Alternative predatory tactics of an araneophagic assassin bug (Stenolemus bituberus)

Predators of dangerous prey risk being injured or killed in counter-attacks and hence may use risk-reducing predatory tactics. Spiders are often dangerous predators to insects, but for a few, including Stenolemus bituberus assassin bugs, web-building spiders are prey. Despite the dangers of counter-attack when hunting spiders, there has been surprisingly little investigation of the predatory tactics used by araneophagic (spider-eating) insects. Here, we compare the pursuit tendency, outcome and predatory tactics of S. bituberus against five species of web-building spider. We found that S. bituberus were most likely to hunt and capture spiders from the genus Achaearanea, a particularly common prey in nature. Capture of Achaearanea sp. was more likely if the prey spider was relatively small, or if S. bituberus was in poor condition. S. bituberus used two distinct predatory tactics, ‘stalking’, in which they slowly approached the prey, and ‘luring’, in which they attracted spiders by manipulating the web to generate vibrations. Tactics were tailored to the prey species, with luring used more often against spiders from the genus Achaearanea, and stalking used more often against Pholcus phalangioides. The choice of hunting tactic used by S. bituberus may reduce the risk posed by the prey spider.     

The energetic costs of fighting in the house cricket, Acheta domesticus L

The cost of performing an agonistic behavior, or tactic, willhave consequences for an individual's rate of cost accrual,the tactic's evolutionary stability if used as an assessmentsignal, and its pattern of use in the behavioral choreographyof a contest. Few studies have attempted to quantify the costsof fighting, particularly with regard to energy expenditure.Flow-through respirometry revealed that house cricket malescan expend energy at relatively high rates when fighting (morethan eight times resting levels) depending on the particulartactic performed. Acoustic signalling (stridulation) constitutedthe least costly of seven measured agonistic tactics, whilewrestling with an opponent, the most energetically costly tactic,consumed oxygen at a net rate more than 40 times that of stridulation.Low-cost tactics are used by opponents more frequently thanmore costly tactics, providing evidence for an escalating tacticalconvention based on energetic costs. The moderate energeticcost of some tactics suggests they may function as reliablesignals in the assessment of wrestling ability. Net energy costsper contest increased linearly with contest duration for bothcontest winners and losers, but winners tended to expend moreenergy per contest than losers. The likely fitness effects ofenergy expended while fighting are discussed. The results ofthis study indicate that energy expenditure is an importantcost shaping contest strategies in Acheta domesticus     

Negative maternal or paternal effects on tactic inheritance under a conditional strategy

Alternative behavioral and life-history tactics are common in animal populations. The conditional strategy model provides a powerful explanation for the evolution and persistence of such tactics, as it allows alternative tactics to be perpetuated even if there is tactic inheritance and tactics yield unequal mean fitness. In many biological systems negative maternal or paternal effects complicate the inheritance of condition and, hence, the inheritance of alternative tactics. Indeed, the inheritance of condition may result in the alternation of tactics across generations. In this paper, we show that the conditional strategy is robust to these effects on progeny condition. There is a unique and stable proportion of tactics under standard inheritance and unequal tactic fitness, and these two important properties of the conditional strategy hold even if negative maternal or paternal effects on progeny condition cause tactics to alternate across generations. However, the dynamics of tactic proportions pursuant to a perturbation of the equilibrium tactic proportions depend on the form of tactic inheritance. An application of our theoretical results to data from a population of smallmouth bass (Micropterus dolomieu) in which negative paternal effects dictate progeny condition reveals that age at first reproduction in males alternates regularly across generations. Furthermore, the model indicates that the population would return rapidly to equilibrium if the proportions of males that mature early or late in life were perturbed from the equilibrium within the system. This example shows how the model of the conditional strategy can be used to gain insight into tactic dynamics in situations where some of the model parameters are difficult or impossible to measure empirically.     

Barriers to psychological care of the dying.

Direct observation of doctors and nurses talking with real, stimulated, or role played patients suffering from a terminal illness has shown that they consistently use distancing tactics. These prevent them getting close to their patients'' psychological suffering and are used to try to ensure their own emotional survival. Since these tactics discourage patients from disclosing their psychological concerns they are a serious barrier to effective psychological care. If those concerned in terminal care are to risk relinquishing these distancing tactics they will need better selection, more appropriate training, regular psychological support, and real opportunities for taking time out.     

