙鼠种群存活率初始最优模型Φ(t)p(g*t)中重捕时序（t）效应显著（ANODEV,F _27,47 =11.05,P <0.001）,月季效应最优模型Φ(month)p(g*t)也显示存活率 季节变化明显（ANODEV,F _5,69 =31.69,P <0.001）,总体呈现从春季到冬季经历下降再升高的“V”字型动态模式。在无环境因子限制条件下,雌鼠（0.788±0.013）和雄鼠（0.781±0.013）存活率差异不明显;存活率年龄差异表现明显的季节特征（ANODEV,F _5,246 = 67.85,P < 0.001）,繁殖消耗在一定时期影响成年个体的存活。长爪沙鼠种群存活的季节格局反映其生活史对策中适应高纬度气候和食物等资源季节波动的重要特征。进一步统计发现种群存活率受密度制约、与降水负相关,其中密度制约效应具有一定的时滞,降水作用是即时的,上述效应的作用强度在雌、雄鼠的存活反应上有所差异。这些结果暗示密度制约整合水热条件介导最适栖息地环境变化,引发雌、雄鼠存活率差异性反应,进而影响其它种群参数变化,调节种群增长。这可能是北半球高纬度地区小哺乳动物种群调节的一个重要机制。     

Dynamic social system in Nubian ibex: can a second mating season develop in response to arid climate?

We studied a population of Nubian ibex Capra ibex nubiana in the eastern extreme of its range, the hyper-arid central desert of the Sultanate of Oman. Long-term data were collected from January 1983 to December 1997 by direct observation, as well as VHF telemetry on 12 animals (eight from 1987 to 1990; four from 1994 to 1996). We recorded 884 sightings: 40.4% of single animals and 59.6% of groups. Although no significant monthly variation of group size (Jarman's Typical Group Size) was found, there were distinct peaks in March (4.0 ind. group⁻¹) and September (5.1 ind. group⁻¹). Groups of males and females formed especially in March and November, and female–kid groups in February and July–August. Our data may suggest two mating periods: the first one in autumn (similar to the rut of ibex in temperate mountain areas), with kids born in spring/early summer, after winter–spring rainfall, and the second one in spring, with kids born in late summer/autumn, before winter–spring rainfalls. We suggest that the second rutting period may have evolved as a micro-evolutionary process, with the local population adapting to hyper-arid environment constraints. The spring mating season may favour only females in prime conditions, who can afford a pregnancy in the local severe summers and will deliver kids when plant greening begins, in the autumn, whereas the autumn (original) mating season may be afforded by any female, but kids will be born in an unfavourable period, before the summer drought.     

Evidence of seasonal migration in a tropical subterranean vertebrate

Many animals undergo migrations that depend on a range of biotic or abiotic factors provoking daily, seasonal or annual movement of individuals and/or populations. Temperate amphibians frequently have their life cycles dominated by annual temperature fluctuations, but in the tropics it is often presumed that distinct rainy seasons will influence amphibians more than small changes in temperature. Here, we direct the seasonal changes in abundance hypothesis to a caecilian amphibian Boulengerula boulengeri found in monthly randomized quantitative surveys in the top 30 cm of soil. Meteorological data are used to interpret the significant changes found in relation to rainfall and temperature variables. Instead of the expected correlation of migration with rainfall, we find that frequency varies significantly and positively with temperature. In addition, data on the depth at which individual caecilians are collected suggest that animals undergo a vertical (rather than horizontal) migration within the soil. This is the first example of vertical migrations with temperature (as opposed to rainfall) of any tropical subterranean fauna. We discuss the possible influences that stimulate migration in this species (abiotic factors, feeding, reproduction and predation). The ecology of caecilians has lagged behind that of all other tetrapods, and this study has importance for future ecological studies, as well as biodiversity assessments and monitoring methodologies.     

云南瑞丽桔小实蝇成虫种群数量变动及其影响因子分析

分别于1997、2000、2003和2004年通过诱蝇谜对云南瑞丽桔小实蝇种群动态进行了全年监测,并就气候因子及寄主植物对该种群变动的影响进行了系统分析.结果表明,桔小实蝇在瑞丽常年发生,当年11月至翌年1月份,桔小实蝇种群处于较低水平,2月份以后种群数量逐渐上升,至6月份形成种群的年增长高峰,此后至10月份种群数量迅速下降.经逐步回归分析表明,月均温、月平均最高温、月平均最低温、月极端最高温、月极端最低温和月雨日数是影响瑞丽桔小实蝇种群月变动的主要气候因子.通径分析和决策系统分析表明,月均温对种群数量变动具有正效应,是直接影响桔小实蝇种群变动的重要指标,月均最低温是影响种群增长的最主要的限制因素,月雨日数对种群动态的综合影响力最大.瑞丽各月平均温度位于桔小实蝇各虫态生长发育温度范围内,但11～翌年1月份的月均最低温低于桔小实蝇的适温范围,对桔小实蝇种群数量有一定抑制作用.2～5月份雨日数逐渐增多,雨量逐渐增大,有利于种群数量增长;7～8月份持续的强降雨过程被认为是桔小实蝇在该时期种群数量下降的主要原因.而瑞丽的多种瓜果成熟期的交替出现保证了桔小实蝇的食物供应.     

