ANTELOPE ISLAND — Warm weather is bringing visitors back to Antelope Island State Park even though the Great Salt Lake has receded from the island's traditional shores.

Some of the visitors, though, have been arriving via nontraditional means — on ATVs across drought-born mudflats, for instance — and are trespassing in protected areas, officials say.

Ron Taylor, park manager, said he and others were surprised by the horde of visitors Memorial Day — which marked the park's summer-season opening. But new amenities at the park, plus people staying closer to home for the holiday, probably played a part.

Rangers have groomed the sands at Bridger Bay for the first time in years. Fresh-water showers are operating and a concessionaire has opened a pavilion on the beach with food service, adding to the park's attraction, Taylor said.

A horse ride has been expanded to a four-hour trip that gives riders a stunning view of both sides of the island from its peaks. In all, some 35 miles of trails are open to hikers, bikers and horse riders, but motorized vehicles are not allowed on the trails.

Taylor said the receding lake level has allowed some ATV drivers to ride up to the south side of the island, which is prohibited by state law. The south half of the island is reserved as an animal refuge for the park's bison, antelope, deer and other creatures.

"We don't let people down to the south side because of the protected wildlife habitat, but then trespassers try to go down there," Taylor said.

Taylor said rangers have increased their patrols and cited about a dozen trespassers.

It's not easy to get on or off the island without being spotted by ranger patrols or volunteers, but a recent incident has rangers shaking their heads. They recently found a large inner-tube raft on a southwest beach but no evidence of who it belonged to.

"We fear the worst. Were they there to poach animals? Were they lost in the lake? Were they OK? This was a strange thing, and we'd like to get a handle on it," he said.

Trespassing is not a major problem, Taylor said, but he'd like to stop it from becoming one. "We appreciate the thousands of hikers who obeyed the rules."

June 23-29 is designated as heritage week for Antelope Island. The park will feature events at the Fielding Garr Ranch House.