Beyond the prey: male spiders highly invest in silk when producing worthless gifts

In the spider Paratrechalea ornata, males have two gift-giving mating tactics, offering either a nutritive (prey) or a worthless (prey leftovers) silk wrapped gift to females. Both gift types confer similar mating success and duration and afford males a higher success rate than when they offer no gift. If this lack of difference in the reproductive benefits is true, we would expect all males to offer a gift but some males to offer a worthless gift even if prey are available. To test this, we allowed 18 males to court multiple females over five consecutive trials. In each trial, a male was able to produce a nutritive gift (a live housefly) or a worthless gift (mealworm exuviae). We found that, in line with our predictions, 20% of the males produced worthless gifts even when they had the opportunity to produce a nutritive one. However, rather than worthless gifts being a cheap tactic, they were related to a higher investment in silk wrapping. This latter result was replicated for worthless gifts produced in both the presence and absence of a live prey item. We propose that variation in gift-giving tactics likely evolved initially as a conditional strategy related to prey availability and male condition in P. ornata. Selection may then have favoured silk wrapping as a trait involved in female attraction, leading worthless gift-giving to invade.

Male Barn Swallows Tolerate Nestling-Like Courtship Calls of Rival Males

Animals often exhibit conspicuous, and sometimes curious, courtship traits, such as nestling-like courtship display in birds, though modern studies of nestling-like courtship display (and calls) are virtually lacking. An exception is previous experiments on the barn swallow Hirundo rustica, demonstrating that females are equally attracted to playback of two structurally similar calls, nestling-like male courtship calls and nestling food-begging calls. The experiments support the sensory trap hypothesis, i.e., that male signals mimic nestling stimuli to exploit female parental care for nestlings. However, female attraction might not be the sole function of nestling-like traits, and males might also have a sensory bias toward nestling-like traits, in which males would be less aggressive toward characteristics typical of immature individuals. Here, I conducted playback experiments to study the function of nestling-like male courtship calls in the context of male–male interactions. Playback of male courtship songs induced frequent approaches by neighbouring males, while nestling-like male courtship calls or nestling food-begging calls induced fewer approaches, though male responses to the latter two vocalisations increased when approaching the nestling period. The observed pattern indicates that, by mimicking immature individuals, males attract intended signal receivers (i.e., females) while avoiding interference from eavesdroppers (i.e., neighbouring males). This unique function can explain why species with parental care exhibit immature-like behaviour.

The dual benefits of synchronized mating signals in a Japanese treefrog: attracting mates and manipulating predators

In dense mating aggregations, such as leks and choruses, acoustic signals produced by competing male conspecifics often overlap in time. When signals overlap at a fine temporal scale the ability of females to discriminate between individual signals is reduced. Yet, despite this cost, males of some species deliberately overlap their signals with those of conspecifics, synchronizing signal production in the chorus. Here, we investigate two hypotheses of synchronized mating signals in a Japanese treefrog ( Buergeria japonica ): (1) increased female attraction to the chorus (the beacon effect hypothesis) and (2) reduced attraction of eavesdropping predators (the eavesdropper avoidance hypothesis). Our results from playback experiments on female frogs and eavesdropping micropredators (midges and mosquitoes) support both hypotheses. Signal transmission and female phonotaxis experiments suggest that away from the chorus, synchronized calls are more attractive to females than unsynchronized calls. At the chorus, however, eavesdroppers are less attracted to calls that closely follow an initial call, while female attraction to individual signals is not affected. Therefore, synchronized signalling likely benefits male B. japonica by both increasing attraction of females to the chorus and reducing eavesdropper attacks. These findings highlight how multiple selective pressures likely promoted the evolution and maintenance of this behaviour. This article is part of the theme issue ‘Synchrony and rhythm interaction: from the brain to behavioural ecology’.