Age‐dependent male mating tactics in a spider mite—A life‐history perspective

Males often fight with rival males for access to females. However, some males display nonfighting tactics such as sneaking, satellite behavior, or female mimicking. When these mating tactics comprise a conditional strategy, they are often thought to be explained by resource holding potential (RHP), that is, nonfighting tactics are displayed by less competitive males who are more likely to lose a fight. The alternative mating tactics, however, can also be explained by life‐history theory, which predicts that young males avoid fighting, regardless of their RHP, if it pays off to wait for future reproduction. Here, we test whether the sneaking tactic displayed by young males of the two‐spotted spider mite can be explained by life‐history theory. We tested whether young sneaker males survive longer than young fighter males after a bout of mild or strong competition with old fighter males. We also investigated whether old males have a more protective outer skin—a possible proxy for RHP—by measuring cuticle hardness and elasticity using nanoindentation. We found that young sneaker males survived longer than young fighter males after mild male competition. This difference was not found after strong male competition, which suggests that induction of sneaking tactic is affected by male density. Hardness and elasticity of the skin did not vary with male age. Given that earlier work could also not detect morphometric differences between fighter and sneaker males, we conclude that there is no apparent increase in RHP with age in the mite and age‐dependent male mating tactics in the mite can be explained only by life‐history theory. Because it is likely that fighting incurs a survival cost, age‐dependent alternative mating tactics may be explained by life‐history theory in many species when reproduction of old males is a significant factor in fitness.     

Alternative male mate-finding tactics in burying beetles

Male burying beetles, Nicrophorus vespilloides Herbst (Coleoptera:Silphidae), use two alternative mate-finding tactics: malescan (1) search for carcasses that serve as oviposition sitesor (2) attract mates via pheromone emission. In the laboratory,all males tested used both tactics, but there were significantdifferences among males in the time they spent employing eithertactic. These differences appear to be partially geneticallybased. Time of day also affected the tactic used. A comparisonof the benefits of the two tactics, based on field and laboratoryexperiments, suggests that the search tactic results in higherreproductive success than the attraction tactic. However, pheromoneemission may be favored toward the end of the activity phase,when female activity is high but carcass availability may belowest. Females readily mate with pheromone-emitting males eventhough this tactic is less profitable than mating with a malethat has already found a carcass. However, it is likely thatfemales can distinguish between males with and without a carcassonly after physical contact. Also, fresh sperm permits femalesto rear offspring if they find a carcass without a conspecificmale.     

Fighting for shells: how private information about resource value changes hermit crab pre-fight displays and escalated fight behaviour

Pre-fight displays typically provide honest, but sometimes dishonest, information about resource holding potential and may be influenced by assessment of resource value and hence motivation to acquire the resource. These assessments of potential costs and benefits are also predicted to influence escalated fight behaviour. This is examined in shell exchange contests of hermit crabs in which we establish an information asymmetry about a particularly poor quality shell. The poor shell was created by gluing sand to the interior whereas control shells lacked sand and the low value of the poor shell could not be accurately assessed by the opponent. Crabs in the poor shell showed changes in the use of pre-fight displays, apparently to increase the chances of swapping shells. When the fights escalated, crabs in poor shells fought harder if they took the role of attacker but gave up quickly if in the defender role. These tactics appear to be adaptive but do not result in a major shift in the roles taken or outcome. We thus link resource assessment with pre-fight displays, the roles taken, tactics used during escalation and the outcome of these contests.     

