Riverine rabbit

This is a good article. Click here for more information.
Source: Wikipedia, the free encyclopedia.

Riverine rabbit
Temporal range: middle Pleistocene, 0.4 million years ago
Bunolagus monticularis in Western Cape, South Africa

Critically Endangered  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Lagomorpha
Family: Leporidae
Genus: Bunolagus
Thomas, 1929
Species:
B. monticularis
Binomial name
Bunolagus monticularis
(Thomas, 1903)
Map
Historic distribution of the Riverine rabbit as described by the IUCN in 2019
  Extant (resident)

The riverine rabbit (Bunolagus monticularis), also known as the bushman rabbit or bushman hare, is a

only member of the genus Bunolagus. It is classified a critically endangered species by the International Union for Conservation of Nature
(IUCN); the most recent estimates of the species' population range from 157 to 207 mature individuals, and 224 to 380 total.

First identified in 1903 as a member of the

alluvial soils of its habitat near seasonal rivers for protection from the heat and for females to nest and protect the young. It is the only African rabbit known to dig its own burrows. Riverine rabbits are polygamous
, and live alone throughout the year.

Unlike most rabbits, female riverine rabbits produce only one to two young per year. This contributes to its status as critically endangered, along with habitat loss from agricultural development, soil erosion, and predators.

Human impacts on the environment
have a significant impact on the species' continued survivability. Currently, there are conservation plans being enacted to stabilise its population and protect its habitat.

Taxonomy and evolution

The riverine rabbit's

monotypic genus.[7][8]

Other

Kaffrarian Museum, mammalogist Guy C. Shortridge.[10] It is also known as the doekvoetjie, 'cloth foot', referring to the rabbit's furred hind feet,[9] and oewerkonyn, 'shore rabbit'.[6]

Bunolagus monticularis is most closely related to the European rabbit, the hispid hare, and the Amami rabbit.[9] The following cladogram is based on work done by Matthee and colleagues in 2004 and clarifications from Abrantes and colleagues in 2011, and is based on nuclear and mitochondrial gene analysis:[11]

Lagomorphs

Nesolagus (striped rabbits)

Poelagus
(Bunyoro rabbit)

Pronolagus
 (red rock hares)

Romerolagus
(volcano rabbit)

Sylvilagus (cottontails)

Brachylagus (pygmy rabbit)

Bunolagus (riverine rabbit)

Oryctolagus (European rabbit)

Caprolagus (hispid hare)

Pentalagus
 (Amami rabbit)

Lepus (hares)

There are no confirmed

Great Escarpment.[6][14]

Characteristics

Klein Karoo
from two angles, showing the rufous nuchal patch and brown tail

The riverine rabbit has an adult head and body length of 33.7 to 47.0 centimetres (13.3 to 18.5 in), and typically has a dark brown stripe running from the lower jaw over the cheek and upwards towards the base of the ears, and a white ring around each eye.

dental formula is 2.0.3.31.0.2.3 × 2 = 28—two pairs of upper and one pair of lower incisors, no canines, three upper and two lower premolars on each side, and three upper and lower molars on either side of the jaw—as is the case with all leporids.[18]

The riverine rabbit appears similar to hares (lagomorphs in the genus Lepus). It most closely resembles the Cape hare (Lepus capensis) in its morphology, but not in its fur patterns. The skulls of hares and the riverine rabbit are similar, with the main difference being that the riverine rabbit's is smaller and lacks an opening (foramen) near the premolar teeth.[6] The bulla, a bone structure enclosing the base of the ear, is much larger than that of most other rabbits; the volcano rabbit (Romerolagus) and pygmy rabbit (Brachylagus) have similarly large bullae, but smaller pinnae (the externally visible part of the ear).[19] It is sometimes compared to the red rock hares, some of which overlap it in distribution;[20][1] in its first description, it was noted as being about the same size as the Natal red rock hare (Pronolagus crassicaudatus),[3] though it has been later described as smaller than all red rock hares besides Smith's red rock hare (P. rupestris).[21]

Habitat and distribution

Karoo
in South Africa, the location of the riverine rabbit's habitat

The riverine rabbit lives in riverine vegetation on

indicator species within its distribution.[23] Plants in the family Amaranthaceae, those in the genus Lycium, and Salsola glabrescens dominate the rabbit's habitat.[16]

The riverine rabbit has a disjunct distribution and historically[12] occurred in two restricted regions in the Karoo, with the most populated regions being the Upper Karoo and Bushmanland Vloere (salt pan[24]) areas.[6] Nine distinct populations occur within the species' northern habitat on elevated ground north of the Great Escarpment, and two[14] or three southern populations, which have only been known since 2004, occupy the regions surrounding the Breede, Gourits and Olifants River systems. None of these subpopulations contain more than 50 individuals. Historically, there were five additional subpopulations in localities near the tributaries of and alongside the Vis and Renoster rivers, but it is now considered locally extinct in these regions.[1]

