Delbarco-Trillo J, Ferkin MH.. Male mammals respond to a risk of sperm competition conveyed by odours of conspecific males. Nature 431: 446-449

Department of Biology, University of Memphis, Ellington Hall, Memphis, Tennessee 38152, USA.
Nature (Impact Factor: 41.46). 10/2004; 431(7007):446-449. DOI: 10.1038/nature02845
Source: PubMed


Sperm competition occurs when a female copulates with two or more males and the sperm of those males compete within the female's reproductive tract to fertilize her eggs. The frequent occurrence of sperm competition has forced males of many species to develop different strategies to overcome the sperm of competing males. A prevalent strategy is for males to increase their sperm investment (total number of sperm allocated by a male to a particular female) after detecting a risk of sperm competition. It has been shown that the proportion of sperm that one male contributes to the sperm pool of a female is correlated with the proportion of offspring sired by that male. Therefore, by increasing his sperm investment a male may bias a potential sperm competition in his favour. Here we show that male meadow voles, Microtus pennsylvanicus, increase their sperm investment when they mate in the presence of another male's odours. Such an increase in sperm investment does not occur by augmenting the frequency of ejaculations, but by increasing the amount of sperm in a similar number of ejaculations.

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Available from: Javier delBarco-Trillo, Oct 14, 2015
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    • "Functional Ecology 2015 doi: 10.1111/1365-2435.12521 (delBarco-Trillo & Ferkin 2004, 2007) and the butterfly Pieris napi (Larsdotter-Mellstr€ om & Wiklund 2009). Butterfly males produce a complex ejaculate during copulation that can contain eupyrene (fertilizing) sperm, apyrene (nonfertilizing) sperm (e.g. "
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    ABSTRACT: 1.When females mate with multiple partners, the risk of sperm competition depends on female mating history. To maximize fitness, males should adjust their mating investment according to this risk. In polyandrous butterflies males transfer a large, nutritious ejaculate at mating. Larger ejaculates delay female remating and confer an advantage in sperm competition.2.We test if male ejaculate size in the butterfly Pieris napi (Lepidoptera) varies with female mating history and thus sperm competition, and whether males assess sperm competition using the male-transferred anti-aphrodisiac Methyl salicylate (MeS) as a cue.3.Both sexes responded physiologically to MeS in a dose-dependent manner. Males; however, were more sensitive to MeS than females.4.Ejaculates transferred by males mating with previously mated females were on average 26% larger than ejaculates transferred by males mating with virgin females, which conforms to sperm competition theory and indicates that males tailored their reproductive investment in response to sperm competition. Furthermore, ejaculates transferred by males mating with virgin females with artificially added MeS were also 26% larger than ejaculates transferred to control virgin females.5.Male-transferred anti-aphrodisiac pheromone not only functions as a male deterrent, but also carries information on female mating history and thus allows males to assess sperm competition.This article is protected by copyright. All rights reserved.
    Functional Ecology 07/2015; DOI:10.1111/1365-2435.12521 · 4.83 Impact Factor
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    • "Males that are better able to recall the location of females when they enter PPE will be more likely than those that cannot do so to have a greater mating success (Ferkin et al. 2008). Males may also compete with other males by tailoring their sperm allocation when they mate with females (delBarco-Trillo 2011; delBarco-Trillo and Ferkin 2004; Parker and Pizzari 2010). "
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    ABSTRACT: For numerous species of terrestrial mammals, postpartum estrus, PPE, is a period of heightened attractivity, proceptivity, and receptivity that occurs shortly after the female delivers her litter. Many mammals mate almost exclusively during PPE. However, we know little about the behavior of PPE females and how male conspecifics behave towards them. This review focuses on the results of recent studies that tried to examine systematically the behavior of PPE female meadow voles, Microtus pennsylvanicus, and the responses of males to them. Our review is divided in five parts. First, we introduce the topic of PPE in rodents. Second, we discuss the outcome of studies showing that PPE female voles were more attractive to males, directed more proceptive behaviors towards males, and were more sexually receptive and likely to get pregnant compared to females that were not in PPE. Third, we discuss studies that examined how male voles respond and adjust their behavior when they encounter PPE females. Males increase the likelihood of mating with PPE females by recalling the reproductive state of females and the location of their nests, and by anticipating how long or when each of these females would be in PPE. Fourth, we focus in how food availability, an ecological constraint facing gestating female voles, affected their attractivity, proceptivity, and receptivity postpartum. Fifth, we revisit the benefits of seeking out and mating with PPE females and introduce the costs of doing so for both males and PPE females. We close our review with a list of questions that can be used to formulate testable hypotheses surrounding the behavior of PPE females and the responses of male conspecifics to them.
    Mammalian Biology - Zeitschrift fur Saugetierkunde 01/2014; 79:81-89. DOI:10.1016/j.mambio.2013.06.003 · 1.48 Impact Factor
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    • "At high population densities, females are more likely to remate, producing a greater risk of sperm competition compared with low-density populations (Gage, 1995; Parker, 1970), and males show an increased investment in ejaculate production as population density increases (Gage, 1995; Hoi et al., 2011). Males have also been shown to invest more in their ejaculates when exposed to environmental cues of rival male presence, such as olfactory, visual, auditory, and tactile cues (Bretman, Westmancoat, Gage, & Chapman, 2011; delBarco-Trillo & Ferkin, 2004). Female attractiveness can also provide a cue to risk of sperm competition (Kelly & Jennions, 2011; Reinhold, Kurtz, & Engqvist, 2002). "
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    ABSTRACT: Sperm competition is the competition between the sperm of two or more males to fertilise the ova of a single female. Over the past few decades, the extent to which sperm competition has acted as a selective pressure throughout human evolution has been hotly contested. This review aims to assess the current evidence for sperm competition in humans, the limitations of that evidence, and directions for future research. We conclude that humans have primarily evolved defensive adaptations in response to the risk of sperm competition. Thus men exhibit behaviors designed to anticipate and address their partner’s infidelity, the success of which may have relaxed selection on physiological and morphological adaptations to tackle sperm competition offensively. However, the extent to which humans can perform offensive tactics has been sorely understudied and requires considerable further research before firm conclusions can be drawn.
    Advances in the Study of Behavior 01/2014; 46:1-44. DOI:10.1016/B978-0-12-800286-5.00001-8 · 2.57 Impact Factor
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