How Do Infanticidal Male Bank Voles (Myodes glareolus) Find the Nest with Pups?

Infanticide, the killing of conspecific young, occurs in most mammal species, like in our study species, the bank vole (Myodes glareolus). Infanticide by adult males is regarded as a strong factor affecting recruitment of young into population. It is considered as an adaptive behaviour, which may increase male fitness via resource gain or an increased access to mates. When an intruder is approaching the nest, the mother should not be present, as her nest guarding is very aggressive and successful. Pups use ultrasonic vocalisation to call their mother when mother leaves nest for foraging but it is not know which cues do infanticidal males use to find the nest with vulnerable pups to commit infanticide? We studied whether the pups' sounds or the olfactory cues of the nest guide the males of known infanticidal behavioural trait towards the nest with vulnerable pups. Four nest boxes in a large indoor arena offered different nesting cues: nest odour, pup vocalisation, both odour and sound or control with no cue. The result showed that infanticidal males were more active in their searching behaviour than non‐infanticidal males and seemed to target the nest providing only acoustic cues. Four of the males, all infanticidal, intruded the nest box. Infanticidal males seem to actively search for nests with vulnerable pups by eavesdropping pup begging calls for absent mother. However, under natural conditions, mother presence and aggressive nest protection may be an effective counter strategy against strange male infanticide. When trapping study voles from the wild, we monitored occurrence of male infanticide across the breeding season from early to late summer. Proportion of infanticidal males was between 25 and 29% of all males tested along the breeding season. Our results suggest that male infanticide seems to cause a stable threat for pup mortality in increasing breeding season density.     

Do Male Desert Gobies Compromise Offspring Care to Attract Additional Mating Opportunities?

Males often play a critical role in offspring care but the time and energy invested in looking after young can potentially limit their ability to seek out additional mating opportunities. Recent studies, however, suggest that a conflict between male parental effort and mating effort may not always be inevitable, especially if breeding occurs near the nest, or if parental behaviours are under sexual selection. Accordingly, we set out to experimentally investigate male care and courtship in the desert goby Chlamydogobius eremius, a nest-guarding fish with exclusive paternal care. Despite courtship occurring near the nest, we found that when egg-tending males were given the opportunity to attract additional females, they fanned their eggs less often, engaged in shorter fanning bouts, and spent more of their time outside their nests courting. Our findings highlight the importance of understanding the circumstances under which reproductive tradeoffs are expected to occur and how these, in turn, operate to influence male reproductive decisions.     

Is Self‐Grooming by Male Prairie Voles a Predictor of Mate Choice?

Self-grooming by mammals is a form of scent dissemination in which individuals anoint themselves with salivary, anogenital, and other body odours. Self-grooming has been proposed to be a sexually selected trait favoured in reproductive competition and sexual attraction. We tested the hypothesis that females would show a mating preference for males that self-groomed more than a reproductive competitor that groomed less. In mate-choice experiments in which females had a choice of two tethered males, non pair-bonded females did not choose males based on their frequency of self-grooming. In a second experiment in which pair-bonded females in postpartum oestrus had access to their current mate and two strange males, strange males groomed significantly more than pair-bonded mates, yet attained the fewest copulations. Non pair-bonded females and pair-bonded males and females groomed significantly less often than did non pair-bonded males. Self-grooming behaviour was consistent with the sexual attraction hypothesis, but the frequency of self-grooming did not increase a male's mating success. We conclude that the frequency and time spent self grooming are not good predictors of mating success.     

The Sex Specific Genetic Variation of Energetics in Bank Voles,Consequences of Introgression?

Interaction between mitochondrial and nuclear genomes is expected to affect energetic phenotypes of traits linked to mitochondrial physiology, further influencing the fitness. A rodent, the bank vole (Myodes glareolus), has a population structure completely or partially introgressed with mitochondria from its relative, the red vole (M. r utilus). Females that carried either bank vole mitochondria or mitochondria from the introgressed species were repeatedly mated with males of both mtDNA types. We found that in males, but not in females, morpho-physiological phenotypes are affected by sire type, causing decreases in body mass (BM) and basal metabolic rate (BMR; including BM corrected, rBMR) in individuals sired by fathers carrying introgressed mitochondria. Higher effect sizes for the proportion of additive genetic variation (and 5.6, 1.9 and 3.6 times higher narrow sense heritability for BM, BMR and rBMR, respectively), and lower for proportion of environmental variation were detected in progeny of non-introgressed males. Our data indicate that co-adapted and possibly co-introgressed nuclear genes related to energetic physiology have an important role in adaptation to the northern conditions in bank voles, and that sex linked nuclear genes are a potential source for variation in basal metabolic rate.     

