Text | Xiaofeng talks about history
Edit | Xiaofeng talks about history
"Have you ever seen a drowned fish?"
The Mara River, located in Kenya, Africa, was once a watershed with an abundance of aquatic life. But I don't know when the originally clear waters began to become turbid, and a large number of dead fish appeared downstream.
Originally, everyone thought that someone was maliciously poisoning, or the result of the loss of pesticides inadvertently caused by the upstream.
But what everyone didn't expect was that it was none other than the hippopotamus who "killed" these fish.
1. The excretion of hippopotamus terror
On the African continent, there lives a semi-aquatic behemoth - the hippopotamus.
Although herbivores, they attract attention for their surprising appetite and unique physiological characteristics, especially their surprising bowel movements.
In fact, hippos' daily diet consists of grass on the shore, reeds in the water, and many other aquatic plants. However, their digestive systems are not efficient and cannot fully digest these foods.
One is that hippos do not have the ability to ruminate, and the other is related to defects in the structure of their digestive system, which together lead to a large amount of undigested forage remaining in the feces.
It has been reported that 4,000 adult hippos have up to 8.5 tonnes of bowel movements per day, which contain undigested forage residues.
This large amount of manure discharge has a twofold impact on the river ecosystem.
Its manure contains forage residues and nutrients that promote the growth of river organisms. After all, the silica in hippopotamus droppings helps the reproduction of diatoms in rivers, which in turn are a food source for many fish.
But at the same time, especially in the rainy season, the large amount of hippopotamus manure has also adversely affected the river ecology. When the feces decay in the water, they release toxic gases and consume oxygen, causing severe hypoxia in the river water.
And this is vividly demonstrated in the Mara River Basin......
2. Schools of fish that have been "drowned" in feces
Africa's Mara River basin is supposed to be a paradise for vibrant fish, but the ecological imbalance caused by hippopotamus droppings has become dangerous.
During the dry season, the rivers become "thin" due to reduced rainfall, and hippos are forced to live in isolated ponds.
Because they can avoid insect bites and are cooler by hiding in the water, they spend up to 16 hours a day in the water getting worse and worse.
In fact, researchers have found that in ponds where hippos are rarely inhabited, there is a greater diversity of fish and invertebrates with higher oxygen levels.
But ponds where hippos congregate have much lower oxygen levels, less than half the biodiversity, and only about 4% of the fish population, largely because of the large amount of manure emitted by hippos.
These excrements not only prevent oxygen from entering the water body, but also produce ammonia, hydrogen sulfide, methane and carbon dioxide, which are toxic to fish after being decomposed by microorganisms.
Especially in the summer, they excrete a large amount of feces every day, which consumes a lot of dissolved oxygen, which also indirectly leads to the collapse of the pond ecosystem.
It can be said that the once abundant water resources of the Mara River basin are now in jeopardy, and the huge amount of excrement produced by the hippos has become the source of ecological disaster.
And this is not an exaggeration, considering that each hippopotamus contributes more than 60,000 kilograms of manure every year. Although the nitrogen, carbon, phosphorus and undecomposed substances in it can also be a source of nutrients for aquatic organisms.
But as we said, during the dry season, these excretories accumulate in excretion, resulting in toxic chemicals.
When the dry season passes, and with the onset of the rainy season, the swollen river water will sweep the pond again. The sludge and manure will carry the dead fish downstream.
This phenomenon, known as "silting flow", can also cause a significant drop in the dissolved oxygen content of downstream river water. This further aggravates the death of fish and causes secondary damage.
But the destruction of the environment in the basin is not the sole responsibility of the hippos.
Reasonable people know that increasing human activity, over-irrigation and destruction of forests have led to water depletion and climate change, which eventually led to the near end of the Mara River during the dry season.
As for the serious situation caused by the excrement of hippos, there is no need to intervene excessively. After all, the death of fish also provides abundant food resources for other animals, and nature is more resilient to each other, and the surviving fish species are more powerful.
In addition to the "survival of the fittest" after removing a large number of "inferior" fish, when the dead fish are washed onto the river beach, it also attracts a large number of predators.
Countless vultures and local wolves have relied on these dead fish to grow their population. In fact, hippopotamus feces are just like what we said, and they not only have disadvantages but also advantages.
But in the end, the main reason for solving the problem of fish mortality in the river is not to reduce the number of hippos, but to reduce human activities and try to restore the normal water cycle of the Mara River.
This is the only way to ensure a steady flow of the river during both the dry and rainy seasons, thereby reducing the impact of hippo droppings on the ecosystem and ensuring the safety of fish stocks.
However, in addition to the huge amount of defecation, the most curious thing is how this creature manages to "pull" and poop everywhere anytime and anywhere?
3. Strange but reasonable
As one of the large mammals on the African continent, hippos have an amazing size and strong collision force, and they are also very territorial.
The reason why hippos like to defecate at will is not only a matter of survival, but also a manifestation of the social status of hippos. In their group, defecation is not only a sign of territory, but also a display of strength.
Male hippos attract the opposite sex by throwing their droppings farther away in order to constantly show their strength and speed.
This behavior is similar to how some birds decorate their nests or dance with flowers and droppings during courtship.
It's just that to tell the truth, hippopotamus's courtship is really "stinky".
In addition to courting to show strength, feces can also help them remember their route better. Be aware that hippos are very easy to get lost due to poor eyesight.
Especially when looking for food in the grasslands, they tend to get disoriented.
In order to be able to return to the colony smoothly, they rely on a keen sense of smell and a special way of defecating to mark their routes.
It can be said that it is by throwing the manure on the way that the hippopotamus leaves a scent path for itself. Even if you really lose your direction because of foraging, you can follow the taste back to your territory.
What's even more interesting is that this bowel Xi habit of the hippopotamus is not Xi acquired, but innate.
Both in wild hippos and in zoos where they have not been exposed to other hippos have shown similar bowel movements.
The author thinks
Hippos are not only keen to defecate, but also have an amazing bite force. And the temper of the wild hippopotamus is unusually short-tempered. When it is angry, even elephants do not provoke easily.
After all, the hippopotamus is a social animal, and once its group really gets angry, the lethality is not to be underestimated.
At the same time, I also advise everyone that when you go to the zoo to see the hippos, it is best to go when the weather is a little colder, otherwise you will definitely feel the smell of "straight to the heavenly spirit cover".
However, even if you are visiting in winter, remember to stay a little farther away. Its "flying attack" is not very damaging, but its durability is ridiculously strong.
However, it is also hoped that the problem between hippos and fish in the Mara River basin can be solved as soon as possible, after all, those fish that were "drowned" by feces are really a bit unjust.