One large class of animals are the mammals. What identifies them is that they give birth to their young alive, and feed them on milk from mammary glands found on the female.
For such an important organ I think relatively little research has been done into them. Not that I am sure how such research might be undertaken. What I have noticed is that there appear to be three main configurations.
Common among hoofed animals is an arrangement of two or four teats between or near the hind legs. Such creatures are, by and large, grass eaters and live on the plains and savanna. They include cattle, sheep and goats, as well as antelopes, gnus, moose, deer, along with horses, zebras, and other asses. Included among them, though not necessarily as grass eaters, are such animals as Giraffes. As a rule these animals give birth to only one or two young at a time. They live exposed and need to be able to run to escape their predators.
Another common arrangement is two rows of teats which reach from the hind legs to the fore legs. These animals often live in dens and have many young at a time. We can include here dogs and cats, mice and other rodents, and pigs. Often the smallest of the young get pushed away from the central teats which carry more milk and are forced to gain their sustenance from the teats closer to the forelimbs.
The last arrangement is common to the monkeys and apes which have two teats at the heart or chest level. This arrangement is not common in nature but is shared, interestingly, with elephants as well as humans.
I don’t pretend to offer an exhaustive study here. I have tried to research Rhinoceros and Hippopotamus, and they appear to suckle from their hind quarters.
Why is this important? What is his obsession? you might ask. I consider the energy within the body, following the laws of the chakras. The lower centres, the sex chakra and the base, inevitably provide a more material energy, more gross we may say. Further up the body towards the heart the energy becomes finer. For those runts of a litter feeding on the heart milk while they may not get as much milk the quality of the milk will be much more subtle.
Something to think about.
As I said at the beginning, I have no idea how one would research this. What does an intellectual pig look like? How does it spend its day differently?