Costs of Mate Guarding and Opportunistic Mating Among Wild Male Japanese Macaques

A trade-off relationship between mating and feeding effort is important when considering reproductive strategies of long-lived species. I compared the influence of male sexual activities, female mate-choice behaviors and the daily activity budget on male mating success among males in a group of wild Japanese macaques (Macaca fuscata yakui) on Yakushima Island. The 1st-ranking male, which had immigrated into the troop at this rank, more frequently approached peri-ovulatory females, spent more time grooming peri-ovulatory females and in mounting series and spent less time feeding than subordinate males did. The 1st-ranking male attained the highest mating success as a result of his high expenditure of time and energy in sexual behaviors directed toward peri-ovulatory females. Mating success of subordinate males did not relate to the amount of sexual effort, but instead to the frequency of female approaches, female rush toward males and the number of peri-ovulatory females within the group. The pattern of intermale competition shifted from nearly contest competition to scramble competition as the number of peri-ovulatory females in the group increased. Feeding time of subordinate males did not vary between the days when they copulated and the days when they did not. The findings demonstrate that mate guarding in the 1st-ranking male is a high-cost mating tactic, while opportunistic mating in subordinate males is a low-cost mating tactic. The differences in male mating tactics are probably related to male life history and to the formation of groups with a high socionomic sex ratio.     

Atomic Force Microscopy Study of Nano-Physiological Response of Ladybird Beetles to Photostimuli

Background

Insects are of interest not only as the most numerous and diverse group of animals but also as highly efficient bio-machines varying greatly in size. They are the main human competitors for crop, can transmit various diseases, etc. However, little study of insects with modern nanotechnology tools has been done.

Methodology/Principal Findings

Here we applied an atomic force microscopy (AFM) method to study stimulation of ladybird beetles with light. This method allows for measuring of the internal physiological responses of insects by recording surface oscillations in different parts of the insect at sub-nanometer amplitude level and sub-millisecond time. Specifically, we studied the sensitivity of ladybird beetles to light of different wavelengths. We demonstrated previously unknown blindness of ladybird beetles to emerald color (∼500nm) light, while being able to see UV-blue and green light. Furthermore, we showed how one could study the speed of the beetle adaptation to repetitive flashing light and its relaxation back to the initial stage.

Conclusions

The results show the potential of the method in studying insects. We see this research as a part of what might be a new emerging area of “nanophysiology” of insects.     

The High Price of Success: Costs of Mating Effort in Male Primates

While males are generally the low investing sex when it comes to offspring care, males of many species experience intense and persistent mating effort. Mating effort incurs a variety of costs which are expected to have non-negligible effects on fitness, as well as how reproductive tactics are selected and investment in mating activity is moderated over time. This special issue features contributions investigating the costs of male mating effort across primate species. Here, we place these exciting new works in context, addressing the specific types of mating effort expected for male primates and the significance of these costs for our understanding of primate life histories and socioecology.     

The Foraging Costs of Mating Effort in Male Chimpanzees (Pan troglodytes schweinfurthii)

Costs of mating effort can affect the reproductive strategies and lifetime fitness of male primates, but interspecific and interindividual variation in the magnitude and distribution of costs is poorly understood. Male costs have primarily been recognized in seasonally breeding species that experience concentrated periods of mating competition. Here, we examine foraging costs associated with male mating effort in chimpanzees (Pan troglodytes schweinfurthii), a polygynandrous species, in which mating opportunities occur intermittently throughout the year. To quantify male feeding, aggression, and mating, we conducted focal follows on 12 males in a wild community (Kanyawara, Kibale National Park, Uganda) for 11 mo. Males fed less on days when high-value mating opportunities (estrous parous females) were available than on days without any mating opportunities. Reductions in feeding time were related to increased rates of aggression and copulation, indicating that the proximate cause of changes in male foraging was mating effort. Surprisingly, however, there was no relationship between dominance rank and the extent to which feeding time was reduced. High costs of mating effort may reduce the degree of reproductive skew and limit the use of possessive tactics in chimpanzees. We suggest that male bonding in chimpanzees may be favored not only for its benefits but because intragroup competition is so costly. Our results complement the available data on mammals, and primates in particular, by showing that mating effort can have measurable foraging costs even in species, in which breeding is aseasonal and only moderately skewed.     

Neither Mating Rate Nor Spermatophore Feeding Influences Longevity in a Ladybird Beetle

Females of many species experience costs associated with mating. Seminal products, including nuptial gifts, may mitigate these mating costs or exacerbate them. For example, nuptial gifts derived from male accessory glands may transfer nutrition or potentially harmful seminal proteins to females. In this study, we assay the costs of multiple mating and the consumption of seminal products in a ladybird beetle. We compared longevity in females mated singly or multiply, while allowing or preventing spermatophore consumption at each mating. In order to distinguish a cost of mating per se from a cost of elevated reproduction, we prevented reproduction by using nutrient‐stressed females. Mating singly or multiply had no effect on female longevity, nor did spermatophore feeding influence longevity. The results imply, first, that intermediate mating rates do not directly harm females, though females may experience other indirect costs of mating (e.g. reduced foraging efficiency) or costs of reproduction; and second, that spermatophores transfer neither food nor directly harmful substances to female ladybirds.     

