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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Range mass: 386 to 602.5 g.
Range length: 234 to 321 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger
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.
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.
Range elevation: 2800 to 4250 m.
Average elevation: 3252 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: forest ; scrub forest ; mountains
Other Habitat Features: agricultural
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.
Communication Channels: acoustic ; chemical
Other Communication Modes: pheromones ; scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
US Federal List: endangered
CITES: appendix i
State of Michigan List: no special status
IUCN Red List of Threatened Species: endangered
Romerolagus diazi occasionally feeds on cultivated plants. If it were more abundant, it may have a significant negative affect on local agriculture.
There are no known positive effects of Romerolagus diazi on humans.
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.
Commensal/Parasitic Species:
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.
Plant Foods: leaves; wood, bark, or stems; seeds, grains, and nuts; flowers
Other Foods: dung
Primary Diet: herbivore (Folivore ); coprophage
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.
Biogeographic Regions: nearctic (Native )
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.
Mating System: monogamous
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.
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: 4.
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.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; induced ovulation ; fertilization ; viviparous
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.
Parental Investment: altricial ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female)
The volcano rabbit (Romerolagus diazi), also known as teporingo or zacatuche, is a small rabbit that resides in the mountains of Mexico.[4] It is the world's second-smallest rabbit, second only to the pygmy rabbit. It has small rounded ears, short legs, and short, thick fur and weighs approximately 390–600 g (0.86–1.3 lb). It has a life span of 7 to 9 years. The volcano rabbit lives in groups of 2 to 5 animals in burrows (underground nests) and runways among grass tussocks. The burrows can be as long as 5 m and as deep as 40 cm. There are usually 2 to 3 young per litter, born in the burrows. In semi-captivity, however, they do not make burrows and the young are born in nests made in the grass tussocks.[5]
Unlike many species of rabbits (and similar to pikas), the volcano rabbit emits very high-pitched sounds instead of thumping its feet on the ground to warn other rabbits of danger. It is crepuscular and is highly active during twilight, dawn and all times in between. Populations have been estimated to have approximately 150–200 colonies with a total population of 1,200 individuals over their entire range.[6]
The volcano rabbit’s adult weight goes up to 500 g.[7] It has short, dense fur that ranges in color from brown to black.[8] The rabbit is a gnawing animal that is distinguished from rodents by its two pairs specialized of upper incisors that are designed for gnawing.[7] Their body size and hindlimb development demonstrates how they need extra grass-cover for evasion from predators.[4][7] Their speediness and their hind limb development relative to their body size correlate to their necessity for evasion action.[7] They are relatively slow and vulnerable in open habitats; therefore they take comfort in high, covered areas.[7] They also have difficulty breeding in small enclosures.[7] Volcano rabbits have a very narrow gestational period: In one study, all females gave birth between 39 and 41 days after coitus.[9] They create runways similar to those made by microtine rodents to navigate their habitat.[7] The burrows consist of dense grass clumps, with a length of 5 m and depth of 40 cm.[7] Their small size relates to their selective dietary habits.[7] As of 1987, they were used in one piece of scientific research.[10]
