Researchers led by Dalhousie University inflated the penises of dead dolphins, before simulating sex to find out how these organs fit inside the female. There could be many functions of sex.'After blowing up the genitalia, they used computed tomography (CT) scans to visualise how deeply the penis penetrates the vagina and where the two touch.They discovered that the females have unusual folds in their vaginas which the male's penis must navigate to fertilise the egg.'There's this unparalleled level of vaginal diversity that we had no idea existed before', Dr Dara Orbach of Dalhousie University told New Scientist. There could be many functions of sex.'Dr Orbach's team examined the reproductive tracts of dolphins, porpoises and seals that had died naturally in order to find out more about their sex lives. They also created silicone models of the interior of the dolphin vagina to explore how its shape might have co-evolved with the shape of the male penis.
'By looking at how the genitals align, we can now say certain body positions are more likely to lead to successful fertilization than others, which might be for purposes other than reproducing,' Dr Orbach told Science. From looking at the genitalia, scientists could make predictions about what positions the dolphins would use in real life.'Body positioning during copulation is predicted based on anatomy', Dr Orbach explained.Most research on genitalia has focused on the penis alone but this study looked at how the penis and vagina fitted together.'While it may seem intuitive that the penis fits well into the vagina during copulation, the biomechanics and details of the anatomical fit can be quite complex and have seldom been explored,' said Dr Orbach.The vaginal folds of the porpoise and bottlenose dolphin make penis entry much more difficult.These sneaky females make small movements during sex so undesirable male suitors can't get in the best position for fertilisation, researchers found.No studies used a biological outcome and all asked about peers in general rather than about specific relationships.
Studies were heterogeneous in their use of theoretical frameworks and means of operationalizing peer influence concepts.All studies found evidence for an association between peers and sexual behaviour for at least one peer exposure/outcome/sub-group association.Of all 37 outcome/exposure/sub-group associations tested, there was evidence for 19 (51%).The team found there were particular parts of the vagina that were stimulated during sex which could help captive breeding programmes.Adolescents in sub-Saharan Africa are highly vulnerable to HIV, other sexually transmitted infections (STIs) and unintended pregnancies.Male bottlenose dolphins generally form teams of two to four individuals to guard their females. As part of the study, researchers wanted to find out how often dolphins have sex for 'fun'. Researchers found that there was an optimal position for the vagina and penis to fit together which varied with overall body positioning.'The deeper the male is able to extend his penis within the vagina, the shorter a distance his sperm must travel to reach her egg', Dr Orbach told Mail Online.'In some species it appears belly-to-belly copulation will enhance genital alignment, while in other species it appears a sexual approach from the female's side will result in deeper penetration', she said.