Behaviour and ecology

Riverine rabbits are solitary and nocturnal. They feed on grasses, as well as the flowers and leaves of dicotyledons. During the day, they rest in forms (hollow excavations scraped in the soil under shrubs).[25] The riverine rabbit is polygamous, and it lives and browses for food alone.[16] The size and overlap of home ranges varies based on sex: the males' home ranges overlap slightly with those of various females, with males having an average home range size roughly 60% larger than females (20.9 hectares (52 acres) compared to 12.9 hectares (32 acres)).[26] This home range size is the largest of all rabbits, though it is smaller than those of most hares.[27] The breeding season takes place between August and May, wherein females will make a grass- and fur-lined nest in a burrow, blocking the entrance with soil and twigs to keep out predators. The average length of a generation is two years; in captivity, individuals have been recorded as living up to five years.[26]

Lycium, a staple of the riverine rabbit diet

The riverine rabbit mainly feeds through

cecotrophy.[25]

Populations in the more northern areas of the species' distribution are more strongly associated with vegetation that grows narrowly along seasonal rivers; those in the southern parts of its distribution are not as closely tied to this type of vegetation and have been observed feeding on newly grown plants in fallow land.[6]

The riverine rabbit has a polygamous mating system, wherein males will mate with multiple females. Based on limited observations, the breeding season takes place from August through May, and gestation takes 35 to 36 days. It bears its young underground for protection, relying on soft soil in the

diploid chromosomes,[6] as do several closely related rabbits, the European rabbit (Oryctolagus cuniculus)[29] and hispid hare (Caprolagus hispidus).[30]

The young that the rabbit produces, one to two kits per litter, are

altricial—born bald, blind, and helpless. Each kit weighs from 40 to 50 grams (0.088 to 0.110 pounds). The helpless young stay with the mother until they are capable of living on their own.[6]

Verraux's eagle
, a predator of the riverine rabbit

The riverine rabbit is hunted by Verreaux's eagles,[31] African wildcats,[25] and caracals, the latter two of which have seen population increases due to the decline of the black-backed jackal in the region.[16] To escape predation, the riverine rabbit makes use of forms during the day to stay hidden.[25]

Status and conservation

The riverine rabbit is considered to be in extreme danger of extinction. From 1947 to 1979, it was thought to be extinct, having not been recorded by scientists at all in the intervening years.[10] In 1981, it was first labelled as an endangered species. The International Union for Conservation of Nature (IUCN) classified it as critically endangered in 2002.[9] The National Red List of South Africa maintained by the South African National Biodiversity Institute (SANBI) uses this same classification. Both organizations maintain this position as of their most recent evaluations from 2016.[26] In 2016, the species was estimated to have a population of 157 to 207 mature rabbits[23] and up to 380 overall, which continues to decline. This species' population is divided into several isolated groups, about 12 in total, all with less than 50 rabbits in each. These isolated populations are separated by jackal-proof fencing that surrounds extensive livestock farms.[1] A 1990 study put forth that the remaining habitat was only able to support 1,435 rabbits,[32] and in 2019, it was estimated that the species occupied a region spanning 2,943 square kilometres (1,136 sq mi) in total.[1] Later studies in 2020 and 2022 put forth that there may be more subpopulations than originally thought, and that the extent of species' endangerment could be exaggerated.[14]

The decline in the riverine rabbit population is largely due to the alteration of its historically limited

habitat loss, with much of the rabbit's former habitat rendered inhabitable or closed off.[1] The remaining land left to support the species is being damaged by climate change and logging.[14] Removal and exploitation of trees limits the rabbit's opportunities for shelter from heat and predators. Structures on rivers like dams isolate subpopulations from each other, discouraging population regeneration.[9] Relatively recent threats to the riverine rabbit are fracking and wind farm developments in the Nama Karoo, the former of which could alter the region's hydrology, and both of which will further fragment the available habitat.[6]

In addition to being threatened through loss of habitat, the riverine rabbit may also be susceptible to myxomatosis, as it shares genes that are affected by the Myxoma virus with the European rabbit, which is significantly impacted by the resultant disease. If the riverine rabbit species were to be exposed to the virus, its numbers could be reduced drastically.[6] The species is also suspected to be hunted for bushmeat or accidentally trapped[33] by farm workers and for sport,[26] though its preference for dense vegetation may thwart hunting efforts that use dogs.[34]

Relative to other similar species, known information about key aspects of the riverine rabbit, such as behaviour and diet, is deficient. Conservation efforts are better informed by researching this species and involving local communities, particularly farmers.[9] Plans to protect the remaining populations have been criticized, with experts claiming that a large part of the remaining land that can support the rabbit is outside the area being preserved for it.[32] Additionally, studies are susceptible to sampling bias, and failure to account for climactic and biological variables can lead to error, which can impact conservation recommendations.[23] Efforts have been made to form agreements with and educate landowners to ensure that certain measures are taken to help and reduce harm to rabbit populations,[9] though as of 2018 few private reserves or protected areas overlapped regions where the riverine rabbit is present.[6] A 2016 assessment by SANBI noted that there were increased sightings of the species within its extent of occurrence, and that camera traps and further observations were needed to confirm the spread of subpopulations in regions south and eastward of the rabbit's native range.[26]