Mating Resets Male Cricket Aggression

An animal’s motivational state can significantly impact its behavior. We examined the effects of mating on the aggression of male Acheta domesticus crickets. Pairs of males were allowed to establish dominance and subordinance and were then physically separated. Subordinate males were then allowed to either copulate with a female or to have chemo-tactile contact with, but to not copulate with, a female. Less than 15 min after separation, all male pairs engaged in a second agonistic encounter. Subordinate males that copulated with females were significantly more aggressive toward their dominant partners than un-mated subordinate males. Many mated subordinates became dominant. Allowing a subordinate male to contact, but not copulate with, a female had a similar effect, suggesting that chemo-tactile cues from the female are sufficient to elicit this change in aggression.     

Costs of Reproduction in Male Bicyclus anynana and Pieris napi Butterflies: Effects of Mating History and Food Limitation

Life history theory predicts trade‐offs arising from the costs of reproduction: individuals investing more into reproduction should have less energy available for their own somatic demands. Despite a wealth of research on such costs for females, very few studies have looked at the male side. We investigated the costs of reproduction in males of two butterfly species, Bicyclus anynana and Pieris napi. The males of these species differ tremendously in their allocation of nutrients to reproduction: virgin male spermatophores were 18.5 times larger in the latter compared with those in the former. Based on this striking difference, we expected to find a longevity cost of mating in P. napi, but not necessarily in B. anynana. In line with our predictions, we found no evidence for a survival cost of mating in B. anynana, while there was some evidence for such a cost in P. napi. Here, virgin males lived longer than once‐ or twice‐mated ones. However, this overall trend did not hold for all treatment groups, and there was no linear relationship between the number of copulations and longevity. Adult food limitation reduced longevity throughout, but had otherwise very little impact. Spermatophore dry mass decreased in later compared with first spermatophores, while water content increased, indicating that spermatophore production is indeed physiologically costly. Additionally, adult food limitation tended to reduce spermatophore fresh and dry mass, and tended to increase spermatophore water content. Based on our results we tentatively conclude that longevity and reproduction may not always be traded off against each other, as in our study organisms’ longevity seems to depend in first place on adult carbohydrate income, while male reproduction seems to be primarily (although not entirely) fuelled by larval storage reserves.     

Alternative Mating Behaviors of Young Male Bullfrogs

Yearling male bullfrogs often attempt to intercept and matewith females attracted to older, larger males (male parasitism)instead of defending a territory and attracting their own mates.Mating behaviors like male parasitism are thought to occur onlywhen individuals suffer some strong disadvantage in using thebehaviors that are more typical of their species. In this paper,I consider the relative benefits and costs of territorialityvs male parasitism for yearling males. Yearlings employing maleparasitism are only occasionally successful at mating, and inyears of reduced male-male competition, they produce significantlyfewer young than territorial males of their age. Yearling malesthat vary in the degree to which they employ territorial behaviorsinstead of male parasitism do not differ measurably in growthrate or chances of mortality; however, indirect informationsuggests that territoriality should entail a greater chanceof mortality. A computer simulation based solely on observeddemographic parameters predicts that yearling males should beterritorial whenever they can compete as effectively as two-year-oldmales. This condition appears to provide little restrictionon the breeding tactics of yearling males; however, data onmale-male aggressive encounters show that the size differencesbetween one-year-old and two-year-old males are usually sufficientto preclude yearling males from competing successfully. Thus,the observed behavioral plasticity of yearling males may bebest interpreted as a means of adjusting their behavioral tacticsto levels of male-male competition that can vary within andbetween breeding seasons.     

Explosive Adaptive Radiation and Extreme Phenotypic Diversity within Ant-Nest Beetles

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Courtship Disruptions and Male Mating Strategies: Examples from Female-Defense Mating Systems

Males frequently interrupt the copulation attempts of other males, and these courtship disruptions may limit the extent to which a few males are able to monopolize mating access to females. Males actively defend sexually receptive females in many species in which females form dense aggregations during the breeding season. Across and within such species there is considerable variation in the mating tactics adopted by males, with males in some cases defending groups of females and in other cases sequentially consorting with individual females. Colonial blackbirds have been central to studying this mating system, and we develop a conceptual model for how courtship disruption may account for variation in male mating tactics in this group. Our model assumes that the frequency of disruptions increases with greater colony size. As a consequence, successful copulations are less likely to occur at large colonies than at small colonies, and males are expected to switch from defending multiple females at the colony to consorting individual females away from it. Results from two species of blackbird support the basic assumptions of this model. In one species, the Montezuma oropendola, disruptions occur rarely and males defend groups of females, whereas in the other species, the yellow-rumped cacique, disruptions are frequent and males defend single females. Moreover, consistent with a key prediction, within each species, males associated with small colonies remain at the colony and defend groups of females, whereas males spend little time defending groups of females at large colonies and rarely attempt copulations there. This model has the potential to explain variation in male mating strategies and female monopolization for other taxa in which females form breeding aggregations.     

