Romerolagus diazivolcano rabbit

Geographic Range

Romerolagus diazi is native to the Chichinautzin range of extinct volcanoes 200 miles south of Mexico City. Primarily, they live in a 280 sq. km region spread across the slopes of the mountains Pelado, Tialoc, Popocatepetl and Ixtaccíhuatl. Romerolagus diazi is endemic to the Chichinautzin Mountains. (Bell and Fa, 1990; Hoffman, 1990)


Romerolagus diazi lives on the upper slopes of an extinct volcanic range south of Mexico City, ranging from 2800 m to 4250 m, and an average elevation of 3252 m. Although it is near the equator and in the tropics, conditions are temperate as a result of high altitude and local weather patterns. Winters constitute the dry season, and summers are exceptionally rainy. Aside from the wet and dry seasons, conditions are relatively stable throughout the year, leaving a long growing season, with an average temperature of 9.6 C. Vegetation throughout consists of tall zacatón bunch grass under sparse pine and alder coverage. Romerolagus diazi relies heavily on these grasses for survival and evasion of predators. It can also be found in dense patches of secondary forest. (Chapman, 1984; Chisholm, 1911; Lopez-Paniagua, 1992; Nowak, 1999; Velazquez and Heil, 1996)

  • Range elevation
    2800 to 4250 m
    9186.35 to 13943.57 ft
  • Average elevation
    3252 m
    10669.29 ft

Physical Description

Romerolagus diazi has small, short hind legs and feet; small, rounded ears; and a vestigial tail. Dorsal and lateral fur is yellowish brown, and individual hairs are black at the tips and base, resulting in a grizzled appearance. The venter is buff or light grey. Like all members of the family Leporidae, it has large, well positioned eyes that give it a broad viewing range. It is considered the most primitive of extant leporids and is often described as the second smallest leporid behind Brachylagus idahoensis. Romerolagus diazi is sexually dimorphic, with males weighing on average 417 g and females, 536 g. Newborns are altricial and have closed eyes, laid-back ears, and extremely fine brown fur at birth. The vestigial tail is visible in newborns, but not in adults. Romerolagus diazi bears a striking resemblance to members of the family Ochotonidae, and its skull resembles that of Ochotonidae, as both lack an anterior bony projection above the eye socket. (Cervantes and Martinez, 1992; Chapman, 1984; Hoffman, 1990; Hoth and Granados, 2007; Lopez-Paniagua, 1992)

  • Sexual Dimorphism
  • female larger
  • Range mass
    386 to 602.5 g
    13.60 to 21.23 oz
  • Range length
    234 to 321 mm
    9.21 to 12.64 in


Only captive Romerolagus diazi have been observed during mating. Thus, no data are available concerning mating systems of wild populations. It communicates with conspecifics via scent glands under the chin and in their groin, and scent glands likely play a significant role in mating and signaling social status to conspecifics. In captivity, R. diazi is serially monogamous (e.g., multiple pair bondings). Mate access is determined by social status, and only the dominant female and dominant male mate. If either individual dies, however, they are replaced by the highest ranking individual in the hierarchy. (Hoth and Granados, 2007)

Breeding occurs year round in Romerolagus diazi but peaks during spring. Females have induced ovulation and in captivity reach sexual maturity by 8 months old. Captive males reach sexual maturity by 5 months old. Gestation lasts for 38 to 40 days and results in 1 to 4 offspring per litter, which weigh about 80 g per kitten. Females can have 4 to 5 litters per year. Typically, offspring are weaned by 3 weeks of age. (Chapman, 1984; Chisholm, 1911; Hoffman, 1990; Hoth and Granados, 2007; Macdonald, 2001; Nowak, 1999)

  • Breeding interval
    Romerolagus diazi can mate 4 to 5 times per year
  • Breeding season
    Breeding in Romerolagus diazi occurs year-round, but peaks in spring and early summer
  • Range number of offspring
    1 to 4
  • Average number of offspring
  • Range gestation period
    38 to 42 days
  • Average gestation period
    39 days
  • Average weaning age
    3 weeks
  • Average age at sexual or reproductive maturity (female)
    8 months
  • Average age at sexual or reproductive maturity (male)
    5 months