Is There Selective Mating in Tetrahymena During Genomic Exclusion?1

SYNOPSIS. Genomic exclusion is characterized by 2 rounds of mating. If exconjugants from different pairs remated at random after the first mating, we would expect a 1:2:1 ratio for genes present in heterozygous condition in the normal parent. An excess of homozygotes is observed which is similar for 2 different genes, suggesting that 10% of the rematings occur between exconjugants from the same Round 1 pair. Some but not all of these homozygotes can be attributed to a lack of separation of mates after the first round of mating. The rest may result because of differential mortality, induced autogamy or preferential remating.     

Variability of Female Responses to Conspecific vs. Heterospecific Male Mating Calls in Polygynous Deer: An Open Door to Hybridization?

Males of all polygynous deer species (Cervinae) give conspicuous calls during the reproductive season. The extreme interspecific diversity that characterizes these vocalizations suggests that they play a strong role in species discrimination. However, interbreeding between several species of Cervinae indicates permeable interspecific reproductive barriers. This study examines the contribution of vocal behavior to female species discrimination and mating preferences in two closely related polygynous deer species known to hybridize in the wild after introductions. Specifically, we investigate the reaction of estrous female red deer (Cervus elaphus) to playbacks of red deer vs. sika deer (Cervus nippon) male mating calls, with the prediction that females will prefer conspecific calls. While on average female red deer preferred male red deer roars, two out of twenty females spent more time in close proximity to the speaker broadcasting male sika deer moans. We suggest that this absence of strict vocal preference for species-specific mating calls may contribute to the permeability of pre-zygotic reproductive barriers observed between these species. Our results also highlight the importance of examining inter-individual variation when studying the role of female preferences in species discrimination and intraspecific mate selection.     

Better to Live with Allogenerics Than to Live Alone? The Case of Single Male Cercopithecus pogonias in Troops of Colobus satanas

We report the integration of single male crowned guenons (Cercopithecus pogonias) into troops of black colobus (Colobus satanas). We observed one male Cercopithecus pogonias in three troops of Colobus satanas on 30% of observation days (n = 231). Activities of single males guenons did not differ significantly from those of the colobus with which they associated. Moreover, both species performed simultaneously the same activities more often than expected by chance. Interspecific grooming occurred on several occasions. Furthermore, single male guenons spent as much in time social activities when part of a colobus troop, as they typically do when part of a conspecific group. Unlike solitary male crowned guenons, which are silent, a male that is integrated into a troop of colobus is vocal and emits social alarm calls to which colobus monkeys respond. During the single file movements of colobus troops, single male crowned guenons were integrated in the core of the troop and used the same branches at the same height with the colobus. Thus, the life of a single male crowned guenon with black colobus was social. We suggest that the main benefits that he gained is the possibility to live in a social context. Social interactions could be the key element to explain why single males Cercopithecus pogonias join troops of monkeys so different from their natal groups.     

Is the Expression of Male Traits in Female Lesser Kestrels Related to Sexual Selection?

Some lesser kestrel females (Falco naumanni) show male plumage traits, i.e. grey rumps and tails. This phenomenon has seldom been analyzed in birds, and two hypotheses have been suggested to explain it. The first proposes that, when sexual selection acts favouring the expression of a trait in males, females could show the analogous character by genetic correlation (indirect sexual selection). Alternatively, the expression of these traits in females could be favoured by intra-sexual competition or even by male mate choice selecting ornamented females (direct sexual selection). We have tested if females with male traits are favoured by direct sexual selection, through a 3-yr observational study of 239 female lesser kestrels. Our results cannot support the predictions, as females with grey plumages do not achieve access to better breeding opportunities or fitness benefits. These traits do not seem to be honest signals of phenotypic quality, since physical condition and survival did not differ between females which showed male traits and those which did not. The expression of male traits in these females increased with their ages, but showing a high individual variability. Finally, since the genetic correlation hypothesis is unlikely in this species because all males have grey rumps and tails, we propose a new age-related hormonal explanation.     

