Reading Practice: The dugong: sea cow

A

The dugong is a large marine mammal that resembles a combination of a robust dolphin and a walrus. Its body, flippers, and fluke resemble those of a dolphin but it lacks a dorsal fin. Its head resembles that of a walrus but without the long tusks.

B

Dugongs, along with other Sirenians, primarily feed on seagrass. Their distribution closely follows the presence of marine flowering plants. Seagrasses grow rooted in sediment and depend on light availability, thus are predominantly found in shallow coastal waters, similar to dugongs' habitats. However, dugongs show a preference for seagrass with higher nitrogen content and lower fiber.

C

Due to their poor eyesight, dugongs rely on smell to find edible plants. They have a strong tactile sense, using long sensitive bristles to explore their surroundings. They uproot entire plants, shake off sand, and may collect them in piles before consumption. Their flexible upper lip is adept at excavating plants, which are consumed whole, including roots. In times of scarcity, they may supplement their diet with algae and occasionally eat invertebrates like jellyfish, sea squirts, and shellfish, despite being primarily herbivorous.

D

A seagrass meadow that has been heavily grazed resembles a lawn mowed by an intoxicated person. Dugongs feed seemingly randomly within the seagrass bed, their paths meandering in various directions along the seabed. This inefficient method of seagrass removal leaves numerous small clumps behind. However, this inefficiency benefits dugongs because the species that recover most quickly from this disturbance, spreading vegetatively from the remaining clumps, are those preferred by dugongs for consumption. Furthermore, the new growth in these areas tends to be exactly what hungry dugongs prefer.

E

Dugongs are semi-nomadic creatures, often traveling long distances in search of food while remaining within a specific range throughout their lives. They frequently move in large groups from one area to another, likely driven by changes in seagrass availability. Their memory enables them to return to specific locations after extensive journeys. Dugongs predominantly move within localized seagrass bed areas, with individuals in the same region displaying unique movement patterns.

F

Official dugong population records are generally believed to underestimate actual numbers due to inadequate survey accuracy. Despite this, the global dugong population is declining, with a 20% decrease over the last 90 years. They have disappeared from the waters of Hong Kong, Mauritius, and Taiwan, as well as portions of Cambodia, Japan, the Philippines, and Vietnam. Further disappearances are anticipated. In the late 1960s, herds of up to 500 dugongs were observed off the coast of East Africa and nearby islands. However, current populations in this area are extremely small, numbering 50 or fewer, with extinction likely. Large populations, numbering in the hundreds, inhabit the eastern side of the Red Sea, with similar populations thought to exist on the western side. In the 1980s, an estimated 4,000 dugongs were thought to inhabit the Red Sea. The Persian Gulf hosts the world's second-largest dugong population, primarily along its southern coast, with current estimates around 7,500 individuals. Australia boasts the largest population, ranging from Shark Bay in Western Australia to Moreton Bay in Queensland. The Shark Bay population is considered stable with over 10,000 dugongs.

G

Experiences from various parts of northern Australia indicate that extreme weather events such as cyclones and floods can devastate hundreds of square kilometers of seagrass meadows and even wash dugongs ashore. The recovery of seagrass meadows and the expansion of seagrass into new or previously destroyed areas can take over a decade. For example, approximately 900 km2 of seagrass was lost in Hervey Bay in 1992, likely due to turbid waters from local river flooding and subsequent cyclone-induced turbulence three weeks later. Such events can cause extensive damage to seagrass communities due to severe wave action, shifting sands, and reduced salinity and light levels. Prior to the 1992 floods, the extensive seagrass meadows in Hervey Bay supported an estimated 1,750 dugongs. Eight months after the floods, the affected area was estimated to support only about 70 dugongs. Most animals presumably survived by migrating to neighboring areas, although many perished attempting to find better feeding grounds, with emaciated carcasses washing up on beaches up to 900 km away.

H

If dugongs do not obtain sufficient food, they may delay calving and produce fewer offspring. Food shortages can arise from various factors, such as habitat loss, death and degradation of seagrass quality, and disruption of feeding caused by human activities. Sewage, detergents, heavy metals, hypersaline water, herbicides, and other waste products all have negative impacts on seagrass meadows. Human activities such as mining, trawling, dredging, land reclamation, and boat propeller damage also increase sedimentation, smothering seagrass and blocking light. This sedimentation is the most significant negative factor affecting seagrass. One of the preferred seagrass species of dugongs, Halophila ovalis, experiences rapid decline due to light deprivation and dies completely after 30 days.

