Omilteme cottontail

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Omilteme cottontail
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Lagomorpha
Family: Leporidae
Genus: Sylvilagus
Species:
S. insonus
Binomial name
Sylvilagus insonus
(E.W. Nelson, 1904)
Omilteme cottontail range
Synonyms

Lepus insonus E.W. Nelson, 1904

The Omilteme cottontail (Sylvilagus insonus), or Omiltemi cottontail (Spanish: conejo de Omiltemi), is a species of cottontail rabbit in the family Leporidae found only in the Mexican state of Guerrero in the Sierra Madre del Sur mountain range. It is a nocturnal, large rabbit, rufous to black in fur color, with long ears and a short tail. This cottontail is restricted to cloud forests at elevations of up to 11,499 feet (3,505 meters).

First identified in 1904 by

Sylvilagus, the cottontail rabbits. It is closely related to the Mexican cottontail (S. cunicularius) and the desert cottontail (S. audubonii); the former species overlaps in distribution
with the Omilteme cottontail.

The Omilteme cottontail is considered one of the most endangered mammal species in the world, and is only known from a few specimens. Once listed by the International Union for Conservation of Nature and Mexican authorities as critically endangered, it is now considered a data deficient species. From the early 1900s up until the 1990s, no confirmed sightings of the cottontail were recorded, but two individuals were discovered in 1998, and more were found through the 2020s using camera traps. It is threatened by poaching and habitat destruction, and much about its natural history is unknown.

Taxonomy and systematics

The Omilteme cottontail was first described by

Sylvilagus.[5]

There is no fossil evidence of Sylvilagus insonus, and it is only known from its

type locality in the province of Guerrero, Mexico.[6] Phylogenetic analysis of the relationships between S. insonus and other species in the genus Sylvilagus yielded evidence that it is closely related to both the Mexican cottontail (S. cunicularius) and the desert cottontail (S. audubonii).[7] The former species is sympatric with S. insonus.[8] Prior studies indicated a relationship with the common tapeti (S. brasiliensis), and it has been variously placed in the subgenera Tapeti and Sylvilagus,[9] but morphological studies find that the common tapeti is more closely related to Dice's cottontail (S. dicei) than it is to S. insonus.[7]

Characteristics

The Omilteme cottontail is a large rabbit (head and body length from 15.7 to 17.3 in (398 to 440 mm)) with long ears (2.4–3.0 in (60–76 mm)), hind feet of medium length (3.5–4.1 in (89–104 mm)) and a short tail (1.6–1.8 in (40–45 mm)).

ventral side is darkly buff[7] or yellowish.[11]

Anatomy

The anatomy of Sylvilagus insonus has been described with particular focus on the skull. The skull is large, approximately 3.1 in (78 mm) in length and 1.3 in (32 mm) in depth, with a large

auditory bullae with a length of less than 0.38 in (9.6 mm). The width of the basioccipital is narrow: less than 0.35 in (9 mm), but broad across the carotid canals. The width of the infraorbital canals is very narrow, being less than 0.72 in (18.3 mm). The width across the nasal structures is very narrow, and their length is less than 1.26 in (32.1 mm).[6][8]

The mouth consists of a

dental formula is 2.0.3.31.0.2.3.[13] The length of the first upper incisor is generally less than 0.30 in (7.5 mm).[6]

Similar species

Sylvilagus insonus differs from other Central American species in its skeletal and external characteristics. Compared to the

carotid arteries, and dorsal extensions of the premaxillaries. S. insonus also has a narrower basioccipital and narrower post-dental process. The Omilteme cottontail has a longer bicolored tail (rufous and black) instead of a uni-colored tail (solely brown); hind feet with white and brown versus hind feet of only brown; and longer ears.[6][8] These characteristics are also useful in differentiating the species from the Mexican cottontail (S. cunicularius), with which it shares its habitat.[11] S. insonus is smaller in the length of its upper incisors, its skull length, nasal length, width of the basioccipital, auditory bulla length, the depth of shield bullae, skull depth, width across infraorbital canals, mandible height and mandible ramus depth. The Omilteme cottontail is a rufous-black color dorsally, whereas the Mexican cottontail is only gray in the same areas.[8]