Little is known of parental care in Romerolagus diazi in the wild. In captivity, mothers nurse semi-altricial young until weaning is complete at around 3 weeks of age. In the wild, R. diazi digs shallow holes in clumps of zacaton bunch grass, which hide nests and protect young. Nests consist primarily of vegetation fragments and fur. In captivity, R. diazi females avoid their nests unless young vocalize distress calls. (Hoffman, 1990)

  • Parental Investment
  • altricial
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female


While there is no data on the lifespan of Romerolagus diazi, similar species have been observed to live less than a year in the wild. Some lagomorphs, however, may live up to 12 years in the wild. (Macdonald, 2001)


Romerolagus diazi is semi-social, usually living in groups of 2 to 5. Groups are dominated by the breeding pair, with the breeding female at the top of the hierarchy. Generally, only the top male and female reproduce. Within the group, interactions such as fights and play are often observed. Dominant females are often agonistic toward subordinate males and females. DOminant males, however, never show aggression to subordinate individuals. Although R. diazi is active throughout the day, activity peaks during dusk and dawn. (Chisholm, 1911; Hoffman, 1990; Macdonald, 2001; Nowak, 1999)

  • Range territory size
    2,500 to 35,000 m^2

Home Range

There is no information available regarding home range in Romerolagus diazi; however, it has been estimated to be between 2,500 and 35,000 m^2. Territorial behavior has not been documented in this species. (Chisholm, 1911; Hoffman, 1990; Macdonald, 2001; Nowak, 1999)

Communication and Perception

Romerolagus diazi is the only member of family Leporidae that is known to vocalize, reacting to help their young and making noises themselves when startled, similar to pikas. They make two different types of calls: a short high-pitched bark, and a more subtle, slightly less audible squeak. They also communicate through thumping their hind feet on the ground. Reproductive status is communicated via scent glands located on the chin and groin. (Cervantes and Martinez, 1992; Chisholm, 1911; Hoffman, 1990; Macdonald, 2001; Nowak, 1999)

Food Habits

Romerolagus diazi feeds primarily on zacaton grass, but also consumes young herbs and bark. During the summer rainy season, it sometimes feeds on cultivated plants. In captivity, R. diazi eats zacaton grasses provided in their enclosure, as well as other traditional rabbit foods, including high-protein chinchilla pellets, fruits, grasses, and other vegetable material. Young R. diazi begin eating solid food at 15 to 16 days after birth and are completely weaned by 3 weeks of age. Similar to other lagomorphs, R. diazi sometimes consumes their feces as a method of retaining as much nutrition and water as possible. Specific plant species eaten by R. diazi include aromatic mint plant, numerous species of zacaton grass (Festuca amplissima, Stipa ichu, Epicampes), two genera of spiny grass (Erynigium and Cyrsium), lady's mantle, and Museniopsis arguta. (Chapman, 1984; Lopez-Paniagua, 1992; Velazquez and Heil, 1996)

  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • flowers
  • Other Foods
  • dung


Romerolagus diazi lacks the speed of many of its close relatives. Instead, it relies on finding cover in the grasses and rocks of its habitat. To protect their young, female volcano rabbits create burrows in and around patches of zacaton grass, digging slightly into the ground and reinforcing these burrows with the nearby grasses to offer both shelter and security. Romerolagus diazi has also been observed to make noise vocally when threatened. Major predators of this species include long-tailed weasels, bobcats, coyotes, and red-tailed hawks. (Chisholm, 1911; Macdonald, 2001; Nowak, 1999)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Little is known of the ecological role that Romerolagus diazi fills in its ecosystem. It is a folivore and may disperse seeds throughout its habitat. This species is prey for bobcats, long-tailed weasels, coyotes, red-tailed hawks and probably a number of other carnivorous mammals and birds. Romerolagus diazi is host to a number of endoparasites including roundworms (Boreostrongylus romerolagi, Thichostrongylus calcaratus, Longistrata dubia, Dermatoxys veligera), whipworms (Trichuris leporis), and flatworms (Anoplocephaloides romerolagi). It is also host to a number of ectoparasites, including various species of flies, ticks, and fleas. (Hoffman, 1990; Velazquez and Heil, 1996; Velazquez, 1994)

