What Rodent has the Longest Lifespan?
When you think of rodents, the first animals that might come to your mind are pesky rats and mice that infest homes. But rodents are actually a wide variety of animals that includes beavers, squirrels, capybaras, and more. Aside from their diverse characteristics, rodents also have varying lifespans that are helpful for comparative aging studies.
So what rodent species have the longest lives? Naked mole rats have an extremely long lifespan for an animal of its size. These hairless rodents can live up to 32 years. They are also important in the field of medicine, biology, biogerontology, and other sciences because of their longevity.
Naked Mole Rats: The Age-Defying Rodent
Heterocephalus glaber, also known by its common name, naked mole rat, is the only species in its genus. It used to belong in the same family as African mole rats but it was placed in a separate family because it possesses unique qualities such as pain insensitivity, cancer resistance, and thermoregulation. These characteristics allow it to thrive in harsh underground conditions.
Naked mole rats are known for their long lifespan. Other rodents such as mice and rats can live up to 4 years at most. For their size, naked mole rats are expected to live around 6 years, but they managed to survive for up to 32 years instead. Even at this age, breeding females can still reproduce pups.
Another interesting thing about naked mole rats is their ability to defy signs of aging. Most mammals, including humans, experience increased risks of death as they grow old. But naked mole rats do not experience a spike in age-specific hazard of mortality as they age. This quality makes the naked mole rat an ideal model for biogerontology, the study of biological factors of aging and age-related conditions.
Here are some other important factors to know about the naked mole rat:
Naked mole rats are recognizable because of their pink or pinkish-brown wrinkled skin that is also loose and folded. Their skin reduces abrasion and allows them to easily move in confined spaces. They also appear to be hairless, but their body is actually covered with coarse sensory hairs that allow them to navigate through tunnels in the dark.
Another noticeable feature of naked mole rats is their protruding front teeth that are large and curved. They utilize these incisors for digging tunnels. Their teeth are also sharpened whenever the upper and lower incisors scrape against the other.
Naked mole rats are not blind, but their small eyes are usually shut because of the thick eyelids. They only open their eyes when they are alarmed. They also have small ears which appear as raised rings of skin around the opening at the sides of their head.
These rodents typically weigh around 30 to 35 grams with a head to body length of 70 to 110 mm. Their tails are also longer than their hind foot at 30 to 50 mm.
Naked mole rat diet consists of tubers and other plant parts that they encounter as they dig tunnels. They also don’t eat much, as one tuber is enough to last the whole colony for months. They also don’t need water because they acquire enough hydration thanks to their plant-based diet.
These rodents also practice coprophagy – the manner of eating their own feces – which allows them to establish the intestinal flora of the young pups.
Colonies and Roles
Despite being rodents, naked mole rats live in colonies like many insects. Each rodent has a specific duty to fulfill for their community and there is only one dominant naked mole rat – the queen. Like bees and ants, the queen is the only female in the colony that can reproduce because its presence suppresses the production of sexual hormones in other female mole rats.
Colonies can have around 20 to 300 individual naked mole rats, but the average population is 75.
The Queen and Its Reproduction
Although there is more than one female mole rat in a colony, only the queen is sexually mature to bear pups. After the queen dies, another female mole rat will take its place after violently fighting with others. Queens will also act hostile towards other female mole rats who are behaving like a queen.
A queen naked mole rat can have up to three males to reproduce with. They can start breeding one year after their birth and continue to do so for many years. The gestation period for naked mole rats takes around 70 days. Each litter will have around 11 pups or more.
Inbreeding can happen in a colony of naked mole rats, but this might lead to weaker pups. That’s why dispersers are also an important part of a naked mole rat colony. Their role is to eventually escape from the colony to outbreed with the queen of another community.
Any naked mole rat that isn’t a queen, a male breeder, or a disperser is a worker. Smaller mole rats are tasked with maintaining the underground tunnels and gathering food. On the other hand, larger workers act as guards to protect the colony from outside predators.
Although naked mole rats can either be male or female, they are all sterile except for the queen and its male partners. A female may only reach sexual maturity once the queen dies and it won against other female naked mole rats.
What’s Unique About Naked Mole Rats?
Aside from their longevity, naked mole rats also have certain characteristics that make them excellent subjects of research. Two of these characteristics are their inability to feel pain and their resistance to cancer.
