Hibernation is a luxury enjoyed by different animals in different climates, where much colder weather inhibits activity through winter. Gophers take no such extended time off here. They merely work less diligently through the cooler and rainier times, and maybe get out of the way if the soil they live in gets too saturated. Their minimal damage had probably been easier to miss or ignore.
Now it is spring! The weather is warming. The soil is draining. All the roots and vegetation that gophers eat are growing. The gophers that were here and somewhat active all through winter are really making a scene now, as they clean mud from their homes and excavate new tunnels. Babies are growing up fast and leaving home, and excavating new homes of their own. What a mess!
Many of the primitive techniques that were used in the past to mitigate gopher problems are ineffective, impractical or even dangerous. Pouring gasoline into tunnels and waiting a few minutes to ignite the fumes can start fires anywhere such tunnels resurface, and possibly out of view! Bare razors dropped into tunnels are potentially dangerous to anyone who happens to dig them up later.
Traps take some work and experience to set properly, but are still the best way to deal with gophers. They do not involve poison that can be dug up and eaten by someone else, or eaten by a gopher who staggers from underground to get eaten by someone else. As long as dogs are not allowed to dig them up, traps are likely only be dangerous to gophers and those setting the traps.
Conventional traps are set in pairs, in each of both directions of a lateral tunnel that is found by excavating back from the tunnel under an active gopher volcano (pile of displaced soil). Once set, the tunnels must be back filled to eliminate air circulation into the tunnel, which would warn a target gopher of intrusion. A bit of weedy vegetation added before back fill might help attract a gopher.
Setting gopher traps is easier to read about than to do safely. It is best to learn how to do it from someone who is proficient at it..