Omilteme cottontails (Sylvilagus insonus) have a very limited distribution. They are found in the Sierra Madre del Sur, located near the small town of Omilteme, Guerrero, Mexico. Omilteme cottontails are an extremely rare species, with a geographic range of less than 500 km2. They occur sympatrically with Mexican cottontails (Sylvilagus cunicularius) and eastern cottontails (Sylvilagus floridanus). (Cerballos and Navarro, 1991; Diersing, 1981; Nelson, 1904; Nelson, 1909)
Sierra Madre del Sur is a semi-isolated mountain range near the small town of Omilteme, Guerrero, Mexico. Omilteme cottontails are restricted to this mountain range, which offers the humid, dense forests that they prefer. They live amongst dense undergrowth, tunneling to hide movement and digging under rocks or other object to create burrows. Omilteme cottontails are restricted to pine and pine-oak forests in the Sierra Madre del Sur mountains, which have elements of temperate forests such as pine species, oaks, and alders. (Diersing, 1981; Nelson, 1904; Nelson, 1909)
Omilteme cottontails are large rabbits with long ears, short tails and average sized hind feet. Only three specimens have ever been collected, so measurements and observations are based on a very small sample size. Their ears, which are estimated to be between 53 and 63.5 mm (measured from notch), are dark blackish-brown on the convex side with a black border and tip. The dorsal body is greyish-black with a mixture of rufous and black on the back and they have white ventral surfaces. The tail, which is between 30 and 45 mm, is reddish-black on the dorsal side and white on the ventral side. The hind feet have white tops with black soles. Omilteme cottontails lives sympatrically with Mexican cottontails and eastern cottontails, but are notably smaller in all measurements.
Omilteme cottontails have large skulls with a long palate, broad brain case, large maxillary and mandibular tooth rows, short diastema and incisive foramina, and a shallow skull depth. Omilteme cottontails have a dental formula of: incisors 2/1, canines 0/0, premolars 3/2 and molars 3/3, totaling 28.
Of the three collected specimens, measurements were taken of two. The two specimens had cranial and external measurements of: mean mass, 2.58 kg; mean body length (including the head but excluding the tail), 425 mm; mean length of the tail, 43 mm; mean length of hind foot, 94.5 mm; mean diameter of bullae, 9.1 mm; mean interorbital breadth, 17.6 mm; mean basilar length, 58.1 mm. (Diersing, 1981; Nelson, 1904; Nelson, 1909; Nowak, 1999; cervantes and lorenzo, 1997)
Nothing is known about Omilteme cottontail mating systems, although they are thought to be similar to other cottontail species, where males and females meet with multiple mates. (Hall, 1981; Lumpkin and Seidensticker, 2011; Nowak, 1999)
No reports of Omilteme cottontail reproduction exist. All female rabbits are thought to be induced ovulators, meaning they need stimulation of courtship and copulation to ovulate. Most Sylvilagus species have a gestation length of 28 to 30 days, generally with altricial young. Cottontails construct underground nests that they line with vegetation and shed fur. Breeding is seasonal, even for species living near the equator, generally from March to August. (Hall, 1981; Lumpkin and Seidensticker, 2011; Nowak, 1999)
No reports of Omilteme cottontail reproduction exist. Cottontails construct nests, generally underground, lined with vegetation and shed fur and nurse their young until they become independent at about 2 weeks old. Young cottontails are generally born in an altricial state. (Hall, 1981; Lumpkin and Seidensticker, 2011; Nowak, 1999)
The lifespan of Omilteme cottontails is not documented. It may be assumes that lifespan is similar to the closely related species Mexican cottontails and eastern cottontails, which are short lived. There is a general relationship among body size and longevity, as larger species generally live longer than smaller ones. Assuming this relationship holds, Omilteme cottontails are larger than eastern cottontails, so their lifespan may surpass the average age of eastern cottontails, which is 3 years. Omilteme cottontails are smaller than the larger Mexican cottontails, which live up to 5 years. Most cottontail species do not live past their fifth year in the wild. (Cervantes, et al., 1992; Diersing, 1981; Lumpkin and Seidensticker, 2011; Nelson, 1909)
Little is documented about Omilteme cottontail behavior. They are nocturnal and may be active at dusk and dawn as well. Most cottontails are asocial and solitary, only coming together during the breeding season or rare aggregations at feeding sites. (Cervantes, et al., 1992; Lumpkin and Seidensticker, 2011; Nelson, 1904; Nelson, 1909; Nowak, 1999)
Nothing is known about the home range of this species. (Cerballos and Navarro, 1991)