Are Male Orangutans a Threat to Infants? Evidence of Mother–Offspring Counterstrategies to Infanticide in Bornean Orangutans (Pongo pygmaeus wurmbii)

International Journal of Primatology - Sexually selected infanticide by males is widespread in primates. Female primates employ a variety of strategies to reduce infanticide risk. While infanticide...     

Female Choice or Male Sex Drive? The Advantages of Male Body Size during Mating in Drosophila Melanogaster

The mating success of larger male Drosophila melanogaster in the laboratory and the wild has been traditionally been explained by female choice, even though the reasons are generally hard to reconcile. Female choice can explain this success by virtue of females taking less time to mate with preferred males, but so can the more aggressive or persistent courtships efforts of large males. Since mating is a negotiation between the two sexes, the behaviors of both are likely to interact and influence mating outcomes. Using a series of assays, we explored these negotiations by testing for the relative influence of male behaviors and its effect on influencing female courtship arousal threshold, which is the time taken for females to accept copulation. Our results show that large males indeed have higher copulation success compared to smaller males. Competition between two males or an increasing number of males had no influence on female sexual arousal threshold;—females therefore may have a relatively fixed ‘arousal threshold’ that must be reached before they are ready to mate, and larger males appear to be able to manipulate this threshold sooner. On the other hand, the females’ physiological and behavioral state drastically influences mating; once females have crossed the courtship arousal threshold they take less time to mate and mate indiscriminately with large and small males. Mating quicker with larger males may be misconstrued to be due to female choice; our results suggest that the mating advantage of larger males may be more a result of heightened male activity and relatively less of female choice. Body size per se may not be a trait under selection by female choice, but size likely amplifies male activity and signal outputs in courtship, allowing them to influence female arousal threshold faster.     

Is Female Visual Signaling to Male Song Socially Regulated in Brown‐headed Cowbirds?

This research focused on how adult female brown‐headed cowbirds, Molothrus ater, regulate social feedback on a group level to shape the development of male song. Specifically, females produce rapid wing movements in response to male song, termed ‘wing strokes,’ which have been shown to shape male song and predict song quality. These effects have been documented in captive dyads and triads, but not in more naturalistic flocks, where song development actually occurs. Here, we studied wing stroking in small seminatural flocks of differing female‐to‐male ratios. Despite differences in the number of females and their social selectivity, the same pattern of female feedback emerged in seven of eight flocks: One female produced the majority of wing strokes to male song, making her the primary wing stroker in her flock. Previous studies on large flocks have demonstrated females to facilitate male song improvisation and development if they exhibited higher social selectivity by approaching immature males less. Here, we found that primary wing strokers were indeed more socially selective than non‐primary wing strokers. This research is the first to document social stimulation being facilitated at the group level to ensure that more highly selective females deliver the most feedback.     

The Huge Reduction in Adult Male Mortality in Belarus and Russia: Is It Attributable to Anti-Alcohol Measures?

Background and Aim

Harmful alcohol consumption has long been recognized as being the major determinant of male premature mortality in the European countries of the former USSR. Our focus here is on Belarus and Russia, two Slavic countries which continue to suffer enormously from the burden of the harmful consumption of alcohol. However, after a long period of deterioration, mortality trends in these countries have been improving over the past decade. We aim to investigate to what extent the recent declines in adult mortality in Belarus and Russia are attributable to the anti-alcohol measures introduced in these two countries in the 2000s.

Data and Methods

We rely on the detailed cause-specific mortality series for the period 1980–2013. Our analysis focuses on the male population, and considers only a limited number of causes of death which we label as being alcohol-related: accidental poisoning by alcohol, liver cirrhosis, ischemic heart diseases, stroke, transportation accidents, and other external causes. For each of these causes we computed age-standardized death rates. The life table decomposition method was used to determine the age groups and the causes of death responsible for changes in life expectancy over time.