Mating and Residence Patterns of Male Patas Monkeys

A longterm study of a population of patas monkeys (Erythrocebus patas) in Kenya indicated fluid male residence patterns. While a single adult male was present in each of the two main study groups for most of each year, several males were present and mating in groups during some conception periods. Tenures of males in heterosexual groups were generally short; some males were resident in both groups and some had more than one tenure in the same group. When not in heterosexual groups, males lived as solitaries or in all-male associations.     

A Test for Rare Male Mating Advantage with DROSOPHILA PSEUDOOBSCURA Karyotypes

Inbred diploid yeast strains heterozygous or homozygous for the rad18-2 allele and carrying markers for detection of mitotic recombination were constructed. The homozygous rad18-2/rad18-2 strain was highly sensitive to killing by UV light, showed greatly elevated frequencies of spontaneous and induced mitotic recombination and was more sensitive to trimethoprim than the wild-type diploid. The heterozygous strain RAD18/rad18-2 was intermediate in its response for these same phenotypic characters. These findings are discussed in the light of other studies in which incomplete dominance of genes involved in some aspect of DNA repair has been reported.     

Material Benefits from Multiple Mating in Female Mealworm Beetles (Tenebrio molitor L.)

In yellow mealworm beetles (Tenebrio molitor), females are sexually receptive throughout their adult lives. We examined how access to mates affected female fecundity by varying the number of matings per female and quantifying cumulative egg production. Also, we dissected females at successive intervals after a single mating to assess the relationship among time since mating, sperm supplies, egg load, and oviposition rate. Females that mated at intervals greater than 2 days did not produce as many eggs as females that mated every 2 days or were allowed to mate ad libitum. Dissections showed that the amount of sperm remaining in a female spermatheca was correlated with the number of eggs she had laid recently, which suggests sperm replenishment as the material benefit gained through multiple mating. However, females mate more frequently than necessary for sperm replenishment, and therefore material benefits alone may not fully explain the continuous receptivity of T. molitor females.     

Extreme Promiscuity in a Mating System Dominated by Sexual Conflict

Coelopids live in wrack beds consisting of seaweed washed up on beaches. Their mating system is characterized by sexual conflict and convenience polyandry, with females resisting male mating attempts. We estimated the level of harassment by males and the success rate of rejection by females collected from a high density wild population. Males mounted a female every 8.41 min. Of these mounts 35% resulted in copulation. This suggests that females could be mated up to 5 times every 2 h. Females typically live for 3 weeks, and thus, could mate with hundreds of males during their lifetime. We found a 50:50 sex ratio throughout the wrack bed revealing that females do not avoid male harassment by leaving the wrack bed when not ovipositing.     

Male and Female Soldier Beetles Relax Choice for Mate Quality Across Daily Courtship Periods

Mutual mate choice occurs when members of each sex will reject some potential mates in efforts to encounter better prospects later. The decision to reject may represent the interaction between mate preferences, mate availability, and temporal constraints. Theory predicts that mutual mate choice will favor relaxed choosiness as mate availability and time for courtship decline. We explored mutual mate choice in the soldier beetle, Chauliognathus pennsylvanicus (Cantharidae), where courtship consisted of males attempting to secure evasive females. We employed field observations, laboratory experiments, and stochastic simulations to investigate the decline in choosiness over the daily courtship period, during which individuals can mate at most once. We found that reproductive success of males and females increases with mate size and mating frequency. Females biased copulations toward larger mates by attempting to evade suitors, while males biased copulations by releasing the smaller females they capture. However, late in the day males and females may increase reproductive success by accepting rather than rejecting lower quality mates to maintain high mating rates. Stochastic simulations indicated that reproductive success, the product of mating frequency and mean mate size, was maximized in males and females by incrementally reducing mate standards across daily courtship periods. In the field, large males who rejected small females early in the daily courtship period rarely did so later. Large females used less effective evasive maneuvers later in the courtship period, resulting in copulations with progressively smaller males. These results support models of mutual mate choice that predict that individuals of high quality will maximize reproductive success by relaxing choosiness as the courtship period wanes.     

Male Courtship Song Frequency as an Indicator of Male Mating Success in Drosophila montana

Drosophila montana females have been found to prefer overwintered males with short and dense (high-frequency) sound pulses in the wild. In the present study males producing high-frequency song succeeded in their courtship more often than males producing low-frequency song in mate-choice experiments. Male mating success correlated with the carrier frequency of the male song recorded after, but not before, an artificial winter (flies kept 6 months at 4°C). The finding that female preference is based on a male song trait changing considerably during overwintering suggests that this trait may reflect the viability and condition of the males during the mating season of the flies in spring.     

Mating Costs versus Parental Investment: A Reply to Gwynne

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