Hormone levels of male African striped mice change as they switch between alternative reproductive tactics

Alternative reproductive tactics occur when individuals of the same species follow alternative ways to maximize reproductive success. Often younger and smaller males follow tactics that result in lower fitness than that of dominant larger males. The relative plasticity hypothesis predicts that hormone levels change as males change tactics, but direct tests of this hypothesis are missing. It has been demonstrated in a number of studies that males following different tactics also differ in hormone levels (unpaired data), but not that individual males change their hormone levels as they change tactic (paired data). We compared hormone levels in the same individuals before and after they changed their tactic, using field samples collected over a period of 6 years. We studied male striped mice (Rhabdomys pumilio) following three alternative reproductive tactics: 1. alloparental philopatric males; 2. solitary roaming males, and 3. group-living dominant breeders. Testosterone levels increased and corticosterone levels decreased when philopatric males became roamers or breeders. The increase in testosterone levels tended to be higher in philopatric males that became roamers than in philopatric males that became breeders. Testosterone levels decreased when roamers became breeders. Prolactin levels increased when males of any other tactic became breeders. Thus, males significantly changed their hormone profiles as they changed tactics. These results are in agreement with the hypothesis that changes in hormone levels are associated with the switch from one alternative reproductive tactic to another.     

Hormone levels of male African striped mice change as they switch between alternative reproductive tactics

Alternative reproductive tactics occur when individuals of the same species follow alternative ways to maximize reproductive success. Often younger and smaller males follow tactics that result in lower fitness than that of dominant larger males. The relative plasticity hypothesis predicts that hormone levels change as males change tactics, but direct tests of this hypothesis are missing. It has been demonstrated in a number of studies that males following different tactics also differ in hormone levels (unpaired data), but not that individual males change their hormone levels as they change tactic (paired data). We compared hormone levels in the same individuals before and after they changed their tactic, using field samples collected over a period of 6 years. We studied male striped mice (Rhabdomys pumilio) following three alternative reproductive tactics: 1. alloparental philopatric males; 2. solitary roaming males, and 3. group-living dominant breeders. Testosterone levels increased and corticosterone levels decreased when philopatric males became roamers or breeders. The increase in testosterone levels tended to be higher in philopatric males that became roamers than in philopatric males that became breeders. Testosterone levels decreased when roamers became breeders. Prolactin levels increased when males of any other tactic became breeders. Thus, males significantly changed their hormone profiles as they changed tactics. These results are in agreement with the hypothesis that changes in hormone levels are associated with the switch from one alternative reproductive tactic to another.     

Computer Simulation Suggests that the Spatial Distribution of Males Influences Female Visiting Behaviour in the River Bullhead

It is known from previous laboratory studies that female choice in the river bullhead, Cottus gobio, is mainly influenced by the size of the male, and that the presence of eggs in the nest also plays a role. However, the process by which females visit and choose among prospective mates is still poorly understood. We examined eight possible tactics of female choice through computer simulation, and we compared their fit to the reproductive patterns observed in two natural populations. Neither of the tactics proposed for other species, nor combinations of them, were able to predict accurately the field data, although one of them (fixed threshold) provided a fairly good fitting. Conversely, a new model (cluster sampling), which takes into account the spatial distribution of males, produced for both populations a set of predictions on the male mating success not significantly different from the data recorded in the field. Under this model, females sample more males when males are clumped, thus reducing substantially, on the average, the ratio between the distance travelled before spawning and the number of sampled males. When models incorporated the preference for already mated males, good fitting was obtained if females preferred nests containing eggs not older than 36 h, a finding that agrees with field results.     

Female mate assessment and choice behavior affect the frequency of alternative male mating tactics

Explanations for the existence of alternative male mating tacticsfocus primarily on male–male competition. Mating systems,however, are composed of interactions both within and betweenthe sexes, and the role of female behavior in shaping male matingtactics should not be overlooked. By using a dynamic state variablegame model, I examine how female mate assessment and choicebehavior affect the frequency of alternative male mating tactics.When females can accurately assess the quality of males, onlymales with high quality are likely to be chosen as mates, andthus, lower-quality males gain little fitness from courtingfemales. This leads lower-quality males to switch to an alternativemating tactic that attempts to circumvent female mate choice.In contrast, if the abilities of females to accurately assessmales are constrained by assessment costs, imperfect information,or time constraints, or if the pool of available males is smaller,then lower-quality males are increasingly chosen as mates andthey less often use alternative mating tactics. Thus, femalebehavior shapes the frequency of alternative male mating tactics.A consequence of this game between the sexes is that male behavior(i.e., increased alternative mating tactics) decreases the benefitsfemales might otherwise gain from lower assessment costs, clearersignals of male quality, more time to choose a male, and moremales from which to choose a mate.     

Why are Male Columbian Ground Squirrels Territorial?