Pain is a natural response and survival mechanism which tells an organism that there is something wrong with their body. If an animal is dropped in a pool of boiling water, their predicted response is to feel the extreme temperature and swim out of the water before it causes more damage to their body.
But in 2016, a study published by Cell Press reported that naked mole rats do not experience pain the same way other rodents do. They are a lot less insensitive to pain than other rodents, but not enough that it can be dangerous for them.
According to the research, naked mole rats’ insensitivity to pain can be attributed to the amino acid changes in one section of their pain receptors. The study also found out that newborn mole rats have roughly the same amount of pain sensors as newborn mice, but the count declines as they enter adulthood.
A 2013 study involving the introduction of cancer-causing genes to naked mole rats showed amazing results: the rodents’ cells did not turn cancerous. They did this by putting the genetically-altered rodents’ cells on soft agar – a substance that supports the growth of cancerous cells. They found out that the cells did not grow on the soft agar. When the same test was conducted on mice, the smaller rodents developed tumors in their body.
The Evolution of Rodent Lifespan
Despite being related, animals from the order Rodentia have diverse lifespans. For example, tree squirrels and chipmunks have a maximum lifespan of around 20 years and 9.5 years respectively even when they belong in the same family, Sciuridae.
From the family Muridae, old-world rats, hamsters, and mice can live up to 5 years. On the other hand, new world species that are similar to their body size such as woodrats can survive up to 10 years.
Beavers from the Castoridae family can live up to 23 years in zoos. But capybaras, the world’s largest rodents, only have a maximum lifespan of 15 years. This can seem short for an animal its size.
But the rodent with the longest lifespan is considered to be the naked mole-rat. These rodents are only expected to live for around 6 years because of their small size, but they can reach up to 32 years of age.
The drastic difference of lifespans between rodents is suspected to root from their predation patterns. Short-lived rodents have more predators, while long-lived ones only have a few. Additionally, rodents with longer lifespans have developed special defenses that allow them to escape from predators. For example, tree squirrels live above ground and naked mole rats collectively defend against snakes.
How Do Other Rodent Lifespans Compare?
Although naked mole rats are considered as the rodents with the longest lifespan, other animals within the same order can live up to around 20 years. Several factors affect the diversity of rodent lifespans including their size and lifestyle.
Let’s take a look at the biology of other rodents to see how they compare to that of the naked mole rat.
House mice are a lot smaller than rats in terms of size. But their presence is also harmful to humans because they can contaminate food and water. They are also carriers of diseases like lymphocytic choriomeningitis.
Although they prefer nuts and seeds, house mice are opportunistic feeders that will consume anything available to them. These rodents can survive a variety of conditions. They are also extremely cautious and secretive, which is why it might be difficult to detect their presence immediately.
House mice can live up to 2 years if they manage to escape from different extermination methods.
These rodents are agricultural pests that mainly feed on grasses and field crops. They don’t cause as many structural damages as other rodent pests, but they can still infest a home if they find food available for them. Cotton rats can be found in areas like Florida, California, Virginia, and Kansas. Some sightings were also reported around Illinois.
Cotton rats have a short lifespan: an individual can only live around 6 months.
Also known as brown rats, Norway rats are bigger than most rodent pests. They can reach up to 40 cm in length and weigh up to 500 grams. These rodents are notorious home pests because they weaken the building’s foundations by burrowing.
Norway rats are burrowers and prefer to build their nests close to the ground. Their diet mostly consists of fruits, grains, nuts, and meat. They also consume the carcass of dead animals and other small rodents like mice.
These furry pests can survive up to 2 years in the wild.
Roof rats are common house pests that live in the upper part of a home. They will build their nests in attics or false ceilings. They are also responsible for structural damages and several rodent-related diseases including murine typhus, leptospirosis, and the bubonic plague.
Roof rats have slender bodies than Norway rats. They are also sometimes referred to as “citrus rats” because of their affinity for fruits. However, roof rats will consume anything available to them including meat and smaller insects.
Roof rats can live up to 12 months if they are not killed during the extermination.
Other Long-lived Rodents
Some rodents in the wild can also live up to around 20 years. Since they have a long lifespan, they are also great subjects for comparative aging studies. Here are some of the rodent species that have the longest lifespans:
Eastern Grey Squirrel
This species of squirrels are used to interacting with humans in their backyards or city parks. Most of the time, eastern grey squirrels can also be considered pests.
