The number of molts in a year, depending on the kind of lagomorph, varies in adults from one (according to Nelson, 1909:31) in the cottontails (genus Sylvilagus) to as many as three (according to Lyman, 1943, and Severaid, 1945) in the varying hare (Lepus americanus). Difficulties that I have experienced in attempting to account for the variations in color and wear of the pelage of the pika, Ochotona princeps, on the basis of two molts per year, make me wonder if it, too, has three molts. Lepus townsendii certainly has at least two molts per year.
Key to Families and Genera of Lagomorpha
- 1. Hind legs scarcely larger than forelegs; hind foot less than 40; nasals widest anteriorly; no supraorbital process on frontal; five cheek teeth on each side above
- Family Ochotonidae, Genus Ochotona, p. [125]
- 1´. Hind legs notably larger than forelegs; hind foot more than 40; nasals widest posteriorly; supraorbital process on frontal; six cheek teeth on each side above
- Family Leporidae, p. [134]
- 2. Interparietal fused with parietals (see fig. 49); hind foot usually more than 105
- Genus Lepus, p. [170]
- 2´. Interparietal not fused with parietals (see fig. 10); hind foot usually less than 105
- Genera Romerolagus and Sylvilagus, pp. [137], [138]
Family Ochotonidae—Pikas
Certain characters in which this family differs from the Leporidae (hares and rabbits) are: hind legs scarcely longer than forelegs; ears short, approximately as wide as high; no postorbital process on frontal; rostrum slender; nasals widest anteriorly; maxilla not conspicuously fenestrated; jugal long and projecting far posteriorly to zygomatic arm of squamosal; no pubic symphysis; one less cheek-tooth above, the dental formula being i. 2/1, c. 0/0, p. 3/2, m. 2/3; second upper maxillary tooth unlike third in form; last lower molar simple (not double) or absent (in the extinct genus Oreolagus); cutting edge of first upper incisor V-shaped; mental foramen situated under last lower molar.
Genus Ochotona Link—Pikas
Revised by A. H. Howell, N. Amer. Fauna, 47:1-57, August 21, 1924.
1795. Ochotona Link, Beyträge zur Naturgesch, I (pt. 2):74. Type, Lepus ogotona Pallas.
Characters.—Five teeth (excluding incisor) in lower jaw; first cheek-tooth (p3) with more than one re-entrant angle; columns of lower molars angular internally; transverse width of any one column of a lower molariform tooth more than double the width of the neck connecting it to the other column.