The Minnesota Zoo has begun an intense lobbying campaign for its nearly $35 million bonding bill request, which will ask the Legislature to fund an aerial walkway, a trolley system and critical infrastructure improvements at its 40-year-old campus.

“The biggest liability we have at this zoo is letting it get old all at once,” director John Frawley told the zoo’s board of trustees on Wednesday night. “If we get too far behind, we’ll never be able to catch up.”

Since taking the zoo’s helm last year, Frawley has shifted focus away from launching blockbuster exhibits toward more bite-sized investments that slowly revitalize what the zoo already has to offer. He hopes the change will result in more buy-in from a polarized Legislature that has shown little enthusiasm for a huge expansion project. (This year, the zoo received only $4 million of its total $24 million request.)

To garner support, zoo officials have led tours for the House Bonding Committee, Republican House members and Gov. Mark Dayton’s staff. This summer, experimental drones helped film a 3-minute promotional video of the zoo’s grounds and animals.

The effort comes amid sweeping changes to the zoo’s strategic plan, which emphasizes connecting guests with nature. The most ambitious plans involve converting the defunct monorail track into an aerial treetop walk — thought to be the first of its kind at an American zoo.

Repurposing the 1980s-era track into a boardwalk — like New York City’s popular High Line park — would provide a new viewing experience for guests, advocates say.

Officials initially hoped to pay for the project with private donations, but the zoo has asked for $5 million from the state to get moving. Also included in the $34.75 million bonding request: $4 million to reopen the nocturnal exhibit that closed in 2008; $9.5 million to renovate the main entrance and the drab snow monkey exhibit, and $2.5 million to fund mobilization, making the zoo more accessible via trolley.

If approved, the 2018 bonding bill would provide the largest lump sum of state aid in the zoo’s history.

Frawley also envisions adding campgrounds, hiking trails and an adventure course to the nearly 500-acre property in coming years.