Today’s animal is a tiny little marsupial from southwestern Australia. It’s called the honey possum, which is a fairly self-explanatory name. They are actually relatively unrelated from other marsupials, having split off from other possums extremely early. It is the only living member of the family Tarsipedidae, and is so unique that some scientists have suggested the honey possum should be in its own superfamily, or even order.
So what makes this animal so unique? Well for one thing, it has a most unusual diet. Despite what its name might suggest, the honey possum does not feed on honey – instead it lives solely on nectar and pollen that it finds in flowers. Living on nectar isn’t unheard of; bees are an obvious example and hummingbirds seem to do quite well. All animals that feed on nectar have one thing in common, however. They all have wings. This lets the animals fly from place to place to find enough food to support their vast needs. The honey possum, however, does not have wings. They are the only flightless animals in the world that live completely on a nectar and pollen diet.
In order to accomplish this successfully, honey possums have evolved a number of useful traits. They are extremely small and very light (up to 16g), which allows them to reach flowers on the end of small branches. Their hind feet have opposable digits, used to grip branches and stems while feeding, and their feet have rough pads on the tips instead of claws, which again helps with gripping. Honey possums have a long, narrow head, perfect for sticking into a flower to get that sweet sweet nectar. But if sticking that funny-looking nose into a flower still doesn’t get the good stuff, they have a long tongue that has little hairs on it that is ideal for licking up nectar.
Any pollen on the honey possum’s tongue is removed by combs on the roof of the animal’s mouth; these are swallowed and digested rapidly. The pollen that the honey possum ingests is the source of the animal’s nutrients, as nectar is only sugar and water. Because of the large amount of nectar the possum must consume to support its active lifestyle (running form flower to flower to get enough nutrients – sounds like hard work to me!), it also takes in a whole lot of water. To deal with this, the honey possum has specialized kidneys, which produce copious amounts of dilute urine. They can excrete their body weight in water in just a day. So if you’re reading this post and thinking the honey possum is really cute and might make an excellent pet, think again. That much urine means a lot of cleanup, and trust me, you don’t want to do that. Just get a hamster.
Honey possums also have some fairly unusual reproductive traits. In many animals, sexual selection leads to an exaggeration of certain traits, as males compete for the attention of females. In many mammals, this presents itself as large horns or antlers used to win females in male-male combat. In birds, often males are more brightly coloured then females, their plumage seen as a sign of good health and fertility by females, who then choose a mate. In animals where females mate with multiple males, the only real way to compete for paternity is to have better sperm than other males. This is the case with the honey possum; males have the largest testes relative to body weight of any mammal. As well their sperm is the biggest of any mammal, which is pretty impressive considering the possum’s size.
Honey possums are marsupials, of course, and the young stay in their mother’s pouch for almost two months. Baby honey possums are the smallest mammals in the world, weighing only 0.0005g at birth. They are able to breed at five or six months old, and females spend the rest of their lives having children. Female honey possums exhibit what is known as embryonic diapause – they can suspend embryonic development until the embryos are needed – which means as soon as their young exit the pouch and stop nursing, another litter is developed and born.
Honey possums are strange and somewhat silly creatures in my opinion, but I still like them. Living on nectar and pollen seems a bit boring, but it works for the possums. Overall I’ve become a fan of these guys, though as I said before, they’d make terrible pets.