Their diet mainly consists of nesting birds, insects, nuts, and different seeds. They climb and spend most of their time in trees. The only time they’re seen on the ground is when they are foraging, burying nuts, or digging out their stored food. These squirrels are usually hunted by snakes, raccoons, foxes, owls, and hawks. But they can get away from their predators easily because of their jumping and climbing ability.
Most eastern grey squirrels live up to 6 years, but their maximum lifespans are 12 years in the wild and 20 years in captivity.
Beavers are the second largest rodents next to capybaras. They are semi-aquatic mammals that have displayed complex social behavior that makes them unique from other mammalian species. They also build homes and modify their environment to survive, as humans do.
Another unusual behavior of beavers is their monogamy – a beaver mates with only one partner until one of them dies. These creatures are also herbivores that feed on trees, shrubs, roots, grasses, and leaves. Their predators include wolverines, wolves, lynx, bears, and humans. Beavers fight back by pulling their predator and drowning them underwater.
American beavers survive up to 15 years in the wild and 20 years in captivity.
North American Porcupine
Porcupines are known for the quills in their back which they use as a defense mechanism when threatened. The quills are usually flattened against their body unless they sense danger. In this case, they will swing their quilled tail against the direction of the predator. They also evolved as slow movers because their quills are enough to protect them from predators.
These rodents are also excellent climbers and spend most of their time eating flowers, fruits, leaves, and seeds on trees. During winter, porcupines survive by consuming conifer needles and tree bark. They are also solitary creatures that live most of their lives alone in the wild.
North American porcupines can live up to 18 years.
Possible Reasons for Naked Mole Rat Longevity
Since other rodents of the same size only live up to 4 years at most, it’s puzzling how naked mole rats manage to survive up to 32 years in the wild. After several studies by different scientists worldwide, they managed to find two important factors that contribute to the rodent’s amazing longevity.
Resistance to Oxidative Stress
Oxidative stress is described as the imbalance in the body’s antioxidants and free radicals. The latter is essential in fighting off infection-causing pathogens. But too much free radicals can also damage the proteins, DNA, and fatty tissues in the body. Oxidative stress is also a major contributor to aging and other age-related diseases.
But naked mole rats seem to be unaffected by the damages brought by oxidative stress. In a study by the American Physiological Society, it was found that despite experiencing great oxidative stress in their bodies, naked mole rats did not show signs of damage.
Scientists suspect that the reason for this response is that naked mole rats experienced higher levels of oxidative stress in their natural habitat than they did in the laboratory experiment. Since naked mole-rats are exposed to low oxygen levels and high oxidative stress at a young age, they might have developed great resistance to these conditions already.
According to a 2014 study published by the Federation of American Societies for Experimental Biology (FASEB), naked mole rats have a high level of quality-control chaperone proteins that quickly eliminates other damaged proteins before they become a problem.
They also found out that the amount of chaperone protein, called HSP25, in other rodent species is directly correlated with the length of their lifespan. These proteins allow the rodents to maintain cell health by disposing the faulty proteins into the “cellular garbage dumps.”
Since several neurodegenerative diseases including Parkinson’s and Alzheimer’s are caused by the presence of defective proteins in the cell, HSP25 allows naked mole rats to be resistant to these age-related diseases.
What Does This Mean for the Scientific Community?
Albino mice are typically used in studying human diseases because of their similarities to human anatomy, genetics, and physiology. They are also cost-effective and low maintenance, so researchers won’t need to worry much about them. But because of their short lifespan, it’s difficult for scientists to study aging in mice.
This is why naked mole rats are the perfect subject for research in the field of biogerontology. Their long life, cancer resistance, and pain insensitivity can help doctors find the right answers that can lengthen human life.
Rodent Problems at Home? Contact Pinnacle Pest Control Now
While naked mole rats are unlikely to infest your home, some of their relatives like mice and rats are notorious pests. They will bring damages to your home and put your family at risk of different diseases.
For an accurate inspection and quick removal of house pests, contact Pinnacle Pest Control now. Our team has the right skills and tools to effectively eliminate pests and keep them from returning. We also offer structure repair and attic re-insulation services.
Read more: Where Do Roof Rats Live?