DALLAS -- Visitors to the Houston Zoo can now pack a little something extra besides a camera and picnic basket.

The nearly century-old institution recently lifted its longtime firearms ban amid a broader push by gun-rights advocates who are pressuring zoos in Texas and elsewhere to do the same.

Gun-rights supporters say publicly owned zoos have misinterpreted laws and are illegally posting signs that ban firearms. Some zoos have countered calls for policy changes by claiming they are considered amusement parks, day cares or educational institutions - venues that legally can enforce gun bans in many states.

An advocacy group in Texas is singling out zoos under a newly enacted state law allowing complaints about unlawful gun restrictions to be forwarded to the state's attorney general for potential steep fines. Similar efforts have occurred elsewhere, including in Missouri where the St. Louis Zoo went to court to prevent an Ohio man from bringing a gun to the zoo to test its no-weapons policy.

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"I am not anti-zoo," said Edwin Walker with Texas Law Shield, the group that recently filed complaints against the Houston and Dallas zoos. "I guarantee there's not going to be a license-holder that's going to go to the zoo and shoot a baby giraffe in front of schoolchildren."

"If you have the right to carry, you should be able to carry," said Chrissy Richey, zoo visitor. "That's my opinion. Everyone should be safe. If you think carrying a gun makes you safe."

Many zoos across the country - from Milwaukee to Omaha, Nebraska - do not allow guns on the premises. But laws vary state to state. In Kentucky, for instance, a 2012 law revision permits people to openly carry firearms into facilities owned by municipalities, such as libraries, parks and zoos.

The Houston Zoo has already felt backlash after the city ordered it Sept. 10 to take down its no-gun signs because it operates on public land. Parents and children gathered last month to greet zoo visitors with warnings about the policy change, with some holding signs such as "Panthers not Pistols" and "Hey Gun Lobby, quit monkeying around!"

"Why would you want to bring a gun to the zoo? I mean that's kind of crazy," said Damian Manuel, a zoo visitor.

"There are places in our public lives where guns are inappropriate," Stephanie Lundy, a mother attending the protest, told KHOU-TV. "And the zoo is one of those places."

Texas authorizes licensed gun owners to carry concealed weapons in public but the law exempts a variety of places - amusement parks, churches and schools, among them - and officials at the state's larger zoos cite some of those exemptions in arguing that firearms are not permitted.

The St. Louis Zoo made a similar argument in June when it won a temporary restraining order against the Ohio man, saying that allowing guns "will cause a chilling effect" on zoo visitors.

Fort Worth Zoo says it's licensed as a day-care facility, and the Dallas Zoo contends it's considered both an amusement park and an educational institution.

"We continue to believe that we're complying with state law," said Dallas Zoo spokeswoman Laurie Holloway, adding that it receives questions about its gun policy every few months.

In a complaint sent last month to Dallas Zoo officials, Walker argues the zoo "does not offer any degrees, have any standardized course of study, nor is it certified or overseen by any state educational agency. Further, the Dallas Zoo does not meet the definition of 'amusement park' ... in that it does not have amusement rides."

Walker said he'd consider filing a complaint with the attorney general's office, but first wants to see if the zoo provides a written response.

Meanwhile, the Houston Zoo says it's reviewing legal options in light of evolving gun laws, spokeswoman Jackie Wallace said. Zoo officials previously believed they could ban firearms because they offered an "educational attraction" for children and others.

"We do recognize that this has the potential to confuse or concern our guests and members," Wallace said. "This will not alter our No. 1 priority, which is the safety of our guests, employees and animals."