Nonchalant neighbours: Space use and overlap of the critically endangered elongated tortoise

To prevent population extirpations we need to understand species’ requirements, especially for critically endangered species inhabiting biodiversity hotspots. Studying animal movement provides insights into such requirements and gauges protected area effectiveness. Southeast Asian protected areas are becoming isolated; thus, we must ensure existing areas can sustain populations. We used multi-year radio-telemetry with the critically endangered Elongated Tortoise (Indotestudo elongata) to assess: movements, space-use, and conspecific overlap in a small protected area –Sakaerat Biosphere Reserve, Thailand. Movements were weakly seasonal, increasing in hot and wet seasons compared to the dry season. Individuals annual space-use varied (4.24–55.57 ha), while frequently overlapping with conspecifics. Conspecific comparisons revealed males (n = 5) moved similarly to females (n = 12) but used larger areas. Explorations of temporal avoidance versus attraction reveal more instances of conspecific attraction than avoidance (20:8). Avoidance/attraction behaviour appeared disconnected from carapace length or mass; therefore, that conspecific interaction patterns may potentially be a result of resources (mates or food) rather than competition (i.e., no apparent evidence of smaller individuals avoiding larger individuals). Female-female attraction suggests an absence of resource exclusion tactics at the temporal resolution of our data. Male-female attraction may indicate reproductive movements coinciding with hot season, but we failed to detect significant interactive effects linking conspecific attraction or step length to proximity to breeding activity. Our observations of annual space-use and space overlap present critical components when designing robust population assessments; assessments that will underline any successful I. elongata conservation effort. When considered in the context of previous work connecting space overlap with population viability, our results suggest the biosphere population of I. elongata to be reproductive, with enough resources to be potentially viable; the findings help emphasise the importance of even relatively small protected natural areas.

A long tail of truth and beauty: The developmental basis of complexity, symmetry, and beauty in the evolution of the peacock’s tail

ABSTRACTDarwin’s theory of sexual selection based on female choice has become a standard explanation for sexually dimorphic traits such as the peacock’s long train. Darwin believed that the peacock’s long train has developed as a result of female choice favouring long-tailed mates because of the train’s beauty, in which iridescent eyespots play a major role. Female choice theory requires genetic variation in female preference and in the number of eyespots and a genetic correlation between the two, yet there is little variation in either of these traits in natural and feral peafowl populations. We examined the anatomical plan of feather development and found that eyespot feather follicles originate in alternating rows of 10-11; this precludes intrinsic one-at-a-time eyespot variation. The developmentally determined annual addition of new feathers results in a fixed number of total feathers in fully mature individuals. Feather number and coordinated growth of feather length together determine the size of the train, which we propose would have an asymptotic fitness function due to the aging of the male. These results confirm previous speculations that eyespot number may be anatomically determined and complement recent findings indicating that eyespot number alone does not determine reproductive success. We propose an alternate hypothesis: that the driving force behind female attraction and female mate choice is male drive, or male-driven female choice based on male (train) size, quality and vigor, and variation in train display, and not eyespot number. In other words, we propose that, contrary to Darwin’s premise, the beauty (eyespot) does not drive the train; rather, it rides the train. The theory proposed here not only provides a simple mechanism for the evolution of the peacock’s train, but it also explains past, often contradictory, results. A detailed longitudinal study with cohorts would be ideal to shed light on the details of the process.

Synchronized mating signals in a communication network: the challenge of avoiding predators while attracting mates

Conspicuous mating signals attract mates but also expose signallers to predators and parasites. Signal evolution, therefore, is driven by conflicting selective pressures from multiple receivers, both target and non-target. Synchronization of mating signals, for example, is an evolutionary puzzle, given the assumed high cost of reduced female attraction when signals overlap. Synchronization may be beneficial, however, if overlapping signals reduce attraction of non-target receivers. We investigate how signal synchronization is shaped by the trade-off between natural and sexual selection in two anuran species: pug-nosed tree frogs ( Smilisca sila ), in which males produce mating calls in near-perfect synchrony, and túngara frogs ( Engystomops pustulosus ), in which males alternate their calls. To examine the trade-off imposed by signal synchronization, we conducted field and laboratory playback experiments on eavesdropping enemies (bats and midges) and target receivers (female frogs). Our results suggest that, while synchronization can be a general strategy for signallers to reduce their exposure to eavesdroppers, relaxed selection by females for unsynchronized calls is key to the evolution and maintenance of signal synchrony. This study highlights the role of relaxed selection in our understanding of the origin of mating signals and displays.

