Is the predation risk of mate-searching different between the sexes?

Males signalling their attractiveness to females are at risk from predators that exploit mating signals to detect and locate prey. Signalling, however, is not the only risky activity in sexual interactions: mate searching can incur risk as well. Male Neotropical pseudophylline katydids produce both acoustic and vibrational signals (tremulations). Females reply to male signals with tremulations of their own, and both sexes walk to find one another. We asked if movement increases predation risk, and whether tremulation or walking was more attractive to predators. We offered the Neotropical gleaning bat Micronycteris microtis a series of two-choice tests, presenting the bats with katydid models that were motionless or moved in a way to mimic either tremulating or walking. We found that prey movements do put prey at risk. Although M. microtis can detect motionless prey on leaves, they preferred moving prey. Our study shows that movement can put searching or signalling prey in danger, potentially explaining why silent female katydids are frequently consumed by gleaning bats.

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Sex differences in alternative reproductive tactics in response to predation risk in tree crickets

10.1101/848630 ◽

2019 ◽

Author(s):

Viraj R. Torsekar ◽

Rohini Balakrishnan

Keyword(s):

Predation Risk ◽

Mating Success ◽

Empirical Studies ◽

Search Strategies ◽

Negative Effects ◽

Reproductive Tactics ◽

Mate Searching ◽

Searching Behaviour ◽

Mate Search

AbstractPredation risk has been hypothesised to drive the evolution of alternative mate-search strategies, but few empirical studies have examined this. In crickets, mate-search involves acoustic signalling by males and acoustic-mediated movement by females. It is unclear whether predators affect fitness of both sexes directly, by reducing survival, or indirectly, by affecting mate-searching. We empirically examined effects of increased predation risk on mate-searching behaviour and survival of male and female tree crickets, and their effects on mating success, using field-enclosure experiments with tree crickets Oecanthus henryi and their primary predator, green lynx spiders, Peucetia viridans. Crickets were allocated into three treatments with differential levels of predation risk. Increased predation risk strongly reduced survival, and thereby mating success, for both sexes. With increasing predation risk, males reduced calling and increased movement towards neighbouring callers, which had negative effects on mating success. Using simulations, we found male movement was significantly directed towards other calling males implying a switch to satellite strategies. Female movement behaviour, however, remained unaltered. Males and females thus differed in their response to comparable levels of predation risk, showing that the role of predation as a driver of alternative mate search strategies is sex and strategy-specific.

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Is the predation risk of mate-searching different between the sexes?

10.1101/363507 ◽

2018 ◽

Author(s):

Viraj R. Torsekar ◽

Kavita Isvaran ◽

Rohini Balakrishnan

Keyword(s):

Predation Risk ◽

Natural Populations ◽

Pair Formation ◽

Mate Searching ◽

Direct Benefits ◽

Extensive Field ◽

Tree Cricket ◽

Manipulative Experiments ◽

Sexual Selection Theory ◽

Behavioural Strategies

AbstractIn animals that communicate for pair formation, generally one sex invests more effort in mate searching. Differential predation risk of mate searching between the sexes is hypothesised to determine which sex invests more effort in mate searching. Although searching by males is prevalent in most animals, in orthopteran insects and some other taxa females physically move to localise signalling males who are predominantly sedentary. Although the two sexes thus share mate searching effort in orthopterans, their behavioural strategies are different and sexual selection theory predicts that signalling males may be following the riskier strategy and incurring higher costs. However, relative levels of risk posed by the two mate searching strategies remain largely unexplored. Hence, we estimated the relative predation risk experienced in natural populations by signalling males and responding females. We did this by quantifying predation risk as a probability of mortality in the context of acoustic communication in a tree cricket, Oecanthus henryi from its ecologically relevant predator, a lynx spider, Peucetia viridans. Spiders may perceive calling in males and movement in females by their ability to detect both airborne acoustic cues and substrate-borne vibratory cues. Probability of mortality was quantified by partitioning it into three spatial components at which crickets and spiders interact, using a combination of extensive field observations and manipulative experiments in a semi-natural setup. We found no differences in predation risk faced by calling males and responding females, supporting the prediction that similar sex-specific costs can explain shared mate searching responsibilities. Our findings therefore suggest that direct benefits offered by males to females upon pair formation may better explain shared mate searching effort between the sexes in orthopterans.

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Vigilance in human groups: a test of alternative hypotheses

Behaviour ◽

10.1163/15685390260136771 ◽

2002 ◽

Vol 139 (5) ◽

pp. 695-711 ◽

Cited By ~ 13

Author(s):

◽

Keyword(s):

Predation Risk ◽

Group Size ◽

Inverse Relationship ◽

Mate Guarding ◽

Mate Searching ◽

Clear Cut ◽

Vigilance Behaviour ◽

Alternative Hypotheses

AbstractHumans exhibit the same inverse relationship between group size and vigilance rates that has been classically described in animals. We collected data on natural human vigilance behaviour in two different contemporary environments (a large refectory-style cafeteria and open parks) to test between four alternative hypotheses for this relationship: predation risk, searching for friends, mate searching and mate guarding. The results demonstrate that, at least in contemporary city environments, humans monitor their surroundings largely for reasons motivated by mate searching. Data on whom subjects look at in a busy environment indicate that males are significantly more likely to attend differentially to female passers-by, but that females show a less clear-cut discrimination. We conclude that vigilance patterns are determined by locally salient functions.

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Elevated nest predation risk promotes offspring size variation in birds with prolonged parental care.

10.32942/osf.io/h2mpw ◽

2019 ◽

Author(s):

Gretchen F. Wagner ◽

Emeline Mourocq ◽

Michael Griesser

Keyword(s):

Predation Risk ◽

Reproductive Cycle ◽

Perceived Risk ◽

Nest Predation ◽

Bird Species ◽

Size Variation ◽

Egg Laying ◽

Offspring Size ◽

Natural Predation ◽

Risk Spreading

Predation of offspring is the main cause of reproductive failure in many species, and the mere fear of offspring predation shapes reproductive strategies. Yet, natural predation risk is ubiquitously variable and can be unpredictable. Consequently, the perceived prospect of predation early in a reproductive cycle may not reflect the actual risk to ensuing offspring. An increased variance in investment across offspring has been linked to breeding in unpredictable environments in several taxa, but has so far been overlooked as a maternal response to temporal variation in predation risk. Here, we experimentally increased the perceived risk of nest predation prior to egg-laying in seven bird species. Species with prolonged parent-offspring associations increased their intra-brood variation in egg, and subsequently offspring, size. High risk to offspring early in a reproductive cycle can favour a risk-spreading strategy particularly in species with the greatest opportunity to even out offspring quality after fledging.

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