Coast Black-tailed Deer
Odocoileus hemionus columbianus
An Edgewood visitor is almost guaranteed to see the graceful Columbian black-tailed deer, often found grazing in small family groups. Their gentle beauty is admired by all, even though they have a marked preference for eating wildflowers!
Appearance
These small deer have large, dark, mule-like ears, a gray face, slender, buff-colored legs, and a characteristic black tail. Their summer coat is reddish brown, changing to light grayish brown in winter. The fawn is spotted.
When mature, the buck (male deer) develops antlers in late spring and summer, and drops them in late winter after the mating season.
ID Tips
The Columbian black-tailed deer is smaller and darker than the larger Sierran subspecies Odocoileus hemionus californicus (California mule deer), which is not found in the Bay Area.
At Edgewood
Protected open spaces like Edgewood provide the space and resources deer need to live and raise their young. These camera-trap videos and images show Columbian black-tailed deer in action at Edgewood, including frolicking fawns, fawns following mom, and a leaping buck.
Check out iNaturalist for more observations of Columbian black-tailed deer at Edgewood.
Habitat and Range
In California, Columbian black-tailed deer range from coastal regions to western foothills, and from central to northern California. They prefer mixed habitat, with forested cover for protection and open areas for feeding.
Food Habits
As both grazers and browsers, deer graze a broad variety of grasses and forbs (herbaceous flowering plants), and browse the leaves of shrubs and small trees. They favor foods that grow rapidly because tender new growth is more easily digested, more nutritious, and is less likely to have potentially toxic or bitter secondary compounds than older growth. Acorns are a particularly rich food source and are especially valuable in the fall, when the deer are putting on fat prior to winter when food is scarce.
Typical Edgewood plants browsed by deer include currant (Ribes species), blackberry (Rubus species), arroyo willow (Salix lasiolepis), blue elderberry, chamise, buckbrush, poison oak, soap plant, and oak (foliage and acorns). And some of our favorite wildflower species!
According to Edgewood naturalist Paul Heiple, there are more deer in the preserve than the land can support without reducing its biodiversity. Native plants that are having trouble reproducing due to overbrowsing include blue oaks, valley oaks, and many perennial wildflowers. In the past, wolves and bears, as well as mountain lions, would have kept the deer population in check.
Predators
The major predators are mountain lions (Puma concolor), coyotes (Canis latrans), and bobcats (Lynx rufus). Coyotes and bobcats primarily prey on fawns.
Watch this buck, possibly fleeing a perceived threat, leap across a dry stream bed, from grasslands into the cover of oak woodlands.
Lifecycle
Columbian black-tailed deer breeding season typically begins in October and lasts to mid-December. Watch for bucks closely following does in late fall. A mated doe commonly gives birth to 2 fawns (sometimes only 1) in May or June, after a gestation period of about 7 months. Fawns have spotted coats and remain odorless and hidden for the first week of life. Within 4 months, fawns are weaned and lose their spotted coat. Deer typically live about 7-10 years.
When they are old enough, young bucks grow a set of antlers in the spring. The growing antlers are nourished by a velvety tissue until they reach full size for that year. The velvet then dries and starts to slough off. The buck aids this process by thrashing and rubbing antlers in shrubs and trees. (You might see branches and trunks at deer height that a buck has torn or mangled.) With bare, hardened antlers, a buck is now ready to spar with other males for dominance during rut (the breeding season). Bucks shed their antlers every winter after rut and grow a new larger set every spring.
Behavior
Deer are usually active morning and evening, and periodically through the night.
Columbian black-tailed deer form small family social groups consisting of an alpha (dominant) doe and her female relatives (typically a sister or a daughter), and the previous year’s fawns. The small social groups will stay in the same area most of their lives.
When a young buck reaches maturity, the alpha doe will drive him out of the family herd. A bachelor herd will also form for a short time in summer, which is when the buck defines his place in the hierarchy by sparring with other males.
Name Derivation
- Odocoileus – from the Greek odoús, “tooth,” and koîlos, “hollow,” referring to the hollow teeth of deer in this genus
- hemionus – from the Greek hēmĭ́onos, “half ass, mule”
- columbianus – Latin for “Columbian,” referring to western North America
Fun Fact
What is the difference between a buck and a stag? A buck is any male deer. A stag is a large, mature male deer.
Learn More
National Park Service. Horns versus antlers.
References
Alden, P. 1998. National Audubon Society Field Guide to California. Alfred A, Knopf. New York, and in Canada by Random House of Canada Limited, Toronto.
Feldhamer, G. 2003. Wild Mammals of North America: Biology, Management, and Conservation. The Johns Hopkins University Press, Baltimore, Maryland.
Hood, C. 2019. A Californian’s Guide to the Mammals Among Us. Heyday. Berkeley, California.
Innes, R. 2013. Odocoileus hemionus. Fire Effects Information System. United States Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
Jameson, E. 2004. Mammals of California. University of California Press, Berkeley and Los Angeles, California.
Morris, B. 2005, Apr. 1. The deer next door. Bay Nature.
Smith, K. 2000. Black-tailed deer of California. Western Hunter. J & D Outdoor Communications.
Wilson, D. 1999. The Smithsonian Book of North American Mammals. Smithsonian Institution Press, Washington and London.