Romerolagus diazi
volcano rabbit

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)

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)

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)

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)

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)

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)

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)

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)

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)

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

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)