Geographic range and habitat

Sylvilagus insonus is

habitats ranging from 6,998 to 11,499 ft (2,133 to 3,505 m) in elevation.[7] Surrounding the wooded area is the village of Omiltemi at 7,651 ft (2,332 m) above sea level (in Municipio Chilpancingo).[10] The Omilteme cottontail is restricted to a region of less than 193 sq mi (500 km2).[10][14]

The Omilteme cottontail lives at the summit of a steep-sloped mountain range with many ravines covered with dense cloud forests.[10] Common tree genera in the forests it inhabits are pine (Pinus), oak (Quercus), and alder (Alnus).[7]

Behavior and ecology

Sylvilagus insonus shares its habitat with 37 other mammal species,

undergrowth where it makes runways and burrows under rocks and other objects. It is a mainly nocturnal mammal. The only known predator of the species is humans through hunting,[7] though its habitat is frequented by predators such as the wolf,[15] jaguar, and cougar.[16] Very little is known regarding its ecology and reproductive habits.[7]

Status and conservation

The

Red List of Endangered Species, lists the Omilteme cottontail as "data deficient",[1] though it previously listed the species as critically endangered in 1996 and 2004. A similar evaluation was given by the Mexican government around this time;[17] as of 2019, the same authority describes it as "endangered".[11] The major threats to the survival of this species are poaching and habitat destruction caused by deforestation.[6][10] This rabbit went unreported in the wild from the early 1900s to the 1990s; however, two specimens were captured in 1998, confirming that the species was still extant.[6][10] A team of scientists began searching for evidence of the species in 2019, with several specimens received in 2020 from local hunters and additional rabbits discovered from 2020 to 2022 in the Sierra Madre del Sur area within Guerrero, Mexico.[18] In ten regions surveyed by camera traps, seven showed evidence of the species.[19] The expedition was part of a larger effort to rediscover species without documented observations in at least 10 years.[18] Prior to this expedition, the species was only known from five museum specimens[7] and less than 10 total records.[9]

Sylvilagus insonus is considered one of the most endangered mammals in the world, and though it is known to live within a

National Commission of Natural Protected Areas, as additional studies are needed on the species' natural history to produce useful proposals.[7][19] Efforts to study the species further have been stymied by the rough terrain of the Sierra Madre del Sur and social issues in the inhabited areas.[11]

References

  1. ^
    doi:10.2305/IUCN.UK.2019-2.RLTS.T21207A45180771.en
    . Retrieved 24 January 2025.
  2. Proceedings of the Biological Society of Washington. 17: 103–110 – via BioStor
    .
  3. LCCN 2017004268
    .
  4. doi:10.3996/nafa.29.0001
  5. doi:10.3996/nafa.29.0001
  6. ^
    JSTOR 3504381
    .
  7. ^
    LCCN 2017004268
    .
  8. ^
    JSTOR 1380401
    .
  9. ^
    OCLC 62265494
    .
  10. ^
    doi:10.1078/1616-5047-117
    .
  11. ^
    ISBN 978-3-031-41660-6
    , retrieved 24 February 2025
  12. ISBN 978-3-031-50824-0
    .
  13. ISBN 978-0-8117-3309-0
    .
  14. ^
    ISBN 978-0-8061-2343-1
    .
  15. ^ "Sierra Madre Oriental & Occidental Pine-Oak Forests". World Wide Fund for Nature. 2013. Archived from the original on 9 November 2013. Retrieved 4 March 2025.
  16. ISSN 0006-3207
    .
  17. ISBN 978-3-540-72446-9
    , retrieved 4 March 2025
  18. ^ a b Devin, Murphy (23 January 2025). "Found: Small enigmatic rabbit with black tail lost to science for more than 120 years rediscovered hopping around mountain range in Mexico". rewild.org. Re:Wild. Retrieved 25 January 2025.
  19. ^ a b "Mexico's "lost" rabbit resurfaces after more than a century". Earth Touch News Network. 23 January 2025. Retrieved 3 March 2025.
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