Experimental manipulation of reproductive tactics in Seba’s short-tailed bats: consequences on sperm quality and oxidative status

To reproduce, males have to fertilize the female’s eggs, sometimes in competition with ejaculates of other males. In species where males display alternative reproductive tactics, whereby territorial males secure mating and non-territorial males have to sneak copulations, the latter might be expected to invest relatively more resources towards sperm quality compared with the territorial males. Sperm cells are especially vulnerable to oxidative stress, which reduces male fertility. Therefore, antioxidant resources are expected to modulate sperm quality, and might be allocated differently between reproductive tactics. To test the link between reproductive tactics, redox profile and sperm quality, we experimentally induced changes in the reproductive tactics of 39 captive males Seba’s short-tailed bats Carollia perspicillata. We monitored the blood and ejaculate oxidative balance, and the sperm quality before, 7 days and 21 days after the manipulation of reproductive tactic. Although ejaculates’ oxidative damage was negatively related to sperm velocity, males exhibited similar blood and ejaculates redox profiles and similar sperm quality, regardless of their reproductive tactic. Possibly, these results arise as a consequence of some constraints having been lifted during the experiment. Our results also suggest that, in Seba’s short-tailed bats, the expression of alternative reproductive tactics is not subjected to strong oxidative constraints. Furthermore, our results could reflect an absence of trade-off between pre- and post-copulatory traits in harem males, as they could be selected to invest both in female attraction and sperm quality, as a consequence of their inability to fully monopolize females.

Ethology of the cricket Endecous (Endecous) chape Souza-Dias & de Mello, 2017 (Orthoptera: Grylloidea: Phalangopsidae) I: Agonistic and reproductive behavior

The mating behaviors of crickets, especially those related to agonistic encounters and oviposition, are poorly known. For example, only 10 of the 1005 valid species of Phalangopsidae have been studied to some extent. Here, we describe the reproductive behavior of Endecous (Endecous) chape, characterizing the actions involved in agonistic encounters, mating behaviors (female attraction, pair-formation, courtship, mating, and post-copulatory behavior), and oviposition. We recorded and timed agonistic, mating, and oviposition behaviors in staged trials. The male-male interactions ofE.chaperanged in aggressiveness from low intensity (only antennal interaction) to high intensity (reciprocal fights). In the mating behavior, males courted females through antennation of the females’ abdomen and cerci, followed by production of acoustic signals (with the exception of two males). Copulation occurred with females positioned above males (as is typical of Phalangopsidae), with an average elapsed time of 684.13 s, which is shorter than in other Phalangopsidae. We observed oviposition behavior only when three gravid females were placed together in an arena. Here, we contribute new knowledge of phalangopsid cricket behavior and provide useful information for understanding the evolution of reproductive behaviors. New characters described here can be used in phylogenetic analysis and for future studies about sexual selection and natural history.

Telling a Story Via Tumblr Analytics: Europe’s Young Muslim Female Attraction to ISIS

This article is part of an effort to understand the enthusiasm, attraction and admiration of the organization “Islamic State in Iraq and Syria” (ISIS) among the young Muslim female in Western Europe. The article specifically focuses on microblogging (Tumblr and Twitter) contents of young Muslim girls from Western Europe. The study offers a review of ISIS-adoring Tumblr fangirls in the West through the prism of cultural interpretation. The young girls, whether themselves manipulated or manipulating others, become part of a worldwide viral system produced in perfect unison and generating propaganda enticing more and more young Muslim girls in the West to become viral ISIS recruits. After maintaining for a while Tumblr and Twitter accounts, some of them even undergo the “giant leap” and migrate to the “Islamic State” in Syria, continuing there to reinforce their blogging and twittering efforts, reporting on their daily lives and attempting to tempt or to trap more young girls to join the new “Islamic State”.