The IUCN recommends further conservation measures in addition to those already planned and advised by SANBI. They recommend capturing the animal as to safely allow it to reproduce without danger of predators or starvation. They also recommend different methods of managing the habitat and the population in the wild.

wild dog, though efforts in the early 1990s were met with failure due to poor planning and low genetic diversity.[10] Monitoring of rabbit populations to evaluate effectiveness of current and potential conservation actions has been carried out in part by the Endangered Wildlife Trust.[33] One location being monitored is Sanbona Wildlife Reserve, a protected wilderness area with a successful breeding population where the species is being researched,[31] though efforts to improve population numbers in the wild are favored over captive breeding options according to SANBI.[26] The species' extent as of 2024 is being evaluated through analysis of droppings across the Karoo region.[36]

References

  1. ^
    doi:10.2305/IUCN.UK.2019-1.RLTS.T3326A45176532.en
    .
  2. ^ Wilson, Don (2005). "Bunolagus monticularis". Integrated Taxonomic Information System.
  3. ^
    doi:10.1080/00222930308678727
    .
  4. ^ "Collection specimens - Specimens - 1902.12.1.27". Natural History Museum Data Portal. Retrieved 7 April 2025.
  5. ^
    ISSN 1469-7998
    .
  6. ^
    LCCN 2017004268
    .
  7. JSTOR 1380524
    .
  8. PMID 15503672
    .
  9. ^ a b c d e f g "Bunolagus monticularis (Riverine rabbit)". Biodiversity Explorer. Archived from the original on 6 October 2010.
  10. ^ a b c Ferguson, J.W.H. (July 1994). "The riverine rabbit saga". South African Journal of Science. 90.
  11. PMID 29208424
    .
  12. ^
    ISBN 978-0-520-25721-4
    .
  13. OCLC 62265494
    .
  14. ^
    ISSN 1064-7554
    .
  15. ^ a b Schai-Braun & Hackländer 2016, p. 72.
  16. ^ a b c d e f Schai-Braun & Hackländer 2016, p. 112.
  17. Struik Publishers
    . p. 119.
  18. ^ Bertonnier-Brouty, Ludivine (3 July 2019). Dental development and replacement in Lagomorpha (Doctorate thesis). University of Lyon. Retrieved 10 March 2025.
  19. PMID 25802812
    .
  20. ^ Johnston 2018, pp. 108–113
  21. ^ Sen, S.; Pickford, M. (2022). "Red Rock Hares (Leporidae, Lagomorpha) past and present in southern Africa, and a new species of Pronolagus from the early Pleistocene of Angola" (PDF). Communications of the Geological Survey of Namibia. 24: 89. Retrieved 10 March 2025.
  22. ^ Schai-Braun & Hackländer 2016, p. 75.
  23. ^ a b c Collins & Du Toit 2016
  24. ISBN 978-1-919976-21-1
    .
  25. ^ a b c d e f Pintus, Kathryn; Bourne, Debra. "Bunolagus monticularis - Riverine rabbit". Wildpro. Twycross Zoo. Archived from the original on 2 March 2019. Retrieved 10 April 2025.
  26. ^ a b c d e f Collins, Kai; Bragg, Christy; Birss, Coral; Matthee, Conrad; Nel, Vicky; Hoffmann, Michael; Roxburgh, Lizanne; Smith, Andrew (May 2016), Child, MF; Roxburgh, L; Do Linh San, E; Raimondo, D; Davies-Mostert, HT (eds.), "Bunolagus monticularis Thomas Bayne, 190", The Red List of Mammals of South Africa, Swaziland and Lesotho, South Africa: South African National Biodiversity Institute and Endangered Wildlife Trust
  27. ISBN 978-3-319-55065-7
    , retrieved 4 March 2025
  28. ^ Schai-Braun & Hackländer 2016, p. 89.
  29. LCCN 2017004268
    .
  30. LCCN 2017004268
    .
  31. ^ a b Awaad, Rania (2007). "Bunolagus monticularis". Animal Diversity Web. Retrieved 13 February 2025.
  32. ^
    doi:10.1016/0006-3207(89)90064-5
    .
  33. ^
    Earth Touch News Network
    . Retrieved 2 November 2017.
  34. ^ Duthie, Andrew Graeme (March 1989). The ecology of the riverine rabbit Bunolagus monticularis (PDF) (MSc (Zoology) thesis). Pretoria, South Africa: University of Pretoria.
  35. ^ Collins, Jocelyn (1 February 2001). "Riverine rabbit". Enviro Facts. University of the Western Cape. Archived from the original on 6 May 2015. Retrieved 3 October 2015.
  36. doi:10.1038/d44148-024-00039-4
    .

Sources
Retrieved from "https://en.wikipedia.org/w/index.php?title=Riverine_rabbit&oldid=1297770364"