Canine Feeding Behavior
Wild canids such as wolves, coyotes and foxes, detect prey through scent, tracking and chance encounters. Although these animals are skilled predators, researchers have long noted that they are opportunists as well, preferring to take down the very young, the very old, the weak, or the diseased of its prey species. As you might expect, these disadvantaged animals are the easiest to catch. Weakened animals are easy to spot, advertising their condition to canid predators through body stance, uncoordinated or slow movements, the smell of wounds or infection or some other tangible signal. The only animal that habitually preys upon prime, mature animals is man.
Despite the preference for easier kills, the wild canids’ predation efficiency is surprisingly low. Contrary to popular belief, most prey chased by wild canids actually gets away. However, once a weak individual is selected, it is usually brought down after a chase. Generally, the chases are short but there are exceptions. The actions of a predator pack are dependent on many things, including how hungry they are, which prey species they are hunting, and, the reaction of their targeted prey. Prey that runs is usually chased while prey that stands its ground may be able to bluff off its pursuers.
When studying the relationship between predator and larger prey animals we see that it is not only prey species that are at risk during confrontations. Large prey such as deer or moose can easily inflict serious wounds to attacking predators, sometimes even fatal ones. Cracked ribs, open wounds, and even broken legs are a major risk for the hunters.
Wild canids use various strategies when hunting. Although somewhat unclear, it appears they employ what seems to be a conscious strategy - sending out one or two animals in the pack to herd prey into an ambush. For instance, they prefer to attack sheep from above. They may split-up to skirt both sides of an area and then flush herbivore prey toward a middle point where they cannot escape. They reputedly lay low in the grass, switching their tails from side to side to attract curious prey. They have been observed herding prey onto lake ice where the large animals loose their footing.
Unless the wild canid locates their prey by chance encounter, their manner of approaching the prey animal usually goes unchanged. Direct scenting and tracking both allow the sensing of prey for long distances moving directly upwind. As they close the gap between themselves and their prey they become eager but remain restrained. They quicken their paces, wag their tails, and peer ahead intently. They seem anxious to leap forward at full speed but continue to hold themselves in check. This stalking scenario is true whether hunting alone, in a small pack or a large one. In cases where the stalk is used, they steal as close to the prey as they can without making it flee.
The phase of the hunt that immediately follows the stalk is the encounter, the point at which prey and predator confront each other. The prey animal responds by approaching the predator or standing its ground, or fleeing. Seldom do prey animals approach the wild canid however; moose, elk, and musk oxen are known to stand their ground, probably due to their formidable sizes. As soon as the predators see their quarry has sensed them but is not running, they stop their stalk. Larger prey is usually able to fend off a pack of predators. Smaller prey such as deer or the calves of larger prey are almost defenseless.
The flight of the prey during the encounter stage of the hunt almost always results in an immediate rush. The rush is the most critical stage of the hunt. If the canid predator fails to get close to their quarry during this stage, the prey runs off at top speed and the predators may never get close to it.
The final stage of the hunt is the chase, which is really a continuation of the rush, in which the prey flees and the predators follow. If they catch up to their quarry, they may attack. If they fall behind, they give up quickly. Although the pursuit sometimes goes on for miles, it usually covers a shorter distance and lasts only a few minutes.
When the canid predators attack they usually seize their prey, especially larger species, by the rump or the nose. The actual death of the prey usually results from massive blood loss, shock, or both. With smaller prey, such as hare, a neck bite will often snap the backbone.
Although wild canids will gorge if they have gone hungry for several days, or even an entire week, they do not overeat. The ingestion of food is regulated by the liver, which stores excess glucose as glycogen, and by the hunger and satiety centers in the brain. When the liver is topped up with glycogen, their satiety centre is activated and they will not eat. After going hungry for a time, the liver's supply of glycogen is released into the blood as glucose. When the supply is depleted the hunger centre is activated.
