Alpacas are the only mammals known to science in which males deposit sperm directly into the uterus. This unusual reproductive method inflicts small internal injuries that may help improve the chances of pregnancy.
at Mount Holyoke College in Massachusetts and her team examined and dissected the reproductive systems of 10 female alpacas that were euthanised within 24 hours of mating. They found bloody abrasions throughout the whole reproductive tract, suggesting that the male alpacaâs penis had thrust its way through the vagina, past the cervix and all the way into the horns of the uterus.
These findings confirm something alpaca researchers have long informally known, says at the University of Saskatchewan in Canada. This assumption was based in part on the alpaca penis: it is long, stretchy, thin and has a hard tip of cartilage that lets it push through flesh.
Advertisement
Alpacasâ intense intercourse â which can last for up to an hour and does not seem to cause the animals any pain â may seem unhelpful because it leaves the femaleâs insides wounded and inflamed. But there may be an evolutionary upside.
Adams suggests the woundsâ purpose could be related to alpaca ovulation, which isnât cyclical like in other mammals but rather induced by the act of mating. The inflammation could help the female alpacaâs body better absorb proteins in semen that help trigger ovulation. Prior research from his team .
Meanwhile, Brennan points out that a little bit of inflammation in the uterus helps the fertilised egg successfully stick to the uterus walls â that is why doctors often during IVF treatments in humans. The alpaca penis pushing its way through the uterus may serve a similar purpose.
âWe think that alpacas represent an extreme example of the âgood inflammation hypothesisâ,â says Brennan.
More research is needed to flesh out why alpacas evolved this peculiar method, and to confirm whether related camelid species, such as llamas and camels, have a similar system for insemination.
PLOS ONE
