One day in June 2019, on the coast of northern Scotland, UK, Braden Thomson was curled up, leaning on the breezy peat ground, and looking into the distance along the binoculars. Wherever he looked, there were rocks covered with algae, brown kelp protruding from the water, and the sea being blown by the wind… Unfortunately, the target he was looking for had not yet appeared. He waited patiently…Suddenly, the rock was wet, and the target appeared—a few chubby heads stuck out. I saw the mother otter first out of the water, followed by its three cubs. They wriggled their smooth bodies freely, moving gracefully and smoothly, swimming towards the bay of Hyères in the northern Shetland Islands like a master swimmer. …
Suddenly, the rock was wet, and the target appeared-several chubby heads stretched out.
Braden is a zoologist who grew up in the Shetland Islands in northern Scotland, England, and has been studying these cute mammals for more than 30 years. But to this day, whenever he observes wild otters, his enthusiasm and excitement remain unabated. He knows all about the otters here. He introduced to friends who came to the inspection: “This female otter is 9 years old. It is really special, because most otters can only live 4 to 5 years old. Not only that, but it is also a good mother. Many infants have been raised under the conditions.”
Cub and mother
Eurasian otters can reproduce offspring at any time of the year, especially those that live on river banks. However, in coastal areas where fish resources are more seasonal, the otters living here also have a specific breeding season. In the northern and western islands of Scotland, most otter cubs are born in midsummer. Since autumn, the entire population has almost no newborns. In winter, families like the ones seen above will be busier. Otter parents will be busy taking their children along the coastline for food.
Otter, mammal, mustelidae. The head is broad and flat, the tail is long, the limbs are short and thick, the toes are webbed, the hair is brown, dense, soft, and shiny. Otters usually live burrows by the river and come out at night. They are good at swimming and diving, and eat fish, frogs, and water birds.
The Eurasian otter is a type of otter found in rivers in Europe and Asia. It mainly feeds on fish, but also eats birds, insects, frogs, crustaceans and small mammals. They usually live in freshwater environments (including lakes, rivers, streams and ponds, etc.), and they also live in coastal areas, but they need to return to freshwater areas to clean regularly.
However, in addition to looking for food, otters also enjoy a lot of playing time-either rolling and tossing on the rocks on the shore; or biting each other with their companions in the water, chasing and playing. Sometimes, playfulness also attracts the gray seals, who want to join the game with their big and innocent eyes. At this time, the brave otter cubs will use their superb underwater sports skills to swim like lightning, drive away the seals and quickly return to their safe homes.
Even though the cubs are so lively, the otter is to a large extent an animal that likes to be alone. Except for raising offspring and breeding and mating periods, most of the time, adult otters live alone on this cold shore, which is blown by wind all the year round. In winter, these cubs are about 6 months old, and when they are 10 months old or 1 year old, they will leave their mothers and go out to survive on their own. According to observations, some female otters will miss a breeding season for their cubs to rest and recover when their cubs are adults, while most female otters steadily maintain their annual breeding rhythm. Of course, if a female otter is in good physical condition and has sufficient food supply that year, she will also choose to conceive again before the cubs reach adulthood. And forcing the underage cubs to leave early. Separation from the mother is certainly uncomfortable for children, but after all, this is the law of nature, and growing up is the only way for every life.
At present, these three energetic little guys still have a lot to learn, such as how to hunt. As they continued to move forward, Brighton cautiously continued to follow along the beach, and carefully kept himself leeward so as not to be discovered by them. Along the way, these little otters did not eat less, they dived into the water for a while to devour small fish, and then went ashore to play with clumsy crabs. Crustaceans are easily preyed, and at the end of winter when fish populations are small, they are common food for otter cubs. But for adult otters, the nutritional value of crustaceans is too low, even at the end of winter, they will still concentrate on fishing as their main source of food.
From the perspective of animal behavior, one of the most significant differences between riverside otters and coastal otters lies in the difference in the time of day when they are most active. Otters living in freshwater habitats are basically active at night, while otters in coastal areas are mostly active during the day. Coastal otters not only move out at low tides, but also adjust their foraging behavior to match the habits of their prey.
Scientists have found that demersal fish are more popular with otters than some shallow or middle-level fish. Coastal otters mainly eat eels, and sometimes sea cod, sculpin, and pomfret. These fish species eat at night and are sleepy during the day and are very easy to catch. Perhaps this is the reason why coastal otters appear during the day.
Over the past decade, the diet of otters along the northern coast of Scotland seems to have changed. This may be due to changes in fish populations in the Shetland Islands. Nowadays, due to the increase in sea temperature, the number of eels is far less than before. Once upon a time, the breeding season of otters in the Shetland Islands and the flood season of eels appeared almost simultaneously, but now this seasonality seems to have disappeared.
Recently, researchers have often seen scenes of otters hunting octopuses. After all, in warm waters, octopus populations will flourish rapidly. In fact, these otters do not care whether their prey comes from the sea or the shore. Pipe-nose swallows, cormorants, red-breasted mergansers, puffins, and water ducks may all enter their menu. If it encounters stormy weather, they will even look at rabbits as prey targets.
