Alpacas have weird sex life : they are the only mammal we know of in which the penis enters the womb to directly deposit sperm . It ’s a reproductive strategy that ’s never been confirmed in any other mammal before , and new enquiry suggest it may help the crisp camelids ’ chances of pregnancy .

Alpacas ( Vicugna pacos ) – not to beconfused with llamas – have long been suspected of pair like this , which would make them unequalled among mammals , but until now there has only been circumstantial evidence that this is the lawsuit .

matte up in the animal kingdom can bepretty weird , andoften unmanageable , meaning there are a multitude of strategies used by different metal money to maximize their chances of success . In most mammalian , the penis is stick in into the vagina and insemination occur in the cranial vagina or fornix . But for some , known as intrauterine inseminators , insemination happens in the uterus . Species thought to do this let in horses , mice , rats , and ferrets .

Alpacas , however , were believe to be unequaled in that they have intrauterine inseminationandintrauterine penile insertion – meaning that the penis is inserted into the womb itself where it directly deposits sperm cell .

To rule out if this was really the guinea pig , researchers try the reproductive systems of 10 distaff Lama pacos cull for meat either one 60 minutes or 24 hr after mating . They found evidence of “ blazing haemorrhage ” along the reproductive tracts , including the virginal membrane , cervix , and bakshis of the uterine horn , which was not present in alpacas that had not recently mated .

This , they have conduct as evidence that manlike Lama pacos thrust their penises through the females ’ intact reproductive tract , penetrating to the very tip of the uterine horn , and in doing so stimulate abrasions and breaking fine blood watercraft .

Sperm were then deposited at the uterine papillae of the oviduct entry , the work generator write , and from there were able to enter the oviducts within just one 60 minutes ofmating .

These decision are supported by the alpaca ’s strange penis sound structure : males have a long , thin , and fibro - pliant penis with a laborious gristle lead , which is probably responsible for the attrition the squad documented .

It may seem a freakish method of reproduction – and the researcher do n’t controvert that – but it could have evolutionary benefits for the curious camelids .

“ A peculiar copulatory mode in alpaca may ameliorate the betting odds of successful fertilization and pregnancy , ” the team reason . “ The fact that the entire generative tract in alpaca is basically functioning as a vagina during copulation in all likelihood has some immunological consequence deserving further investigation . ”

They add that the inflammation triggered by the interior wounds may avail the fertilized egg implant in the womb walls or could help to rush ovulation .

Whatever the reason , alpacas ’ unknown intimate habits are a mammalian anomaly ( at least for now ) – but there are plenty of other examples of quirky coitus out there , from bat regurgitate without insight because of theirseven - fourth dimension - too - big dongstosloths screaming in D needlelike .

The study is published in the journalPLOS ONE .