Male territorial defence is a component of many vertebrate mating systems and is often regarded as a tactic for acquiring mates. Traditionally considered within the context of overt site‐specific defence, territoriality actually may have several components which encompass a variety of behavioural tactics (e.g. post‐copulatory mate‐guarding, defence of resources that females need, defence of area around females) that underlie a mating system. The purpose of our study was to evaluate such influences on the territorial behaviour of male Columbian ground squirrels in southwestern Alberta, Canada. Males were dominant and territorial if they defended a minimum convex polygon activity range by chasing other males more within the activity range than they were chased. Subordinate males had no territory and were chased throughout their ranges, but they competed for mates by increasing chases in their activity range when nearby females were oestrous. Dominant males exhibited conditional breeding tactics, tending to chase other dominant males from their territory when nearby females were oestrous, but travelling outside their activity ranges to chase subordinate males when females were not oestrous. Although females mated first with a dominant male on whose territory they resided (and in order from oldest to youngest if several territories overlapped), mating pairs were not exclusive, as females usually mated with additional males. Males also guarded females after copulation and defended females directly just before oestrus, rather than defending territory per se during those times. Thus, males possess a repertoire of behaviours that complement site‐specific territoriality, and territory ownership serves to facilitate a first mating with females that live on the territory.     

Primates and the evolution of long, slow life histories

Primates are characterized by relatively late ages at first reproduction, long lives and low fertility. Together, these traits define a life-history of reduced reproductive effort. Understanding the optimal allocation of reproductive effort, and specifically reduced reproductive effort, has been one of the key problems motivating the development of life-history theory. Because of their unusual constellation of life-history traits, primates play an important role in the continued development of life-history theory. In this review, I present the evidence for the reduced reproductive effort life histories of primates and discuss the ways that such life-history tactics are understood in contemporary theory. Such tactics are particularly consistent with the predictions of stochastic demographic models, suggesting a key role for environmental variability in the evolution of primate life histories. The tendency for?primates to specialize in high-quality, high-variability food items may make them particularly susceptible to environmental variability and explains their?low reproductive-effort tactics. I discuss recent applications of life-history theory to human evolution and emphasize the continuity between models used to explain peculiarities of human reproduction and senescence with the long, slow life histories of primates more generally.     

Foraging strategy of a mantid,Paratenodera angustipennis S.: Mechanisms of switching tactics between ambush and active search

Summary Foraging strategies of a mantid, Paratenodera angustipennis de Saussure were investigated both in the laboratory and in the field to determine how mantids assess the profitability of their location, and based on it, how they switch their tactics. Although mantids are often considered to be ambush predators, nymphs and adult females changed their tactics from ambushing to active searching when they did not capture any prey for more than about 2 days (nymphs) and 3 days (adult females). Switching between the two tactics was such that the females and nymphs spent more searching effort in sites with higher prey density. As opposed to the females and nymphs, male mantids did not change their tactics according to their hunger level (in our definition, and the prey density in the hunting site. The males moved around more than twice as much as did the females. In the field, female mantids moved less frequently at higher female densities.     

Organization and ontogeny of alternative tactics

This paper considers the ways in which substantial discontinuous variation in behaviour (called alternative tactics) arise during the course of the lives of individuals. First, it considers a scheme into which examples of alternative tactics can be placed. This scheme reveals specific assumptions that are frequently made about alternative tactics and the problems involved in their measurement. The paper then discusses the shortcomings of dichotomizing alternative tactics into discrete categories, focusing particularly on the genes/environment distinction. Developmental phenomena that can give rise to discontinuous variation in behaviour are then related to specific examples from species that show alternative tactics. Several developmental phenomena are likely to be involved in the origins of any particular case of intraspecific variation in behaviour. Factors in development may have canalizing effects, facilitating effects, or they may maintain variation in behaviour. They may also enable alternative tactics to occur or initiate their appearance in either juveniles or adults. Three aspects of the processes involved in generating such variation in behaviour are also discussed. These are the interactions between genetic and environmental influences, alternative routes in development, and learning. However, in no case is a particular developmental phenomenon or process likely to be solely responsible for a particular example of discontinuous variation in behaviour; new ontogenetic analyses are required to uncover the multiple influences.     