As with most aspects of its biology, there is little known about specific Omilteme cottontail communication. However, other cottontail species have superb olfactory, hearing, and visual systems. They often emit distress calls, squealing during copulation and grunting if an intruder is in sight. (Cervantes, et al., 1992; Hall, 1981; Lumpkin and Seidensticker, 2011)
Omilteme cottontails are herbivores. They may eat similar foods to the sympatric Mexican cottontails, which eat clumped grasses including Stipa ichu, Muhlenbergia macroura and Festuca amplissima. Preferred vegetation is tender grass shoots, cortices of shrubs, cultivated plants (such as oats, barley and maize) and young leaves of forbes. Omilteme cottontails may prefer slightly different foods, if there is ecological character displacement in these similar, sympatric species. They also engage in coprophagy. (Cervantes, et al., 1992; Diersing and Wilson, 1980; Lumpkin and Seidensticker, 2011; Luna and Bousquets, 1993; Nelson, 1909)
Humans are the only recorded predators of Omilteme cottontails. Pumas (Puma concolor), jaguars (Panthera onca), gray wolves (Canis lupus), coyotes (Canis latrans) and zone-tailed hawks (Buteo albonotatus) frequent the Sierra Madre del Sur region, and are likely predators of Omilteme cottontails. Like other rabbits, they are cryptically colored and can flee quickly for short distances. (Cervantes, et al., 1992; Chapman and Ceballos, 2013; Monroy-vilchis, 2013; World Wildlife Fund, 2013; cervantes and lorenzo, 1997)
Omilteme cottontails may impact their habitat through the plants they eat. They are also a food source for many predators (Hall 1981; Lumpkin and Seidensticker 2011). (Hall, 1981; Lumpkin and Seidensticker, 2011)
Omilteme cottontails are hunted by humans for their fur and for a food source and are now considered one of the most endangered rabbits in the world.
There are no known negative impacts of Omilteme cottontails on humans.
Omilteme cottontails are extremely rare due to their fragmented habitat and extremely restricted range in Sierra Madre del Sur, Guerrero, Mexico, which is less than 500 square kilometers in size. The last reported sighting of an Omilteme cottontail in the wild was in the early 1900’s; however, there was a possible sighting in 1991. This species was listed as extinct in 1990, endangered in 1994, and critically endangered in 1996. However, they are currently listed under the IUCN Red List Category as endangered, and critically endangered in the Mexican Official Norm, due to the recovery of a skin in 1998. Following the finding of this skin, a survey within the Omilteme cottontail range took place, approximately 52 days, which resulted in no Omilteme cottontail sightings.
Many sources consider the Omilteme cottontail to be extinct. Deforestation of the Omilteme cottontail habitat is seen as the main factor for their endangerment, or possible extinction. Previously, Sierra Madre del Sur was extensively logged, causing wide scale habitat fragmentation. Poaching is also a present concern. Though a natural reserve area, referred to as the Omiltemi State Ecological Park, currently covers the Omilteme cottontail habitat, illegal hunting of the Omilteme cottontail is still a concern. (Cervantes, et al., 1992; Cervantes, et al., 2004; Jimenex, et al., 1993; Nelson, 1904; Nelson, 1909; Romero Malpica and Rangel Cordero, 2013; cervantes and lorenzo, 1997)
Omilteme cottontails are considered the rarest and least understood of rabbits. There are only three museum specimens of this species and the last observation of an Omilteme cottontail was in 1998 by a hunter. The phylogenetic relationships of S. insonus are unknown. Tapeti were once considered to be the closest sister species of S. insonus based on morphology and were put into the subgenus Tapeti. However, they were transferred to the subgenus Sylvilagus after genetic comparison and are now considered to be more closely related to eastern cottontails and Mexican cottontails. As a result of this taxonomic confusion, Omilteme cottontails have been re-classified three times. Originally this species was referred to as Tapeti insonus, then renamed to Lepus insonus and is currently known as Sylvilagus insonus. (Cerballos and Navarro, 1991; Diersing, 1981; Hershkovitz, 1950; Lumpkin and Seidensticker, 2011; Nelson, 1909; Tate, 1993; cervantes and lorenzo, 1997)
Christine Quiring (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
an animal that mainly eats the dung of other animals
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
having more than one female as a mate at one time
specialized for leaping or bounding locomotion; jumps or hops.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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Sierra Madre Oriental and Occidental pine-oak forests" (On-line). World Wildlife Fund. Accessed November 11, 2013 at http://wwf.panda.org/about_our_earth/ecoregions/sierramadre_pineoak_forests.cfm.
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