Sylvilagus aquaticus (Bachman, 1837)

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 : 119

16.

Swamp Rabbit

Sylvilagus aquaticus

French: Lapin aquatique / German: Sumpfkaninchen / Spanish: Conejo de ciénaga

Other common names: Cane-cutter

Taxonomy. Lepus aquaticus Bachman, 1837 ,

“...western parts of that state.” Restricted by E. W. Nelson in 1909 to “Western Alabama,” USA.

Genetic analysis showed that S. aquaticus and S. palustris are sister taxa. As taxonomists are still trying to clarify the species differentiation in Sylvilagus , the subspecific taxonomy is not elaborated yet. 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. It has been shown that the variability is clinal in more careful investigations. Hence, the distinction in subspecies might be arbitrary and unreasonable. Two subspecies recognized.

Subspecies and Distribution.

S.a.aquaticusBachman,1837—NoftherangefromSEKansas,SMissouri,andSIIlinois,SEtoWtipofNorthCarolinaandNWGeorgia,andStoAlabama,Mississippi,Louisiana,andTexas(SEUSA).

S. a. littoralis Nelson, 1909 — coastal Gulf of Mexico section of the range in SE Texas, S & E Louisiana, SE Mississippi, and SW tip of Alabama (S USA).

Descriptive notes. Head-body 450-550 mm, tail 50-74 mm, ear 60-80 mm, hindfoot 90-113 mm; weight 1:6.2-7 kg. The Swamp Rabbit is the largest species of Sylvilagus . Ears are medium-sized in relation to body size. Head and dorsal fur are dark and rusty brown to black. Ventral fur, throat, and tail are white. There are distinctive cinnamon eye rings. Swamp Rabbits are not sexually dimorphic, but there is probably a latitudinal size gradient.

Habitat. Primarily swamps, areas adjacent to rivers, floodplains, and lowland areas. In the northern part of their distribution, Swamp Rabbits inhabit mature forests, fiveyear-old regenerating forest tracts, and canebrake ( Arundinaria gigantea, Poaceae ) communities at about the 24°C isotherm. They are never far from water. Forms and runways are found in tangled marsh vegetation and brier bushes. Holes in the ground or in trees but also stumps, logs, low crotches oftrees, tangles, cane patches, and open grassy places are common form sites . Elevated objects such as logs are used as defecation sites, and these latrines probably serve as territorial markers. Hence, elevated objects are important habitat requirements. The nominotypical subspecies aquaticus is associated with mature forests, but littoralis is associated with coastal and riparian areas.

Food and Feeding. The Swamp Rabbit feeds on a variety of plants. One study reported that plants eaten in order of preference were crossvine ( Bignonia capreolata, Bignoniaceae ), sedges ( Cyperaceae ), poison ivy ( Rhus radicans, Anacardiaceae ), grasses ( Poaceae ), catbriers ( Smilax sp. , Smilacaceae ), and tree seedlings. Another study showed that plants were eaten according to their relative availability and were mainly sedges ( Carex lupulina) but also blackberry ( Rubus sp. , Rosaceae ), hazelnut ( Corylus sp. , Betulaceae ), deciduous holly (Zlex deciduas, Aquifoliaceae ), and spicebush ( Lindera benzoin, Lauraceae ).

Breeding. The Swamp Rabbit is a postpartum synchronous breeder, with estrus lasting generally less than an hour. A series of behaviors precedes estrus: the female chases or threatens males, and males dash and preform a jump sequence. The male chases the female before copulation. Gestation lasts 35-40 days, with 36-37 days being most common. Timing of reproduction varies slightly throughout the distribution of the Swamp Rabbit. Breeding season is longest in the south-central USA and becomes progressively shorter with increasing latitude. Breeding is year-round in Texas but starts in mid-February and ends in August in northern Alabama. Captive females build their nests against or under fences, bases of trees, and wooden structures. Some nests were built a few days before parturition, but others were built the same night. Females regularly build dummy nests but only one-half as many dummy nests as active nests. Young are sometimes scattered among nests at birth. The female lines a nest with her abdominal fur. One female lined her nest with fur just prior to giving birth and began nursing immediately after birth. Most nursing occurred at dawn and dusk, and nursing periods lasted 10-20 minutes. Young continue to nurse after leaving the nest. One nest found in the wild was built on top of the ground in a heavy weed patch, with stalks of dead weeds pulled around an inner lining of fur. Nests are 4-7 cm deep, 15 cm wide, and 18 cm high, and they have side entrances. Meanlitter sizes of Swamp Rabbits vary by region but are 1-6 young, with three young most common.First litters are smaller (e.g. 2.7 in Missouri and 2-8 in Alabama) than second litters (4-1 in Missouri and 3-2 in Alabama). Yearling females may produce largerlitters and more litters per year and thus might have a higher reproductive success than older females. Captive Swamp Rabbits had 1-5 young/year. Adult sex ratio is slightly shifted in favor of females (52-57%). Neonates have dark fur on back, and white fur ventrally and on abdomen. Eyes open at b—8 days of age, and young leave the nest at 12-15 days of age. Young born early in spring reach adultsize in December at ¢.10 months old; young born later in summer do not attain adult weight until the following spring. Juveniles are capable of breeding at 23-30 weeks old, but there are few reports ofjuveniles actually breeding.

