Rabbits: The Animal Answer Guide

2 Form and Function of Rabbits

What are the largest and smallest living rabbits? Lagomorphs can be roughly divided into pikas, which are small, rabbits , which are medium-sized, and hares, which are medium-sized to large. Overall lagomorphs exhibit a relatively small range of sizes, from around about 80 grams to about 6 kilograms (2.8 ounces to 15 pounds), but some can weigh as much as 10 kilograms (22 pounds). Compare this with rodents, which range from 6 grams to 66 kilograms (0.21 ounces to 145 pounds). The lagomorphs collectively also fall into a rather odd size class among mammals. The vast majority of mammals, about 80 percent, are small to very small. Most of these are rodents (2,277+ species of 5,416), bats (1,116+ species), and shrews. In fact, some biologists think the optimal size for a mammal is about 100 grams (3.5 ounces), although the modal, or typical, size is about 40 grams (1.4 ounces). For comparison, four slices of Wonder Bread weigh about 100 grams. Among the lagomorphs, only the smallest of the small pikas are close to the modal size, while larger pikas hit near or exceed the optimal size. The smallest pikas appear to be Thomas’s pika (O. thomasi) at 45 to 110 grams (1.6 to 3.9 ounces), the Gansu pika (O. cansus) at 50 to nearly 100 grams (1.7 to 3.5 ounces), and the Tsing-Ling pika (O. huangensis) at 52 to 108 grams (1.8 to 3.8 ounces). Even these diminutive mammals are large compared with most bats, rodents, and shrews—the smallest of which, Remy’s pygmy shrew (Suncus remyi), tips the scales at a mere 1.8 grams or 0.06 ounces. Most pikas are somewhat larger, falling in the range between about 100 and 300 grams (3.5 and 10.6 ounces). In only a few pika species do individuals exceed 300 grams (10.6 ounces). The largest species, the alpine Chapter 2 Form and Function of Rabbits 29 30 Rabbits: The Animal Answer Guide pika, weighs from 226 to 360 grams (7.8 to 12.7 ounces), while the Chinese red pika (O. erythrotis) weighs from 184 to 352 grams (6.5 to 12.4 ounces). The northern pika, while generally smaller, approaches the size of alpine pikas when they live at the same high latitudes, an illustration of Bergman’s rule, which states that animals tend to get larger as temperatures get colder, either due to increasing latitude or increasing elevation. Pygmy rabbits are the smallest rabbits at from 373 to 458 grams (13.1 to 16.1 ounces), followed closely by volcano rabbits, which range from 387 to 602 grams (13.6 to 21.2 ounces). Among the cottontails, the smallest tapeti ranges from an average of 778 grams to 1.2 kilograms (27.4 ounces to 2.6 pounds), depending on the population, while the largest swamp rabbit reaches 2.7 kilograms (6 pounds). Mexican cottontails (S. cunicularius) are also quite large, ranging from 1.8 to 2.3 kilograms (4 to 5 pounds). Among the rest of the rabbits, the smallest are the European rabbit, which average just 1 kilogram (2.2 pounds) in the southwestern population and 2 kilograms (4.4 pounds) in the northeastern one. The Sumatran striped rabbit’s weight is estimated at 1.5 kilograms (3.3 pounds). On the large end, the Bunyoro rabbit ranges from 2 to 3 kilograms (4.4 to 6.6 pounds). Domestic rabbit breeds range in size from just under 1 to more than 10 kilograms (2.2 to 22 pounds). The smallest hares average about 1.5 kilograms (3.3 pounds), and this group includes the snowshoe hare, the Hainan hare (L. hainanus), and the Yarkand hare (L. yarkandensis) of China. The largest hare is the Alaskan hare, which averages about 4.8 kilograms (10.5 pounds), with the largest reaching 7.2 kilograms (nearly 16 pounds). Body size in hares generally follows Bergmann’s rule, with the largest hares living in the far north, the Gansu pikas, native to China, are among the smallest of their family. Photo © Andrew Smith 31 Form and Function smallest at the equator, and medium-sized species in the temperate zone, although there are clearly exceptions like the snowshoe and Yarkand hares. Unusual among mammals, in most leporid species females are larger than males, although the differences are fairly...