The four caribou herds on the Kenai National Wildlife Refuge are the result of reintroduction efforts by the U.S. Fish and Wildlife Service and Alaska Department of Fish and Game in the 1960s and again in the 1980s.  Caribou, by all reports an endemic woodland population (Rangifer trarandus stoneii), were originally present on the Kenai Peninsula until their extirpation circa 1912 due to a combination of overhunting and habitat loss from human-caused fires. Subsequent reintroduction efforts used barrenland caribou captured from the Nelchina herd near Glenallen, Alaska.  The first reintroduction resulted in the establishment of the Kenai Mountain and Kenai Lowland herds; the second effort established the Killey River and Fox River herds.

The Kenai Mountain herd numbers 200-400 caribou.  It inhabits the northeastern portion of the Refuge, ranging over 350 square miles from the Chickaloon River, Big Indian Creek, and Resurrection Creek drainages in Game Management Unit 7 on the east side of the Sterling Highway. Hunting is currently allowed in this herd through the Alaska Department of Fish and Game drawing permit system (see current ADF&G hunting regulations for details) and for qualified Federal subsistence users (see current Federal Subsistence Regulations for details).

The Kenai Lowland herd numbers 130-150 caribou.  The herd ranges over 550 square miles, wintering in the Kenai Lowlands on the Refuge, but calving in and around Kenai River Flats. This population is vulnerable to vehicular collisions and harassment by dogs as it migrates in and around the communities of Sterling, Soldotna and Kenai.  Hunting is currently not allowed in the Kenai Lowland herd.

The Killey River herd numbers around 250 caribou and occupies 300 square miles in the upper Killey, Funny and Skilak River drainages on the Refuge.  This herd once numbered over 700 animals until three avalanches in 2001-03 killed about ~200 caribou. Hunting is currently allowed in the Killey River herd through the ADF&G drawing permit system.

The Fox River herd numbers 50-75 caribou, ranging over 50 square miles south of the Tustumena Glacier in the Upper Fox River and Truli Creek drainages.  This herd appears to be expanding its range eastward into the ice fields of Kenai Fjords National Park.  Hunting is currently allowed in the Fox River herd through the ADF&G drawing permit system.

Refuge biologists, working with the Alaska Department of Fish and Game and Chugach National Forest, help monitor and manage caribou populations in GMUs 15 and 7 guided by the 2003 Caribou Management Plan.  This plan specifically caps desired caribou population densities at 2 caribou per square kilometer to prevent degradation of alpine tundra, a minimum fall count of 20-25 calves:100 cows, and a minimum post-hunting season ratio of 30-40 bulls:100 cows. Aerial surveys are conducted somewhat opportunistically when caribou congregate for spring calving and fall breeding.  Kenai Peninsula caribou can be difficult to count as they do not congregate as tightly as larger herds elsewhere in Alaska. Consequently, radio collars are used to locate individual caribou after which an expansive aerial search of the area is flown to count all observable adults (bulls and cows), calves, and yearlings.  Aerial caribou surveys are minimum counts without error estimation.