Rattlesnakes are always around in the regional parks and other East Bay open spaces, but lately people have reported seeing more of them on the trails. So now is as good a time as any for the annual rattlesnake advisory.

I've seen two rattlers myself in recent weeks: one on Black Diamond Way at Black Diamond Mines Regional Preserve in Antioch, another on Lower Big Springs Trail at Tilden Regional Park in Berkeley. People have also encountered the reptiles on the trail around Contra Loma Reservoir in Antioch, at Briones Regional Park near Martinez and no doubt in other parks.

This isn't surprising, because now's the time of year when female rattlesnakes give birth. Unlike other snakes, which lay eggs, rattlesnakes bear their young live.

There's no cause for alarm, though. Rattlesnake bites are extremely rare. More often than not, the bites result from attempts to handle the snakes. The good news, relatively speaking, is that the bite, though painful, is very seldom fatal. However, the victim needs to get to a hospital as quickly as possible. Don't try the cut-and-suck first aid treatment. It has long been discredited as doing much more harm than good. Call 9-1-1 instead.

Here's some more rattlesnake lore, mostly courtesy of park district naturalists who have been studying the reptiles for years: The local variety is the Northern Pacific rattlesnake. They usually live under logs, in rock piles or among scattered leaves, twigs and tall grass.

Snakes regulate body temperature by moving back and forth between sun and shade. So you may see them basking in sunny spots, or they may be out of sight cooling off under the brush.

The best way to avoid rattlesnakes is simply to be aware of your surroundings. Stay on the official trails; don't take shortcuts through tall grass and brush. If you stop to rest, avoid the rock piles and logs that are snake habitat. If you do see a snake on a trail or fire road, take a wide detour. Be observant as you walk along; the snakes' color pattern blends well in dappled shade. And they don't always rattle a warning.

Northern Pacific rattlesnakes are not aggressive. They would much rather hide or run away than confront large animals such as ourselves. So give them an escape route, and they are likely to take it.

Dogs can be at risk. Curious by nature, they may run right up to a snake, barking and sniffing. If they've found a rattler, the result can be a very sick pet and a very expensive vet bill. So keep your dog under control at all times.

If you see a rattlesnake at a parking lot, picnic area or other place where people congregate, contact a park ranger, and the ranger will relocate it.

Gopher snakes look a lot like rattlesnakes, and will even mimic the rattler by vibrating their tails rapidly in leaves and pebbles to produce a rattle-like sound. Their bite is painful, too, but they don't inject venom. Information panels at many regional parks have posters illustrating the differences between the two kinds.

From snakes to wildflowers: If you'd like to learn more about the bloomers and how to identify them, there's a slide show and talk scheduled from 2 to 3 p.m. April 28 at the Environmental Education Center in Tilden Regional Park, Berkeley.

The host is interpretive student aide Morgan Rani Evans. The center is located at the north end of Tilden's Central Park Drive. Call 510-544-2233 for information. And there are two wildflower walks scheduled this weekend at Black Diamond Mines. The first is a 2-mile hilly hike through the Chaparral Loop from 10 a.m. to 12:30 p.m. April 27, led by naturalist Bob Kanagaki. The second is a more rugged 6-mile hike with lots of ups and downs, from 9:30 a.m. to 2 p.m. April 28, led by naturalist Eddie Willis.

Bob's hike is for ages 7 and older, Eddie's is for 10 and older. Both hikes are free, though Black Diamond Mines has a parking fee of $5 per vehicle when the kiosk is attended. For either hike, meet at the parking lot at the end of Somersville Road, five miles south of Highway 4 in Antioch. Rain cancels. Details: 888-327-2757, ext. 2750.

sharks: Sharks are the catch of the day in a free program from 2 to 3 p.m. April 27 and 28 at Crab Cove Visitor Center in Alameda. The program will highlight sharks of San Francisco Bay, which don't normally include Great Whites. Some of Bay sharks live in the center's large aquarium. Crab Cove is at 1252 McKay Ave. Details: 510-544-3187.

Email Ned MacKay at nedmackay@comcast.net.

FAMILY WALKS: The Hikes for Tykes series continues with a one-mile stroll from 10:30 to 11:30 a.m. on Tuesday, April 30, at Huckeberry Regional Preserve on Skyline Boulevard south of the intersection with Grizzly Peak Boulevard in Oakland.

Hikes for Tykes is designed for small children accompanied by a parent. The hikes are free, easy and registration is not required. Your leader is naturalist Sharol Nelson-Embry. Bring a snack for the tyke; strollers are not recommended.

Saturday Strolls is another family-friendly series. There's one scheduled from 10 a.m. to noon Saturday at Redwood Regional Park in Oakland. Dogs are welcome, but bring a leash, too. This is a vigorous, hilly, 4-mile hike.

Meet at the Wayside picnic area, which is accessed via the park's Redwood Road entrance, about 2 miles east of the intersection with Skyline Boulevard in Oakland. For information on either Hikes for Tykes or the Saturday Strolls, call 510-544-3187.