Risky Courtship: Background Contrast,Ornamentation, and Display Behavior of Wolf Spiders Affect Visual Detection by Toad Predators

Males that search widely for females and perform conspicuous courtship displays run a high risk of being detected by their predators. Therefore, gains in reproductive success might be offset by increased mortality due to predation. Male brush‐legged wolf spiders (Schizocosa ocreata) with larger decorative traits (foreleg tufts) are preferred by females as mates, but are more readily detected by predators. However, predation risk may also be influenced by the interaction between components of signals and the environment in which signaling occurs. Courting male spiders were readily accepted as prey by a sympatric predator, the American toad (Anaxyrus americanus). We used video playback to tease apart the interactive effect between visual signals and the signaling environment on the ability of toads to detect courting spiders as a function of distance, background contrast, the presence or absence of male foreleg tufts, and behavioral activity. The response of toads to video sequences of male spiders was similar to their response to live male spiders. Toad response varied over distance toward spiders displayed against high contrast (sunny) vs. low contrast (shaded) backgrounds. Beyond 30 cm, more toads detected courting male spiders against light, ‘sunny’ backgrounds and detected them faster when compared to the same spider stimulus against darker, ‘shady’ backgrounds. In choice tests, toads oriented more often toward courting males with leg tufts than those without. Toad responses also varied with male spider behavior in that only videos of moving males were attacked. Latency to orient and detection by toads was significantly greater for walking males than courting males, and this effect was most evident at distances between 30 cm and 50 cm. Results supported that courting wolf spiders are at significant risk of predation by visually acute predators. Distance, background contrast, and the presence of foreleg decorations influence detection probability. Thus, the same complex visual signals that make males conspicuous and are preferred by females can make males more vulnerable as prey to toads.     

Age and Sex-Based Differences in the Use of Prey Sensory Cues in Wolf Spiders (Araneae: Lycosidae)

Differences in foraging patterns mediated by sensory cues were examined between adult and juvenile male and female wolf spiders (Schizocosa rovneri; Lycosidae). Patch residence time for thirty-one spiders were tested among juveniles and adults in artificial foraging patches. Patches varied in sensory information provided by live prey (crickets) as follows: visual stimuli alone; vibratory stimuli alone; visual and vibratory stimuli together; and control (no stimuli). Spiders moved between patches for one hour, but could not feed. Adult Schizocosa rovneri use primarily visual information to determine patch residence time, but juveniles use vibratory cues as well. Significant age and sex-based differences in the use of sensory cues suggest that observed divergent foraging strategies are partly due to the use of different perceptual cues in prey detection.     

田间蜘蛛集团对飞虱的每日捕食量与室内、盆栽水稻的捕食作用比较

采用控制论中的脉冲采样法结合杀死飞虱计数法研究了田间蛛蛛对飞虱的每日捕食量估计并与室内,盆栽罩笼水稻功能反应的捕食作用进行了比较,结果表明田间蜘蛛平均每头每日对飞虱的捕食量为0.669头,这一捕食量比室内和盆栽水稻的捕食量要小得多;田间捕食百分率与飞虱密度呈二次抛物线关系,即飞虱低密度和高密度捕食百分率均低于中等密度,在每穴10头飞虱左右,捕食量和捕食百分率最高,在有一定存量蜘蛛时,捕食量与微蛛,狼蛛数量呈显著的二元线性回归关系,但偏相关系数为负,由此表明随蜘蛛密度的增加捕食量反而下降,这与一些多物种共存系统和田间罩笼的研究结果相一致。     

Body Size, Leg Autotomy, and Prior Experience as Factors in the Fighting Success of Male Crab Spiders, Misumenoides formosipes

Game theory predicts which characteristics of male crab spiders should affect their success in mate-guarding contests. Previous data on Misumenoides formosipes suggested that body size and leg number influenced fight outcome, but the study had methodological problems. Using improved methods, we corroborated the size advantage but refuted the disadvantage of leg reduction. We also conducted the first test for an invertebrate on the effect that a single contest has on the outcome of subsequent contests. When size and residency status were controlled, prior winners defeated prior losers after only one contest experience. We discuss the importance of controlling for previous experiences in studies of contest resolution and the ramifications for both past and future studies.     

