Ungulates of Hawaiʻi

Black-tailed Deer

(Odocoileus hemionus)

Range: Kauaʻi

Region of origin: Continental United States (Oregon)

Date of first introduction: 1961 (35 individuals introduced to Kauaʻi)

Average size: Female - 35 to 45kg, Male - 45 to 65kg

Litter frequency: 1 litter per year

Litter size: 1 to 2 (twinning common, triplets rare)

Home range: 0.3 km to 138.5 km

Diet: Opportunistic grazer on broadleafs, ferns, and fruits

2

References: Tomich 1986, Innes 2013

Identifying Markers

Physical Appearance: Reddish-brown coat in summer and gray in winter, a short, wide tail with a black top and white underside, and large, mule-like ears (pictured).

Tracks: Two-toed cloven hoof prints, shaped like an upside-down heart, about 2–3 inches long.

Scat: Droppings are small, oval pellets, dark brown or black, left in scattered clusters, typically found along trails, bedding areas, and near browse zones.

Browse Lines: Feeds on leaves, shrubs, and saplings up to 5 feet high, leaving twigs with clean 45 degree angled snips.

Environmental Impacts

Black-tailed deer in Hawaiʻi, especially on Molokaʻi, cause significant environmental damage by browsing heavily on native shrubs and saplings, which hinders forest regeneration and reduces plant diversity. Their preference for upland forests and shrublands puts pressure on rare and fragile ecosystems, leading to soil erosion and habitat degradation. Unlike axis deer, which graze in large herds, black-tailed deer browse more selectively but still contribute to the loss of culturally important plants and the decline of native bird habitats dependent on dense understory vegetation.