The River Walk's new Christmas lights are being tampered with, and the city's sleuths have identified some most surprising culprits.

Squirrels!

The little rodents have been gnawing away at the wires of the 1.76 million LED bulbs, which are wrapped around the trunks and branches of trees — in other words, the squirrels' homes.

The damage is so extensive that the city is strongly considering removing the lights between the current holiday season and next year, which would push the project's costs above what was budgeted.

When it was decided to replace the traditional incandescent bulbs (which draped over the River Walk's tree canopy) with LEDs, the plan was to remove only the first 15 feet of lights on each tree after the holidays and leave the remaining lights as a cost-saving measure.

The city anticipated some damage from rodents, but not to this extent, said Paula Stallcup, director of downtown operations.

The city and contractor have brainstormed to find a solution to the squirrel nuisance, but so far, the problem's been a head-scratcher.

“We have not been able to come up with a solution that would prevent the squirrels from chewing on the lighting,” Stallcup said. “It's one of those things. We've got that habitat on the River Walk that we need to manage through.”

As any gardener knows, when squirrels take a liking to something, it's hard to keep them away.

“I have no idea of what goes on in a squirrel's mind,” said Steve McCusker, executive director of the San Antonio Zoo.

He said there are several reasons that could explain the vandalism.

For one, the lights are new to the squirrels' habitat, so they're curious about them.

But the bottom line is that squirrels are natural chewers; it's what they do best.

“If they have to go around (the lights) or over them, they will sniff at them, play with them, and if they get their hands on them, they are going to chew,” McCusker said.

Stallcup attributes the squirrel damage to better accessibility in the tree trunk-wrapped design.

“In previous years, the lighting hung out at the very tip of the limb and so the squirrels weren't going out that far,” Stallcup said. “In this case they are wrapped right around the branches where it's very convenient for them.”

McCusker said he wouldn't be surprised if squirrels chomped on the incandescent lights of years past. But back then, the Paseo del Rio Association, which was responsible for purchasing the 85,000 lights at an annual cost of $75,000, purchased fresh lights every year, so the damage was not an issue.

Aside from chewed-up wires, there has been evidence of human vandalism, too, where wires were cut clean. But Stallcup said that accounts for just a small portion of the damage.

A cost estimate for replacing the lights is not yet available because the city and contractor Preferred Landscape & Lighting still are calculating the figure.

“We know that there is squirrel damage,” Stallcup said. “We have to factor that in now . ... I do not know what that total damage number is.”

Even the contractor couldn't put a number on the extent of the damage.

“I know there has been damage, but I don't know how much,” said Mark Metzger, partner with Boerne-based Preferred Landscape & Lighting.

In August, the City Council approved a contract worth $580,374 to Preferred Landscape & Lighting for purchasing the LEDs, complementary lights on bridges and at the base of trees, as well as installation and removal.

The majority of the cost is being funded by hotel occupancy tax money.

The contract includes a renewal option for 2012 and 2013 at a cost of $114,461 and $141,531, respectively. Should the city decide to stick with LED lights for the 2012 holiday season, 10 percent of the projected cost, about $26,600, was budgeted for replacing lights.

But large-scale damage from squirrels and vandals wasn't factored into that figure.