Breaking up is hard to do. And for Craig Dershowitz, it's getting awfully expensive. The 34-year-old New Yorker's ex-girlfriend, Sarah Brega, took their dog, Knuckles, when she moved to California after their split, and he's suing to get the puggle — half pug, half beagle — back. So far, he has spent $60,000 on the cross-country legal fight. Here, a brief guide to this canine custody battle, and the increasing number of cases just like it:

Why is this guy so desperate to get his dog back?
Dershowitz says Knuckles is more than a pet to him... the animal is his "son," his "baby boy," his "everything." He says he raised "Knux" and cared for the dog since it was a puppy, registering it in his name and paying its vet bills. Dershowitz says he left the dog with Brega until he found a new place after they ended their four-year relationship. He agreed to share custody, but then, he says, Brega and Knuckles disappeared.

What did he do after Brega took the dog?
Dershowitz says he hired two private investigators to track down Brega, whom he accused of "dognapping" Knuckles. Then he filed a lawsuit to get the dog back. Dershowitz says his lawyer's bills have drained his bank account, so he has set up a website, "Rescue Knux," to solicit donations to finance his ongoing court battle. He's offering donors a "virtual kiss" from Knuckles for a $10 donation, a "Free Knux" T-shirt for $25, and a portrait of the dog for $200. For $250, you can play fetch with the dog if it's returned to New York. So far, he has raised about $1,200.

What does his ex say?
Brega says in court documents that Dershowitz "unconditionally gifted" her the dog. Besides, she says, "Knuckles lives a happy and healthy life in California with me, where he has ample room to play, and lives in close proximity to a beach for off-leash dog-park outings." Dershowitz initially got a default judgment demanding the dog's return, but Brega has since hired a lawyer to fight for the dog in New York and California courts.

Are there other cases like this?
Yes. In fact, the number of pet custody battles is rising. But these issues can give judges headaches, because while shared custody is common for children, pets are technically property. So like other things divvied up in divorce court, they must go to one party or the other. But as more people resolve to fight for their pets, that's changing, divorce attorney Ken Altshuler tells The Associated Press. "Judges are viewing them more akin to children than dining room sets. They are recognizing that people have an emotional attachment to their animals."

Sources: Associated Press, Business Insider, New York Post, Village Voice