cardenolides | BC Write

A maned rat (Photo by Kevin Deacon, CC BY-SA 3.0 license)

The maned rat (Lophiomys imhausi) is an interesting animal. It’s also known as the African crested rat. It’s a rodent, as its name suggests, but it’s an unusual one. It’s about the size of a rabbit and has long hair. It’s also very poisonous. The animal stores plant toxins in its fur and is the only mammal known to do this. The rat has provided additional surprises for the scientists who study it.

Physical Features of the Animal

The maned rat is classified in the order Rodentia and the family Muridae, like other rats, mice, and gerbils. Its fur is an attractive mixture of black, white, grey, and brown in color. Its undercoat is dense and is covered by longer guard hairs. Like its relatives, the rat has a long tail, but it’s covered by hair.

The black and white mane or crest of the animal runs along its back from its head to its tail. The mane has long hair that is coarser than that on the rest of the body. The animal erects the mane when it’s alarmed, which makes it look a bit like a porcupine. The scene is shown in the photo above. When the mane is erect, glandular skin is revealed.

Unfortunately, the animal in the video below is in a cage, but the close-up view in the video enables a person to examine the rat’s appearance in more detail than in the photo.

Daily Life and Diet

The maned rat lives in East Africa. It inhabits areas with trees and is nocturnal. During the day, it sleeps in an area where it can hide, such as a hole in a tree or the banks of a watercourse. It will also sleep in a place where it’s obscured in another way, such by a tangle of roots or a pile of rocks. Its ability to climb increases its options for hiding places.

During the day, the rat looks for food. It appears to be a vegetarian, though this impression may be due to our ignorance. It eats leaves, shoots, and fruits. In captivity, it also eats root vegetables, insects, and even pieces of meat.

For a long time, scientists have thought that the rats were solitary animals. Recent discoveries suggest that this idea is wrong, at least in some parts of the animal’s range or in some cases. Researchers say that the animal seems to be monogamous in some areas and that it may live in a family unit instead of being solitary. The evidence is indirect but interesting.

A team of scientists investigating the animals captured a female in a particular location. Two days later, they captured a male in the same area. They put the animals in the same enclosure. To their surprise, the animals began “purring and grooming each other” when they met. This implied that they knew each other. They may have been friends and perhaps much more than friends. Later, the researchers livetrapped several juvenile rats from the area where the male and female were found.

The researchers built a home in a shed for the first pair of animals. They tried to mimic the natural habitat with raised areas, nest boxes, and ladders. They also put cameras in the habitat so that they could record the animals’ behavior. The film showed that the pair spent “more than half of their time” touching each other. The animals frequently followed each other around the habitat. In addition, they made a wide variety of sounds.

The Poison Stored by the Maned Rat (and the Monarch Butterfly)

The poison arrow tree (Acokanthera schimperi) is a traditional source of poison for hunters’ arrows in the habitat where it grows naturally. The significant chemicals are called cardenolides and are found in the tree’s bark. Cardenolides are a natural type of cardiac glycoside, which are chemicals that affect the heart. Cardiac glycosides are used medicinally in tiny and precise concentrations for those who need them. When prescribed by a doctor and used in the correct dose, they increase the force of the heart beat and decrease its rate. If they are used beyond our body’s requirements, they are dangerous.

The maned rat chews the branches of the poison arrow tree and then licks specialized hairs on his or her body to coat them with the poison. The animal appears to be unaffected by the poison that they carry. Presumably, the chemicals protect the rat from attacks by predators.

Interestingly, the milkweed plant also contains cardenolides. The caterpillars of the monarch butterfly feed on milkweed and store the bitter-tasting poison of the plant in their bodies to protect themselves. The adult butterflies feed on the nectar from a variety of flowers, but the cardenolides stay in a caterpillar’s body during metamorphosis and help to protect the adult population. Potential predators such as birds may destroy an individual monarch butterfly, but they quickly learn that the species tastes bad and avoid eating it.

Effects of the Poison

The rat is encountered by humans at times, who are sometimes accompanied by their dogs. Observers report that the animal raises its mane when it feels threatened by the viewers. Unfortunately, some dogs have died after contacting the animal. Those that have recovered have learned to avoid the rat. Researchers suspect that the poison protects the rat from multiple types of mammalian predators. The poison is probably very dangerous for us as well as dogs.

An Interesting Animal

The maned rat is an interesting animal that may have more surprises to reveal. It’s said to be rarely encountered in the wild and is rarely seen in camera trap photos, but I think it’s an animal that’s worth investigating.

One goal of the researchers who are studying the animal is to get a reasonably accurate estimate of its population numbers. If it needs help, we should know this. Further studies may reveal some more fascinating and intriguing information about the maned rat.