The roof rat or the black rat as it is commonly called was originally given the Binomial name, Mus Rattus in the 18th century. However, over the years, the scientific name of Black rats has changed to Rattus Rattus.
Let’s tell you everything you need to know about these rodents.
How do I identify Roof rats?
According to research conducted by The University of Arizona College of Agriculture and Life Sciences, roof rats may vary in different shades from brown to black to grey. More often they have smooth black hair with a contrasting white or lighter underbelly. They are about 7-8 inches long and their weight is approximately 150-250 grams. They have a rough, dark-colored tail which is usually longer than the length of its body and head. They have large ears and a narrow, sharp nose.
Did you know – In the olden days, these rats traveled across the world on sailing ships, earning them the name of ship rats!
Black rat Vs. Brown rat: How to differentiate between a Roof rat and a Norway rat?
The roof rat looks like the Norway rat. The key ways to differentiate between the roof rat and the Norway rat are:
- Roof rat size is smaller than the Norway rat
- The shape of the upper first molar is different in both rats.
- The black rat has a slender body compared to the Norway rat
- Its ears and eyes are also larger than the Norway rat.
Note: Roof rats are also known by names like—palm tree rat and fruit rat.
Which are the different types and species of Roof rats?
According to the Invasive Species Specialist Group (ISSG) roof rats have three subspecies:
- The black rat
- The Alexandrine rat
- The fruit rat
These subspecies are differentiated by the color of their fur. While the black rat is mostly black in color, the Alexandrine rat has a brownish back streaked with grey and a greyish underbelly, and the fruit rat also has a brownish fur but it has a white underbelly.
Why is the black rat considered to be an invasive species?
The Roof Rat is believed to be a very invasive species. They result in deep devastation of native vegetation and animal life. They eat away vegetation at a rapid pace, sometimes leading to the extinction of local vegetation. They transmit deadly diseases to local animal species and compete for their food and shelter, often resulting in an irreversible negative effect on local fauna.
The lifespan of Roof rat & Reproduction
How long do roof rats live? As researched by the University of Michigan—Animal Diversity Web, roof rats in the wild live up to is about 12 months. However, there are reports of black rats living up to 4 years under captivity.
Roof rats are prolific breeders and multiply at a frighteningly fast rate. Though the most popular breeding seasons are fall and spring, they may breed through the year if there is an abundant supply of food and suitable climatic conditions. A female black rat starts producing around the age of 3 months. Since they have a short gestation period of 22 to 24 days, they can give birth to approximately 3 to 6 litters during their seemingly short life. Litter size may vary from 6 to 20 newborns.
Habitat—where do Roof rats live?
Roof rats adapt easily to different habitats. They make their homes in both rural as well as urban areas. They are also commonly found near coastal areas as they spread across the world through ships and trading vessels.
In the wild, they are commonly found in arboreal habitat, in high shrubs, rocks, cliffs, vine-covered fences, and trees. They are sometimes found even in high trees like palm trees and pine trees, earning them names like palm tree rat or tree rat.
According to University of California – Integrated Pest Management Program, black rats are mostly found in roof space like attics, lofts, high cabinets, cupboards, and false ceilings, and hence they are commonly known as roof rats.
Food Habits – What do Roof rats like to eat?
Roof rat diet mostly consists of vegetarian food. A roof rat needs about ½ to 1 ounce of food daily. In the wild, tree rats eat vegetative food like fruits, berries, and nuts. Their favorite fruits include fruits like avocados, coconuts, sugar-cane and citrus fruits. It also feeds on leaves, plant stems, tree barks, seeds, cocoa, coffee beans, and grains.
If needed, they may also follow an omnivorous diet eating food like snails, insects, lizards, and slugs.
In farms, they often eat through food items stored in storage rooms or processing facilities. They may also eat on food provided to domesticated animals like cows, chickens, and even canine and feline food.
According to Almeda County Vector Control, roof rats living in cities often eat pet food, bird food, and food found in garbage and trash cans.
Roof rats consume about 1 ounce of water daily. They drink water from leaky pipes, pets’ water bowls, irrigation pipes, and even high bird baths to suffice their water requirements.
Roof Rat Behavior Habits– Are Roof rats nocturnal?
Roof rats are nocturnal in nature. During the day, roof rats will hide in their shelters and will commence their search for food and water after the onset of twilight. They are also color-blind.
According to the Internet Centre for Wildlife Damage Management, roof rats have a stronger sense of smell, taste, touch, and hearing compared to eyesight. They identify their food items with the help of their sharp olfactory senses. They have a strong gustatory sense and are known to have strong food preferences. They are able to escape from predators and danger due to their sharp auditory senses. Their long, sensitive whiskers and the guard hairs on the body act as efficient tactile sensors and help them to travel in darkness.
Tree rats are also great climbers and they are the most common rodents to be found in roofs.
Roof rats are great climbers and possess a superior sense of balance. They are also able to run very fast. They can swim but are not very fond of. However, they are known to use sewers and canals to travel to newer places.