云南西双版纳桔小实蝇种群动态

于1997年、2000年和2003年在云南西双版纳通过性诱剂诱捕对桔小实蝇种群动态进行了全年监测,并就气候因子及寄主种类对该种群变动的影响进行了系统分析.结果表明,桔小实蝇在西双版纳常年发生.当年11月至次年2月,桔小实蝇种群处于较低水平,3月以后种群数量逐渐上升,至6～7月形成一个种群增长高峰,此后至10月种群数量迅速下降.分析表明,影响桔小实蝇种群变化的重要因子是温度、降雨量和寄主种类.西双版纳各月均温位于桔小实蝇适温范围内,但12～2月的月平均最低温度低于桔小实蝇的适温范围,对桔小实蝇种群数量有一定抑制作用.降雨量是影响桔小实蝇种群数量变动的另一重要因子.月降雨量低于50 mm以下对桔小实蝇种群不利,而100～200 mm的月降雨量有助于桔小实蝇种群的增长.月降雨量大于250 mm以上将导致桔小实蝇种群数量下降.6～7月强降雨过程被认为是桔小实蝇在该时期种群数量下降的主要原因.芒果、番石榴、桃、梨、柑桔、龙眼和荔枝是桔小实蝇在该地区的主要寄主水果.其中,芒果和龙眼是当地桔小实蝇最喜好的寄主水果,其种植面积、挂果期和产量对桔小实蝇种群数量变动影响较大,被认为是影响该地区桔小实蝇种群变动的又一主要因素.     

Effects of spring drought and irrigation on farmland arthropods in southern Britain

1.  Information is lacking on how possible future changes in the seasonal occurrence and intensity of precipitation in Europe will affect the arthropod community of arable farmland.
2.  We used a novel experimental approach to investigate the responses of farmland arthropods to spring precipitation in a spring-sown legume. Replicated plots were subjected to spring drought (plots shielded from rainfall), actual rainfall (reference) and spring irrigation. Shielding plots extended an existing drought to 58 days.
3.  The response of epigeic arthropods was investigated using principal components analysis (PCA) and principal response curves (PRC). Temporal changes in treatment effects at the community level were more clearly displayed by PRC than by PCA, while PRC improved the interpretation of individual species' responses. PRC analysis has potential for wider application in ecological experiments and monitoring.
4.  Short-term manipulation of precipitation in May affected the arthropod community for at least 97 days, despite exceptionally high rainfall in June. The effects of drought on the abundance of herbivores, mycophages, omnivores and predators were negative, while those of irrigation were positive. There were no differences in the responses of beneficial and pest taxa.
5.  In addition to their intrinsic importance, these findings illustrate that spring weather might affect the availability of arthropod prey for insectivorous wildlife. Food availability has been implicated in the population declines of several insectivorous farmland birds.
6.  The difficulty of manipulating rainfall in a temperate climate precludes realistic field studies of how farmland arthropods respond to precipitation. We suggest that automated rain shielding of experimental plots provides a technique for wider application in drought studies.     

Abiotic factors influencing the ecology of wild rabbit fleas in north-eastern Spain

During 1992, the population dynamics of rabbit fleas were compared at two sites in north-eastern Spain. The sites differed mainly in terms of annual rainfall and soil type. All flea species showed seasonal cycles of abundance, although peaks in numbers occurred at different times, reflecting their specific adaptations for coping with climatic variables. Adult Spilopsyllus cuniculi (Dale) (Siphonaptera: Pulicidae) were found largely parasitizing rabbits in spring and adult Caenopsylla laptevi (Beaucournu etal.) (Siphonaptera: Ceratophyllidae) in the autumn. In contrast, monthly flea indices of Xenopsylla cunicularis (Smit) (Siphonaptera: Pulicidae) and Echidnophaga iberica (Ribeiro et al.) (Siphonaptera: Pulicidae) peaked in summer. Spilopsyllus cuniculi was present at both sites, but was less common on the drier site, where monthly mean temperature and annual rainfall approached the flea's physiological limits. By contrast, E. iberica, X. cunicularis and C. laptevi, known to be better adapted for dryness, showed the opposite patterns of abundance. Nevertheless, even these arid-adapted species took advantage of the milder and wetter spring (X. cunicularis and E. iberica) or autumn (C. laptevi) for breeding and larval development. Although environmental temperature, rainfall and soil texture will influence the microclimate of the burrows where the flea larvae develop, burrow humidity seems to be more dependent on soil characteristics and past rainfall rather than the humidity of the external air.