Rodents (Rodentia)

Rodent Retreat is hairless, with short limbs, a tail, and specialized teeth for chewing. They give birth to live young (no eggs). They are a significant source of meat and fur.

The order Rodentia contains about a third of all mammals. Its diverse species are used by humans for food, fur, and pets. They can be terrestrial, arboreal, or aquatic. Rodents include mice, rats, squirrels, kangaroo rats, dormice, gerbils, hamsters, guinea pigs, chinchillas, porcupines, beavers, rat-tailed anteaters and jerboas, crocodiles, caimans, and other reptiles. They are renowned for their ability to adapt to many habitats and environments.

The ancestors of modern rodents first appeared in the fossil record during the Paleocene epoch. They were closely related to a group of eutherian mammals called multituberculates and had features similar to those seen in nonrodent groups of mammals, such as the shrews, moles, and hares (which are now considered to belong to their own order, Lagomorpha).

In addition to the gnawing specialization that gave them their name, rodents are distinguished by having a pair of ever growing chisel-shaped incisor teeth that form a gap with the cheek teeth (called a diastema). This arrangement allows them to chew on any type of hard or soft matter, whether edible or not. The incisors are then discarded and the molars grind the edible material.

The earliest known rodents were small, nocturnal creatures with large eyes and long tails. They are believed to be the direct ancestors of the modern squirrels, chipmunks, and raccoons. Their evolutionary history is well-documented, and it is possible that they also contributed to the evolution of other nocturnal placental mammals such as blue whales and pygmy shrews.

Habitat

Rodents (Rodentia) are the most numerous order of mammals and the largest group of mammals adapted to a wide variety of habitats. They are small animals with short limbs, long tails, and sharp incisors that they use to gnaw food, excavate burrows, and defend themselves from predators. Rodents live all over the world except Antarctica and some ocean islands and are important parts of ecosystems from rainforests to deserts, tundra, coniferous forests, and grasslands. They range in size from the smallest mouse to the pig-sized capybara.

Adaptation to habitat is manifested in a rodent’s behavior, which organizes activity in time and space to maximize fitness. Testing rodents from different natural habitats in the same laboratory environment can reveal how the environment affects their behavior.

For example, a study showed that Tristram’s jirds, a species that occupies flatlands, avoids cliffs when placed in a three-dimensional arena with cliffs around the edge while sand rats, which forage by climbing on shrubs, stay near the cliffs.

When exploring new environments, rodents typically take several roundtrips to explore the area. After a number of these trips, the rodent chooses a home-base in an accessible location and usually crouches there. The home-base is a terminal for outbound excursions and often has a fast direct inbound section. This is a key adaptation that allows rodents to learn and adapt to complex environments. It also makes them less susceptible to extinction by environmental changes.

Feeding

A good quality pellet diet will provide most of the protein, fiber, vitamins and minerals that rodents need. Supplemental foods such as whole seeds, berries, vegetables, unsalted popcorn and pasta can also be offered in small amounts as enrichment and treats. These should not comprise more than 10% of the daily diet. It is important to introduce any new food item slowly and in a way that does not overwhelm the rodent. This is because rodents are neophobic and will generally avoid food items they have not previously eaten.

Rodents are omnivorous creatures that eat a wide range of plants and meats. They are particularly drawn to fruits and berries, and may even become a nuisance when fruit or berry bushes are left untouched in backyards. They are also highly attracted to baked goods, seeds and nuts. In addition, they are avid consumers of grain, including a number of cereals like rice, quinoa and birdseed that can be found in pantries and cabinets.

In the wild, they are able to acquire these foods through foraging and hunting, but they also consume garbage and scraps, stored foods and growing crops. Because of the morphology of their skull and masticatory muscles, rodents have highly specialised teeth. Their incisors are made of enamel and dentine, while their cheek teeth are mainly composed of dentine. The unique construction of these teeth makes them self-sharpening.

Behavior

Rodents are small animals that can be found in nearly every terrestrial habitat. They may be arboreal, fossorial (digging), saltatorial or richochetal, but all have a unique combination of adaptations that allow them to move easily through the landscape using both their front legs and their tail. They have sharp incisors for gnawing food, short limbs for climbing and running, a high metabolic rate and a specialized vomeronasal organ to sense pheromones that are used in reproduction and social behavior.

Typically, rodents are very curious and explore their environment. They are also capable of learning and remembering, which makes them a useful model organism for studying neurological disorders that have cognitive components, such as schizophrenia and Alzheimer’s disease. However, there are many factors that need to be considered when interpreting behavioral outcomes in rodents.

For example, if rats are allowed to wander in people’s yards, they will use piles of wood, vegetation, garbage and other items for shelter. Rats and other rodents can introduce human pathogens such as salmonella, which causes food poisoning, or leptospirosis that can cause fever, chills, muscle aches and headaches.

Laboratory studies of rodents often involve tasks that are designed to measure spatial navigation abilities. The classic task is the Morris water maze, in which a rat is placed in a tank of opaque water containing a hidden escape platform. The test animal learns to locate the platform by analyzing visual cues on the wall and floor of the tank.

Diseases

Rodents can carry a number of diseases that can spread to people. Some are parasitic (worms) and others are bacterial or viral. Among the diseases transmitted by rodents, rat bite fever, bubonic plague, leptospirosis and lymphocytic choriomeningitis virus are bacterial; hantavirus and tularemia are viral.

Those with close contact with rodents, such as veterinarians and those who work in laboratories may be at risk for hantavirus infection. It is also possible to get the illness by touching contaminated soil, food or water. The bacterium Francisella tularensis which causes tularemia can be spread through tick and deer fly bites, skin-to-skin contact, exposure to contaminated rodents or by inhalation of contaminated dusts or aerosols.

Some of the other diseases rodents can transmit to humans include leptospirosis and lymphocytic (abnormal) choriomeningitis virus. LCMV infections can cause an influenza-like illness and sometimes meningitis, an inflammation of the fluid that surrounds the brain and spinal cord. Infection from a pet rat is rarely seen but infection in pregnancy has been reported and may lead to fetal death or congenital problems affecting the central nervous system.

Most domestic pets are bred and raised under strict hygienic conditions so they do not transmit diseases to humans. However, wild rodents, especially those captured and sold for sale in pet stores, often carry zoonotic diseases. It is important to purchase only those rodents that have been bred under pathogen-free conditions.

Treatment

Rodents spread a number of diseases to humans and animals. Some of these diseases (including plague, leptospirosis, hantavirus pulmonary syndrome and rat bite fever) are transmitted through direct contact with rodents. Others are spread through indirect contact with fleas, ticks and mites that feed on infected rodents.

Rodents can also cause damage to buildings, destroying insulation and chewing electrical wires. They also leave droppings and urine which can contaminate food and water.

The first step in eliminating rodents is removing their food and water sources. Keep kitchen counters and floors clean and store food in airtight containers. Keep pet foods and water away from the floor, and clean up spills immediately. Locate and seal cracks, crevices and holes that rodents can crawl through with caulking or copper mesh, preferably mixed with mortar. Block openings around plumbing pipes, air conditioning and drain lines with steel wool or chew-proof hardware cloth and metal screens.

Use traps or bait stations outside and inside your house to capture and kill rodents. Be sure to follow all product application instructions and wear personal protective equipment when using rodenticides. If you choose to use bait, be sure it is a non-toxic product and that it will not affect dogs, cats or birds. Stop baiting after a month and start again; skipping months helps prevent the development of resistance by the rodents. If you decide to use a poison, hire a professional pest control company to ensure proper application and avoid exposure to harmful ingredients.