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Lagomorpha (Pikas, Rabbits, and Hares)
... The mammalian order Lagomorpha (pikas, rabbits and hares) has been a common study system because the locomotory diversity of this clade spans generalist to cursorial modes (Bramble, 1989;Camp & Borell, 1937;Fomin & Lobachev, 2000;Kraatz & Sherratt, 2016;Seckel & Janis, 2008;Trotter, 1885;Williams et al., 2007a) with relatively minimal body size variation (Tomiya & Miller, 2021). The clade comprises two extant families, the Leporidae (rabbits and hares; 11 genera) and Ochotonidae (pikas; 1 genus) (Chapman & Flux, 2008;Graham, 2015). True hares, or jackrabbits (genus Lepus), are the largest and most cursorial lagomorphs (Chapman & Flux, 1990), whereas rabbits (other genera including Sylvilagus and Oryctolagus) are typically smaller and more generalised (Camp & Borell, 1937;Young et al., 2014) and pikas are all small locomotory-generalists (Smith & Weston, 1990). ...
... True hares, or jackrabbits (genus Lepus), are the largest and most cursorial lagomorphs (Chapman & Flux, 1990), whereas rabbits (other genera including Sylvilagus and Oryctolagus) are typically smaller and more generalised (Camp & Borell, 1937;Young et al., 2014) and pikas are all small locomotory-generalists (Smith & Weston, 1990). Variation in running ability in lagomorphs occurs as a result of their differing ecologies: pikas inhabit burrows or rocky slopes (talus) with natural cover, relying upon brief, hopping locomotion between refuges to escape predation (Gambaryan, 1974;Reese et al., 2013;Graham, 2015); hares typically occupy open environments such as grassland and desert, and evade predators through speed and endurance (Camp & Borell, 1937;Swihart, 1984); rabbits, like pikas, tend to dart through woodland cover to obscure the view of predators (Stott, 2003;Cowan & Bell 1986). However, a greater necessity for agile acceleration between refuges ensures speed is vital enough to their survival that rabbits lie closer to hares than pikas in terms of cursorial ability (Temple, 1987;Young et al., 2022). ...
Highly cursorial animals are specialised for fast, sustained running via specific morphological adaptations, notably including changes in limb segment length and mechanical advantage. Members of the order Lagomorpha (hares, rabbits and pikas) vary in cursorial ability; hares are generally highly cursorial, rabbits more frequently saltate, and pikas predominantly trot. Previous investigations of lagomorphs have identified anatomical trends correlated with this ‘cursoriality gradient’, however, the phylogenetic sampling of such investigations has been limited to three American species, namely the American pika (Ochotona princeps), brush rabbit (Sylvilagus bachmani), and black-tailed jackrabbit (Lepus californicus). Here, we expand the phylogenetic sample and body size range by including novel data from Australian samples of the European rabbit (Oryctolagus cuniculus) and European hare (L. europaeus), alongside unpublished data on the Eastern cottontail (S. floridanus). X-ray Computed Tomography and digital landmarking were used to capture proportions within the appendicular skeleton of ~ 40 specimens of each European species. In doubling the number of species studied, we find the previously-identified morphological gradients associated with cursorial behaviour are complicated when evaluated in the larger sample. The relative length and joint velocity of limbs was found to be lower than predicted in European rabbits and hares. Furthermore, we present a novel assessment of morphological integration in the lagomorph appendicular skeleton, finding between-limb covariation patterns that are generally similar to those of other mammals. Broadly, these results suggest cursoriality is only one of many selective forces driving lagomorph skeletal evolution, with variations in body size and fossoriality potentially having measurable impacts.
Members of the order Lagomorpha comprise two families, the Leporidae (domestic and wild rabbits and hares) and the Ochotonidae (pikas). There are over 60 extant species of rabbits and hares. In the wild, rabbits and hares are herbivorous, non-hibernatory, and invariably terrestrial but are found in a diversity of natural habitats on multiple continents, ranging from the subtropics to open desert to boreal forests and arctic tundra (Nowak and Walker 1999) (Table 42.1). It is noteworthy, however, that many populations of Leporidae are not native, instead introduced to their respective regions or continents by humans (Nowak and Walker 1999). The European rabbit (Oryctolagus cuniculus), for example, is not native to Australia but was introduced to the continent in the nineteenth century and has become an invasive species, reported to have a negative impact on native ecosystems (Barrio et al. 2010; Fenner 2010). The Leporidae are preyed upon by many terrestrial and avian carnivorous species, and follow predominantly crepuscular and/or nocturnal activity patterns (Delaney et al. 2018). Despite similarities in habitat and activity, social structure differs between rabbits and hares, with rabbits tending to form colonies and hares being predominantly solitary animals (Flux and Angermann 1990). At birth, rabbit kits are blind and lack fur whereas leverets (baby hares) are born with a full fur-coat and are precocial (Delaney et al. 2018).
Due to their global distribution, invasive history, and unique characteristics, European rabbits are recognizable almost anywhere on our planet. Although they are members of a much larger group of living and extinct mammals [Mammalia, Lagomorpha (rabbits, hares, and pikas)], the group is often characterized by several well-known genera (e.g., Oryctolagus, Sylvilagus, Lepus, and Ochotona). This representation does not capture the extraordinary diversity of behavior and form found throughout the order. Model organisms are commonly used as exemplars for biological research, but there are a limited number of model clades or lineages that have been used to study evolutionary morphology in a more explicitly comparative way. We present this review paper to show that lagomorphs are a strong system in which to study macro- and micro-scale patterns of morphological change within a clade that offers underappreciated levels of diversity. To this end, we offer a summary of the status of relevant aspects of lagomorph biology.
OBJECTIVE
To use duplex Doppler ultrasonography to compare gastrointestinal activity in healthy sedated versus nonsedated rabbits and to evaluate agreement between B-mode and pulsed-wave Doppler (PWD) ultrasonographic measurements.
ANIMALS
10 healthy client-owned rabbits brought for routine physical examination and 11 brought for routine ovariohysterectomy or castration.
PROCEDURES
Duplex Doppler ultrasonography of the gastrointestinal tract was performed once for the 10 rabbits that underwent physical examination and twice (before and after presurgical sedation) for the 11 rabbits that underwent routine ovariohysterectomy or castration. Mean number of peristaltic contractions during a 30-second period was determined for the stomach, duodenum, jejunum, cecum, and colon from B-mode and PWD ultrasonographic images that had been video recorded. Findings for the duodenum and jejunum were compared between B-mode and PWD ultrasonography and between sedated and nonsedated rabbits.
RESULTS
Duodenal and jejunal segments had measurable peristaltic waves; however, the stomach, cecum, and colon had no consistent measurable activity. B-mode and PWD ultrasonographic measurements for the duodenum and jejunum had high agreement. No significant difference was identified between nonsedated and sedated rabbits in mean number of peristaltic contractions of the duodenum or jejunum.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that both B-mode and PWD ultrasonography of the duodenum and jejunum may be suitable for noninvasive evaluation of small intestinal motility in rabbits and that the sedation protocol used in this study had no impact on measured peristaltic values. (Am J Vet Res 2019;80:657–662)
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