Cute on the outside, but fierce on the inside! The protagonists of the fish sacrifice? The “otters” are on this small island in Zhejiang →

Most of the time we can't see otters. Otters have black bodies and often appear in the water at night without making any sound. When you find them, they are already very close and you can only see their two eyes like two light bulbs. So they have some other names. Some places call them water ghosts or water monkeys .

The otter's teeth are very sharp, and its tail is about 96 cm to 1.3 meters long. It is the top predator in freshwater ecosystems . Otters in many places can even prey on crocodiles.

The legend of the otter fish sacrifice

There are 13 species of otters in the world. In China, there are Eurasian otters, small-clawed otters and smooth-coated otters . Among them, Eurasian otters are the most widely distributed in China, from the northeast to Xinjiang, and all the way south to Hainan. Small-clawed otters are relatively rare in China. They are relatively small in size. Now they are only found in a few areas of Hainan and Yunnan in China. There has been no record of smooth-coated otters in China for 30 years, but smooth-coated otters were once widely distributed. The skull of a smooth-coated otter was dug out in the Tang Dynasty ruins in Jiangsu.

Otters were once a very common animal, with a very wide distribution. Among the 24 solar terms, there is a solar term called Rain Water , which has three phenological events: the otter offering fish, the arrival of wild geese, and the budding of grass and trees . For a long time, scientists did not know what the otter's fish offering behavior was, but in fact, this behavior is very common among carnivores. It is a kind of overkilling behavior , that is, when there are many prey, otters will kill more first and keep them for backup. However, the ancients believed that this was a sacrificial behavior, and thus named it "otter offering fish." In the late Qing Dynasty and early Republic of China, some fishermen used otters as a tool for fishing, so there are many examples that show that otters were once very common.

The current status of otter populations

From the distribution map of otters 50 years ago, we can see that otters were found all over the country at that time and there were many of them. However, as time went by, the population of otters dropped sharply, and we even thought that otters in the eastern region might be extinct.

But in 2018, during another Chinese Crested Tern conservation project, a volunteer accidentally photographed an otter, but it was found on an island, and it was an island very far away from the mainland, and there was not even any fresh water on that island. So our thinking changed, because we couldn't find otters on the mainland, whether in the mountains or on the plains, so we started to go out to sea to look for otters .

We spent three years visiting about 100 islands in Zhejiang, and found that there were definite otter distributions on about 9 of them . But we couldn't see the otters, and most of the time we could only determine whether there were otters by their feces . During this process, we also picked up an otter on Baisha Island in Zhoushan. It was about 30 days old at the time, and its fur was already covered with seawater and was dying. We rescued it. Now it has grown into a big girl, very lively and cute, and likes to roll around.

New Possibilities for Otter Conservation on Jintang Island

Finally, we decided to set up the otter protection site on Jintang Island . The transportation and infrastructure here are very convenient, and the otter population is very stable. This island should be the island with the highest otter density in China . We found out that there were otters here because an otter ran into a resident's home on Jintang Island. Later, after field tracking and investigation, and some information provided by the police, we found that there was a pile of otter feces every 5 to 10 meters in the river. Otters use their feces to mark their territory , so we knew there were otters on this island at that time.

We started to stay on the island in October 2023 and began to place infrared cameras all over the island. After the infrared cameras are installed, if there is a heat source in front of them, usually wild animals running by, they will take photos or videos. We have 100 infrared cameras on the entire island.

Our second job is to " scoop up poop" because through feces, we can know how many otters there are, the gender of these otters, how many populations there are, and whether they are related. Sometimes the ingredients in otter feces are different, and we can know what the otter has eaten through feces. Later, we rented a house directly on this island, so that we can collect its feces at any time for molecular investigation of DNA. We now have a new technology that can do some pretreatment to improve the efficiency of molecular extraction.

In addition, because there are many mudflats near Jintang Island, we can see many otter footprints . Otter footprints are also different. They have five fingers and webbed feet. Based on these otter footprints, we know where the otter came from. We made a large map and marked many otter traces with red dots on it. We can see that there are otters on almost all sides of the island.

Since October last year, we have captured more than 1,000 videos of otters on this island. We found that all otters actually swam in from the sea, and they are very cautious. Therefore, there is a big problem. Many times, our infrared cameras cannot capture otters, because infrared cameras are triggered by the heat of animals, but otters are not hot after coming out of the sea, and there is still water on their bodies, so they cannot trigger infrared cameras. Therefore, many of them are captured by them. So there should actually be more otter images, but the infrared cameras did not capture them.

Jintang Island is different from other wildlife reserves. It is a very artificial environment . It is also a very large industrial island. It produces 75% of China's small hardware called screws. It has a very advanced ocean-going terminal, and Jintang Island will be connected to the high-speed rail in 2028. Therefore, the living environment of wild animals on Jintang Island is completely different from what everyone imagines, which also shows that the otter species may not be far from humans. So we hope to do more research and popular science on this island to make Jintang Island a very good place for protection.

New possibilities for harmonious coexistence between otters and humans

I went to Singapore in May this year. The otters there were on a very artificial lawn. There were cars and people walking around. They rolled on the grass. In order to protect the otters, the locals used fences to enclose a circle, which was enough. There was a fountain across the road. These otters would go to the fountain in groups to play, and then come back. They were not afraid of people at all.

Singapore also started to have otters living in the city in 2016, so it has not been many years since the otters here reached this state. So we hope that we also have such an otter island in China to protect our own otters. I think it is not difficult, but it requires some efforts and measures.