Conclusion

Our results do not lead us to conclude that the schedule of anti-alcohol measures corresponds to the schedule of mortality changes. The continuous reduction in adult male mortality seen in Belarus and Russia cannot be fully explained by the anti-alcohol policies implemented in these countries, although these policies likely contributed to the large mortality reductions observed in Belarus and Russia in 2005–2006 and in Belarus in 2012. Thus, the effects of these policies appear to have been modest. We argue that the anti-alcohol measures implemented in Belarus and Russia simply coincided with fluctuations in alcohol-related mortality which originated in the past. If these trends had not been underway already, these huge mortality effects would not have occurred.     

Is There Enough Science for Conservation Action?

We argue that there is not enough science to appropriately support many of the conservation measures currently being proposed, and hence, we cannot be sure of the objectivity of the conservation actions being implemented. The objectivity claimed to be underlying conservation actions is more assumed than real. We also suggest that the approach to conservation is driven more by moral commitments than by tested concepts, and it is further biased by our anthropocentric evaluation of ecological processes and their outcomes. Conservation science is a young subject, which needs to be nourished while it continues to feed on its roots-ecology and evolutionary biology.     

Amphotericin B: How Much Is Enough?

The total curative dose of amphotericin B for any given fungal infection or specific patient is not precisely known. Prior to the availability of lipid formulations of amphotericin B (LFAB), dosing of amphotericin B was dictated by its associated toxicity. The unique pharmacokinetic features of each LFAB have led to differences in their recommended doses. Most published data have evaluated doses of 3–5 mg/kg/day, although niches exist for both higher and lower doses. Low-dose LFAB allows for intravenous broad-spectrum antifungal coverage without drug-drug interactions and with reduced toxicity. High-dose LFAB demonstrates increased fungal clearance in animal models, although this has not translated to improved clinical outcomes for most invasive fungal infections. Although available data do not demonstrate significant benefit associated with high-dose therapy, for liposomal amphotericin B, the data also demonstrate no significant harm. As such, the use of high-dose liposomal amphotericin B for salvage therapy may be a consideration.     

Why Do Male Tree Weta Aggressively Evict Females from Galleries After Mating?

The sexually dimorphic Wellington tree weta ( Hemideina crassidens Blanchard) (Orthoptera: Anostostomatidae) is a harem-defending polygynous insect in which males use their enormous mandibles to fight conspecifics for access to harems residing in tree cavities (gallery). Tree weta ejaculates (spermatophores) do not include a nuptial meal (spermatophylax) to delay removal by females as in some ensiferan Orthoptera. Consequently, male tree weta are predicted to remain with their mates post-copula to ensure complete sperm transfer. Contrary to prediction, however, males forcibly eject females from the mating site (gallery) soon after copulation. Results suggest that forcible ejection occurs apparently because females consume the previous spermatophore if either the resident male or a rival initiates a subsequent copulation attempt. Thus, ejection appears to reduce the resident male's risk that his ejaculate will be eaten and his mate will copulate with another male.     

The Evolution of Large Testes: Sperm Competition or Male Mating Rate?

A positive relationship across species between the extent to which females mate with more than one male and relative testes mass has been demonstrated in a wide range of vertebrate taxa and certain insects. At least two hypotheses, which are not necessarily mutually exclusive, could account for this pattern: (1) the numerical sperm competition hypothesis, which assumes that larger testes enable the male to transfer more sperm to each female, giving the male an advantage in sperm competition and (2) the male mating rate hypothesis, which proposes that larger testes allow the male to produce a greater number of (potentially smaller) ejaculates to engage in frequent copulations with different females. Of these hypotheses, the former has won broad acceptance, while the latter has tended to be dismissed. Here, we argue that the lines of evidence commonly used to support the numerical sperm competition hypothesis in favour of the male mating rate hypothesis are not as clear cut or generally applicable as they are purported to be and that, consequently, the male mating rate hypothesis cannot be excluded with confidence on the basis of the current evidence. Furthermore, some evidence, such as the finding that ejaculate mass and/or sperm number is negatively correlated with testes mass across species in some insects and that larger testes in Drosophila can evolve in response to an increase in the number of females available for mating in the laboratory, provides support for the male mating rate hypothesis. Further work is needed to disentangle the relative effects of these selective pressures on the evolution of testes size.     

Is Assembly of the SNARE Complex Enough to Fuel Membrane Fusion?