Volcano rabbits are an endangered species endemic to Mexico.[11] Specifically, the rabbit is native to four volcanoes just south and East of Mexico City, the largest of these volcanic regions is within the Izta-Popo National Park, other areas include the Chichinautzin and Pelado volcanos.[4][12][6] The range of the volcano rabbit has been fragmented into 16 individual patches by human disturbance. Vegetation within these patches is dominated by native grasslands and include Nearctic and Neotropical varieties. Elevation of these patches is between 2900 and 3660 meters above sea level.[11] The soil consists mostly of Andosol and Lithosol. The local climate is temperate, subhumid, and has a mean annual temperature of 11 °C. Annual rainfall averages at about 1000 millimeters. In the patches that are the most heavily populated with volcano rabbits, the plants Festuca tolucensis and Pinus hartwegii are most abundant.[11] Volcano rabbits show strong preferences for habitat types that are categorized as open pine forests, open pine woodland, and mixed alder pine forest. Human activity in the area has had a great impact upon the preferred habitat of the volcano rabbit.[11] Humans have fragmented the rabbits' habitat by constructing highways, farming, afforestation (i.e. planting trees where they don't belong), and lack of sound fire and grazing practices. Ecological fragmentation has been caused by environmental discontinuity.[4][12][13]
Volcano rabbits are commonly found at higher altitudes.[7] Almost 71% of volcano rabbits are found in pine forests, alder forests, and grasslands.[7] Volcano rabbits are more abundant near tall, dense herbs and thick vegetation, and are adversely affected by anthropogenic environmental disturbances like logging and burning.[7] A study on the effects of climate change upon volcano rabbit metapopulations concluded that fluctuations in climate most affected rabbits on the edge of their habitable range.[14] The volcano rabbit's range encompasses a maximum of 280 km2 of grasslands in elevated areas in the Trans-Mexican Neovolcanic Belt.[7]
The last unconfirmed sighting of the species at Nevado de Toluca (where no permanent colony has been historically documented) occurred in August 2003 when supposedly one volcano rabbit was observed. Since 1987, however, research conducted by Hoth et al., in relation to the distribution of the Volcano Rabbit already found no records of this species in the Nevado de Toluca, including the site where Tikul Álvarez (IPN) collected a specimen in 1975 (Nevado de Toluca, 4 km S, 2 km W Raíces, 3350 masl).[4] Notwithstanding, although no permanent colony has been documented in Nevado de Toluca, the volcano rabbit was declared "extinct" within this portion of its range in 2018;[15] populations exist elsewhere within the Trans-Mexican Volcanic Belt and in captivity.[4][5][16] Due to the above, the International Union for the Conservation of Nature (Red Data Book, IUCN 2019), no longer mentions the Nevado de Toluca as a current or potential site for the distribution of this species.[17]
The IUCN/SSC Lagomorph Specialist Group has created an action plan for this rabbit that focuses upon the need to manage the burning and overgrazing of its Zacatón habitats and to enforce laws prohibiting its hunting, capture, and sale.[7] Studies about the volcano rabbit's geographical range, role in its habitat, population dynamics, and evolutionary history have been recommended.[7] In addition, habitat restoration and the establishment of Zacatón corridors to link core areas of habitat are needed.
The volcano rabbit feeds primarily on grasses such as Festuca amplissima, Muhlenbergia macroura, Stipa ichu, and Eryngium rosei.[18] The rabbits also use these plants as cover to hide from predators. M. macroura was found to be in 89% of pellets of the volcano rabbits, suggesting that this is the base of their diet, but it does not actually provide the necessary energy and protein needs of the rabbits. Supplementing their diet with 15 other forms of plant life, volcano rabbits can get their required nutrition. Other plant species that also are responsible for supporting the volcano rabbit are the Muhlenbergia quadidentata, the Pinus hartwegii, F. tolucensis, P. hartwegeii.[18] Volcano rabbits also consume leaves, foliage, and flowers indiscriminately under poor conditions, as habitat loss has eliminated much of their food sources.[18] In fact, protein acquisition is the primary limiting factor on the size of the populations of each of the four volcanoes on which the species is located. Studies show that many individuals of the population suffer from serious weight loss and starvation.[18]
Seasonal changes also affect the diet of the volcano rabbit greatly. The grasses it normally consumes are abundant during wet seasons. During the dry season, the volcano rabbit feasts on shrubs and small trees, as well as other woody plants. During the winter plants, these woody plants make up most of their diet, as well as the primary building material for their nests.[18]
