Have you wondered why there are so many stray cows in the sheriff’s calls lately? West Marin cows tend to get out more often in the winter, and the explanation can be traced to an age-old idiom: The grass is always greener on the other side of the fence. “I would say the cows are more interested in the grass that is outside the fence line than the grass they are on,” said Guido Frosini of True Grass Farms, in Tomales. “Since the county mows [the roadside] once or twice a year, that grass has more time to grow and is more palatable. In my experience, if it’s similar forage on both sides, they won’t put their necks out.” But there are other challenges to keeping cows fenced: Storms can cause herds to gather in one corner of a pasture and press upon the fences, breaking them, and cows are often bothered by lice in the wet months, which can lead them to scratch and push against lines. Most fences on the coast are decades old, and ongoing contraction and expansion with wet and dry weather can loosen posts. “Everyone’s cows get out in the winter,” said Loren Poncia of nearby Stemple Creek Ranch. Despite extensively rotating herds on his pastures, Mr. Poncia said it’s hard to keep up with the winter grass growth. He receives calls all the time from his neighbors, many of whom are also ranchers, and from the Marin County Sheriff’s Office about a loose cow in the area. Often deputies call a rancher who lives nearby; since it can take a few tries to find the correct owner, everyone pitches in. “We all take care of each other,” Mr. Poncia said. Sergeant Brenton Schneider said during his 13 years he hasn’t seen many instances of vehicle collisions or property damage from loose cows, but he encouraged drivers to be cautious on the coast.