Sylvilagus insonus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Sylvilagus insonus
Species Authority: (Nelson, 1904)
Common Name(s):
English Omilteme Cottontail, Omiltemi Rabbit
Spanish Conejo De Omiltemi
Taxonomic Notes: There are no recognized subspecies of Sylvilagus insonus (Hall 1981).

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(ii,iii) ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Mexican Association for Conservation and Study of Lagomorphs (AMCELA), Romero Malpica, F.J. & Rangel Cordero, H.
Reviewer(s): Smith, A.T. & Boyer, A.F. (Lagomorph Red List Authority)
Sylvilagus insonus is a very rare species, thought to be possibly extinct by some sources, though a skin was obtain from local hunters during a survey conducted in 1998 (Cervantes et al. 2004). S. insonus is known from fewer than ten specimens (Chapman and Ceballos 1990), and occurs in a highly fragmented habitat with an extent of occurrence less than 500 km² (Cervantes and Lorenzo 1997).
1996 Critically Endangered

Geographic Range [top]

Range Description: Sylvilagus insonus is restricted in range to the Sierra Madre del Sur, near Omiltemi, in Guerrero, Mexico (Chapman and Ceballos 1990). Records of S. insonus show an elevational range of 2,133-3,048 m (Cervantes and Lorenzo 1997). The species is known from the type locality only (Cervantes and Lorenzo 1997). S. insonus occupies a highly fragmented area of less than 500 km² (Cervantes et al. 2004).
Possibly extinct:
Mexico (Guerrero - Native)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Very little is known about the population status of Sylvilagus insonus. Prior to the recovery of a skin in 1998 (Cervantes et al. 2004), S. insonus was known from only three specimens with suspect diagnosis (Cervantes and Lorenzo 1997). A 1998 survey, lasting approximately 52 days, within the known range of S. insonus did not yield any S. insonus sightings, but a sympatric species, S. cunicularius, was observed (Cervantes et al. 2004). The investigators found local inhabitants that managed to hunt two specimens and collected the one remaining skin, placing it in the collection at the Instituto de Biologia, Universidad Nacional Autonoma de Mexico, No. 40390 (Cervantes et al. 2004). The hunting sight was approximately 1 km SSE Omiltemi at an elevation of 2,300 m (Cervantes et al. 2004). A possible live sighting in 1991 may be the most recent (Ceballos and Navarro 1991). Prior to the 1998 finding of S. insonus skin specimens, many sources considered S. insonus possibly extinct (Cervantes et al. 2004).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Sylvilagus insonus occupies dense cloud forests, dominated by pine with elements of temperate forest (Pinus, Quercus, and Alnus) (Chapman and Ceballos 1990, Cervantes and Lorenzo 1997). S. insonus occurs sympatrically with S. cunicularius (Cervantes et al. 2004).

This species is predominantly nocturnal (Cervantes and Lorenzo 1997). Diersing (1981) recorded the following mean measurements (mm) from two collected specimens: total length - 435.00; tail length - 42.50; body length - 392.50; hind foot length - 92.50; ear length (wet) - 65.00; and greatest skull length - 77.45.
Systems: Terrestrial

Threats [top]

Major Threat(s): Deforestation of habitat is a serious threat to Sylvilagus insonus, as the forests within the known range have been extensively logged, resulting in habitat fragmentation (Cervantes and Lorenzo 1997). Cattle grazing accompanies deforestation, intensifying the threat (Chapman and Ceballos 1990). Hunting of S. insonus remains a concern even after much of the known range was incorporated into a natural reserve area (Cervantes and Lorenzo 1997).

Conservation Actions [top]

Conservation Actions: Sylvilagus insonus is listed as Critically Endangered in the Mexican Official Norm NOM-059-ECOL-2001.

The type locality of S. insonus is located within the Omiltemi State Ecological Park, which has been declared a natural reserve area (approximately 3,613 ha in area) by the state (Cervantes and Lorenzo 1997). The Mexican government listed S. insonus as endangered in 1994 (Cervantes and Lorenzo 1997).

Habitat conservation and management, hunting regulation, and captive breeding programs are necessary to protect S. insonus from further decline (Cervantes and Lorenzo 1997).

Much research is needed to determine the status and conservation needs of S. insonus, primarily to determine its current distribution and population status, as well as research to determine the effects of threats (Chapman and Ceballos 1990, Cervantes and Lorenzo 1997).

Citation: Mexican Association for Conservation and Study of Lagomorphs (AMCELA), Romero Malpica, F.J. & Rangel Cordero, H. 2008. Sylvilagus insonus. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 01 July 2015.
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