Officials say construction will begin on projects as early as 2018, and will include the replacement of water and sewer infrastructure for Nico, a giant anteater, and the other animals.

The fate of the proposed sales tax increase to pay for Reid Park Zoo upgrades was in limbo Tuesday night, with voters splitting on the two propositions that had to pass for the tax to be approved.

Proposition 202, which would amend the city charter to implement the sales tax increase, was slightly ahead 52 percent to 48 percent.

And Proposition 203, which approved the temporary sales tax hike, was narrowly being defeated with 50 percent against, and 48 percent in favor, early results show. Only a few hundred votes separated the votes on Prop. 203.

The county still has an unknown number of provisional and uncounted ballots left to count, which may not occur until Wednesday, that could affect the outcome of this issue.

In a recent poll, a one-tenth of a cent increase in the sales tax to benefit Reid Park Zoo was supported in the city by 55 percent of those polled. It was opposed by 33 percent of the respondents.

The proposal requires both Proposition 202, altering the city charter, and Proposition 203, approval of the tax hike, to pass.

The propositions, or the Future of Your Zoo initiative, would raise between $8 million and $10 million annually, by increasing the city's sales tax.

The zoo just celebrated its 50th anniversary, and officials are proud to have witnessed its growth, however, they say the aging facilities are creating some financial strain.

Underground sewer, broken water pipes and guardrails need replacing.

Some of the animal habitats are reaching 30 on up to 50 years old and need replacement to meet zoo standards, said Nancy Kluge, president of the Reid Park Zoological Society, in an earlier interview.

The society has been successful over the years in raising funds for new exhibits, but the infrastructure needs are beyond the scope of fundraising, Kluge has said.

Plans are to give the Malayan tigers more space by creating a tiger conservation center that will educate the public about the endangered species. There are only 300 left in the world, said Kluge.

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The zoological society has been in talks with a Tucson company that creates overhead crossing trails, like one at the Cleveland Zoo. The society is also considering other ideas, including a treetop playground where children would be at treetop-level and eye-to-eye with lemurs that are crossing through trails.

It also is considering have hippos with underwater viewing, and the society wants to build an African safari lodge where, from the second-floor, people would be able to view giraffes, elephants and rhinos.

The zoo attracts 500,000 visitors a year, and Kluge said it is "the largest attended cultural attraction in Southern Arizona."

Critics say a sales-tax increase is the wrong way to finance such changes, especially since not all who would pay the tax support the concept of zoos or visit Reid Park's.

In an earlier story, critic Robert Reus said he believed the people who support the zoo should donate the funds for it. He said the zoo uses city land tax free, the staff is paid by the city and the zoo itself is already subsidized very heavily. Reus said he does not object to those subsidies.