CAPTURING PREY
A mountain lion is the personification of power, grace, strength, speed, and agility, largely due to heavy musculature attached to a light but strong skeleton. The majority of a cougar's body weight is muscle and sinew, with only a relatively small portion made up of bone and organs. Long, muscular legs and a flexible backbone allow strong extended strides, while its long, heavy tail provides balance on quick turns and uneven ground.(15) Horizontal leaps of 45 feet have been recorded, along with vertical leaps of 15 feet . This ability may be partly due to the fact that the cat's rear legs are longer than its front legs. An adaption for jumping is a valuable characteristic both for attacking prey and moving through the rugged terrain most cougars inhabit.(8) Further, the anatomy of a cougar's front limbs allows the animal to pivot sharply without losing lateral traction,(14) an important feature when grasping large prey at high speed.
The big cat is built for speed, not endurance. Writer Jim Bob Tinsley relates that, "It [the cougar] can easily outrun a pack of dogs for a few hundred yards, but its small lungs limit the distance it can cover at full stride. When out of breath, it must seek the temporary shelter of a tree or some other natural protection."(16) Ralph Schmidt, who works with Alberta lion researchers Martin Jalkotsy and Ian Ross, believes cougars are the fastest predator in North America. "I've seen cougars jump out of trees and run up a slope at an unbelievable rate of speed," says Schmidt, with a pronounced tone of respect.(17) Apparently no cougar has ever submitted to the stopwatch, but it is telling to consider that in some parts of the western United States, cougars have been known to occasionally kill pronghorn (Antilocapra americana), the fastest land animal in North America.(16, 18)
The skull is short and round, with 16 teeth in the upper jaw and 14 in the lower jaw.(6) Cougars have a powerful bite because of the reduced length of their jaws and their large jaw-closing muscles, the temporalis and masseter. Atop its skull, the cat has a bony ridge called the sagittal crest, which provides a large surface area for the attachment of the temporalis, the larger and stronger of the two muscles, and the one that lifts the jaw up and back.
The other end of the temporalis attaches to the lower jaw. At a wide gape, such an arrangement gives the temporalis a greater mechanical advantage in driving the large canine teeth through the prey's muscle and bone. The masseter originates on the zygomatic arch, a bony arch on the side of the skull, attaches to the outside of the jaw, and lifts the jaw up and back. The masseter is more important as the jaws close at the end of the bite and when the cat uses its carnassials during feeding. Carnassials are modified molars and premolars that act as shears to cut through tough hide and tissue, which is why cats turn their heads to the side when they are biting through tissue while feeding. Cats do not chew their food, but rather use their carnassials to cut their prey up into small pieces or strips, which are swallowed whole.(13) Even the puma's tongue is specially adapted, with sharp, horny protuberances that help remove meat from bone and also aids in grooming.(21)
The cougar seems to tolerate the bitter cold of the Canadian north or the blistering heat of the Amazon equally well. Its remarkable physique is covered with a tawny coat that is short year-round in warmer climates but grows longer and thicker during the winter in temperate regions.(22)
DIET
Because cougars are one of the most widely ranging cats, their diet varies depending on the prey available; almost completely carnivorous, they rarely eat vegetation.(25) As noted, deer are at the top of the menu - mule deer in western North America and white-tailed deer in eastern North America.(6) Exactly how much of the lion's diet deer comprise varies with each state and province.(25) Mule deer are the primary prey in Oregon, Alberta, and Utah, while in Florida, white-tailed deer (Odocoileus virginianus) and wild hogs (Sus scrofa) are at the top of the menu.(26) Other large prey are taken as well. Hornocker found that cougars in the Idaho Primitive Area fed primarily on mule deer and elk (Cervus canadensis).(27) In Nevada, the ever-adaptable lion occasionally augments its diet with wild horses and desert bighorn sheep (Ovis canadensis ).(28) Even moose (Alces alces) have been known to fall to the powerful cat in Alberta(29) and British Columbia.(30)
Opportunistic predators, cougars also feed on a variety of smaller prey, especially in times of seasonal abundance. Columbia ground squirrels are frequently the cat's main course during the warmer summer months in Idaho,(31) while during years of peak snowshoe hare abundance in British Columbia, over a quarter of the cougar's diet was composed of hares.(30) In the southwestern United States, peccaries (Tayassu tajacu) are taken.(6) Additional prey includes rabbits, marmots, beaver, porcupine, an assortment of birds, domestic livestock, and even carrion, as well as other carnivores, such as bobcats, coyotes, and other cougars.(18, 32)
The puma's dependence on smaller prey is more pronounced in South America. In Chile's Torres del Paine National Park, pumas subsist primarily on European hares (Lepus europaeus), followed by guanacos (Lama guanicoe) and domestic sheep (Yanez et al. 1986). Biologist Louise Emmons found that pumas in the jungles of Peru preyed on small rodents, oppossums, bats, and lizards. The majority of their prey were agoutis and pacas, rodents weighing 2 to 22 pounds.(34) The big cats are able to kill and eat most animals in their home range.
When the abundance of their primary prey declines, cougars have been known to switch their diet. This occurred in Big Bend National Park in western Texas, where cougars and male bobcats usually feed on deer. When the mule deer population crashed in 1980-1981, both cats were forced to switch to peccaries and lagomorphs (rabbits and hares), the next largest prey. (35)
Estimated frequencies of kill vary from 1 deer per 10 to 14 days(27) to 1 deer per 2 to 3 days.(36) As stated previously, females with dependent kittens require greater quantities of meat, quantities that increase as the kittens grow. Ackerman estimated the following kill rates for a resident female in southern Utah:
- Solitary resident female - 1 deer per 16 days
- Resident female with 3-month-old kittens - 1 deer per 9 days
- Resident female with three 15-month-old kittens - 1 deer per 3 days
Having evolved as an opportunistic predator, that may go without eating for days at a time, cougars exhibit fast-and-gorge feeding behavior. Captive cougars will eat 5 to 12 pounds of meat per day, more after deprivation, which is typical of this behavior.(25) Sensitive to spoilage, cougars seem to prefer their meat fresh, though they have been known to eat carrion when near starvation. In the warm temperatures of Arizona, spoilage of the carcass will typically restrict a cougar's use of a kill to no more than four days.(38) Kills can be fed on for longer periods in more temperate regions. This is a decided advantage during cold winters when metabolic demands are high. One researcher in Idaho observed a cougar remain with an elk carcass for 19 days during one particularly cold winter.(31)
PREDATORY BEHAVIOR
The prey is normally killed with a bite to the back of the neck at the base of the skull. The large canines are
inserted between the vertebrae like a wedge, forcing the vertebrae apart and breaking the spinal cord.(13) The speed with which this takes place indicates that the concentration of nerves in its canines allows the cat to "feel" its way to the vertebrae in a fraction of a second.(5) In the case of larger prey such as elk, the neck may be broken by pulling the head down and back, breaking it directly or in a fall.(45) If this fails the cougar may grasp the throat, crushing the windpipe. This necessitates death through asphyxiation and takes longer, exposing the cougar to possible injury.(6, 38) The efficiency of the kill will vary, depending on prey size, cougar size, angle of attack, and other circumstances. Hornocker found that cougars were successful 82 percent of the time in attacks on mule deer and elk in the Idaho Primitive Area.(27)
Renowned biologist Paul Errington believed that removal of some prey animals by predators increased productivity in the rest of the prey population by reducing overall competition. Thus, predation compensates for initial deaths by improving the chances of survival for other members of the herd. This concept, called compensatory mortality, is generally supported by research and is frequently cited in wildlife management circles as the theoretical rationale to support recreational hunting.(51) Current evidence seems to indicate that the losses of healthy or unhealthy deer to cougars are at least partly compensatory in nature.
Science can only take us so far in our examination of the cougar. Objective and empirical methods have revealed much about the lions' biology, but this is only one facet of the feline enigma. A broader perspective can be gained by going back in history, to a time when the division between fact and fable was less clear. It was a time before science, when the lives of Felis concolor and Homo sapiens were more intertwined than today. It was a time when the American lion was a god.
No comments:
Post a Comment