North American water vole facts for kids
Quick facts for kids Water vole |
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Microtus
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richardsoni
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The North American water vole or just water vole (Microtus richardsoni) is the biggest North American vole. You can find it in the northwestern United States and southern parts of western Canada. For a long time, people thought this animal belonged to a different group of voles called Arvicola. However, new scientific tests show it is actually more closely related to other North American Microtus species.
Water voles are on a special list for protection. This is because their populations are very small. Also, there is worry that their homes, which they need to survive, might be getting smaller.
These animals have fur that is gray-brown or red-brown. Their bellies are gray. Their large back feet help them swim very well. They live in mountain meadows close to water. They eat grasses, leaves, roots, and seeds. Sometimes, they also eat small bugs. Water voles dig tunnels that connect to water. This makes them a semi-aquatic species, meaning they live partly in water.
They are active all year long. In winter, they dig tunnels through the snow. Their burrows often have entrances at the water's edge or even underwater. They usually live in groups of 8 to 40 voles along a waterway.
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What is a Water Vole?
The word "vole" first appeared around 1805. It is short for "vole-mouse," which means "field mouse." The word comes from the Norwegian word vollmus. Voll means field, and mus means mouse. The Swedish word vall, also meaning field, might have also played a part.
Microtus richardsoni has many other names. Some of these include Richardson's water vole, Richardson vole, and water rat. People also call it the big-footed mouse or giant water vole.
Water Vole Family Tree
Scientists used to think the water vole was part of the Arvicola group. But new genetic tests show it is more closely related to North American Microtus species. These tests suggest that the closest relative to Microtus richardsoni is the Microtus pennsylvanicus, also known as the meadow vole.
Fossils suggest that the water vole's ancestors came from Siberia. This happened about 1.5 million years before the Arvicola group appeared in Europe. This might mean the water vole is a very old type of Microtus. The similarities between water voles and Arvicola are likely due to them adapting to similar environments. Today, there are about 60 species in the Microtus group.
How Water Voles Look
Water voles have unusually large back feet. These feet are usually between 25 and 34 millimeters long. This helps tell them apart from other small rodents. It also helps them move quickly in water. Male water voles tend to be larger than females.
On average, these animals are about 20–27 centimeters long. This includes their tail, which is 6–10 centimeters long. They usually weigh between 125 and 178 grams. The water vole is the second largest rodent of its kind in its area. Only the muskrat is bigger.
Their fur is grey-brown, dark brown, or reddish-brown on their backs. Their underside is grayish-white. Water voles have large front teeth. They also have a very large skull and strong jaw muscles. These features help them dig tunnels well. They can also chew through tough roots easily.
Water Vole Behavior and Habitat
Where Water Voles Live and What They Eat
Water voles live in two main areas across the western United States and Canada. These areas stretch from British Columbia and Alberta. They also include parts of Oregon, Washington, Montana, Idaho, Wyoming, and Utah. They prefer alpine or semi-alpine meadows near water. These areas are usually found between 914 and 3,201 meters high.
Their homes can be very different from place to place. This is because of natural barriers like large forests, mountains, and wide valleys without water. However, water voles can travel over land to find other groups to reproduce with. This travel is more common between nearby groups. It happens less often over longer distances. Because water voles live in small, separate areas, they need to be able to move between them. This helps their populations survive if one small group dies out.
Their main food source is plants. This includes leaves, stems, grasses, and willows. Sometimes they eat seeds or insects. What they eat can change a lot depending on where they live. Studies show that water voles have a very fast metabolism. This means they need to eat more food than other rodents their size. Most often, water voles eat the underground parts of plants. These parts are available to them all year. There is no sign that they store food for winter. In winter, they dig tunnels through the snow. They usually stay under the snow once it is 6 centimeters deep. This can be for about 7 to 8 months of the year.
Water voles are most active at night. They travel between tunnels, nests, and waterways. They use paths 5–7 centimeters wide through the plants on the surface. Often, their tunnel or burrow entrances are at water level. They can also be underwater along river banks. They build these tunnels and nests just below plant roots. This is about 4–6 centimeters underground. They do this during their breeding season, from June to late September. Females give birth and care for their young in these underground nests. The nests are lined with leaves and grass.
Social Life and Reproduction
Water voles are usually found within 5 to 10 meters of waterways. They have a social system where one male mates with several females. Females tend to stay in their own areas, which do not overlap with other females. Males travel between burrows to mate with different females. Because of this, males travel over a much larger area than females. Males also tend to be more aggressive than females, especially during breeding time. Females become ready to reproduce when they are around active males. This usually happens when new plants start growing in the spring.
Both male and female water voles have large glands on their sides. These glands help them mark their areas. This stops other voles from entering their nests. They also use these scents to signal to mates during the breeding season. Water voles breed for 3 months during the summer. Young are born from June until late September. Females usually have about 5-6 young in a litter. The shortest time for a pregnancy is 22 days. The number of young in a litter tends to increase as the mother gets older. It can range from 2 to 10 young.
Even though water voles can have many babies, their populations stay very small. They live in groups of 8 to 40 individuals. This might be because their breeding season is very short. Other rodents breed for 6 months or more.
Birthing and Parental Care
Newborn voles are born without fur and cannot see. They weigh about 5 grams. They can make sounds right away. Within 3 days, they start to grow fur. By day 10, they are running and climbing. By day 17, they can swim on their own. The mother feeds them milk until they are 21 days old. They stay in the nest together for about 32 days. During this time, the young voles grow about 1.24 grams each day. Even though they might still be in the nest with their mother, she provides very little care after they stop drinking milk. Around 40 days old, they move to their own nests. About 3 weeks later, they are old enough to reproduce themselves.
About 26% of young males and females start to reproduce in the same breeding season they were born. However, most of the reproduction is done by adults who have lived through the winter. Some adult females can have up to two litters in one breeding season. Among adults who have lived through the winter, 90% of females and all males are able to reproduce.
Water Vole Life Cycle
Studies of water vole populations show that new young voles replace adults at a 1:1 ratio. Most water voles only live through one winter. They usually die at the end of their second breeding season. Very few adults survive two winters.
Protecting Water Voles
Scientists have studied the homes of water voles. This is because water voles need very specific places to live. They want to know if things like grazing by animals or the amount of rain affect vole populations. This helps them protect the voles.
It has been found that more rain creates more usable homes for water voles. In wetter years, young water voles become ready to reproduce sooner. This means they can have more babies. The average number of young in each litter also increased in wet years.
Grazing by livestock also affects water vole populations. In areas with light or moderate grazing, fewer young voles survived. The population sizes were also much smaller than in other groups. Where there was severe grazing, it damaged the stream bank so much that it was no longer a good home for voles.
Livestock can cause many harmful changes to the water vole's home. These include changes to the soil, compacted soil, and increased water runoff. They can also cause broken stream banks and erosion. Plus, they eat the plants that water voles use for cover and food. Many ferns, mosses, and shrubs are very important as ground cover. They protect water voles from predators. In areas with grazing, these plants were rare or gone. Because of this, water voles were not often found in those areas.
See also
In Spanish: Microtus richardsoni para niños
