11/22/2013 02:13 pm ET Updated Jan 25, 2014

Jungle Beat: Invasive Deer Threaten Fragile Ecosystems

Hunters love them, as do those who eat venison. But the Axis deer can wreak havoc in Hawaiian ecosystems, where it has no natural predators.

The Axis deer comes from India and other nearby countries. It's a fairly small animal, with a pink-tinged coat spotted with white. Adult males can reach about three feet tall at the shoulder and weigh as much as 170 pounds, with females running a little smaller.

How Did They Get Here?

Axis deer have been in Hawaii, Molokai specifically, since the 1860s when Hong Kong presented some as a gift to King Kamehameha V. They also live on Lanai and in large numbers on Maui, where they were introduced in the 1950s. So far only a small number have been reported on the Big Island since their discovery in 2011.

How on earth does an animal like this "accidentally" arrive on our island? Well, it doesn't. Axis deer have been flown in by helicopter, illegally, as recently as 2009, when a hunting tour operator arranged a deer-for-sheep swap with a Maui rancher. In 2012, the pilot pled guilty to transporting four of these deer from Maui to the Big Island. All three conspirators were convicted under the Federal "Lacey" act. It is also against Hawaii law to intentionally transport or release any kind of feral deer.

Kinds of Damage They Cause

Also called Chital deer, these creatures eat grasses, flowering plants, some fruit and tree branches. In the parts of Hawaii where they exist without controls, their population has been known to increase 20 to 30 percent each year. During periods of drought, they may form herds of more than 1000, destroying all crops or rangeland in their path. They also strip bark from trees for the water it contains. The Hawaii State Department of Land and Natural Resources' Division of Forestry and Wildlife (DOFAW) states that their existence presents, "a serious problem with far-reaching economic and environmental impacts to the agriculture industry and native ecosystems on the island." For example, fences eight feet high would have to be built to keep the deer out of farms and native plant conservation areas, making the construction costs astronomical.

According to Springer Kaye, Manager of the Big Island Invasive Species Committee, "If deer become established here, the cost of refitting conservation fences required by the Federal Endangered Species Act has been estimated at 18.7 million dollars. These are public tax dollars that are sorely needed elsewhere. Most farmers, including Kona coffee farmers, will never be able to afford eight foot fences, and will be driven out of business."

In June 2011, the Honolulu Star Advertiser reported, "In Maui County last year, herds of axis deer devastated crop areas, damaging production of vegetables, cane, pineapple and grapes, and wiping out forage areas that would have supported cattle during the drought. Financial losses to agriculture and impacts to the environment will persist and increase, as will deer-vehicle collisions." Axis deer damage costs approximately 750,000 dollars a year on Maui.

How Can We Control This Invader?

Kanalu Sproat, Axis deer coordinator with the Maui Axis Deer Working Group, said, "fencing is an effective control method, but not many people can afford it. Spotlight shooting as part of an Animal Damage Control Permit issued by DOFAW is another method that is applied, as are organized hunts." On Maui, control is all that can be hoped for, because the number of deer is too large for complete eradication to occur. Some species of animals have been successfully controlled through contraceptive drugs given to them in baited food or through capture, inoculation and release. However, the Axis deer is not a good candidate for this method because, according to the Star Advertiser, they are "cryptic and skittish, and locating animals and successfully administering treatments to the recommended 70-90 percent of the island population of female deer every few years to achieve zero population growth is mathematically and physically impossible."

Kaye added, "On the Big Island, hunters employed by the Big Island Invasive Species Committee and advised by the multi-agency Big Island Deer Working Group have located and dispatched four deer in the vicinity of the site where the helicopter released them in 2009. Our deer team relies heavily on reports provided by members of the public to find the handful of deer on the Big Island's 2.5 million acres. Public cooperation and support for deer eradication has been overwhelming."

What You Can Do

Report any sightings of Axis deer on the Big Island to the Axis Deer Hotline (808) 443-4036. If you're a hunter, keep up the good work.