Numerous studies conducted during the 1980s and 1990s agreed that the habitat of the volcano rabbit was shrinking due to a combination of natural and anthropogenic causes.[19] There is evidence that its range has shrunk significantly during the last 18,000 years due to a 5–6 °C increase in the prevailing temperature, and its distribution is now divided into 16 patches.[19] The fragmentation of the volcano rabbit's distribution has resulted from a long-term warming trend that has driven it to progressively higher altitudes and the relatively recent construction of highways that dissect its habitat.[19]
Declines in the R. diazi population have been occurring due a number of changes in vegetation, climate, and, thus, elevation. The volcano rabbit is extremely vulnerable to the effects of climate change and other anthropogenic intrusions because of its extremely limited range and specialized diet.[19] Patches of vegetation that R. diazi uses for survival are becoming fragmented, isolated and smaller, rendering the environment more open and therefore less suitable for its survival. Because the volcano rabbit inhabits the area surrounding Mexico City, Mexico's most populous region, it has suffered a very high rate of habitat destruction.[19]
The cottontail rabbit, Sylvilagus, is expanding into the volcano rabbit’s niche, but there is “no evidence that [volcano rabbits'] habitat selection is a response to competitive exclusion." The volcano rabbit has been severely pressured by human intrusion into its habitat. Anthropogenic disturbance enables other rabbit species to flourish in grasslands, increasing competition with the volcano rabbit.[7]
Volcano rabbits have been bred in captivity,[5] but there is evidence that the species loses a significant amount of genetic diversity when it reproduces in such conditions. A comparative study done on wild and captive volcano rabbits found that the latter lost a substantial amount of DNA loci, and some specimens lost 88% of their genetic variability. There was, however, one locus whose variability was higher than that of the wild population.[20]
Threats to R. diazi, or the volcano rabbit, include logging, harvesting of grasses, livestock grazing, habitat destruction, urban expansion, highway construction and too frequent forest fires.[4] More recent threats include unsound management policies of its habitat in National Parks and outside, mainly by afforestation (planting trees in grasslands where they do not belong). [12] These threats have resulted in a loss of 15–20% of the volcano rabbit’s habitat during the last three generations. They have also resulted in ecological displacement and genetic isolation of R. diazi. Hunting is another threat to the volcano rabbit, despite the fact that R. diazi is listed under Appendix 1 of CITES[21] and it is illegal to hunt R. diazi under Mexican law. However, many are unaware that R. diazi is protected and officials do not adequately enforce its protection. Hunting, livestock grazing, and fires can even harm R. diazi within national parks that are protected such as Izta-Popo and Zoquiapan National Parks. In terms of conservation efforts, various captive breeding programs have been established with relative success, but infant mortality in captivity is high.[8] Actions toward conservation should be focused on the enforcement of laws which forbid hunting and trading of the volcano rabbit. Furthermore, efforts must be put toward habitat management, specifically the control of forest fires and livestock overgrazing of grasses. Lastly, it would be beneficial to enact education programs regarding R. diazi and the various threats that face it. The public should also be educated about the volcano rabbit’s protected status, as many are unaware that it is illegal to hunt R. diazi.
The volcano rabbit (Romerolagus diazi), also known as teporingo or zacatuche, is a small rabbit that resides in the mountains of Mexico. It is the world's second-smallest rabbit, second only to the pygmy rabbit. It has small rounded ears, short legs, and short, thick fur and weighs approximately 390–600 g (0.86–1.3 lb). It has a life span of 7 to 9 years. The volcano rabbit lives in groups of 2 to 5 animals in burrows (underground nests) and runways among grass tussocks. The burrows can be as long as 5 m and as deep as 40 cm. There are usually 2 to 3 young per litter, born in the burrows. In semi-captivity, however, they do not make burrows and the young are born in nests made in the grass tussocks.
Unlike many species of rabbits (and similar to pikas), the volcano rabbit emits very high-pitched sounds instead of thumping its feet on the ground to warn other rabbits of danger. It is crepuscular and is highly active during twilight, dawn and all times in between. Populations have been estimated to have approximately 150–200 colonies with a total population of 1,200 individuals over their entire range.