The British poet Ted Hughes once described it in his poem “Otter”: “It (referring to the otter) is neither a fish nor a beast. It has all four legs but is proficient in water…” It is not difficult to see from the poet’s description. In the United Kingdom, otters have strong adaptability to survive in different environments. River otters can use rivers or waterways up to 80 kilometers long as their habitat. In coastal habitats, a large number of foraging opportunities can shorten the survival range of coastal otters (such as those in the Shetland Islands) to 4 ~5 kilometers.
Pipe-nose swallows, European cormorants, red-breasted goosanders, puffins, and dabbling ducks are all likely to enter the otter’s menu.
However, since there is no need to travel long distances, how did the otters reach these remote islands in the north? There are no native mammals in the Shetland Islands. Some scholars believe that the otters may have hitchhiked and arrived with the early settlers. In 3000 BC or earlier, farmers from the Neolithic Age lived here. Another theory is that the otter is a species introduced by the Vikings in order to obtain their fur after hunting.
The furs of these coastal otters are the same as their relatives living on the banks of the river, but they have found a way to deal with the trouble caused by the sea. In the water, the otter completely relies on its thick, long and dense fur to keep warm, and the salt in the sea water will make the hair sticky, which greatly reduces the warmth retention effect. Therefore, coastal otters need to be cleaned in fresh water once or twice a day. To keep the fur smooth. Fortunately, near the coast of the Shetland Islands, such freshwater pools can be seen everywhere. In the Orkney Islands not far to the south, the geological structure is loose and porous, and there is very little fresh water on land, so the number of otters living there is also very small.
Unique territory mark
Braden and his party continued to move forward facing the salty sea breeze, and slightly distanced themselves from the otter family. What they are looking for are freshwater ponds that otters use to clean their bodies, and otter nests on land. The natural features here are very rough—land, ocean, and sky. All the landscapes seem to be hurriedly drawn by nature with extremely wide brushstrokes. This unobstructed view makes it easier to find the Otter Territory.
Otters will use these feces to mark their territory. And share information with each other.
A strong stench in the wind indicates that they are not far from the otter’s nest. Otter feces composed of fish bones, fish scales and some crab shells began to appear on the ground, spreading around like chalk gray. Otters will use these feces to mark their territories and share information with each other (such as their identities and breeding status, etc.) to communicate. After moving on for a few steps, they found a long and narrow ground crack in the soft peat soil, which was filled with still black water. This is the freshwater pond used by otters to clean their hair. Freshwater pools like this are very common and not far from the rocky shore. Next to the freshwater pond, there is a raised land resembling the keel of a boat. This is the otter’s nest. Under this plot, the mother otter will scrape away the soil layer to form a sofa-like shelter for rest and rejuvenation during the day.
Usually, otters build several nests in territories with a range of several kilometers. Scientists once carried out an investigation and research on the population of otters in the Shetland Islands from 1988 to 1993. At that time, they counted a large number of otter nests in different habitats along the local coast and estimated the total number of otters on the archipelago and the length of the coastline where they lived. The data obtained is staggering: There are nearly 2,000 otters living on a coastline of 1,287 kilometers. This shows that the Shetland Islands is one of the most densely populated areas of otter populations in Europe. But what is the situation now?
Coastal otters need to be washed in fresh water once or twice a day to keep their fur smooth.
The number of nests is declining
The head of the northern islands of the Scottish Natural Heritage Committee said: Currently we do not have exact data on the population of otters in the Shetland Islands. Every year, the committee conducts surveys on specific areas (such as the special protected area on the coast of Hyères and several small islands) and compares them with the population data of previous years. The survey found that the number of otter nests will decline in some years. At the same time, the content of crab remains in otter feces of that year will also increase relatively. Scientists are a little worried, because it means that there is a shortage of fish in the otter’s diet. However, they are still optimistic about this, thinking that this may also be just a cyclical phenomenon.
When foraging in large numbers of kelp. The otter will blend into the surrounding background.
Knowing that they still live around us is enough to be comforting.
It is generally believed that the population of otters inhabiting the Shetland Islands appears to be relatively stable. To find out exactly the number of these slippery animals, we need to work harder. The researchers formulated a coastal otter survey plan to encourage the public to participate and record their sightings. Otters like to be secretive by nature, and are protected by strict laws in the UK. However, it is difficult for otters to adopt research methods for other animals. In addition, only about 40% of the entire otter population will settle in nests, and the remaining 60% will move widely. Therefore, although it is helpful to calculate the nest, it can only provide an estimate.
The research of zoologists and conservation experts did not stop there. Not long ago, researchers have entered the early stages of development of a new calculation method for the study of otter populations. Of course, more relevant researches on the coastal otters are also gradually being carried out. The marine environment is very important to the otter population. These smart coastal otters are gradually expanding their living range: beaches, dunes, piers, salt marshes, estuaries and rocky coastlines all have their presence.
Most of the time, people can only rely on a pile of fresh feces or paw prints left in the damp mud to confirm the existence of otters, but knowing that they still live around us is enough to make people feel relieved. This time, the experience of this coastal otter family is even more precious. At sunset, the otters disappeared at the edge of the coastline, blending into the background of brown rocks and seaweed…