Somehow, Sri Lanka snuck them through customs. No part of their convoy was delayed or detained. Not even New Zealand's biosecurity officers - a more fastidious breed than most - were wise to their transit. As of Tuesday afternoon, all five specimens had arrived intact in Christchurch ahead of the first Test.
Though their official names are long and unpronounceable to most in the country, their wrangler, Chaminda Vaas, believes they can thrive in these conditions. They hope to do as well as the other invasive breeds to make New Zealand's shores. Like the possum or the European rabbit, Sri Lanka's pace quintet of Suranga Lakmal, Shaminda Eranga, Dhammika Prasad, Nuwan Pradeep and Dushmantha Chameera are well-placed to raise hell when set loose, Vaas said.
"All five seamers on tour have a lot of ability," he said. "It's very rare that we get five guys together who can all bowl 140kph. The conditions in New Zealand are great for quicks, and as a seamer you are overjoyed when you see tracks like what you have here, because you don't get that in Sri Lanka. The pitches give you swing, and then if you bowl well, you can trap batsmen."
Vaas knows plenty about prospering in New Zealand. Of the nations he played in, he was most efficient in New Zealand, taking 36 wickets at an average of 22.55. Sixteen of those scalps came in 1995, when Vaas led Sri Lanka to their first-ever away series win, and as on that tour, he was largely the sole seam threat through his career. With a core cordon of quicks of roughly equivalent age and ability now having developed, the new group has an opportunity to become the best pace attack Sri Lanka have fielded, he said.
"Being a fast bowler is all about learning and adding to your game. We share a lot among the group, and that's when we develop together. What I try to tell the guys is to think about how you can be better than the other bowlers. That's not to encourage jealousy or disunity - but to try and help us as a group to raise our standards. You have to be thinking that when someone else gets five wickets, you also want to get five. When you have that mentality and that competition, it's easier to get wickets on any pitch.
"They all have a responsibility to look after themselves, in terms of diet and discipline, because the demands of the international game are high. Their fitness has to be at an optimum level all the time, and their mental approach has to be the same. That's what they need to do to get the best out of themselves, and the rest is up to their ability and the conditions."
Sri Lanka have been reliant on Rangana Herath's left-arm spin since Muttiah Muralitharan's retirement, but have this year begun to bank on their quicks as well. Their three overseas Test wins in 2014 - in Dubai, Dhaka and Leeds, have all been largely forged by the quicks. With the exception of uncapped Chameera, each of the other fast bowlers have played key roles in Sri Lanka's recent Test successes.
"In England we didn't have Suranga, and now that he is back, it is a big strength," Vaas said. "After Lasith Malinga, he is the guy who is in a similar place. His rhythm is excellent, and the other bowlers have something to learn from him."
Control and modest movement have been the Sri Lanka quicks' hallmarks this year, but Prasad's inclusion for the Headingley Test injected some hit-the-deck intensity that paid dividends on the fourth afternoon when he claimed four top-order wickets in one spell to set up that victory. No fast bowler in the attack has yet played more than 21 Tests, but Sri Lanka pose a varied threat nonetheless, Vaas said.
"Suranga gets swing at pace and is a wicket-taking threat all the time. Eranga is very similar. None of these bowlers are very experienced, which is why it's imperative that they improve every time they play. Dhammika Prasad has been in the team for a while, but he has only recently been able to play at a stretch because of his injuries. Thankfully he has been able to get his body 100%, and is at a very good fitness level.
"They all have minor differences, but in key criteria, they are the same: they all bowl 140, they can all do something with the ball, and they have good control. Dhammika is a little different, because he hits the deck and then gets movement, while Suranga and Eranga move it more in the air."
Chameera, 22, took 3 for 13 in the warm-up match on a Queenstown greentop, but is unlikely to be in the XI on Boxing Day. Described by some coaches as the quickest young bowler in Sri Lanka's domestic circuit, Vaas believed him to be an outstanding prospect.
"He's very talented and quite raw. Even though he doesn't have much experience, he bowled very well in the last match. In a year, I trust he will be able to hit that 150kph mark. He just needs to take good care of his body, his rest, his diet and his mental approach."
Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando