Ecological Role of Cougars
The cougar’s extensive distribution throughout the Americas, its adaptability to a wide array of habitats, and its superior predatory ability may afford it a more important ecological role than any other top carnivore in the western hemisphere.
Through their interactions with prey, cougar influence energy flow in ecosystems and thus influence the structure and function of ecosystems. A powerful selective force on prey, cougars can regulate the size of ungulate populations such as deer and elk and thus indirectly affect the impacts of ungulates on plant communities. They also influence competitive interactions between herbivores.
One of the most vivid illustrations of the ecological changes wrought by the disappearance of cougars and large carnivores comes from research by ecologist John Terborgh and his colleagues on newly-formed forested islands created by a large scale water impoundment in Venezuela.
On those islands that were too small to sustain predators (i.e., cougars, jaguars and Harpy eagles), herbivore populations increased dramatically and overran the islands, leading to the reproductive failure of vegetation and a rapid decline in overall biodiversity. Within seven years, 75% of the remaining vertebrate species had disappeared. Terborgh and his colleagues concluded that “the presence of a viable carnivore guild is fundamental to maintaining biodiversity”.
Studies in North America have also linked cougar disappearance to ecosystem decline and biodiversity loss. In the eastern U.S., John McShea and his colleagues have determined that the historical elimination of cougars and gray wolves led to an overabundance of white-tailed deer populations that have degraded native forests and caused the decline of many bird species.
In the western U.S., Eric Ripple and Robert Beschta’s research in Zion and Yosemite National Parks found that the abandonment of these park’s main valleys by cougars in the early 1900s due to increased human activity led to significant vegetation and landscape changes from overbrowsing by mule deer.
These and other studies provide evidence of the transformative effects of the disappearance of cougars and other large carnivores on ecosystem health and biodiversity.
Today, cougars and other large carnivores such as wolves and grizzly bears are used by scientists as important focal species for efforts to conserve native ecosystems and biodiversity at the large landscape level.
Cougar Habitat and Territory
Cougars are very adaptable and are found from western Canada to southern Chile in nearly any environment that supports enough prey to sustain them. They can be found in forests, mountains, deserts, swamps, and areas of human development. They prefer habitat with enough brush to aid their ambush hunting style, but can also be found in more open areas.
Home range size depends on the density of prey, and in North American ranges from 32 to 1,031 km2. Home ranges of male cougars are larger than those of females, are strongly defended against other males, and often overlap the ranges of several females. Females avoid contact within areas of overlap through extensive scent marking with urine, feces, scratches and scrapes.
Cougar Reproduction and Maturation
Cougars in Washington are capable of breeding at any time of year, although birth pulses have been observed in January and August. Because adult male cougars have large home ranges that may overlap with those of several females, an adult male may breed with several females in any given year. Breeding males and females spend only a short time together after which time they separate, with the male playing no role in the rearing of young.
Cougars become sexually mature at about 24 months of age. However, sexually mature cougars seldom breed until they have established a home range. Cougars have a gestation period of approximately 92 days. They will generally give birth to between one and four kittens, although two or three is typical.
Kittens (also called cubs) weigh just over a pound at birth. Until they are two weeks old the kitten’s eyes and ears are closed. Kittens have blackish-brown spotted coats, which serve as camouflage to help conceal them from other predators, including adult male cougars. These spots begin to fade at about 12 to 14 weeks and continue fade as the kitten gets older before disappearing completely in about 18 months.
Within minutes of being born kittens will begin nursing. Over the next few weeks they will gain weight rapidly, their eyes and ears will open, and they will begin to move in and around their den. Their canine teeth, crucial for their life as a predator, first appear at about 20 to 30 days, with the molars following a few weeks later. Their permanent teeth begin emerging at about five and a half months.
When raising kittens, the mother cougar will leave them alone for brief periods of time as she hunts for food to sustain herself and her young. In the beginning she will hunt relatively close to the den, but as the kittens grow she will venture out further across her home range.
