extended female sexuality extended female sexuality extended female sexuality is where the female of a species mates despite being infertile. in most species, the female only engages in copulation when she is fertile. however, extended sexuality has been documented in old world primates, pair bonded birds and some insects (such as carrion beetles). extended sexuality is most prominent in human females who exhibit no change in copulation rate across the ovarian cycle. although this behaviour incurs costs to females, such as energy and time, many researchers have proposed reasons for its existence. these hypotheses include the male assistance hypothesis, which proposes that females gain non-genetic benefits (such as food and shelter) in exchange for sexual access. a sub-hypothesis of this is hrdy's, proposing extended female sexuality as an adaptive process aiming to creating paternity confusion in males. alternative hypotheses, classified as 'male-driven', claim that extended female sexuality occurs due to male adaptations, resulting from an inability to detect fertility status in females or to dampen immune responses against sperm. finally, spuhler's hypothesis suggests that the behaviour may have arisen as an incidental effect of larger adrenal glands in humans. the human menstrual cycle occurrence in non-humans although not found in all organisms, researchers have identified sexual intercourse patterns in certain animals that reflect extended female sexuality, such as in some old world primates, birds and insects. extensive research has focused on analysing the musk shrew's rate of sexual behaviour. the only period that is associated with a drop in female receptivity to copulation is during mid to late pregnancy; yet, even at this time, occasional mating is reported. therefore, researchers have concluded that this animal has similar sexual receptivity across infertile and fertile phases. within primates, research has consistently found evidence of extended female sexuality in the rhesus monkey and chimpanzees. both of these primates mate at all stages of the ovarian cycle, with only slight increases in sexual receptivity during fertile stages, and decreases during menstruation. in humans human females are considered to exhibit the greatest degree of extended female sexuality, with receptivity to sexual intercourse remaining constant across fertile and infertile phases of the reproductive cycle, including during pregnancy, lactation, and in adolescence. in a study of 20,000 women from 13 countries, frequency of copulation was reportedly the same across all stages of the ovarian cycle. the only notable drop in sexual behaviour occurred during menstruation. therefore, women largely showed the same level of sexual behaviour in the non-fertile phases of their ovarian cycles as in the fertile phases. researchers have investigated the effect of hormonal contraceptive use in women on the frequency of sexual intercourse. many of these contraceptives mimic a pregnancy state in females by altering hormone levels. therefore, women who use these contraceptives do not experience the fertile phases of their cycles. in a systematic review, it appeared that the frequency of sexual intercourse was unaffected by contraceptive use in the majority of women. although artificially created, this adds to the literature documenting the existence of copulation in humans during non-fertile periods. impact of concealed ovulation in order to encourage mating in non-conceptive periods and to encourage males to maintain their proximity, males must possess imperfect knowledge of the female's fertility status. this is achieved through concealed ovulation in most animals that exhibit extended female sexuality. a review of studies revealed that, in humans, females only exhibit subtle changes during estrus, making it difficult for males to assess fertility with precision. in the !kung tribe, for instance, females lack any overt signals of fertility and are continuously receptive to sexual intercourse, encouraging males to remain and provide resources. the trobriand people with bronisław malinowski explanations male assistance hypothesis mating outside the fertile window of their ovarian cycle may incur considerable costs for females, such as in time and energy usage. to counteract these costs, the male assistance hypothesis argues that females exhibit extended sexuality to obtain resources from males. these resources vary between species, but can include food, social alliance, and protection of the female and her offspring. for example, in the trobriand tribe, men give women gifts in exchange for sexual access. from this hypothesis, three predictions can be made. male provision of non-genetic resources firstly, in species that demonstrate extended female sexuality, there should be evidence that the males provide non-genetic resources to females. this prediction is supported in a variety of animals, with reviews revealing that male assistance (such as food or protection), is provided to certain mammals and communally breeding birds in exchange for mating outside the conceptive period. for example, female blackbirds that solicit mating outside the fertile period have increased mate guarding from their pair-bonded partner. this increases protection against other sexually coercive males and ensures the provision of other material benefits. in a review investigating primates that exhibit extended female sexuality, it was noted that females engaging in extended sexuality benefited from increased offspring protection and paternal care from males. enhanced reproductive success secondly, in order to outweigh the aforementioned costs, mating during infertile phases should increase females' reproductive success by increasing the number of offspring produced. current research has only investigated this factor indirectly, and it has predominantly been investigated in insects. for example, when male insects deliver material benefits in exchange for sexual access, the reproductive success of the females increases with the number of matings. it is important to note that the mating behaviour assessed was not limited to extended female sexuality. hence, it only provides indirect support for the second prediction. shifting mate preferences and behaviour across the ovarian cycle