ALISO VIEJO – J.R. Stewart, an animal services officer for the Mission Viejo Animal Shelter, hiked through thick brush, responding to a hiker’s call about what sounded like a frightened dog at the top of the remote trail.

As he crawled forward, the animal’s whimpering turned to growling and barking. Stewart pushed vegetation aside and saw a Nova Scotia Duck Tolling retriever curled up under the tree.

Stewart had called officer Guillermo Rodriguez to help, thinking the dog might be injured. Instead, he realized she was just petrified with fear.

“Once I put a leash on her, she was friendly realizing I wasn’t a threat,” Stewart said. “We walked back down to the truck and took her to the shelter.”

The retriever was among at least 120 dogs either picked up by animal services officers or brought to shelters countywide over the holiday weekend — many of them likely had fled fear-inducing pops, booms and fireworks explosions.

The American Society for the Prevention of Cruelty to Animals reports nationwide that more pets are lost over the Fourth of July weekend than any other time of year.

Shelter officials say pet owners have become more responsible in recent years and have been keeping their dogs locked inside, but still many pets are running away or getting struck by cars as they panic and run from the noise.

With the holiday falling on a weekend this year, some shelter officials reported record numbers, possibly due to more parties and people traveling out of town. In some shelters, nearly half of the dogs found were in the care of pet sitters, officials said.

OC Animal Care, which oversees 17 cities and the unincorporated areas of Orange County, took in 67 dogs Saturday, Sunday and Monday. Twenty-nine of them had been picked up by their owners as of Monday.

Two-thirds of those dogs were impounded by animal control officers in the field. The remaining dogs were brought in by residents who found them running in the streets. That’s an 86 percent increase over the previous weekend, when the county agency took in 36 dogs. At least 16 of the dogs over the weekend came in as injured.

The California Highway Patrol reported at least seven incidents on freeways across the county where dogs were reported on the road. In four of the cases officers retrieved dogs that had been struck and killed.

“We’re already busy with regular calls of a busy holiday weekend but when we get calls about animals, we’re concerned for them and for the commuting public,“ said CHP officer Denise Quesada. “A lot of people try to swerve and avoid hitting the animal, but that can cause traffic accidents, which could result in a serious event.“

Regardless of all of the advice about how sensitive dogs are to the sound of fireworks, dog owners still seem to believe that their own dog will not get out, said Jennifer Hawkins, chief veterinarian and director of OC Animal Care.

“It seems the ‘it won’t happen to me’ philosophy often prevails,” she said. “Some of the dogs impounded are even repeat offenders with owners swearing that they didn’t think that their dog could jump the fence anymore.”

Hawkins said noise phobias in dogs results in severe anxiety when they hear the loud thunder of fireworks. Some dogs will claw through screens, jump through glass windows and scale tall fences in order to escape the offending sounds.

“The fear of fireworks combined with dog owners being away from home or even out of town are the primary factors that seem to lead to the increased impound numbers over this particular holiday,” she added.