Activity patterns. Onset of evening activity of Swamp Rabbits is delayed as sunset becomes progressively later in spring. Delay is greatest for females and lower ranking males. Time and onset of evening activity are variable but occur well before sunset in late spring and summer. In late winter and early spring, onset of evening activity occurs during twilight.

Movements, Home range and Social organization. Home ranges of Swamp Rabbits vary in size. Female home ranges were reported to be 0-5-2-4 ha; males were 1-8-4 ha. One study suggested that males were non-territorial in January—June because home ranges overlapped considerably; otherwise Swamp Rabbits are considered to be territorial. Swamp Rabbits are excellent swimmers. They are vocal, and males display pheromone marking (“chinning”). Social organization of captive individuals consists of two basic behavioral patterns: a linear dominance hierarchy among males that does not include females, and breeding groups of several individuals controlled by a dominant male. The male dominance hierarchy prevents fighting (and injury) among reproductively mature males; alpha-male Swamp Rabbits dominate males below them, particularly immediate subordinates. Subordinate males attempt to minimize contacts with higher ranking males. Number of dominance displays was directly correlated with social status of the male. Male movement and proximity to females were directly correlated with social status. The top two males were responsible for most of the male-female interactions, and the alpha male was responsible for most copulations. It has been suggested that dominant males maintain their status from year to year. Swamp Rabbits use various maneuvers to confuse pursuers. One behavior is to climb onto a log, walk along its length, then backtrack and jump to the side, traveling at right angles to the former course.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Swamp Rabbit is an abundant and important game species in the US states along the Gulf of Mexico. As a game species, harvest is regulated by state wildlife agencies. Habitat in northern parts of its distribution has been destroyed byits alteration and riparian drainages, and as a result, populations of the subspecies aquaticus have begun to decrease. Habitat fragmentation also impedes dispersal. Despite shrinkage of habitats of Swamp Rabbits on distributional peripheries, there are still large areas of prime habitat (e.g. in Louisiana). Populations also have been reported to persist in southeastern Missouri although its habitat has been greatly reduced. Swamp Rabbits occur in many protected areas, but only few studies have been conducted to determine their abundance orstatus.

Bibliography. Angermann (2016), Calhoun (1941), Chapman & Ceballos (1990), Chapman & Feldhamer (1981), Cockrum (1949), Halanych & Robinson (1997), Hall (1951, 1981), Hall & Kelson (1959), Hill (1967), Hoffmann & Smith (2005), Holler & Marsden (1970), Holler & Sorensen (1969), Holler et al. (1963), Holten & Toll (1960), Hunt (1959), Lissovsky (2016), Lowe (1958), Lowery (1974), Marsden & Holler (1964), Nelson (1909), Scheibe & Henson (2003), Smith, A.T. & Boyer (2008c), Smith, C.C. (1940), Sorensen et al. (1968, 1972), Svihla (1929), Terrel (1972), Toll et al. (1960), Vale & Kissell (2010), Zoliner et al. (1996).

Figures

16. Swamp Rabbit (Sylvilagus aquaticus), 17. Marsh Rabbit (Sylvilagus palustris), 18. Omilteme Cottontail (Sylvilagus insonus), 19. Common Tapeti (Sylvilagus brasiliensis), 20. Central American Tapeti (Sylvilagus gabbi), 21. Venezuelan Lowland Rabbit (Sylvilagus varynaensis), 22. Dice’s Cottontail (Sylvilagus dice), 23. Mexican Cottontail (Sylvilagus cunicularius), 24. Tres Marias Cottontail (Sylvilagus graysoni), 25. Eastern Cottontail (Sylvilagus floridanus), 26. Appalachian Cottontail (Sylvilagus obscurus), 27. Robust Cottontail (Sylvilagus robustus), 28. Manzano Mountain Cottontail (Sylvilagus cognatus), 29. Hispid Hare (Caprolagus haispidus), 30. Bunyoro Rabbit (Poelagus marjorita), 31. European Rabbit (Oryctolagus cuniculus)

Subspecies and Distribution. S.a.aquaticusBachman,1837—NoftherangefromSEKansas,SMissouri,andSIIlinois,SEtoWtipofNorthCarolinaandNWGeorgia,andStoAlabama,Mississippi,Louisiana,andTexas(SEUSA). S. a. littoralis Nelson, 1909 — coastal Gulf of Mexico section of the range in SE Texas, S & E Louisiana, SE Mississippi, and SW tip of Alabama (S USA).