Tyrannosaurus rex: Predator or Scavenger?
Tyrannosaurus rex was among the largest of the theropods, a group of mostly carnivorous (meat-eating) dinosaurs that roamed the Earth during the Cretaceous Period, 144 to 65 million years ago. For over a century, paleontologists have debated whether Tyrannosaurus was a predator that hunted living prey, as most scientists have assumed, or whether it was a scavenger that ate only the remains of animals that were already dead. Most recently, Jack Horner of the Museum of the Rockies has argued that the fossil record provides several clues that are inconsistent with a predatory lifestyle for Tyrannosaurus, suggesting instead a scavenging niche. These clues include (1) a relatively small eye that would have prevented long-distance spotting of potential meals; (2) an enhanced sense of smell, useful for detecting distant rotting carcasses (animal remains);(3) limb proportions suggestive of a slow, lumbering gait (manner of moving on foot), inconsistent with chasing down prey; (4) tiny forelimbs apparently useless for holding, let alone killing, prey; and (5) broad teeth unlike the narrow, bladelike teeth of most theropods.
Each of these points has been convincingly refuted by other paleontologists, including Jim Farlow (Indiana University-Purdue University) and Thomas Holtz (University of Maryland). These authors note that a predator does not need a large eye in order to see well. Indeed, although small for the enormous size of the animal, the eye of Tyrannosaurus was large in absolute terms, with increased light-gathering capacity and perhaps a high level of acuity. The fossil evidence is consistent with acute smelling ability, yet it seems reasonable that this sense could have served equally well to detect the living as well as the dead. With regard to foot speed, a number of studies support Horner’s contention that Tyrannosaurus was closer to the lumbering end of the spectrum than the sprinting end. However, other studies demonstrate that the likely prey animals, including hadrosaurs and ceratopsids, were even slower. So the giant predator appears to have been fully capable of catching its probable prey. It is hard to argue against the fact that Tyrannosaurus had ridiculously small arms for its size; the arms of a tall human are roughly the same length as those of the 12-meter-long dinosaur. Yet many carnivores-think of wolves-are highly effective predators without using their arms as weapons. Similarly, crocodiles and toothed whales have managed to remain at the top of their respective food chains for millions of years despite having broad teeth.
It is also important to consider the ecology of the predator-scavenger question and search for clues among the living. Today, carnivore species regularly compete for kills, often with the predator having its meal usurped by larger or more numerous challengers. Tyrannosaurus, many times larger than other predators in its ecosystem, would have been the undisputed bully in conflicts over carcasses. Yet there remains the question of quantity. Was there sufficient carrion (animal remains) available to sustain populations of 5,000-kilogram carnivores? It is difficult to answer this question in the face of important unknown variables such as the metabolic rate of Tyrannosaurus(which influenced daily caloric needs)and the sizes of the herbivore (plant-eater) populations. Nevertheless, a study by Graeme Ruxton and David Houston at the University of Glasgow attempted to estimate all the relevant parameters, modeling the Late Cretaceous ecosystem closely after the Serengeti. The authors’ tentative conclusion, based on a number of untestable assumptions, is that there may have been sufficient carrion available to support populations of enormous carnivores like Tyrannosaurus.
Yet very few living carnivores are exclusive scavengers. Several species long regarded as scavengers, such as hyenas, obtain much of their diet from predation. The vast majority of carnivores turn out to be opportunistic, killing when necessary yet content to feed on a fresh carcass killed by some other animal. Among vertebrates, the only animals that subsist almost solely on carrion are twenty-three species of vultures, which are able to soar from carcass to carcass, expending a minimum of energy in the search for food. In contrast, Tyrannosaurus had to carry its substantial bulk overland, a nontrivial task even on level, open terrain. Interestingly, in a follow-up paper, Ruxton and Houston concluded that animals able to use only scavenging to find food must be large, soaring fliers like vultures. Clearly this strategy was not available to Tyrannosaurus.
1
According to paragraph 1, Jack Horner offered each of the following as a reason for thinking that Tyrannosaurus was a scavenger EXCEPT:
Negative Factual Information Questions否定事实信息题
ATyrannosaurus had a comparatively poor sense of smell
BThe teeth of Tyrannosaurus were broad and flat rather than narrow and bladelike
CTyrannosaurus probably moved at a comparatively lower speed
DThe arms of Tyrannosaurus were too small to have been helpful in attacking prey.
