The illegal trade in wildlife has been described as the second largest criminal activity next to drug smuggling in terms of profits.
It has been the focus of international operations by Interpol and wildlife enforcement authorities, customs and police around the world and is monitored by organisations such as Traffic.
Mr Shepherd said the illegal trade in reptiles had increased rapidly in the past few years and "once in a while" he heard of reptiles coming from New Zealand.
"There needs to be a lot of work on the extent. We should be looking at New Zealand and what is happening there as far as the global reptile trade [is concerned]."
There were three main areas of trade in reptiles: for meat, mostly involving large reptiles, such as turtles and tortoises, which were bound for China; for leather, again involving large reptiles, such as crocodiles, pythons and cobras, bound for China, European Union, North America and Japan; and the pet trade.
The pet trade had taken off "insanely" in the past five years, Mr Shepherd, who is based in Southeast Asia, said.
"The number of species, the volume, the numbers of people, legitimate and illegal, involved is astronomical."
In Southeast Asia, the main problem until recently had been importing rare reptiles, but now it was the export of animals such as geckos and snakes to Japan, the EU and North American collectors.
"They continue to want more exotic and rare species. The rarer the species, the higher the price."
The growing middle class in Southeast Asia was becoming increasingly interested in collecting reptiles.
Prices could range from a few dollars to tens of thousands of dollars each, depending on how rare or exotic the animal was.
"Some buy for colour, others [for] variations in mutated colours."
The closer to extinction as a species the animal was, the higher the price it fetched.
"It is increasing the pressure on the few remaining in the wild."
Traffic kept a close eye on trends in wildlife smuggling and informed authorities on issues such as new smuggling techniques.
The most common way for reptiles to be smuggled was as animals purportedly bred in captivity, followed by smugglers hiding them in their clothing pockets or under a shirt.
"They don't set off metal detectors and [smugglers] just hop on a plane. Just one or two pays for a flight. It happens a lot."
Other common ways of smuggling reptiles included wrapped in cloth in suitcases, although there were more extreme methods, such as the man caught smuggling an iguana out of Fiji in a false leg.
While authorities were having some success in stopping big shipments of illegal wildlife, it was still a losing battle, he said.
"Reptiles are moving through airports all the time. And the internet - everything is for sale there."
There were pet stores, internet websites and other companies selling reptiles. While some sales were legal, there was also a large volume of illegal species being traded.
"There are markets in parts of Jakarta that openly display completely illegal species."
There were similar markets in other parts of Southeast Asia.
"As long as these big markets are operating, those open sales will continue. It boggles my mind these markets still exist."
Laws were improving, with many nations strengthening wildlife smuggling laws.
Interpol co-ordinated a worldwide operation last September combating the illegal trade in reptiles and amphibians, resulting in the seizure of thousands of animals and products worth more than 25 million ($NZ46 million).
Secretary-general of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cities) John Scanlon said in an Interpol release the fact Interpol helped co-ordinate such worldwide operations illustrated the level of serious criminality commonly linked to the illegal trade in wildlife.
