Nonpreferred Females Research Articles

Fitness costs of mating with preferred females in a scramble mating system

AbstractLittle is known about the operation of male mate choice in systems with perceived high costs to male choosiness. Scramble mating systems are one type of system in which male choice is often considered too costly to be selected. However, in many scramble mating systems, there are also potentially high rewards of male choosiness, as females vary dramatically in reproductive output and males typically mate once per season and/or per lifetime. Using scramble mating wood frogs (Rana sylvatica), we tested whether males gain fitness benefits by mating with preferred females. We conducted choice trials (1 male presented simultaneously with 2 females) and permitted males to mate with their preferred or nonpreferred female. Offspring of preferred and nonpreferred females were reared in the laboratory and field, and we quantified various fitness-relevant parameters, including survivorship and growth rates. Across multiple parameters measured, matings with preferred females produced fewer and lower-quality offspring than did those with nonpreferred females. Our results are inconsistent with the idea that mate choice confers benefits on the choosing sex. We instead propose that, in scramble systems, males will be more likely to amplex females that are easier to capture, which may correlate with lower quality but increases male likelihood of successfully mating. Such male choice may not favor increased fitness when the operational sex ratio is less biased toward males in scramble mating systems but is, instead, a bet-hedging tactic benefitting males when available females are limited.

The evolution of postpairing male mate choice.

An increasing number of empirical studies in animals have demonstrated male mate choice. However, little is known about the evolution of postpairing male choice, specifically which occurs by differential allocation of male parental care in response to female signals. We use a population genetic model to examine whether such postpairing male mate choice can evolve when males face a trade‐off between parental care and extra‐pair copulations (EPCs). Specifically, we assume that males allocate more effort to providing parental care when mated to preferred (signaling) females, but they are then unable to allocate additional effort to seek EPCs. We find that both male preference and female signaling can evolve in this situation, under certain conditions. First, this evolution requires a relatively large difference in parental investment between males mated to preferred versus nonpreferred females. Second, whether male choice and female signaling alleles become fixed in a population versus cycle in their frequencies depends on the additional fecundity benefits from EPCs that are gained by choosy males. Third, less costly female signals enable both signaling and choice alleles to evolve under more relaxed conditions. Our results also provide a new insight into the evolution of sexual conflict over parental care.

Investigation of female house mice (Mus musculus domesticus) by males in relation to the presence and absence of anogenital odors from dominant or subordinate males

Females in promiscuous species (e.g. house mice; Mus musculus domesticus) may mate with multiple males, which can negatively influence the reproductive success of males because of the risk of sperm competition or injury due to male-male competition. Thus, selection should favor those that can discern not only if a female has recently been in contact with another male (potential risk of sperm competition), but whether the other male with which the female had been in contact is dominant (potential risk of injury) or subordinate to the investigating male.After establishing the dominance ranks of pairs of males, we determined each male’s preferred (P) and non-preferred (NP) female (Trial 1). In Trial 2, one of the females of the pair (P or NP) was treated with the anogenital odor of the male’s opponent, and we tested if the proportion of time males spent investigating their initially P and NP females was altered by the presence or absence (treated or untreated) of their opponent’s odor.In Trial 2, contrary to our prediction, males did not spend a smaller proportion of time investigating the female that was treated than they spent investigating the female that was untreated. In fact, in Trial 2, all males spent a similar proportion of time investigating both females regardless of which female (P or NP) was treated. In addition, contrary to our prediction, subordinate and dominant males did not respond differently with respect to the presence of their opponent’s odor. Males also spent more total time investigating both females when one of the two females was treated (Trial 2) than when neither female was treated (Trial 1). Our data suggest that males may have been attempting to reduce the risk of sperm competition by spending more time investigating females to determine if either female had recently mated.

Prudent male mate choice under perceived sperm competition risk in the eastern mosquito fish

In contrast to what is known about adaptive mate choice in females, we know far less about how fluctuating reproductive costs might affect male mate choice. In many species, sperm competition can have a direct bearing on male fertilization success, and choosy males should be expected to respond adaptively to the perceived cost of sperm competition and to adjust their mate preferences accordingly. Here, we conducted a series of experiments investigating male mate choice under sperm competition risk in the eastern mosquito fish, Gambusia holbrooki. We tested male association preferences before and after manipulating their perceptions of sperm competition risk associated with initially preferred and nonpreferred females. We found that individuals were consistent in their preferences if they did not have the opportunity to witness other males associating with the initially preferred female. By contrast, males spent significantly less time with initially preferred females if, in the interim, she had been seen in the vicinity of another male. A similar opportunity to observe the initially nonpreferred female with another male had no effect on subsequent male mate choice. Our results suggest that choosy males may be capable of adjusting their preferences in response to shifts in their perception of sperm competition risk. Key words: eavesdropping, intrasexual competition, mate choice copying, Poeciliidae, sexual selection. [Behav Ecol]

Male house mice produce fewer offspring with lower viability and poorer performance when mated with females they do not prefer

We report experimental results consistent with the hypothesis that constraints on the expression of male mating preferences affect breeder fitness, offspring viability and performance. If constraints on the expression of mating preferences are common, tests of fitness variation associated with mate preferences must eliminate as many constraints on mate preferences as possible. We tested whether male mate preferences influenced breeder fitness, offspring performance and viability in typically polygynous house mice, Mus domesticus, from a feral source population. Our ‘free mate choice’ trials not only eliminated female preferences, male–male and female–female competition, but also our best guesses of the traits mediating choosers' preferences. Males mated with their preferred (P) females sired more litters than males mated with their nonpreferred (NP) females. Offspring viability was significantly lower when males' reproduced with females they did not prefer compared with females they did prefer. Adult sons of males that mated with their P females were socially dominant to sons of males that mated with their NP females. Adult offspring from P pairings built better nests than offspring from NP pairings. The slope of the survivorship curve for P offspring was significantly higher than for NP offspring. These results showed (1) males' mate preferences affected their fitness, (2) males that mated with females they preferred produced more litters than males that mated with females they did not prefer, and (3) their offspring were significantly more viable and performed significantly better on standardized performance tests. This is the first demonstration of fitness benefits of male choice behaviour in a mammal species with typical paternal investment. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Free female mate choice in house mice affects reproductive success and offspring viability and performance

We tested a critical assumption of sexual dialectics theory (Gowaty 1997, Feminism and Evolutionary Biology, Chapman & Hall) using house mice, Mus musculus. We asked if female house mice accrue viability benefits for their offspring when they mate with males they prefer versus with males they do not prefer. Our experiment was designed to eliminate or control other mechanisms of reproductive competition besides female mate choice. After allowing females to discriminate behaviourally between two males, which were at random with respect to phenotypic variation discriminating females were paired with preferred (P) or nonpreferred (NP) males. We then tested whether females mating with males they preferred had offspring of higher viability than females mating with nonpreferred males. In pairwise comparisons, we tested for differences in offspring performance in dominance contests and in nest-building skill. At weaning, we exposed half of the pups to cold stress. We tested progeny performance and viability in the laboratory or in outdoor field enclosures. In comparison to P females, NP females produced significantly fewer litters. Sons from P matings were socially dominant to sons from NP matings. Adult offspring from P matings built better nests than those from NP matings. In field enclosures significantly fewer NP than P offspring survived to 60 days after introduction. Male and female progeny from P matings established larger home ranges and constructed better nests than progeny from NP matings. This is the first demonstration of progeny viability differences for females allowed to express mate preferences between males presented to them at random.

Social effects on mate choices of male Japanese quail,Coturnix japonica

In four experiments, we examined effects on affiliative preferences of ‘focal’ male Japanese quail of seeing a conspecific female interact with another male. Each experiment was conducted in three 10-min phases: (1) a pretest during which a focal male chose between two females; (2) an observation phase, when each focal male watched the female he had spent more time near during the pretest (his ‘preferred’ female) interact with another male (referred to as a ‘model’ male); and (3) a post-test, during which each focal male again chose between his nonpreferred and preferred females. Focal males decreased their preferences for preferred females after seeing them together with a model male, even when preferred females and model males were separated by a transparent barrier that prevented them from mating, but allowed them to court. A focal male’s preference for his preferred female did not decrease when the female mated with a model male out of sight of the focal male. These first results could reflect a tendency for males simply to avoid areas where they saw conspecifics courting. However, focal males also showed reduced preferences for preferred females they had seen mate when the locations of preferred and nonpreferred females were reversed between observation and post-test phases of the experiment and the effects of transposition were controlled for. We concluded that male quail tend to avoid areas that recently contained courting pairs, as well as particular females, seen courting.

Mutual mate choice in sticklebacks: attractive males choose big females, which lay big eggs

Brighter red three-spined stickleback,Gasterosteus aculeatus, males have been shown to be preferred by females in the laboratory but in the field, these males did not receive more eggs. Instead, they had heavier eggs in their brood. We investigated the hypothesis that sexual selection for red coloration in male sticklebacks acts through mate choice by preferred males, who can afford to be choosy, for high-quality females which lay heavier eggs. We assume here that heavier eggs provide a direct fitness advantage. In simultaneous choice tests males were presented with two females differing in size. The number of zigzags directed to and the time spent orienting to each female were measured. After the test the females laid eggs, which we counted and weighed. Bigger (i.e. longer and heavier) females laid significantly more and heavier eggs than smaller females. For all 23 males pooled together, the preferred female was the bigger of the two in 17 cases, laid more eggs in 18 cases, but laid heavier eggs in only 13 cases. When bright and dull males were analysed separately, we found that bright but not dull males spent more time oriented to the bigger female, and to the female that laid more eggs. Females preferred by bright males tended to lay heavier eggs than nonpreferred females, although this result was not quite significant. We conclude that in nature this preference for bigger females results in brighter males receiving on average heavier eggs. Assuming higher survival of bigger offspring, we propose that this can explain how brightness can be sexually selected in spite of brighter males not receiving more eggs.