Fitness costs and benefits of antipredator behavior mediated by chemotactile cues in the wolf spider Pardosa milvina (Araneae: Lycosidae)

Animals may exhibit a variety of defensive behaviors in thepresence of indirect predator cues. Such behavior offers immediatefitness benefits but may also incur substantial foraging andreproductive costs. We measured shifts in space use (verticalclimbing) by the wolf spider Pardosa milvina induced by chemotactilecues (silk and excreta) from a co-occurring predatory wolfspider Hogna helluo. We then measured foraging and reproductive costs, as well as survival benefits, of this behavior. For 2weeks, we maintained mated adult female Pardosa in plasticcontainers with one of three treated peat moss substrates:a container previously occupied by a conspecific for 3 days,a container previously occupied by an adult Hogna for 3 days,and a container devoid of either cue (control). We measuredprey capture efficiency, body condition, egg sac production,egg sac weight, and egg number for individuals in each treatment.We also counted the number of Pardosa that survived and exhibitedclimbing behavior in the presence of a live Hogna with andwithout silk and excreta cues. Pardosa climbed container wallssignificantly more often in the presence of Hogna silk andexcreta relative to other treatments. Pardosa exposed to Hognacues coupled with live Hogna survived significantly longerthan spiders that had no predator cues available. Pardosa placedin containers with Hogna cues, but no Hogna, lost weight morequickly, ate fewer prey, were in poorer body condition, producedlighter egg sacs, and produced fewer eggs than spiders in controlor conspecific treatments.     

Nest Predation of Greater Sage-Grouse in Relation to Microhabitat Factors and Predators

ABSTRACT Nest predation is a natural component of greater sage-grouse (Centrocercus urophasianus) reproduction, but changes in nesting habitat and predator communities may adversely affect grouse populations. We used a 2-part approach to investigate sage-grouse nest predation. First, we used information criteria to compare nest survival models that included indices of common raven (Corvus corax) abundance with other survival models that consisted of day of incubation, grouse age, and nest microhabitat covariates using measurements from 77 of 87 sage-grouse nests. Second, we used video monitoring at a subsample of 55 of 87 nests to identify predators of depredated nests (n = 16) and evaluated the influence of microhabitat factors on the probability of predation by each predator species. The most parsimonious model for nest survival consisted of an interaction between day of incubation and abundance of common ravens (w_{ravenXincubation day} = 0.67). An estimated increase in one raven per 10-km transect survey was associated with a 7.4% increase in the odds of nest failure. Nest survival was relatively lower in early stages of incubation, and this effect was strengthened with increased raven numbers. Using video monitoring, we found the probability of raven predation increased with reduced shrub canopy cover. Also, we found differences in shrub canopy cover and understory visual obstruction between nests depredated by ravens and nests depredated by American badgers (Taxidea taxus). Increased raven numbers have negative effects on sage-grouse nest survival, especially in areas with relatively low shrub canopy cover. We encourage wildlife managers to reduce interactions between ravens and nesting sage-grouse by managing raven populations and restoring and maintaining shrub canopy cover in sage-grouse nesting areas.     

Development, growth, and egg production of Ageneotettix deorum (Orthoptera: Acrididae) in response to spider predation risk and elevated resource quality

Abstract.  1. Predation risk to insects is often size- or stage-selective and usually decreases as prey grow. Any factor, such as food quality, that accelerates developmental and growth rates is likely to reduce the period over which prey are susceptible to size-dependent predation.
2. Using field experiments, several hypotheses that assess growth, development, and egg production rates of the rangeland grasshopper Ageneotettix deorum (Scudder) were tested in response to combinations of food quality and predation risk from wolf spiders to investigate performance variation manifested through a behaviourally mediated path affecting food ingestion rates.
3. Grasshoppers with nutritionally superior food completed development ≈ 8–18% faster and grew 15–45% larger in the absence of spiders, in comparison with those subjected to low quality food exposed to spider predators. Growth and development did not differ for grasshoppers feeding on high quality food when predators were present in comparison with lower quality food unimpeded by predators. Responses indicated a compensatory relationship between resource quality and predation risk.
4. Surviving grasshoppers produced fewer eggs compared with individuals not exposed to spiders. Because no differences were found in daily egg production rate regardless of predation treatment, lower egg production was attributed to delayed age of first reproduction. Results compare favourably with responses observed in natural populations.
5. Risk of predation from spiders greatly reduced growth, development, and ultimately egg production. Increased food quality counteracts the impact of predation risk on grasshoppers through compensatory responses, suggesting that bottom-up factors mediate effects of spiders.     