2
Each of these points has been convincingly refuted by other paleontologists, including Jim Farlow (Indiana University-Purdue University) and Thomas Holtz (University of Maryland). These authors note that a predator does not need a large eye in order to see well. Indeed, although small for the enormous size of the animal, the eye of Tyrannosaurus was large in absolute terms, with increased light-gathering capacity and perhaps a high level of acuity. The fossil evidence is consistent with acute smelling ability, yet it seems reasonable that this sense could have served equally well to detect the living as well as the dead. With regard to foot speed, a number of studies support Horner’s contention that Tyrannosaurus was closer to the lumbering end of the spectrum than the sprinting end. However, other studies demonstrate that the likely prey animals, including hadrosaurs and ceratopsids, were even slower. So the giant predator appears to have been fully capable of catching its probable prey. It is hard to argue against the fact that Tyrannosaurus had ridiculously small arms for its size; the arms of a tall human are roughly the same length as those of the 12-meter-long dinosaur. Yet many carnivores-think of wolves-are highly effective predators without using their arms as weapons. Similarly, crocodiles and toothed whales have managed to remain at the top of their respective food chains for millions of years despite having broad teeth.
In stating that “Each of these points has been convincingly refuted by other paleontologists” the author means that the points have been refuted
Rhetorical Purpose Questions修辞目的题
Aseveral times
Bin a believable way
Cwith passion
Dcompletely
3
Each of these points has been convincingly refuted by other paleontologists, including Jim Farlow (Indiana University-Purdue University) and Thomas Holtz (University of Maryland). These authors note that a predator does not need a large eye in order to see well. Indeed, although small for the enormous size of the animal, the eye of Tyrannosaurus was large in absolute terms, with increased light-gathering capacity and perhaps a high level of acuity. The fossil evidence is consistent with acute smelling ability, yet it seems reasonable that this sense could have served equally well to detect the living as well as the dead. With regard to foot speed, a number of studies support Horner’s contention that Tyrannosaurus was closer to the lumbering end of the spectrum than the sprinting end. However, other studies demonstrate that the likely prey animals, including hadrosaurs and ceratopsids, were even slower. So the giant predator appears to have been fully capable of catching its probable prey. It is hard to argue against the fact that Tyrannosaurus had ridiculously small arms for its size; the arms of a tall human are roughly the same length as those of the 12-meter-long dinosaur. Yet many carnivores-think of wolves-are highly effective predators without using their arms as weapons. Similarly, crocodiles and toothed whales have managed to remain at the top of their respective food chains for millions of years despite having broad teeth.
According to paragraph 2, Farlow and Holtz believe which of the following about the eyes of Tyrannosaurus ?
Factual Information Questions事实信息题
AThey did not need to function at a high level because the animal had acute smelling ability
BThey most likely provided very limited vision.
CThey were large enough to bring in a great amount of light.
DTheir position on the head indicates that they were probably not used for hunting
4
Each of these points has been convincingly refuted by other paleontologists, including Jim Farlow (Indiana University-Purdue University) and Thomas Holtz (University of Maryland). These authors note that a predator does not need a large eye in order to see well. Indeed, although small for the enormous size of the animal, the eye of Tyrannosaurus was large in absolute terms, with increased light-gathering capacity and perhaps a high level of acuity. The fossil evidence is consistent with acute smelling ability, yet it seems reasonable that this sense could have served equally well to detect the living as well as the dead. With regard to foot speed, a number of studies support Horner’s contention that Tyrannosaurus was closer to the lumbering end of the spectrum than the sprinting end. However, other studies demonstrate that the likely prey animals, including hadrosaurs and ceratopsids, were even slower. So the giant predator appears to have been fully capable of catching its probable prey. It is hard to argue against the fact that Tyrannosaurus had ridiculously small arms for its size; the arms of a tall human are roughly the same length as those of the 12-meter-long dinosaur. Yet many carnivores-think of wolves-are highly effective predators without using their arms as weapons. Similarly, crocodiles and toothed whales have managed to remain at the top of their respective food chains for millions of years despite having broad teeth.