I

Despite legal protection in many countries, the primary reasons for population decline remain human-induced, including hunting, habitat degradation, and accidental deaths from fishing. Entanglement in fishing nets has resulted in numerous fatalities, though exact statistics are unavailable. Most issues with industrial fishing occur in deep waters where dugong populations are sparse, while local fishing poses the main threat in shallower waters. Dugongs, unable to remain submerged for extended periods, are highly susceptible to entanglement deaths. Historically, shark nets caused significant mortalities but have been largely replaced with baited hooks. Although hunting has been a historical issue, it is no longer prevalent in most regions, except among certain indigenous communities. In northern Australia, hunting remains the most significant threat to dugong populations.

​​Questions 1-4

Complete the following summary of the paragraphs of Reading Passage, using no more than two words from the Reading Passage for each answer. Write your answers in boxes 1-4 on your answer sheet.

Dugongs are herbivorous mammals that spend their entire lives in the sea. Yet Dugongs are picky on their feeding Seagrass, and only chose seagrass with higher……1…….. and lower fiber. To compensate for their poor eyesight, they use their ….2……….. to feel their surroundings. It is like Dugongs are “farming” seagrass. They often leave ……3…….. randomly in all directions across the sea bed. Dugongs prefer eating the newly grew seagrass recovering from the tiny……4……..left behind by the grazing dugongs

Questions 5-9

Do the following statements agree with the information given in Reading Passage 1? In boxes 5-9 on your answer sheet, write

(5) The dugong will keep eating up the plant completely when they begin to feed.

(6) It takes more than ten years for the re-growth of seagrass where it has been grazed by Dugongs.

(7) Even in facing food shortages, the strong individuals will not compete with the weak small ones for food.

(8) It is thought that the dugong rarely returns to the old habitats when they finished the plant.

(9) Coastal industrial fishing poses the greatest danger to dugongs which are prone to be killed due to entanglement.

Questions 10-13

Answer the questions below. Choose NO MORE THAN TWO WORDS AND/OR A NUMBER from the passage for each answer.

(10) What is Dugong in resemblance to yet as people can easily tell them apart from the manatees by its tail?

(11) What is the major reason Dugongs traveled long distances in herds from one place to another?

(12) What number, has estimated to be, of dugong’s population before the 1992 floods in Hervey Bay took place?

(13) What is thought to be the lethal danger when dugongs were often trapped in?

1. Nitrogen (Đoạn B, “Dugongs do not eat all species of seagrass, preferring seagrass of higher nitrogen and lower fibre content.”)
2. Sensitive bristles (Đoạn C, “They also have a strong tactile sense, and feel their surroundings with their long sensitive bristles.”) 
3. Trails (Đoạn D, “their trails meandering in all directions across the bottom.”)
4. Tufts (Đoạn D, “This is rather an inefficient means of removing seagrass that results in numerous small tufts remaining.”)
5. TRUE (Đoạn C, “When eating they ingest the whole plant, including the roots, although when this is impossible they will feed on just the leaves.” → Ăn toàn bộ cây)
6. FALSE (Đoạn D, “ In addition, the new growth found in these areas tends to be exactly what hungry dugongs like.”)
7. NOT GIVEN (không có thông tin về việc tranh giành đồ ăn giữa các cá thể)
8. FALSE (“Their memory allows them to return to specific points after long travels.” → Sau khi ăn xong sẽ quay trở lại vị trí cũ) 
9. NOT GIVEN (Không có số liệu cụ thể về việc mắc vào lưới đánh cá để khẳng định đây lý do hàng đầu dẫn đến cái chết của Dugong.)
10. Dolphin (Đoạn A, “Its body, flippers and fluke resemble those of a dolphin but it has no dorsal fin.”) 
11. Seagrass availability (Đoạn E, “Large numbers often move together from one area to another. It is thought that these movements are caused by changes in seagrass availability.)
12. 1750 (Đoạn G, “Prior to the 1992 floods, the extensive seagrasses in Hervey Bay supported an estimated 1750 dugongs.)
13. Fishing nets (Đoạn I, “Entanglement in fishing nets has caused many deaths, although there are no precise statistics.”)