Sylvilagus bachmani (Waterhouse, 1839)

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Leporidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 107-148 : 114-115

11.

Brush Rabbit

Sylvilagus bachmani

French: Lapin de Bachman / German: Strauchkaninchen / Spanish: Conejo de matorral

Other common names: Riparian Brush Rabbit

Taxonomy. Lepus bachmani Waterhouse, 1839 ,

“between Monterey and Santa Barbara.” Restricted by E. W. Nelson in 1909 to “San Luis Obispo,” California, USA.

Previously, S. bachmani and Brachylagus idahoensis were in the genus Microlagus. Insular S. mansuetus occurring only on San Jose Island (Baja California) derived from S. bachmani . Sylvilagus bachmani and S. mansuetus are the only species of Sylvilagus known to have retained the putative ancestral karyotype (2n = 48), shared by all known species of Lepus and Romerolagus . As taxonomists are still trying to clarify the species differentiation in Sylvilagus , the subspecific taxonomy is not elaborated yet. Firstly, the original descriptions of the subspecies are often not very helpful as they are mostly based on few exterior characteristics and small numbers of individuals. Secondly, the extent of variation has not been studied yet. Thus, researchers cannot understand if this exact feature is some important diagostic mark or just an individual or age-specific variation. Moreover, it has been shown that the variability is clinal in more careful investigations. Hence, the distinction in subspecies might be arbitrary and unreasonable. Thirteen subspecies recognized.

Subspecies and Distribution.

S.b.bachmaniWaterhouse,1839—SpartofcoastalCWCalifornia(SWUSA).

S.b.cerrosensisJ.A.Allen,1898—CedrosI,BajaCalifornia(NWMexico).

S.b.cinerascensJ.A.Allen,1890—SWCalifornia(SWUSA).

S.b.exiguusNelson,1907—BajaCaliforniaexcepttheN(NWMexico).

S.b.howelliHuey,1927—NEBajaCalifornia(NWMexico).

S.b.macrorhinusOrr,1935—NpartofCWCalifornia(SWUSA).

S.b.mariposaeGrinnell&Storer,1916—EpartofCCalifornia(SWUSA).

S.b.peninsularisJ.A.Allen,1898—BajaCaliforniaSur(NWMexico).

S.b.ripariusOrr,1935—WpartofCCalifornia(SWUSA).

S.b.rosaphagusHuey,1940—NWBajaCalifornia(NWMexico).

S.b.tehamaeOrr,1935—SWOregon,andNCCalifornia(WUSA).

S.b.ubericolorMiller,1899—WOregon(SoftheColumbiaRiver)andNWCalifornia(WUSA).

S. b. virgulti Dice, 1926 — S part of inland CW California.

Descriptive notes. Head-body 300-370 mm, tail 10-30 mm, ear 50-60 mm, hindfoot 71-86 mm; weight 511-915 g. The Brush Rabbitis one of the smaller species of Sylvilagus . Dorsal fur is dark brown to gray-brown; ventral fur is whitish. Hindlegs are short, and hindfeet are slender. Ears are small, slightly pointed, and sparsely haired inside. Tail is small, dark above, and white below. Sexual dimorphism exists with females being 1-2-1% larger than males. Fetal sex ratio is essentially 1:1, but adult sex ratios are 80-8-128 males:100 females.

Habitat. Dense brushy cover from sea level to elevations of at least 2070 m. The Brush Rabbit is confined to brushy habitat, as its common name implies.

Food and Feeding. Brush Rabbits feed mainly on grasses, and diets vary according to season and region. In September, they feed on spike rush ( Eleocharis palustris , Cyperaceae ) and grasses ( Poaceae ) such as creeping eragrostis ( Eragrostis hypnoides), foxtail grass ( Hordeum murinum), soft chess grass ( Bromus hordeaceus), and oats ( Avena fatua). Summer diets include wild roses ( Rosa californica, Rosaceae ), Mexican tea ( Chenopodium ambrosioides, Amaranthaceae ), and several plants in the daisy family such as sow thistle ( Sonchus asper), bull thistle ( Cirsium lanceolatum), and Baccharis douglasii; rush ( Juncus sp. , Juncaceae ); and berries ( Rubus sp. , Rosaceae ). In autumn, roots of poison hemlock ( Conium maculatum), stems and leaves of blackberry (R. vitifolia), and berries ( Rubus sp. ) also are eaten. In winter, green clover ( Trifolium involucratum, Fabaceae ) is most preferred, along with new available green grass. Brush Rabbits rarely feed in the open on the mainland, but they prefer to feed in the open and rarely underbrush on Ano Nuevo Island. Before venturing into the open to feed, individuals remain for a while just inside dense brushy cover. After entering an open area next to brushy cover, individuals remain motionless for some time, apparently watching for signs of danger. Several individuals might simultaneously feed in the same area. They rise up on their hindfeet to feed on newly grown tips of plants.

