Predation, Not Habitat Loss, Governs Prey Population Dynamics
Most animal population dynamics are governed by predator-prey relations, not “habitat”. For instance, even though 25 million acres were “set aside” for spotted owls 20 years ago, their population has plunged by 60 percent or more. Yes, there have been millions of acres of old-growth owl forests destroyed by catastrophic fire, but not 60 percent. The main reason for plunging owl populations is the rising populations of their predators: great horned owls, golden eagles, peregrine falcons, and other raptors.
“Habitat loss” has been so ingrained into the mass consciousness though, it is difficult to see how that ecobabble nonsense will ever be debunked. Most scientists are brainwashed, even (especially?) wildlife biologists.
But not all. The following article appeared in the Anchorage Daily News last week. It seems that moose population dynamics are governed by predation of moose calves by bears.
Newborn moose calves battle very slim odds
by Ned Rozell, Alalska Science, Anchorage Daily News, July 18th, 2009 [here]
Any moose calf alive in mid-summer is a lucky animal. If the calf was born a twin, it has probably seen its sibling pulled down and eaten by a bear. If the calf was born alone, it probably stood close to its mother as she reared on her hind legs and pounded a predator with her hooves.
In late May all over Alaska, female moose find a secluded spot to birth a calf, twin calves or sometimes triplets. In the weeks that follow, many of these gangly newborns fall prey to bears and wolves. In most areas of Alaska, more moose calves die than survive.
Mark Bertram is a U.S. Fish and Wildlife Service wildlife biologist at Yukon Flats National Wildlife Refuge. In a study he did more than a decade ago, while a helicopter pilot distracted cow moose from the air, Bertram and others scrambled to birthing sites and attached radio collars to newborn calves. By following radio signals after the calves stopped moving, the biologists were able to find dead calves and determine what killed them.
In the study at Yukon Flats, an area larger than Maryland where Alaska’s longest river reaches north of the Arctic Circle, Bertram has found the remains of a majority of the 29 moose he collared. Fifty-five percent died in one month. Three-quarters of those baby moose were killed by either black bears, which are abundant in Yukon Flats, or grizzly bears. …
“It’s real common for just 30 percent of calves to survive their first year,” Bertram said.
In studies done elsewhere in Alaska and the Yukon, the numbers agree. North of Tok, 25 percent of calves collared survived their first year.
Just 19 percent survived in a study performed in southwest Yukon. Around 30 percent made it through a year in two studies done around Galena and Nelchina.
Terry Bowyer, a biologist formerly with the University of Alaska Fairbanks’ Institute of Arctic Biology, collared cow moose in Denali National Park and kept track of her young for four years.
Only five calves out of 44 made it through their first summers. A vast majority of those were killed by grizzly bears. …
Ned Rozell is a science writer at the Geophysical Institute, University of Alaska Fairbanks.