The three key players in the exocytotic release of neurotransmitters from synaptic vesicles are the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins synaptobrevin 2, syntaxin 1a, and SNAP-25. Their assembly into a tight four-helix bundle complex is thought to pull the two membranes into close proximity. It is debated, however, whether the energy generated suffices for membrane fusion. Here, we have determined the thermodynamic properties of the individual SNARE assembly steps by isothermal titration calorimetry. We found extremely large favorable enthalpy changes counterbalanced by positive entropy changes, reflecting the major conformational changes upon assembly. To circumvent the fact that ternary complex formation is essentially irreversible, we used a stabilized syntaxin-SNAP-25 heterodimer to study synaptobrevin binding. This strategy revealed that the N-terminal synaptobrevin coil binds reversibly with nanomolar affinity. This suggests that individual, membrane-bridging SNARE complexes can provide much less pulling force than previously claimed.The molecular machinery that drives the Ca²⁺-dependent release of neurotransmitters from synaptic vesicles is studied intensively. Three key players in the underlying exocytotic fusion of the vesicle with the plasma membrane are the proteins synaptobrevin 2/VAMP2 (vesicle-associated membrane protein), syntaxin 1a, and SNAP-25³ (for review, see Refs. 1-7). They belong to the so-called SNARE protein family, the members of which are involved in all vesicle fusion steps in the endocytic and secretory pathway. In general, SNARE proteins are relatively small, tail-anchored membrane proteins. Their key characteristic is the so-called SNARE motif, an extended stretch of heptad repeats that is usually connected to a single transmembrane domain by a short linker. Syntaxin and synaptobrevin each contain a single SNARE motif, whereas SNAP-25 contains two SNARE motifs connected by a palmitoylated linker region serving as a membrane anchor. The SNARE motifs of the three proteins assemble into a very tight four-helix bundle between opposing membranes; during this process the plasma membrane proteins syntaxin and SNAP-25 provide the binding site for the vesicular synaptobrevin. Formation of this complex is accompanied by extensive structural rearrangements (8-10). Based on these findings, it was put forward that the formation of the SNARE bundle provides the energy that drives membrane fusion. As the bundle is oriented in parallel, it is thought that formation of this complex starts from the membrane-proximal N termini and proceeds toward the C-terminal membrane anchors, effectively pulling the membranes together (the “zipper” model) (11). Although the zipper scenario is intuitive, it has been difficult to demonstrate directly.A decade ago it was shown that the three neuronal SNARE proteins are sufficient to fuse artificial vesicles (12). However, this reductionist approach yields rather slow fusion rates (12-14). Over the years various different end products of SNARE catalysis (complete fusion, hemifusion, and only tethered membranes) have been reported (15-19). These unsatisfactory results have fueled the debate over whether the assembly process indeed provides enough impetus to fuse bilayers. Not surprisingly, an alternative scenario has been put forward in which repulsive forces between membranes bring the SNARE assembly to a grinding halt. According to this idea, other factors like the Ca²⁺ sensor synaptotagmin or the small soluble protein complexin are needed to induce membrane merging (20-22).In simple terms, to find out whether the SNARE complex assembly is enough for membrane fusion, only the amount of energy released during complex formation and the amount of energy needed for membrane fusion need to be compared. However, the physics of membrane fusion are very complicated, and it is even more challenging to understand how proteins modulate the process. The free energy for bilayer fusion in an aqueous environment is not very high, but fusion is thought to require a large activation energy of about 40 k_BT, as two charged membranes have to be brought into close apposition. According to a theoretical model, the apposing membranes then need to be modified into a stalk-like configuration. Before fusion occurs, the process is thought to pass through a hemifusion intermediate in which only the outer monolayers are merged (for review, see Refs. 23 and 24). The role of fusion proteins is thought to lower the energy barrier for membrane fusion, but understanding how they modulate the lipid membrane and how their conformational changes are translated into a mechanical force is still in its infancy. It is not clear, for instance, whether SNARE-catalyzed fusion indeed proceeds through a stalk-like structure or just locally alters the membranes, a mechanism that might need much less activation energy.As the folding and unfolding transitions of the ternary SNARE complex exhibit a marked hysteresis (25), the question of how much energy is released during complex formation has been difficult to answer as well. To avoid the quasi-irreversibility of the process, the problem has been elegantly tackled by atomic force microscopy by two different research groups (26-28). In these experiments individual complexes affixed to solid supports were ruptured, yielding energy values of 43 and 33 k_BT. In another approach, which used a surface-force apparatus (SFA), a comparable energy of 35 k_BT has recently been determined (29). Strikingly, these values appear to correspond closely with the activation energy needed to fuse two membranes, substantiating the view that SNAREs are nano-fusion machineries. However, one should be cautious about the conclusion that these sophisticated procedures in fact yield the genuine SNARE assembly energy. For example, with the SFA approach, the number of complexes had to be deduced rather indirectly to estimate the free energy. Moreover, these approaches offered only indirect information about the reaction pathway.In this study we set out to determine the SNARE assembly energy more directly by using isothermal titration calorimetry (ITC) complemented by kinetic measurements. ITC is a powerful technique for studying the thermodynamics of macromolecular interactions by directly measuring the heat changes associated with complex formation, which at constant pressure is equal to the enthalpy change (ΔH). The titration approach also yields the stoichiometry (n), the entropy change (ΔS), and the association constant (K_A) of the reaction. We studied the consecutive reaction steps individually to gain deeper insights into the rugged energy landscape of complex formation. To study synaptobrevin binding in isolation, we used a stabilized syntaxin-SNAP-25 heterodimer, which has been shown to greatly accelerate liposome fusion rates (30). This strategy revealed that the N-terminal coil of synaptobrevin binds reversibly, making it feasible to access the free energy of SNARE assembly. Overall, our results suggest that individual SNARE complexes might provide much less pulling energy than previously claimed.     

