Volcano Rabbit

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.

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 crepuscularand 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

### 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.

### Range and Habitat

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.

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.

## Reproduction

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.

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.

## Behavior

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.

## 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.