Coyotes are recent arrivals to Alaska

Posted: Friday, January 08, 2010

Coyotes are newcomers to Alaska, arriving about 100 years ago. They likely came into Southeast Alaska via the Taku and Stikine river valleys, access routes from British Columbia. They moved into the upper Tanana Valley, and from east-central Alaska they spread throughout most of the state south of the Yukon River.

Several years ago biologist Laura Prugh worked with the Alaska Department of Fish and Game to study coyotes in the foothills of the Alaska Range south of Fairbanks. She offered some insights into Alaska's coyotes.

Coyotes extended their range throughout North America coincidental with the arrival of Europeans, Prugh said. "Their original range was the Central Plains, and they've expanded in all directions."

Coyotes likely benefited from forest clearing and agriculture, which increased rodent populations. Road corridors also may have helped expand their range. A major factor was the decline in wolf populations.

"Wolves kill coyotes - where they coexist, wolves are the major mortality factor," Prugh said. "Coyotes tend to live in the 'no mans land' between wolf packs."

When wolves were reintroduced to Yellowstone National Park in the 1990s, the number of coyote dropped significantly. Before the reintroduction of wolves, coyotes in Yellowstone subsisted largely on hares and rabbits. That changed after wolves arrived.

Wolves kill coyotes, but wolves also provide them with food. The smaller canids are adept at scavenging wolf-killed carrion. In Yellowstone, that's elk. In Alaska, it's moose and caribou. Prugh examined more than 1,500 coyote scats (droppings) to determine the coyotes' diet. She found moose and caribou to be the second most common item in their diet, after hares. In years of low hare abundance, scavenged carrion became the mainstay for many coyotes.

Coyotes quickly respond to increases or decreases in prey. They have fewer pups when food is scarce, and have large litters when hares are abundant.

When hare populations crashed, coyotes targeted other prey. Prugh found a variety of prey items in scat, including marmot, grouse, ptarmigan, shrew, red squirrel, ground squirrel and porcupine.

Porcupine was unexpected, Prugh said. Porcupines are less than one percent the coyote diet when hares are abundant, but when hares were scarce, porcupine went up to about 15 percent of the diet. In terms of average biomass, one porcupine equals seven hares or 350 voles. It's not a bad meal if a coyote can catch one.

"We had one pair that was feeding their young with porcupines, and the diet was about 40 percent porky," Prugh said. "But that fall we found the mom dead and her stomach was full of quills and punctured."

Although coyotes are opportunists, they also develop and fine-tune hunting skills and strategies. Some coyotes focused on small rodents, others targeted carrion. In the long run, some strategies had their risks. Coyotes scavenging carrion sometimes had to face wolves, and Prugh found two coyotes that were killed by wolves.

Coyotes hunt cooperatively, but it depends on what they're hunting. Before wolves were reintroduced to Yellowstone, coyote packs with as many as 10 animals would successfully hunt elk. Prugh said with hares, a common strategy is for a pair to trot through the woods, flushing and then chasing down the prey. With small mammals, coyotes are most successful when hunting alone. She said she suspects they team up on porcupines, biting the face and then flipping them over.

The typical social structure is a mated pair and offspring, Prugh said, and most offspring disperse in first year. In Alaska, coyotes are found mostly as mated pairs with an established territory. They use rocky outcrops and old marmot holes as dens. Dens are used only for pupping in the spring, and are abandoned by June or July. They have a stable social structure and they tend to mate for life, but will fairly quickly replace a lost mate.

Lone coyotes are not unusual, but are generally transients without established territories. Prugh did not see packs of coyotes in Interior Alaska.

"They form a strong pair bond," she said. "Once they set up a territory they're pretty stable. They can survive hare lows, if they have a good territory. In our area, a territory is about 40 square kilometers, which is really big for coyotes. In Texas you may have several coyotes in a square kilometer. There's a lot more food and greater diversity of prey there."



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