At first she will bring meat to her young but after about 7 to 8 weeks she will begin bringing the kittens to her kills. After the kittens have weaned (about 2 to 3 months) she will begin to move them to other den sites in her home range. It is important to note that a mother may travel with or without kittens at her side. Therefore, the absence of dependent young does not mean that a female is without dependent young.
Kittens remain with their mother for about 13 to 24 months while they learn the hunting skills necessary to survive. Eventually, the mother will drive off her offspring and they will set out to establish their own home range.
Juvenile male cougars often travel hundreds of miles before finding a suitable area that is unoccupied by another cougar.
Dispersing juvenile females generally travel shorter distances to find a home range and often establish home ranges adjacent to or overlapping their mother’s home range.
Dispersing juveniles are particularly at risk of coming into conflict with resident cougars and with human interests. Resident male cougars will attempt to drive off and even kill juveniles in defense of their home ranges. Moreover, a large percentage of cougar attacks on livestock (and people) are by one- to two-year old cougars.
Where it is permitted, hunting appears to be the main cause of death for adult cougars. Other leading causes of death include fights with other cougars, collisions with cars and other motor vehicles, injuries sustained while hunting prey, and old age. Although cougars also die from disease this appears to be relatively uncommon. In the wild, adult male cougars typically live until 10 to 12 years of age while females live somewhat longer.
Cougars are obligate carnivores, meaning they must eat meat to survive.
Cougars are excellent short-distance sprinters but not long-distance runners like gray wolves. No need to be a long-distance runner when cougars can rely on finely-honed stealth and surprise to hunt and subdue their prey. They may conceal themselves for hours waiting for an opportune moment to pounce. Cougars typically kill prey by using their powerful jaws to drive their large canine teeth into the back of the neck of the prey animal. Their canine teeth are very sensitive. Cougars are able to take advantage of the strength and sensitivity of their jumbo canines to probe very rapidly for the spaces between the neck vertebrae as they quickly bite down and wedge the vertebrae apart. In this manner, the prey animal’s neck is immediately broken without the need for the cougar to crunch through heavy neck bones. The result is a quick and efficient kill.
Cougars also kill prey by biting the throat from the front while clinging tenaciously to their prey using the power and strong claws of their front legs to keep a secure biting grip. The prey animal will quickly suffocate from the bite.
After making a kill, cougars will drag their prey to a more secluded area where they can feed undisturbed.
Once they have eaten their fill, they will cover their prey with grass, leaves and other material to protect it from spoiling and from being eaten other animals. Typically the cougar will remain in the area near this cache for several days and occasionally return to feed on the carcass.
In North America, deer constitute about 60% of the cougar’s diet, though in Washington this percentage is much higher. Adult cougars also prey on elk, mountain goats, moose and bighorn sheep.
Adult cougars, as well as younger animals, also opportunistically prey on smaller species such as coyotes, rabbits, rodents and raccoons, as well as pets and livestock on occasion.
According to the Washington Department of Fish and Wildlife, a large male cougar living in the Cascade Mountains will kill one deer or elk every 9 to 12 days, eating up to 20 pounds at a time and caching the rest for later. These caches provide food benefits for many other species.
Cougar dens are only used by a female when rearing young. They can be crevices in rocks, cavities under tree roots, or a hidden spot in dense vegetation. They are sometimes lined with moss or other vegetation, and might be used for several years.
Cougars communicate through visual, olfactory (scent), and postural signals, and vocalizations such as low guttural growls, spitting, snarls, and hissing.
Cougar mothers growl or hiss when their nurseries are threatened. Nursing cubs emit high-pitched, birdlike chirps and mews. Cougars also purr when together. Older cubs and adults emit whistles. Other sounds include an “ouch” call, and a yowl.
The most spectacular sound is that of a cougar caterwaul, which is an eerie sound that can resemble a child crying, a woman screaming, or the screeching of someone in pain. Caterwaul sounds are made by females during mating season, especially when males are competing for the same receptive female.