Breeding. Breeding season of the Brush Rabbit varies from north to south. In California, it lasts from December to May or possibly June, but in Oregon, it lasts from February to August. Gestation lasts 24-30 days, averaging 27 days. Young are born with fine thin hair, do not open their eyes for c.10 days, and suffer postpartum weight loss. Females give birth in nests with cavities of 7.5-15 cm. Nests are lined mainly with hairs from mothers and small amounts of dried grass; nests are closed with plugs constructed of grasses. Young are nursed at night, grow rapidly, and stay in their nests for c.2 weeks. The Brush Rabbit is believed to breed shortly after giving birth, and different females in a population might breed at the same time. Brush Rabbits might have three litters per year in California, but four litters might be possible. Litter size also varies among regions; mean litter size is three in Oregon, 3-5 in northern and central California, and four in west-central California. Juveniles reach maturity at 4-5 monthsold, but it is thought that they reproduce for the first time in reproductive seasons following their births. In Oregon, a female Brush Rabbit produces an average of 15 young/ year in 5-3 litters. Brush Rabbits may not be as fecund as other species of Sylvilagus .

Activity patterns. Brush Rabbits are basically crepuscular, being most active between sunset and 02:00 h and again from ¢.06:00 h to 10:30 h. Some reports suggest that most activity occurs in the morning. Individuals are least active between 11:00 h and 16:00 h. They spend considerable time sunning, usually in the mornings or afternoons. After feeding, Brush Rabbits return to a form for grooming and basking in the sun. They might climb trees for resting.

Movements, Home range and Social organization. The Brush Rabbit occasionally uses burrows but does not dig its own. Holes and forms in brush also are used. Forms are cleared places, and a maze of extensively used runways connects forms. Runways of voles (Microtus) and harvest mice (Reithrodontomys) were used in June/July in California, and “huts” of Wood Rats (Neotomafuscipes macrotis) also were used. In Oregon, Brush Rabbits live in disjunct patches of brambles, and sizes and shapes of home ranges conform to sizes and shapes of bramble patches. Brush Rabbits did not permanently occupy patches smaller than 460 m?. Home ranges were less than 2000 m? and depended on uniformity of habitat. Males had larger home ranges than females, and juvenile males had larger home ranges than adult males. Home range sizes of reintroduced individuals were similar among males and females and were larger in the breeding season than during nonbreeding. Thumping the ground with hindfeet often occurs just after individuals are frightened; some thumpfor several minutes before stopping. Brush Rabbits emit squeals and cries as vocalization. Young have been reported to squeal. Minimum distance that individuals can approach one another without resulting in a chase is 0-3-7-5 m—lower distances reported forjuveniles. Nose sniffing and touching often precede a chase.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Brush Rabbit is abundant throughout most ofits distribution, and most populations do not appear to be experiencing significant declines. It is a game species in Oregon and California but is hunted little. The subspecies riparius living in the San Joaquin Valley, California, has been listed as endangered by the State of California and the US Fish and Wildlife Service due to decline caused by habitat degradation, wildfires, and flooding. Major threats to the Brush Rabbit are hunting for food and expansion of human settlements, but extent and severity of these threats have not been quantified.

Bibliography. AMCELA, Romero, Rangel & Williams (2008), Angermann (2016), Cervantes, Vazquez & Colmenares (2005), Chapman (1971a, 1971b, 1974), Chapman & Ceballos (1990), Chapman & Harman (1972), Connell (1954), Davis (1936), Dice (1926), Gander (1929), Hall (1951, 1981), Hoffmann & Smith (2005), Kelt et al. (2014), Lissovsky (2016), Mossman (1955), Nelson (1909), Orr (1940, 1942), Pearson (1959a), Shields (1960), Verts (1967).

Figures

33. Indian Hare (Lepus nigricollis), 34. Burmese Hare (Lepus peguensis), 36. Scrub Hare (Lepus saxatilis), 37. African Savanna Hare (Lepus victoriae), 38. Yarkand Hare (Lepus yarkandensis), 39. Ethiopian Highland Hare (Lepus starcki), 40. Cape Hare (Lepus capensis), 41. Abyssinian Hare (Lepus habessinicus), 42. Tolai Hare (Lepus tolai), 43. Desert Hare (Lepus tibetanus), 44. Yunnan Hare (Lepus comus), 45. Woolly Hare (Lepus oiostolus), 46. Snowshoe Hare (Lepus americanus), 47. Black-tailed Jackrabbit (Lepus californicus), 48. Black Jackrabbit (Lepus insularis)

Subspecies and Distribution. S.b.bachmaniWaterhouse,1839—SpartofcoastalCWCalifornia(SWUSA). S.b.cerrosensisJ.A.Allen,1898—CedrosI,BajaCalifornia(NWMexico). S.b.cinerascensJ.A.Allen,1890—SWCalifornia(SWUSA). S.b.exiguusNelson,1907—BajaCaliforniaexcepttheN(NWMexico). S.b.howelliHuey,1927—NEBajaCalifornia(NWMexico). S.b.macrorhinusOrr,1935—NpartofCWCalifornia(SWUSA). S.b.mariposaeGrinnell&Storer,1916—EpartofCCalifornia(SWUSA). S.b.peninsularisJ.A.Allen,1898—BajaCaliforniaSur(NWMexico). S.b.ripariusOrr,1935—WpartofCCalifornia(SWUSA). S.b.rosaphagusHuey,1940—NWBajaCalifornia(NWMexico). S.b.tehamaeOrr,1935—SWOregon,andNCCalifornia(WUSA). S.b.ubericolorMiller,1899—WOregon(SoftheColumbiaRiver)andNWCalifornia(WUSA). S. b. virgulti Dice, 1926 — S part of inland CW California.