As the Inverness Ridge fire raged across the Point Reyes National Seashore last October, it all but exterminated every species of rodent in the burned area - including two of the rarest mammals in West Marin.

Early results of Park Service field studies of the burn zone indicate that the primitive Point Reyes mountain beaver and the tiny Point Reyes jumping mouse were devastated by the blaze.

Large decreases have been found too in the number of birds and the diversity of bird species that live in coastal scrub plants such as coyote bush and lupine and in vegetation along creeks.

Reptiles such as snakes and lizards suffered greatly and perhaps mainly because of bad timing; the fire hit in warm, dry weather when reptiles typically are active on the ground's surface.

And, the studies show, the Inverness Ridge itself held together well during the winter rains. The absence of much vegetation did not lead to any serious erosion despite a near-average rainy season.

The October fire destroyed 45 houses in the Paradise Ranch Estates subdivision of Inverness Park and scorched 12,354 acres of park land. Since then an army of zoologists, biologists, hydrologists, and soil experts have studied the burn area in hopes of aiding the recovery of resident wildlife.

Park biologist Gary Fellers, when asked which rodents were hardest hit by the conflagration, replied, "All of them."

In his book, The Natural History of the Point Reyes Peninsula, naturalist Jules Evens of Point Reyes Station notes, "these two species are probably the among the earliest of the living mammalian inhabitants of the Bay Area...

"They are relics - refugees from an era when the environment was wetter [and] when the boreal forests were continuous from central California northward."

Park biologists say the mountain beaver is a chief concern. They estimate that of the 2,000 mountain beavers that lived within the burn area, only 20 survived. Another 3,000 are estimated to live on Point Reyes outside the fire zone.

The Point Reyes mountain beaver belongs to the genus Aplodontia, of which the mountain beaver is the sole family member. Aplondotia range throughout the Pacific Northwest (although the Point Reyes subspecies is grayer and smaller than the next nearest population in Mendocino County, Evens notes).

Mountain beavers, in fact, are considered a pest in Washington state. They've been seen wandering the halls of the University of Washington, wreaked havoc on gardens and done widespread damage to tree roots in park land.

One of their most notable characteristics - their primitive kidneys can't concentrate urine - may have led to their doom during the Inverness Ridge fire. Each day a mountain beaver must consume up to a pint of water, which it gets mostly from eating vegetation.

On the other hand, Fellers added, the beavers may have been overcome directly by the heat, flames, and smoke. If that was the case, he said, "how much water that was available became somewhat irrelevant."

The beaver was just one of the rodent species annihilated. Harvest and deer mice were also devastated, as were shrews and woodrats. "My experience is that they simply had no place to go," Fellers said.

John Dell'Osso, the Point Reyes National Seashore's chief of interpretation, said only two Point Reyes jumping mice have been captured within the burn zone in preliminary catch-and-release surveys.

The tiny Point Reyes jumping mouse is a subspecies of the Pacific jumping mouse. It's relatively rare, making its loss more noteworthy, Dell'Osso said. Biologists don't know how many jumping mice populated the fire zone before last October.

Of the mountain beaver and the jumping mouse, Dell'Osso said, "it is alarming in the sense that these are specialized subspecies found only at Point Reyes." Although they may breed into higher numbers, "it may take some time," he said

Studies continue on the fire's effects on larger mammals: foxes, bobcats, mountain lions, badgers, and weasels.

As for deer, they were large and fast enough to outrun the fire, and many made temporary homes in such places as the Vedanta Retreat property and Divide Meadow in the Olema Valley.

Biologists have fastened radio collars on 10 native black-tail deer and 10 exotic fallow deer to track their movements. Aerial surveys with after-dark spotlights are being conducted to gauge populations.

The exotic deer are expected to fare better than the blacktails in late summer, when the food supply becomes more scarce and competition increases, the Park Service study predicts.

Most surprising, said Fellers, is the high survival rates of turtles, frogs, and salamanders. "I would not have expected that," he said. "You'd think that they'd be susceptible to the heat and dryness of the fire."

As for birds, Dell'Osso said biologists are most concerned about migratory songbirds, which breed in the brush beneath the canopies of Douglas fir and Bishop pine forests.

Much of that habitat, as well as vegetation along streams and creeks, was wiped out. Dell'Osso noted that songbird habitat in South America has largely been wiped out, and "for them to be losing habitat up here, again that's alarming."

However, researcher Fellers noted, many species of mammals and birds adapt to the natural effects of fires, and for the most part will respond well over the long term.