A lonely-heart buck who experts said was hunting for a mate swam across the East River on Friday — only to get left in the cold by a Manhattan dating scene that has long tormented its residents.

The 2-year-old was first spotted in Jackie Robinson Park in Harlem, prompting neighbors to call police.

“Brother, there ain’t no love in Harlem for this deer,” said neighbor Charles Coleman, 57, a tennis instructor.

“He ain’t going to find any hanky panky here in this park. He went looking for love in all the wrong places.”

The hoofed horndog was later seen in the brush near 154th Street — but he apparently failed to find a mate in the urban jungle.

Experts said the hot-to-trot deer — which could pass for a unicorn with his lone horn — may have dashed over Hell Gate Bridge from The Bronx to Randall’s Island before swimming across a stretch of the East River.

In early December, there’s a mating “rut” that makes bucks act extra wild, said Lindsay Thomas, 46, of the Quality Deer Management Association.

“This time of year, they drop their caution and they chase does everywhere and they end up in weird places,” she said. “This is typically when they end up in grocery stores and downtown and other weird places where you wouldn’t normally see a deer,” he said.

Some Harlem residents fawned over the newcomer to their neighborhood.

“I’m surprised to see a deer in Manhattan, in the city. It’s pretty crazy,” said Martin Livingston, 74, a retired truck driver who lives nearby.

“One thing I’ll say about living uptown, downtown is flat. Up here is more mountainous and more exciting — and now we even have a deer in the park,” he said.

He continued: “I’ve seen lots of deer, but this is the first one I’ve ever seen in the city. I couldn’t believe it. We didn’t expect to see a deer in this neighborhood. I’m wondering how it got here.”

A cop with wildlife knowledge said, “If it comes out of the woods and into the street, it could be a problem. Until then, we are treating it as what it is — a deer in the woods.”