Sexual preferences during artificial menstrual cycles in social groups of rhesus monkeys (Macaca mulatta)

Eight groups of rhesus monkeys each consisting of one male and four ovariectomized females were observed while two of the females were treated with hormones to produce artificial menstrual cycles. These were either synchronized or offset by 7-day increments. Sexually preferred females, defined by the numbers of ejaculations per test, received almost twice as many ejaculations as did non-preferred females during all synchronized and offset cycles and during all cycle phases. However, short-term changes in partner preference occurred when the midcycle phase of non-preferred females coincided with the middle or late progesterone phase of preferred females, suggesting a negative effect of progesterone on behavior during the menstrual cycle. There were highly significant differences between preferred and non-preferred partners for almost all of their sexual and social interactions, and preferred partners showed longer proximity and grooming times as well as higher levels of sexual activity. Partner preferences accounted for more of the behavioral variance between pairs than did female dominance, although males sought the proximity of dominant females independently of their partner preferences. Thus, in a setting uncomplicated by male mate competition, sexual preference by male rhesus monkeys is a robust phenomenon depending on complex interactions between dominance, hormonal status, and the individual behavior of female partners.

Stimulus qualities of a preferred female partner and sexual behavior of old rhesus males

A vaginal lavage from a preferred female sexual partner (donor) with whom old (21–27 yr) rhesus males readily copulated or a distilled water lavage was applied to the perineum of non-preferred females (N=8) with whom old males rarely copulated. The donor and recipients were ovariectomized and were treated with estradiol benzoate (EB) before being tested. Sexual performance of the males did not differ under the two conditions of testing, but the rate of sexual solicitation by the females was significantly higher when treated with the vaginal lavage. One month later the non-preferred females were again treated with EB and paired with the old males. In these tests the preferred female was present in a cage adjacent to and in view of the test pairs. Sexual behavior was not altered significantly, but whereas these males had never threatened or aggressed their partners in previous tests, there was a significant increase in the rate at which they threatened their partners and aggression occurred for the first time. When paired with the preferred female, males ejaculated in 100% of the tests and the average ejaculation latency was less than 2.5 minutes.

Individual copulatory preference and the “strange female effect” in a captive group-living male chimpanzee (Pan troglodytes)

The common chimpanzee has been considered to be a promiscuous species, although transient consort relationships and male possessive behavior have been described byTutin (1975, 1979).A prolific adult male chimpanzee was housed with from four to seven adult female chimpanzees (depending on the females' maternal status) and copulations were recorded from August 7, 1978 until February 16, 1979, during morning feeding periods. Ten females composed the fluctuating available partners.Sixty-four observed copulations involved six females. One female was clearly preferred, including occasions when she was not maximally tumescent (e.g., completely detumescent, pregnant) and other available females were maximally tumescent. The remainder of the observed copulations, with one exception, involved females who had recently been reintroduced into the one-male breeding group. Such copulations took place on and continued temporarily after the day of reintroduction for two females, and after the resumption of menstrual cycling for two females who had been reintroduced while still lactating. Nonpreferred females were impregnated during the period of data collection, even though copulations with them were not observed.These data suggest that the male chimpanzee can form an individual mating preference regardless of the hormonal status of his available partners without lessening his reproductive success with nonpreferred females, but also tends toward maximization of his reproductive success by copulating with novel females.

Effects of the menstrual cycle, social grouping, and exogenous progesterone on heterosexual interaction in laboratory housed stumptail macaques (M. arctoides)

The effects of endogenous fluctuations in ovarian hormones during the female's menstrual cycle on heterosexual interaction was studied in groups of stumptail macaques. When 5 different trios of females were paired for 5 consecutive weeks with each of 5 males no aspect of male-female interaction changed as a function of phase of the menstrual cycle. Moreover, males usually preferred to copulate with the same female of each trio in consecutive tests, regardless of the ovarian condition of any of the females. It appeared that the most dominant females in the trios were sexually most preferred. Subcutaneous implantation of silastic capsules containing progesterone into the sexually most preferred females of each trio affected neither the males' sexual preference, nor the behavior of these females, nor the behavior of sexually non-preferred females in each trio. Likewise, progesterone in sexually preferred females had no effect on male-female interaction in pair tests. It is concluded that in stumptail macaques social factors are more important than ovarian hormones in regulating heterosexual interaction.