Since she started Dogs Finding Dogs in 2008, Wills has found dog theft most prevalent in a handful of areas, including Essex, Dundalk and Parkville in Baltimore County; Brooklyn Park in Anne Arundel and several West and Southwest Baltimore neighborhoods, including the Wilkens Avenue corridor.

Wills says she has been averaging seven new calls a day from Essex alone in recent weeks.

Baltimore and Baltimore County police, including those in the Essex Precinct, say they have noticed no particular spike in dog thefts. But they add that that doesn't mean it isn't happening.

Victimized owners sometimes assume a dog is merely lost and so don't contact law enforcement. And police group animal theft with other property theft, so it's difficult to identify trends.

"There's no specific dog-theft code, so it's labor-intensive to search for those results specifically," says Cathy Batton, a spokeswoman for the Baltimore County police.

Dogs Finding Dogs keeps Wills, her own search dog and her team of nine human and nine canine volunteers so busy she's at work on cases from 8 a.m. to 10 p.m. most days.

Wills works for donations. She says her outfit has recovered more than 2,000 pets, an average of more than one per week.

Wills fell into the field almost by accident. The first dog she ever owned, a mostly German Shepherd pup named Heidi, proved so energetic she was hard to control. Wills' boyfriend, a cop who worked with a canine unit, suggested she put Heidi through police-dog training.

When Wills learned how many citizens contact police dog units asking for help with lost pets — a service they don't offer — she took her dog on a few free calls.

Demand was so high she soon quit her old job.

Each of her volunteer dog-and-human tracking teams is certified through the National Tactical Police Dog Association and can work day or night in any weather.

There were always plenty of calls for lost-pet cases, but Wills says her greatest surprise was learning how often pets are stolen. At first, such cases took up about a third of her time. The portion has jumped to more than 50 percent over the past year.

It is not unusual, she says, to follow a trail to a malefactor's door and see or hear the missing animal inside, only to hear the thief deny it was there at all or try to sneak it out a back door.

Violators are young and old, and of all races. Some are little old ladies who have "found" a new pet and refuse to give it back.

In one case, a dog owner found a man walking her pet on Bel Air Road in Baltimore. When she confronted him, he pulled a gun.

"We're talking about people who are not always the classiest forms of life," says Wills.

While police can't make animal searches a top priority, she says, many officers are willing to assist in making arrests if she or her colleagues have followed the trail to a site and a neighbor can confirm the pet's presence.

Three years ago, McKenzie was living in Brooklyn when her beloved pit bull, Marley, disappeared from her fenced-in backyard. She contacted Dogs Finding Dogs, and was amazed to see Wills and Heidi make a straight line for a rowhouse Marley used to frequent.

Wills encourages owners to supplement the sniff searches by plastering neighborhoods with posters, setting up Facebook pages, taking out online ads and using FindToto.com, a service that can bombard an area with prerecorded alerts, all in hopes of pressuring thieves or turning up a lead.

McKenzie, who took out a Craigslist ad, eventually got an anonymous call from a woman who told her Marley had been left at the Anne Arundel County animal shelter.