How Safe Is Safe Enough? Radiation Risk for a Human Mission to Mars

Astronauts on a mission to Mars would be exposed for up to 3 years to galactic cosmic rays (GCR) — made up of high-energy protons and high charge (Z) and energy (E) (HZE) nuclei. GCR exposure rate increases about three times as spacecraft venture out of Earth orbit into deep space where protection of the Earth''s magnetosphere and solid body are lost. NASA''s radiation standard limits astronaut exposures to a 3% risk of exposure induced death (REID) at the upper 95% confidence interval (CI) of the risk estimate. Fatal cancer risk has been considered the dominant risk for GCR, however recent epidemiological analysis of radiation risks for circulatory diseases allow for predictions of REID for circulatory diseases to be included with cancer risk predictions for space missions. Using NASA''s models of risks and uncertainties, we predicted that central estimates for radiation induced mortality and morbidity could exceed 5% and 10% with upper 95% CI near 10% and 20%, respectively for a Mars mission. Additional risks to the central nervous system (CNS) and qualitative differences in the biological effects of GCR compared to terrestrial radiation may significantly increase these estimates, and will require new knowledge to evaluate.     

Males Benefit from Mating with Outbred Females in Drosophila littoralis: Male Choice for Female Genetic Quality?

The evolution and expression of mate choice behaviour in either sex depends on the sex‐specific combination of mating costs, benefits of choice and constraints on choice. If the benefits of choice are larger for one sex, we would expect that sex to be choosier, assuming that the mating costs and constraints on choice are equal between sexes. Because deliberate inbreeding is a powerful genetic method for experimental manipulation of the quality of study organisms, we tested the effects of both male and female inbreeding on egg and offspring production in Drosophila littoralis. Female inbreeding significantly reduced offspring production (mostly due to lower egg‐to‐adult viability), whereas male inbreeding did not affect offspring production (despite a slight effect of paternal inbreeding on egg‐to‐adult viability). As inbreeding depressed female quality more than male quality, the benefits of mate choice were larger for males than for females. In mate choice experiments, inbreeding did not affect male mating success (measured as a probability to be accepted as a mate in a large group), suggesting that females did not discriminate among inbred and outbred males. In contrast, female mating success was affected by inbreeding, with outbred females having higher mating success than inbred females. This result was not explained by lower activity of inbred females. Our results show that D. littoralis males benefit from mating with outbred females of high genetic quality and suggest adaptive male mate choice for female genetic quality in this species. Thus, patterns of mating success in mate choice trials mirrored the benefits of choice: the sex that benefited more from choice (i.e. males) was more choosy.