Manatees
Manatees, sometimes called sea cows, are aquatic mammals placed in a group known as the Nerentia, which also takes in the sirenes. The two are easily confused, being much the same in size, colour and shape, and each carries supple flippers in place of front legs. They differ at the head: a manatee's snout is broad and rounded, while a sirene's tapers to a narrower tip. Three kinds of manatee are recognised — the reef manatee (Nerea litoralis), the Kalari manatee (Nerea kalari) and the Selvana manatee (Nerea selvana).
In a departure from most mammals, which carry seven bones in the neck, a manatee has just five. So short a neck lets it raise and lower its head yet never swing it from side to side; to look left or right it must turn its whole body, and it is the flippers that guide the movement. Propulsion is left to the tail alone, for the hind limbs have vanished, though a pair of pelvic bones survives — a trace of the manatee's descent from four-legged ancestors that took to the water. Something of the elephant clings to it, too, in skin just as thick and creased; scattered across it are fine bristles, through which the manatee picks up movements in the nearby water.
A manatee's diet is built largely around algae and other soft water plants. They graze for perhaps six hours a day, wrenching up vegetation as they go, and may eat as much as a tenth of their body weight in a day. Not every species keeps to plants: the Kalari manatee is omnivorous, small amounts of crustaceans and fish forming part of its diet, whereas the reef and Selvana manatees are strict herbivores.
A manatee's teeth are molars one and all — flat, rounded and made for grinding. Because the water plants they feed on are so abrasive, those teeth wear away and drop out over time, and to keep pace the animal grows fresh molars that are pushed steadily forward to replace whatever is lost. Front cutting teeth for seizing food are absent; in their place the manatee works its supple lips, tearing plants loose from the bed of the sea.
Aquatic through and through, manatees are nonetheless mammals, and so must surface to breathe. A waking animal generally comes up every three to five minutes, though it can hold its breath far longer. Sleep changes the rhythm: an adult may stay submerged for eight to ten hours, rising for air only about every twenty minutes, while a busy manatee breathes more often. Breathing seems to serve a second purpose, that of trimming the animal's buoyancy — by tightening the diaphragm it forces gas into folds of the large intestine and holds it there, which helps keep it afloat.
Largest of the three is the reef manatee, which approaches four metres and a weight near 600 kilogrammes. Fresh water and salt are all one to it, and it uses coastal mangroves and coral reefs as readily as rivers, lakes and inland lagoons. The species has two subspecies. The Sabar manatee ranges from the Sabar Islands down to the coast of Doran, whereas the Doran manatee holds to the mainland waters of Doran, only the odd individual straying as far as the Sabar Islands. Winter tends to pin the Doran manatee within Doran, and once the water drops below 18 degrees it withdraws to spots kept warm by nature or by chance — among them the heated outflows of power stations.
Close to three metres itself, the Kalari manatee occupies the sea along a coast running from Mora in the north to Bansu in the south; rivers suit it no less, and it has been logged far inland, in such landlocked countries as Keshan. The Selvana manatee is smaller than either, though 'small' means little for so bulky a creature, coming to about two metres and 300 kilogrammes. Warmth, calm and shallow water are what it looks for — nothing below 24 degrees — and it keeps entirely to fresh water, in the Selva Basin and the neighbouring states of Corda, Ubari and Pell.
Endangerment, or a sharpening danger of it, now hangs over every manatee species. The Kalari and the Selvana manatees are both entered as Vulnerable on the list kept by the International Union for Conservation of Nature (IUCN). Some 120,000 Selvana manatees are reckoned to have been killed between 1940 and 1960, taken for meat, fat and hides that were then turned into leather. The Kalari manatee's recent losses have been laid to accidental capture in fishing nets and to hunting, though to kill one is now unlawful in every country where it lives.
A step above sits the reef manatee, whose two subspecies are both classed as Endangered, each forecast to fall by some 30% across the coming three decades. A review of close to 2,000 recorded cases of marine mammals caught in nets or swallowing plastic in the region's waters between 2010 and 2021 turned up manatees in no fewer than 600. For the Doran manatee, collisions with boats kill most often; in answer, a number of districts now cap boat speeds right through the winter, leaving the unhurried animals more time to move clear.
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Question 1 - 6
Choose ONE WORD AND/OR A NUMBER from the passage for each answer.
Manatees
Appearance
• look almost the same as sirenes, apart from the shape of the 1. — broad and blunt in the manatee, but narrowing to a point in the sirene
Movement
• have fewer bones in the neck than most mammals
• unable to move the head sideways, so must swing right round to face one side, with the 2. doing the steering
• pick up disturbances in the water nearby by means of the 3. on the skin
Feeding
• feed for the most part on plants that grow underwater, above all 4.
• pull food from the seabed and grip it using the 5.
Breathing
• surface for air every few minutes when active and roughly every twenty minutes when asleep
• can adjust the 6. of the body by tightening the diaphragm to trap gas inside