They are averse to new objects and will avoid any new things that come their way.
Signs of Roof rat infestation
The main signs of roof rat infestation mentioned by the City of Phoenix- Water Services Department are:
- Sounds: Sounds coming from the roof or attic are the surest indication of the roof rat infestation. Roof rats are nocturnal so most sounds emanating from lofts, attics, and roofs are a strong indication of black rats in your house.
- Damaged fruits or nuts: These rats are known to leave behind signs like partially eaten hollowed fruits on trees like lemons, oranges, and avocados or nuts like walnuts
- Smudge marks: As Roof rats are great climbers they leave behind smudge marks of oil and dirt rubbing off their fur on high structures like beams, pipes, and rafters.
- Gnaw marks: These rats leave behind gnaw marks and teeth signs in higher areas like roof eaves, insulation, plastic covering, and electrical wires.
- Dropping: Droppings can also be used to identify its infestation in your home. Roof rat poop is small in size, dark in color, measure approximately 10-13 mm in length, curved in shape and also has pointed ends.
- Sightings: Rodents seen in high areas like fence tops, roofs, cables, pipes, and trees are commonly roof rats.
Damage caused by the Roof rat:
Roof rats can cause a lot of damage to homes and commercial properties. Some of the damage that roof rats leave behind is:
- Holes in balconies, pipes, soffit, and roof eaves.
- Damage to wires and potential electrical and fire hazard.
- Damage to pipes, causing leakages and water problems
- Tearing down insulation, lessening its effectiveness
- Damage to food storage and processing facilities.
- Damage plants, vegetables, berries, and nuts.
- Gas leakages due to chewing of gas pipes.
- Loss to citrus plants like avocados, oranges, and lemons
- Loss to nut trees like almonds, walnuts, and pine nuts.
- Distress to pets like cats and dogs.
- Loss of seeds, and newly planted seedlings.
Hazards of the Roof rat in the house—do Roof rat spread diseases?
Roof rats are a cause of major health and safety hazard. They are carriers of diseases and transmit diseases through physical touch, bites, urine or feces contaminations, and fleas on rodent fur.
If in jeopardy, black rat behavior may aggressive towards humans. These rats bite humans if they feel jeopardized. As per Iowa State University—The Center for Food Security and Public Health, A roof-rat bite is known to cause a disease called rat-bite fever. Black rats are hosts to an organism called S. moniliformis which is the main cause of rat-fever disease.
Black rats may also lead to transmission of plague due to the presence of bacterium like Yersinia pestis and, vectors like Oriental rat flea.
Also, these rats are known to spread diseases through their urine. Such diseases include – Salmonella, Toxoplasma gondii, Weil’s disease or Leptospirosis, Listeria, and Hantavirus.
Winning the battle against the Roof rat – How to control Roof rats?
Getting rid of roof rats can be an incredibly challenging task. A successful roof rat control asks for a multi-pronged attack. South Africa’s KZN Department of Health has enlisted the following steps to have a roof rat proof home:
- Remove Food Sources: Black rats are hungry creatures. They will frequent places where there is an abundance of food. Obviously, the first step in getting rid of roof rats is to eliminate easy access to food:
- Food should be stored in tight containers
- Garbage cans should be covered properly
- Clean bird feeders and pet feeders at regular intervals
- Pick up fruits and nuts fallen on the ground as well as harvested fruits
- Seal entry points: It is essential to block roof rats from entering your home or premise to ensure victory in your battle against roof rats.
- Steel wool, steel screen mesh, or caulk should be used to fill gaps in walls, doors, and awnings.
- Roof rats are frisky climbers, so roof vents, chimney caps, attic windows, and ventilators should be sealed with utmost care.
- Window screens should be fixed regularly, and holes should be repaired.
- Keep doors closed especially after sunset.
- Trimming branches of trees that extend towards your rooms, loft, and attic to prevent them from entering your home easily.
- Remove sources of water like leaky pipes, dripping sprinklers, pet water dishes, and bird baths.
Traps and Repellents that work against Roof Rat
There are several traps and repellents that you may consider to exterminate roof rats in the attic and other parts of your vicinity. These include:
- Snap Traps: They have a metal bar that cracks down on rats and usually kills them.
- Electronic Traps: These traps use an electric shock to eliminate the rat. They may be used only indoors.
- Live traps: They use baits to catch live rodents in the trap without killing them.
- Glue Traps: They do not require any bait. The strong adhesive in the glue trap glues the rat to the trap preventing it from escaping.
The best bait for roof rats is — dried citric fruits, berries, nuts, and snail shells.
The Summit County Public Health Department of Ohio State has recommended that snap traps, glue boards, and live traps work in terminating roof rats. However, as the roof rat is smaller in size, the most efficient way of eliminating them is by using a combination of glue traps and weatherproof bait blocks.
Roof rat protection can be a lengthy, tedious, and overwhelming task. Like all rodent control, prevention is always a cheaper and better choice than cure. Proactive prevention and control steps are vital for the success of even the most expensive and sophisticated traps and repellents.