In paragraph 2, why does the author mention studies that demonstrate that hadrosaurs and ceratopsids were probably slower than Tyrannosaurus?
Factual Information Questions事实信息题
ATo support the claim that these two dinosaurs were likely Tyrannosaurus’ main source of prey
BTo provide evidence in support of Horner’s theory that Tyrannosaurus had a lumbering gait
CTo demonstrate that researchers have come to different conclusions about the foot speeds of various dinosaurs
DTo challenge the claim that Tyrannosaurus was too slow to catch live prey
5
Each of these points has been convincingly refuted by other paleontologists, including Jim Farlow (Indiana University-Purdue University) and Thomas Holtz (University of Maryland). These authors note that a predator does not need a large eye in order to see well. Indeed, although small for the enormous size of the animal, the eye of Tyrannosaurus was large in absolute terms, with increased light-gathering capacity and perhaps a high level of acuity. The fossil evidence is consistent with acute smelling ability, yet it seems reasonable that this sense could have served equally well to detect the living as well as the dead. With regard to foot speed, a number of studies support Horner’s contention that Tyrannosaurus was closer to the lumbering end of the spectrum than the sprinting end. However, other studies demonstrate that the likely prey animals, including hadrosaurs and ceratopsids, were even slower. So the giant predator appears to have been fully capable of catching its probable prey. It is hard to argue against the fact that Tyrannosaurus had ridiculously small arms for its size; the arms of a tall human are roughly the same length as those of the 12-meter-long dinosaur. Yet many carnivores-think of wolves-are highly effective predators without using their arms as weapons. Similarly, crocodiles and toothed whales have managed to remain at the top of their respective food chains for millions of years despite having broad teeth.
In paragraph 2. what argument is made against the claim that Tyrannosaurus could not have been a predator because of its teeth?
Factual Information Questions事实信息题
AOther predators with broad teeth have been the top predators of their food chains for millions of years
BThe shape of its teeth would have been less important for Tyrannosaurus than other characteristics such as speed and limb length.
CBroad teeth are just as necessary for scavengers as they are for predators.
DBroad teeth evolved millions of years before narrow teeth. and all predators at the time of Tyrannosaurus had broad teeth.
6
It is also important to consider the ecology of the predator-scavenger question and search for clues among the living. Today, carnivore species regularly compete for kills, often with the predator having its meal usurped by larger or more numerous challengers. Tyrannosaurus, many times larger than other predators in its ecosystem, would have been the undisputed bully in conflicts over carcasses. Yet there remains the question of quantity. Was there sufficient carrion (animal remains) available to sustain populations of 5,000-kilogram carnivores? It is difficult to answer this question in the face of important unknown variables such as the metabolic rate of Tyrannosaurus(which influenced daily caloric needs)and the sizes of the herbivore (plant-eater) populations. Nevertheless, a study by Graeme Ruxton and David Houston at the University of Glasgow attempted to estimate all the relevant parameters, modeling the Late Cretaceous ecosystem closely after the Serengeti. The authors’ tentative conclusion, based on a number of untestable assumptions, is that there may have been sufficient carrion available to support populations of enormous carnivores like Tyrannosaurus.
According to paragraph 3, how would Tyrannosaurus’ size have been advantageous to it in the Late Cretaceous ecosystem?
Factual Information Questions事实信息题
AIts extra body weight would allow it go longer without eating between kills
BIt would have easily won conflicts over carrion with other smaller carnivores
CIts large size would have improved its metabolic rate and made its feeding more efficient
DIt would have been stronger than other predators when hunting and killing herbivores.
7
It is also important to consider the ecology of the predator-scavenger question and search for clues among the living. Today, carnivore species regularly compete for kills, often with the predator having its meal usurped by larger or more numerous challengers. Tyrannosaurus, many times larger than other predators in its ecosystem, would have been the undisputed bully in conflicts over carcasses. Yet there remains the question of quantity. Was there sufficient carrion (animal remains) available to sustain populations of 5,000-kilogram carnivores? It is difficult to answer this question in the face of important unknown variables such as the metabolic rate of Tyrannosaurus(which influenced daily caloric needs)and the sizes of the herbivore (plant-eater) populations. Nevertheless, a study by Graeme Ruxton and David Houston at the University of Glasgow attempted to estimate all the relevant parameters, modeling the Late Cretaceous ecosystem closely after the Serengeti. The authors’ tentative conclusion, based on a number of untestable assumptions, is that there may have been sufficient carrion available to support populations of enormous carnivores like Tyrannosaurus.
