The California mule deer (Odocoileus hemionus californicus) is a subspecies of Mule deer whose range covers much of the state of California.
Mule deer can be differed from their close relative the White-tailed deer by their ear size, tail color, and antler configuration. In many cases, body size is also a key difference. The Mule deer's tail is black-tipped, whereas the White-tailed deer's is not. Mule deer antlers are bifurcated; they "fork" as they grow, rather than branching from a single main beam, as is the case with white-tails. Each spring, a buck's antlers start to regrow almost immediately after the old antlers are shed.
This subspecies occurs throughout northern and central California in the California coastal prairie, as well as inner coastal ranges and interior mountains, especially the Sierra Nevada. These deer are much less frequently found on the floor of the interior valleys, and then mostly frequently in riparian zones. They prefer hill terrain, especially oak woodlands.
California mule deer are most active near dawn and dusk. They may also forage at night in open agricultural areas or when experiencing hunting pressure. They usually feed close to lakes or streams providing their water. From that water source, they may roam 1.6-3 km (1-2 mi) and typically make their beds in grassy areas beneath trees within 1-2 km (one-mile) radius from both water and forage. Repeatedly used beds often are scratched to a nearly level surface. On hot summer days, California mule deer often seek shade and rest in the midday. Females and their young usually forage together in family groups, while bucks tend to travel singly or with other bucks. Mule deer are strong runners but they are more often seen stotting (also called pronking), with all four feet coming down together.
California mule deer are herbivores mainly (folivores). Over 90% of their diet includes shrubs and leaves. In summer, they mainly browse on leaves of small trees, shrubs, and herbaceous plants, but also consume many types of berries (including blackberry, huckleberry, salal, and thimbleberry). In winter, they may supplement their diet with conifers, aspen, willow, dogwood, juniper, and sage. Year-round, they feed on acorns; grasses are a secondary food source.
California mule deer are polygynous and don’t form pairs. The rutting (breeding) season occurs in autumn when the females become ready to mate only for several days. During this time males become aggressive and compete for mates. The gestation period is about 200 days, with fawns arriving in the spring. Females usually give birth to 1 or 2 fawns. The young remain with their mothers throughout the summer and are weaned in the autumn. The male's antlers fall off in the winter and commence growing once more in spring in anticipation of next autumn's rut.
Today the most serious threat to wild Mule deer is the prevalence of Chronic Wasting Disease (CWD). This has been diagnosed in deer in the United States Rocky Mountains region, as well as other mid-western states. Further threats include great numbers of predator populations (e.g. feral dogs), competition for grazing with livestock, habitat loss, and other actions by humans. Their habitat in many regions is being lost, and in others dramatically fragmented, due to the human population growth, development, and natural events. Road construction, urban expansion, catastrophic wildfires, and the spread of invasive plant species also have led to habitat loss.
The IUCN Red List and other sources don’t provide the number of the California mule deer total population size. Generally, the Mule deer species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are stable.
