There's probably some information on the shape of the uterus, which can relate to things like litter size, and maybe for a few other features besides, but it tends to be rather less than you'll find for the males. But you won't typically find, in most descriptions, is quite so much information on the female reproductive tract. So male reproductive anatomy can tell us quite a bit. Alternatively, if your species is monogamous then neither of these things are much of a concern. So, in those species, the males tend to be smaller, but their testicles larger (proportionately speaking). Instead, what you really need is to produce so much sperm that yours swamps that of your rivals. But if the females are sexually promiscuous, that's pointless. In order to gather a harem of receptive females around itself, a male has not only attract them to itself with suitably impressive antlers (or whatever) it also has to fight off rivals, and it's going to have to be big and muscular to do that. This is because the rule is not simply "the bigger the animal, the bigger its gonads". Testicular size, for example, can tell us about its mating strategies. Obviously, reproductive anatomy is an important field if we want to really understand how an animal functions and behaves. And there's a high probability that there will be quite a lot of information about the shape of its penis and the size of its testicles. There will also be discussions of the shape and proportion of the limbs and the exact colour of the fur, as well as any horns or antlers it might have. “I think it would be really interesting to work back within the phylogeny to understand exactly how species have diverged in terms of diversity and to understand if it is more about the relatedness or if it relates more towards perhaps the environment, if you mate on land versus in water versus in the mud»”, ponders Orbach, obviously passionate about her subject of study.If you look at any really detailed description of the physical appearance of a mammal species, you will find a lot of intricate information on the shape of the teeth (especially the molars and premolars) and the dimensions of the skull. She was surprised to note the resemblance to the penis of pygmy sperm whales. Recently, Orbach was able to dissect the penis of a hippopotamus, a member of the ungulate family and very closely related to the large cetacean family. Even if further research is needed to better understand the mechanisms of reproduction, the foundations laid by Orbach and her team open new horizons in morphology, evolution and even conservation. In an interview with Discover magazine’s blog, Orbach explains how, thanks to their vaginal folds, a female can voluntarily prevent sperm from advancing deeper with a subtle change of angle in penetration. But now, Orbach, Brennan, Kelly and Solano can also understand how the female can play a more active role in choosing the father of her offspring. With the casts and erect penises placed side by side, it was immediately evident that the shape of the male and female parts of different species were sufficiently distinct to prevent interspecific procreation. “I realized pretty early on in my studies that most of the literature is very biased as to how males acquire paternity and how females were often assumed to have a pretty passive role,” says Dara Orbach, in an interview with Whales Online on the sidelines of the 22 nd Biennial Conference on the Biology of Marine Mammals, after presenting her paper, “Cetacean and pinniped Kama Sutra: Copulatory fit amongst marine mammals.” She believes that in reality, females are much more active in choosing the partner that might fertilize her. Nevertheless, researcher Dara Orbach, currently a postdoctoral fellow at Dalhousie University and research associate at the Brennan Lab at Mount Holyoke College, decided to study the role females play in reproduction. For both ethical and practical considerations, it is impossible to use this technique with whales. To study reproduction in certain insects, one of the techniques developed was to take an insect pair in the middle of mating and flash freeze them in liquid nitrogen in order to study how the male and female parts fit together.
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