As habitat disappears, so does California's deer population

Apr. 09, 2012
As habitat disappears, so does California's deer population
Matt Weiser | The Sacramento Bee

An estimated 445,000 deer live in California, or about equal to the city of Sacramento's human population. Which sounds like a lot, until you realize the deer are spread over the entire state: 99 million acres.

If there were only 445,000 people in California, how long would it take you to find somebody you really wanted to hang out with?

Such is the plight of the state's deer population, our most iconic emblem of the forest. Without much notice, the species has declined slowly but relentlessly in virtually every corner of the state.

The decline has been almost too small to see on an annual basis. But since 1990, California has lost nearly half its deer population, according to the state Department of Fish and Game.

"Our deer are surviving, they're not thriving," said Craig Stowers, deer program manager at Fish and Game. "Quite frankly, until people start taking this seriously, we're going to continue to experience these types of declines."

This forest icon is on the wane mainly for one simple reason: habitat loss.

Between 1990 and 2000, according to the U.S. Environmental Protection Agency, 75,000 acres per year were converted to low-density housing across California. A recent Bee analysis of housing data showed a similar trend over the past decade, at least until the recession began. The rate was even greater before 1990.

This land conversion eliminated food and migratory corridors vital to deer.

"You can't have a good migratory deer population when their wintering ground is covered in residential development for humans," Stowers said. "They're competing for the same resources we need, and they're losing."

The species in question are mule deer and blacktail deer. Both species are lumped together in Fish and Game's 2011 population estimate of about 445,000 deer statewide, a drop from 850,000 in 1990.

The state manages its deer herds according to zones defined by habitat and deer behavior. Of the 45 zones, only about six have deer populations that held steady or increased slightly since 1990. These are generally found in some of the least-populated areas of the state.

All the other zones declined significantly.

Rural residents might tell a different story. They see deer frequently around their yards, in their gardens, and as roadkill. Indeed, deer in these areas are often considered a pest.

Deer require a particular type of forest habitat called "early seral." This means they prefer to eat the tender, nutritious, young vegetation that surges for several years after a forest fire or other land disturbance.

The problem for rural residents, these days, is that deer primarily find this kind of food in the vigorous growth of gardens and landscaping that tend to go with rural housing development.

The natural sources of this deer food have been largely eliminated by a century of fire suppression in forests – the same problem that has caused forests to become overstocked with small, young trees that now pose an enormous fire risk.

Land management agencies such as the U.S. Forest Service now understand this error of excessive fire suppression. The problem is that allowing more fire is difficult because the overly dense forests pose a massive wildfire risk, and because so many people and homes have cropped up in and near forests.

It's a "double whammy" for deer, Stowers said. Much of their habitat has been eliminated by rural development. And the habitat that remains is poor quality.

"If deer numbers are poor, they are a real canary in the coal mine, so to speak," said Randy Morrison, California regional director at the Mule Deer Foundation, a conservation and hunting organization. "They are a real bellwether species for a given habitat. And our habitat is not healthy, no question about it."

Complicating the problem is that, when a wildland fire does occur, there is often a rush to remove the burned trees and replant with seedlings. Often this comes with herbicide spraying to prevent other plants from competing with the seedlings. This impulse eliminates the natural forest regeneration that would support deer populations.

And it's not just deer. A study last year by PRBO Conservation Science, which examined conditions after fires on the Plumas and Lassen national forests, found that dozens of songbird species benefit from the same kind of post-fire habitat that emerges when a burned area is left alone.

"It's a hard sell," said Craig Thomas, executive director of the environmental group Sierra Forest Legacy. "People look at burned trees and they say, 'Oh God, let's get the green ones back.' The early seral habitat could be really diverse and beautiful if we thought about it as a valuable thing. Deer suffer when we don't think that way."

Deer are also an iconic species for hunters, and the population decline has not gone unnoticed in their circles. Mule and blacktail deer are California's primary big-game hunting species. Yet it has become increasingly difficult to harvest one.

The statewide hunter success ratio for deer hunters in 2010 was 15 percent, according to Fish and Game data. That means about four out of five hunters who purchased a license and deer tag from the state and attempted to harvest venison for their family failed to bring any home.

In Colorado, by comparison, the hunter success rate for deer in 2011 was 43 percent, according to that state's Department of Wildlife.

"Our deer numbers are down to a point where success is definitely limited, which has been very discouraging to many hunters," Morrison said.

Because deer are a popular hunting species, they are intensively managed by Fish and Game and vast quantities of data are gathered when a hunter reports a kill. As a result, Fish and Game knows there are problems with the demographics of the remaining deer population.

The leading concern is that the species is now dominated by older females, Stowers said, which do not have the same breeding success as younger females. This makes it more difficult to rebuild the population.

Going back to the habitat problem, many of the fawns that do get born don't make it to adulthood – apparently because there just isn't enough to eat. Fish and Game grades deer on a health scale from zero to 100, and most get a rating of 50 or below.

"We have yet to find a doe in this state that we would rate above a medium to poor condition," Stowers said.

In contrast, bucks are generally healthy. Being larger, they are able to outcompete other deer for whatever food there is.

Complicating matters is the fact that hunting regulations – and many hunters – are focused on harvesting bucks. Only male deer have the showy antlers that make a good take-home trophy.

In 2010, the most recent data available, California hunters harvested 25,956 bucks and just 469 does.

This means the older does, instead of getting culled from the population, are just growing older.

Stowers said regulations need to be adjusted to encourage a larger doe harvest.

Morrison agreed. He said it would be appropriate in some areas – and hunters would support it – if the doe harvest was carefully monitored to avoid harming breeding success.

Many hunters blame the deer decline on mountain lions, which primarily feed on deer. The claim is that a state law that banned mountain lion hunting, passed by voters in 1990, allowed the deer-hungry mountain lion population to grow unchecked.

There has not been a thorough study of the state's mountain lion population in many years, and there are no formal monitoring programs in place. Fish and Game estimates the population at between 4,000 and 6,000 lions, but even this estimate is dated.

There are hints, however, that even mountain lions are running out of deer to eat and turning to other food instead.

Recent evidence of a decline in porcupines across the state could be attributed to mountain lions, one of the few predators known to eat the prickly rodent. There also have been reports of mountain lions eating feral pigs in the state's coastal regions.

Morrison, however, doesn't buy the mountain lion argument.

"I believe it's habitat, habitat, habitat," he said. "So far, I don't believe we're turning the tide at all. I'm concerned. Very concerned."