Harare - This is why you should never throw used car tyres into a water source - especially if there's wildlife nearby.Vets called out Saturday to a special rhino protection zone more than an hour away from Harare had to free a white rhino who'd got a car tyre stuck round his snout.Rangers in the rhino protection zone thought dominant bull "Mark" would be able to dislodge the tyre himself.But as he got more and more frustrated, the tyre got more and more stuck behind his horn stub (all the rhinos in this park were dehorned last month)."Mark's mouth was bound firmly shut and he couldn't eat or drink," AWARE trust vets Keith Dutlow and Lisa Marabini said in a post to Facebook.Happily, they managed to free him in record time.Watch the video by Aware Trust Zimbabwe here. "We found Mark... lying close to his girlfriends, looking decidedly dejected and exhausted from his ordeal on this scorching hot day.""A dart was quickly placed, and a few minutes later he was down. Fortunately the tyre came off in a few minutes with man power, and we did not have to resort to cutting through it," the vets said."Eleven minutes later he was anti-doted and grazing again as if nothing had happened," they added.Drought has caused water levels to drop significantly in a number of Zimbabwean dams.News24 reported earlier that fish were dying in such big numbers in two dams in the Matopos area of southern Zimbabwe that the state wildlife authority had taken the unusual step of trying to relocate the fish.In Mark's case, the vets say that the tightly-guarded bull obviously "fancied" some vegetation out in the shallow water but didn't see the tyre that had washed up there too."Once he stuck his nose to the ground to grasp it, the tyre came up over his horn stub," the vets said.Lake Chivero - near where this rhino lives - is sadly extremely polluted. In 2012, Zimbabwe's state media acknowledged that it was one of the 10 most polluted lakes in the world.With water levels at the lake at their lowest in 20 years, conservationists organised a clean-up of the lake at the beginning of this month.