No soft portion of a large or small prey carcass is ignored by hungry canids and seemingly obscure parts may be important sources of required nutrients or aid in absorbing other sources. Wild canids generally tear into the body cavity of large prey, pulling out and consuming the large internal organs, such as lungs, liver and heart. The large rumen is usually punctured during removal and its content spilled. The plant material in the intestinal tract is of little interest to wolves, but the stomach lining and intestinal wall are consumed. Smaller internal organs, such as kidneys and spleen, are then exposed and eaten without delay. Sometimes the rumen contents, with or without the surrounding rumen wall freeze and become one of few signs left of a winter kill. The liver of prey may be one of the more important organs for wild canids to eat, based on the variety of important vitamins and minerals it provides. Brain tissue contains the highest amount of polyunsaturated fatty acids, some of which are required for body maintenance. Thus the brain of prey animals is inevitably eaten, so long as wild canids are able to break open the skull. Mucous membranes, an important part of ungulate stomachs, intestines and snouts are a vital source of essential fatty acids. Muscle tissue contains only about 1% essential fatty acids, while the heart contains 3-4%, the liver 4-7% and the brain over 11%.
After choice organs are consumed, the large muscle masses (meat) associated with a prey animal provides the bulk of the food consumed. All muscle tissue is very high in protein, containing all of the essential amino acids. Muscle tissue is very low in carbohydrates. The fat content of meat can vary widely depending on the species and breed of animal, and the anatomical part of its body.
Bones and other connective tissue from prey are required by wild canids as the major source of calcium for the maintenance of their own skeletons. Bone combined with meat is extremely well balanced food for canids. In the nineteenth century, dogs experimentally fed only tendons died, but dogs fed only fresh bones thrived for long periods. Single wild canids, which often scavenge, may not see a fresh kill for weeks, yet they maintain themselves on a diet of bones from old kills. Fresh bone, containing marrow, may provide 15-20% protein and an equivalent amount of fat.
The wild canids' diet, except for hide and bone, is highly digestible - generally in excess of 90%, based on experiments with domestic dogs. Fat is the most thoroughly digested component of the diet (97%), followed by protein (93%).
The wild canids’ digestive system is so strong that it usually breaks down every bit of protein that has been eaten. As a result, their scats (stool) contain very little fecal matter. The stool is usually grey or white and contains chips of bone and fur compacted and held together by mucus. Its interior is yellowish and granular and, even in a fresh dropping, little odor reaches the human nose.
Plant matter is consumed separately, particularly ripe wild fruit. Wild canids eat grass (14-43% frequency) possibly to clean the digestive tract and purge the intestines of parasites or the stomach of hair that delays passage of food through the gut. Made up of cellulose, the grass itself is never digested. Grass is particularly favored in the spring and fall when it is most succulent, sweet and interestingly, when the protein content is somewhat higher.
What’s on the Wild Canids’ Menu?
Two wolves consuming a caribou carcass provide an example of wolf feeding behavior. "In the first 15 minutes, the back strap, some skin, haunch muscles, some ribs, a kidney and a piece of small intestine were consumed. A caching trip of 20 minutes was then undertaken and in the ensuing 2 hours, meat from the backbone, rib cage, haunch and legs was eaten and the lungs were removed. In the next 2 hours, meat from the ribs and a leg was eaten; then the carcass was left for 4 hours, presumably while the wolves slept. They returned to feed over a 3 hour period on muscle from the ribs and hindquarters plus mesenteries. After 10 hours, part of the heart was eaten and the remainder cached, the lungs were eaten and another caching trip was undertaken."
Wolves also prey on beaver, snowshoe hare, ducks, marmots, mice, squirrels, grouse, geese, and rabbits. Wolves fish too, by wade-herding and trapping salmon, arctic grayling or whitefish. They eat carrion and occasionally insects, especially when they encounter them in epidemic populations. Perhaps because of the greater availability of fruit, wolves in parts of Europe may feed on plant material more extensively than those in North America. Fruit may provide vitamins for wolves in summer, as even in North America it is not uncommon to find seeds from raspberries and blueberries in wolf scats. Cherries, berries, apples, figs, pears, plums, grapes, melon and watermelon have been reported in wolf scats.
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