D-penicillamine and enzymatic activities.

The influence of incubation with D-penicillamine on pure enzyme preparations and on enzymatic activities of serum and skin homogenates was investigated. Three of the nine enzymatic activities studied underwent significant changes. Such effects of D-penicillamine must be taken into consideration if therapeutic or unwanted actions of this drug are to be fully understood; they are elicited by concentrations reached under conditions used for human therapy.     

Behavioral and hormonal correlates of alternative reproductive strategies in a polygynous lizard: Tests of the relative plasticity and challenge hypotheses

Species with alternative reproductive tacts are good models to investigate the poorly understood question of whether individual variation within sexes results from the same physiological mechanisms that control variation between sexes. We have shown previously that adult male tree lizards, Urosaurus ornatus, of different throat color morphs express different levels of aggression in the laboratory. Further field results support the suggestion that the two morphs practice alternative reproductive tactics because the two morphs express different levels of aggressive behavior under field conditions and exhibit dramatic and opposite responses to aggressive challenges. However, despite these behavioral differences, the two morphs do not differ in levels of testosterone or corticosterone either in undisturbed situations or following aggressive challenge. These results are consistent with the relative plasticity hypothesis which proposes that organizational, rather than activational, actions of steroid hormones will be more important in morph differentiation when morphs are fixed in adult life, as they are in tree lizards. These results also support the hypothesis that steroid hormonal levels are insensitive to social modulation in males of species such as U. ornatus without paternal care.     

Behavioral tactics among rats in a radial maze

The experiments were carried out on rats of Wistar (W) and Krushinsky-Molodkina (KM) lines, differing in the level of task performance in conditions of multiple choice of food sources in a 12ray radial symmetrical maze. It is shown that in the radial maze, the rats of both lines use a number of behavioural tactics. To determine the influence of changes of environmental spatial characteristics while preserving the main experimental strategy--never revisit the places of reinforcement,--on the peculiarities of tactics manifestations maze modifications were elaborated. Besides the environmental procedure was changed. Under all conditions the rats of W line solved the task. According to the situation, they either preserved former tactics or developed some new ones. The rats of KM line could not solve the task in changed conditions. In most sessions, appearance or absence of given tactics was not adequate to new conditions. The presence of the necessary tactics not always facilitated the task solving. Thus, for the realization of adequate reactions, the presence of necessary tactics is not sufficient: their "tuning" is needed depending on situation. The possibility is supposed of genetic determination of rats ability to some tactics. However, it is emphasized, that tactics are not strongly fixed, as their realization depends on environmental conditions.     

Alternative mate-finding tactics in a non-territorial damselfly (Odonata: Coenagrionidae)

Males of the non-territorial damselfly Enallagma hageni have two alternative tactics for finding mates: (1) they search the banks of the pond for unmated females (searching tactic), or (2) wait at oviposition sites for females that resurface prematurely from underwater oviposition (waiting tactic). Although the searching tactic yielded more fertilizations than the waiting tactic, for time invested, the waiting tactic became increasingly successful later in the reproductive season due to changes in female oviposition behaviour. The two tactics can be maintained in the population because males can mate by the waiting tactic during the afternoon when few females are available to searchers. Among males visiting the breeding site an equal number of times, males mating by a mixture of tactics were as successful as males mating only by the main tactic. Because marked males were found to use both tactics, these behaviours are interpreted as evidence of behavioural plasticity within individuals, representing one conditional evolutionary strategy.     

A test of the mate deprivation hypothesis of sexual coercion

According to the mate deprivation hypothesis of sexual coercion, males are more likely to use sexually coercive tactics if they are disadvantaged in gaining access to desirable mates. This hypothesis was tested in a sample of 156 young, heterosexual, mostly single men enrolled in a Canadian university. Differential access to mates was indexed by self-perceived mating success, self-reported sexual history, and relative earning potential. Sexual coercion was assessed using the Koss's sexual experiences survey. Results did not support the hypothesis: men who identified themselves as sexually coercive tended to have higher self-perceived mating success, had significantly more extensive sexual histories, and did not report lower relative earning potential. Coercive men reported a greater preference for partner variety and casual sex. Sexual strategy theory is used to propose two alternative models of sexual coercion.