Paragraph 3 suggests which of the following about the study carried out by Ruxton and Houston?
Inference Questions推理题
AIt produced contradictory results, which led others to challenge ts conclusions.
BIt concluded that Tyrannosaurus could not possibly have survived on carrion alone
CIts conclusion about the diet of Tyrannosaurus is questionable because so little is certain about the Late Cretaceous ecosystem.
DIt concluded that there are other present-day ecosystems besides the Serengeti to better understand the eating behaviors of Tyrannosaurus.
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Yet very few living carnivores are exclusive scavengers. Several species long regarded as scavengers, such as hyenas, obtain much of their diet from predation. The vast majority of carnivores turn out to be opportunistic, killing when necessary yet content to feed on a fresh carcass killed by some other animal. Among vertebrates, the only animals that subsist almost solely on carrion are twenty-three species of vultures, which are able to soar from carcass to carcass, expending a minimum of energy in the search for food. In contrast, Tyrannosaurus had to carry its substantial bulk overland, a nontrivial task even on level, open terrain. Interestingly, in a follow-up paper, Ruxton and Houston concluded that animals able to use only scavenging to find food must be large, soaring fliers like vultures. Clearly this strategy was not available to Tyrannosaurus.
According to paragraph 4. which of the following is true of vultures?
Factual Information Questions事实信息题
AThey often hunt live prey
BThey are the only vertebrates that rely almost entirely on scavenging.
CThey have to use more energy to find food than hyenas do.
DThey are the closest living relatives of Tyrannosaurus.
9
Tyrannosaurus rex was among the largest of the theropods, a group of mostly carnivorous (meat-eating) dinosaurs that roamed the Earth during the Cretaceous Period, 144 to 65 million years ago. [■]For over a century, paleontologists have debated whether Tyrannosaurus was a predator that hunted living prey, as most scientists have assumed, or whether it was a scavenger that ate only the remains of animals that were already dead. [■]Most recently, Jack Horner of the Museum of the Rockies has argued that the fossil record provides several clues that are inconsistent with a predatory lifestyle for Tyrannosaurus, suggesting instead a scavenging niche. [■]These clues include (1) a relatively small eye that would have prevented long-distance spotting of potential meals; (2) an enhanced sense of smell, useful for detecting distant rotting carcasses (animal remains);(3) limb proportions suggestive of a slow, lumbering gait (manner of moving on foot), inconsistent with chasing down prey; (4) tiny forelimbs apparently useless for holding, let alone killing, prey; and (5) broad teeth unlike the narrow, bladelike teeth of most theropods.[■]
Look at the four squaresthat indicate where the following sentence could be added to the passage
Although the discovery of Tyrannosaurus ‘fossils has helped scientists understand many aspects of the dinosaur’s behavior, it remains unclear how Tyrannosaurus got its food.
Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
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Some paleontologists believe Tyrannosaurus was a scavenger, but there is good reason to believe it was probably mainly a predator.
Prose Summary Questions概要小结题
Select 3 answers
AEvidence suggests that members of Tyrannosaurus roamed the Earth together in groups, which would have made scavenging enough food difficult and provided an advantage for hunting live prey.
BTyrannosaurus had superior physical characteristics to predators living today such as wolves, crocodiles, and whales, suggesting that Tyrannosaurus would have been fully capable of catching live prey.
CStudies of today’s scavengers suggest that although Tyrannosaurus may have occasionally eaten carrion, it was too energy inefficient to obtain most of its food by scavenging.
DWhile acknowledging certain physical limitations of Tyrannosaurus some scientists believe that this dinosaur had good enough sight and smell to successfully hunt slower moving prey.
ETyrannosaurus would have beaten other animals in a fight over carrion. but it is unclear whether there would have been enough carrion for such a large animal to feed primarily on it.
FAlthough it is difficult to know what conditions were like in its ecosystem, Tyrannosaurus may have at times relied on vultures to find carrion left behind by other predators or scavengers.
