The world's largest hunting group will begin its annual convention in Las Vegas today, where around 20,000 hunters from the world will take part in a major trophy hunt auction.

The killing of at least 600 animals in 32 counties is on offer at the Safari Club International auction, 28 of those are in New Zealand.

International Trade Policy specialist for Humane Society International Masha Kalinina said very few realize the scale of trophy hunting in New Zealand.

She said a huge part of the group's budget comes from these auctions.

"The New Zealand species that will be trophy hunted are essentially funding this group, and what the group does with its money is fight conservation measures around the world."

Ms Kalinina said some of the animals on offer are classified as vulnerable, and some are threatened with extinction.

"The conservation of these species is critical, and we believe that trophy hunting does not have conservation value for any species.

"If they are hunting those that are being threatened with extinction, they are threatening the survival of the very species."

But National President of the New Zealand Deerstalkers Association Bill O'Leary said a significant proportion of the money raised at the auction would go towards global conservation efforts.

"There are parts of the world where the money coming in from hunting is the sole source of income which goes to protect some endangered animals."

O'Leary said hunting in New Zealand brings in a tremendous amount of money, and is just a fact of life.