It Takes Two to Tango: Relative Influence of Male and Female Identity and Morphology on Complex Courtship Display in a Newt Species

Consistency in behaviour is currently receiving a renewed interest. Although courtship display is generally consistent in terms of behavioural sequence and structure, there is also commonly important variation in the intensity of courtship display between and within males of a given species. Indeed, not all males have the same ability to perform courtship display (variation between males), and each male can potentially adjust his courtship effort in response to the environment (variation within a male). Although the study of male courtship display has received considerable attention in recent years, it is still unclear which part of the variation can be explained by male ability or motivation. We investigated this issue on two phases of the complex courtship display of the palmate newt Lissotriton helveticus. Overall, we found that both male and female identities affected courtship behaviour, but the relative influence of each sex depended on the courtship phase. Male identity explained variation in fan and creep‐quiver display, whereas female identity explained variation in creep‐quiver only. Interestingly, we did not find any link between the expression of courtship display and male or female morphological traits. Our study showed consistency of male courtship display in newts and successfully dissects the different sources of variation that can affect behavioural repeatability/consistency of courtship display.     

水稻红莲型细胞质雄性不育系与保持系mtRNA差异显示和差别片段的分析

将T4 RNA连接酶和AFLP技术特点相结合构建了适于mtRNA的差异显示方法 ,并比较了水稻 (OryzasativaL .)红莲型细胞质雄性不育系、保持系和杂种一代mtRNA的差异。在 4组引物对的选择扩增产物中共找到 6个差异片段 ,其中差异条带DTA为不育系仅有 ,条带DAB为不育系和保持系特有 ,而条带DBF1、DBF2 、DBF3 、DBF4 为保持系和F1杂种共有。这表明水稻红莲型不育系粤泰A与杂种一代泰优 2号mtRNA的差异大于保持系粤泰B和杂种一代泰优 2号mtRNA的差异。Northern杂交证实条带DTA在不育系、保持系和杂种一代的转录确有差异 ,表明它与红莲型细胞质雄性不育有关。条带DTA全长 2 5 9bp ,尽管未发现有同源序列和新的开放阅读框 ,但它可作为探针从cDNA文库中筛选全基因序列 ,进而寻找与细胞质雄性不育有关的开放阅读框架。     

Male disguised females: costs and benefits of female‐limited dimorphism in a butterfly

1. In polymorphic species, two or more discrete phenotypes co‐occur simultaneously. Sex‐limited polymorphism is a particular case of polymorphism, in which several discrete morphs coexist within one of the two sexes only. Several hypotheses were proposed to explain the existence and the maintenance of sex‐limited polymorphism in insects: (i) the morphs have similar fitness, such as similar survival and expected fecundity, and their frequencies vary randomly (i.e. the null hypothesis); (ii) harassment by males is reduced towards the less common female morph, in this case andromorph females (i.e. the male mimicry and learned mate recognition hypotheses); (iii) morphs differ in predation risk (i.e. the predation hypothesis); or (iv) morphs differ in thermoregulation ability (i.e. the thermoregulation hypothesis). 2. Field observations and experiments were employed to compare the relative support of these hypotheses using dimorphic females of the bog fritillary butterfly. Differences were detected between morphs in survival, fecundity, harassment by males, predation pressure and thermal properties, thereby rejecting the null hypothesis. 3. The lifestyle of both morphs is associated with different costs and benefits, with advantages in daily survival and precocious emergence for the gynomorph females, and advantages in fecundity, predation and male harassment for the andromorph females. Besides, as the bog fritillary butterfly is protandrous (i.e. males emerge before females), the longer development of andromorph females puts them at risk of emerging when all the males are dead. The results raise the question as to which mechanisms control the ontogenetic pathways driving the production of the two morphs (i.e. genetic polymorphism or phenotypic plasticity).     

A Quantitative Analysis of the Courtship Acoustic Behaviour and Sound Patterning in Male Sand Goby, <Emphasis Type="Italic">Pomatoschistus minutus</Emphasis>

Many animal groups use sounds in reproduction in order to court mates or repel rivals. We describe the sounds and behavioural context of courtship sound production in male sand gobies, Pomatoschistus minutus, and examine the variability of acoustic parameters and the fine temporal patterning of sound units. Male sand gobies excavate a nest under a suitable solid substrate and attract females to mate, attaching the eggs to the ceiling of the nest. Before mating a female may repeatedly enter and leave a male's nest. Sounds were not detected during the courtship phase outside the nest, but were recorded when females were in the nest before spawning. Sounds were produced in 44–100% of such nest visits, varying with individual males. The sand goby sound consists of a train of pulses repeated at a rate of 23–29 pulses per second. The frequency spectrum of single pulses was continuous from 20–30Hz to 500Hz and reached a peak around 100Hz. The absolute sound pressure level ranged from 118 to 138dB re 1µPa at 1–3cm. The sand goby emits sound in distinct sound groups (bursts). Sound temporal features (duration, pulse repetition rate) vary systematically over the course of the burst. Within- and between-male variation of acoustic parameters was examined from sounds emitted by the male. Sound amplitude (peak-to-peak, mV) and pulse rate varied significantly among males, despite low individual stereotypy. Furthermore, sound pressure level correlated with body size. The potential informative content of acoustic parameters is discussed in the light of a possible role of the sand goby sound in mate choice.     

Survival and Cause-Specific Mortality of Male Mule Deer Under Different Hunting Regulations in the Bridger Mountains,Montana

Abstract: We selected 2 adjacent populations of mule deer (Odocoileus hemionus hemionus) in the Bridger Mountains, Montana, USA, to measure effects on survival rates and causes of mortality of 2 hunting regulations designed to enhance representation of mature males. We compared male survival between the West Slope and South 16 Mile populations considering both hunting and nonhunting sources of mortality with respect to age (fawn, yearling, and mature), month (Jun-May), and year (1990-1995). Harvest rates of mature males were greater than for yearlings, demonstrating hunter preferences. We found no differences in yearling monthly survival rates between October and November or between areas or years. In contrast, we found survival of mature males differed between October and November and across years and study areas. During these months, survival rates of mature males averaged 0.602 on the West Slope under the 2-point regulation and 0.762 on South 16 Mile under the outfitted hunt. Monthly survival during summer also differed by age class, but not area, with estimates of 0.963 for yearling males, and corresponding mature male survival estimates of 0.991, demonstrating greater yearling summer mortality. Winter survival rates of yearlings and matures were similar for both areas with a monthly estimate of 0.986. We found differences in spring monthly survival estimates for the 2 areas, mainly for matures. Yearling male monthly survival estimates were 0.959 and 0.958 for the 2 areas, whereas corresponding mature male estimates during spring were 0.991 and 0.936 on the West Slope and South 16 Mile, respectively. Fawn survival rates varied from 0.101 to 0.770 among years and between areas overwinter. Cumulative effects of nonhunting mortality among all age classes reduced the effectiveness of 2 hunting regulations designed to enhance survival of males to age classes ≥4 years associated with maximum antler development despite accomplishing reductions in harvest rates. Low and variable fawn survival and relatively high nonhunting-related losses of yearling and mature males might be typical of many populations in the Northern Rocky Mountains. Deer managers should avoid populations coexisting with a diversity of large predators in environments with strong year effects when considering opportunities for implementing harvest regulations to improve representation of mature males.     

Spatial Distribution and Uncertainty Assessment of Potential Ecological Risks of Heavy Metals in Soil Using Sequential Gaussian Simulation

The objective of this study is to assess the spatial distribution and uncertainty of the potential ecological risks of heavy metals in soil using sequential Gaussian simulation (SGS) and the Hakanson potential ecological risk index (PERI). We collected 130 soil samples in an area of 150 km² in the High-Tech Park of Wuhan, China, and measured the concentrations of five heavy metals in soil (i.e., Cd, Cr, Cu, Pb, and Zn). We then simulated the spatial distribution of each heavy metal using SGS, and calculated Hakanson PERIs for individual metals and multiple metals based on the simulated realizations. The spatial uncertainty of the Cd PERI and its occurrence probabilities in different risk grades were further assessed. Results show that the potential ecological risks of Cr, Cu, Pb, and Zn are relatively low in the study area, but Cd indeed reaches a serious level that deserves much attention and essential treatment. The total PERI of multiple heavy metals indicates a moderate grade in most of the study area. In general, combining SGS and the Hakanson PERI appears to be an effective method for evaluating the potential ecological risks of heavy metals in soil and the priority areas for remediation.     

Quantifying Fish Swimming Behavior in Response to Acute Exposure of Aqueous Copper Using Computer Assisted Video and Digital Image Analysis

Behavioral responses of aquatic organisms to environmental contaminants can be precursors of other effects such as survival, growth, or reproduction. However, these responses may be subtle, and measurement can be challenging. Using juvenile white sturgeon (Acipenser transmontanus) with copper exposures, this paper illustrates techniques used for quantifying behavioral responses using computer assisted video and digital image analysis. In previous studies severe impairments in swimming behavior were observed among early life stage white sturgeon during acute and chronic exposures to copper. Sturgeon behavior was rapidly impaired and to the extent that survival in the field would be jeopardized, as fish would be swept downstream, or readily captured by predators. The objectives of this investigation were to illustrate protocols to quantify swimming activity during a series of acute copper exposures to determine time to effect during early lifestage development, and to understand the significance of these responses relative to survival of these vulnerable early lifestage fish. With mortality being on a time continuum, determining when copper first affects swimming ability helps us to understand the implications for population level effects. The techniques used are readily adaptable to experimental designs with other organisms and stressors.