Commensal/Parasitic Species
  • roundworms (Boreostrongylus romerolagi)
  • roundworms (Thichostrongylus calcaratus)
  • roundworms (Longistrata dubia)
  • roundworms (Dermatoxys veligera)
  • whipworms (Trichuris leporis)
  • flatworms (Anoplocephaloides romerolagi)
  • flies (Diptera)
  • ticks (Acari)
  • fleas (Siphonaptera)

Economic Importance for Humans: Positive

There are no known positive effects of Romerolagus diazi on humans. (Velazquez and Heil, 1996)

Economic Importance for Humans: Negative

Romerolagus diazi occasionally feeds on cultivated plants. If it were more abundant, it may have a significant negative affect on local agriculture. (Chapman, 1984; Nowak, 1999)

Conservation Status

Romerolagus diazi lives immediately south of Mexico City, one of the largest metropolitan areas in the world containing nearly 21 million inhabitants. As a result, while populations are listed as increasing by IUCN's Red List of Threatened Species, growth and sprawl of the city continues to threaten the habitat of R. diazi. In addition to urban sprawl, other major threats include habitat fragmentation and destruction due to wild fires and agriculture. Recently, R. diazi has increased, likely due to protective legislation focused on habitat preservation. Additionally, part of their range is within protected national parks. Currently, around 7000 individuals are estimated to exist in the wild. (Chapman, 1984; Nowak, 1999)


Maegan Tabbey (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff.



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.

World Map


uses sound to communicate


living in landscapes dominated by human agriculture.


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.

bilateral symmetry

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.

  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates


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.

female parental care

parental care is carried out by females


union of egg and spermatozoan


an animal that mainly eats leaves.


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.

induced ovulation

ovulation is stimulated by the act of copulation (does not occur spontaneously)


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 one mate at a time.


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.

native range

the area in which the animal is naturally found, the region in which it is endemic.


chemicals released into air or water that are detected by and responded to by other animals of the same species

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


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.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


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.

year-round breeding

breeding takes place throughout the year


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Chapman, J. 1984. Latitude and Gestation period in New World rabbits (Leporidae: Sylvilagus and Romerolagus). The American Nautralist, 124 No. 3: 442-445. Accessed March 13, 2011 at

Chisholm, H. 1911. The Encyclopaedia britannica: A dictionary of arts, sciences, literature, and general information, Eleventh edition, Volume 23. New York, NY, USA: The Encyclopaedia Britannica Company.

Hayssen, V., A. van Tienhoven. 1993. Adsell's Patterns of Mammalian Reproduction. Ithaca, NY, USA: Comstock Publishing Associates.

Hoffman, R. 1990. Romerolagus Diazi. Mammalian Species, 360: 1-7.

Hoth, J., H. Granados. 2007. A preliminary report on the breeding of the Volcano rabbit Romerolagus diazi at the Chapultepec Zoo, Mexico City. International Zoo Yearbook, 26: 261-265. Accessed March 13, 2011 at

Lopez-Paniagua, J. 1992. Habitat use by parapatric rabbits in a Mexican high-altitude grassland system. Journal of Applied Ecology, 29: 357-370.

Macdonald, D. 2001. The New Encyclopedia of Mammals. New York, NY: Oxford University Press.

Nowak, R. 1999. Walker's Mammals of the World Sixth Edition. Baltimore, MD, USA: John Hopkins University Press.

Velazquez, A. 1994. Distribution and Population Size of Romerolagus diazi on El Pelado Volcano, Mexico. Journal of Mammalogy, 75 No. 3: 743-749. Accessed March 13, 2011 at

Velazquez, A., G. Heil. 1996. Habitat suitability study for the conservation of the volcano rabbit (Romerolagus diazi). Journal of Applied Ecology, 33: 543-554. Accessed March 13, 2011 at

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington DC: Smithsonian Institution Press in association with the American Society of Mammologists.