Pikas, Rabbits, and Hares: Lagomorpha

views updated

PIKAS, RABBITS, AND HARES: Lagomorpha

PHYSICAL CHARACTERISTICS

Lagomorphs are small to medium-sized mammals categorized into two families: Leporidae (rabbits and hares) and Ochotonidae (pikas [PEE-kuhz]). Rabbits and hares have long hind legs adapted for running at fast speeds over open ground. Pikas are small mammals with large, round ears and resemble guinea pigs in size and appearance. Adult rabbits and hares have a body length of 10 to 28 inches (25.4 to 71.1 centimeters) and weigh 14 ounces to 15.3 pounds (400 to 7,000 grams). They have short, furry tails and ear sizes vary greatly and generally are shorter in rabbits and longer in hares. The main exceptions are the rabbit breeds known as lops, which have long, floppy ears. Females are generally larger than males. Hares generally are larger than rabbits and have black-tipped ears.

Rabbits and hares usually have thick, soft fur that comes in a wide spectrum of colors, shades, and combinations, including black, white, brown, beige, tan, blue, orange, red, pink, cream, lilac, silver, and lavender.

Pikas are small, compact mammals with short front and rear legs. They range in length from 5 to 12 inches (125 to 300 millimeters) and weigh 3.5 to 7 ounces (100 to 200 grams). Pikas lack a noticeable tail. They have long, soft fur that is usually gray or brown.

Lagomorphs have eyes set high on their head, looking sideways, giving them a wide field of vision. They have weak but flexible necks, allowing them to turn their heads with a wide range of motion. Lagomorphs have a single opening to pass both urine and feces. They also have a specialized part of their large intestine, called the cecum (SEE-kum), which acts as a fermentation chamber and aids in digestion of grasses.

GEOGRAPHIC RANGE

Lagomorphs are found on every continent except Antarctica. They are native to every continent they are found on, except Australia where they were introduced.

HABITAT

Pikas are found in two distinct habitats. Some live among rocks and rocky areas. Others live in meadows, steppes (semiarid, grass-covered plains), shrubs and desert. Hares live in arctic tundra, steppes, wetlands, forests, and deserts. Rabbits live in pine and deciduous forests, desert, mountainous areas, scrubland, tropical rainforest, near rivers and streams, rocky outcroppings, grasslands, and areas of dense brush or other low-lying vegetation.

DIET

Lagomorphs are herbivores, meaning they are plant-eaters, with a primary diet of grasses and herbs but also will feed on fruit, seeds, leaves, shoots, and bark.

BEHAVIOR AND REPRODUCTION

Behavior and reproduction differs widely between rabbits and hares, and pikas, and within each group. Pikas are mainly diurnal, meaning they are mostly active during the day. Rabbits and hares are generally nocturnal, meaning they are mostly active at night. Some species are crepuscular (kri-PUS-kyuh-lur), meaning they are most active at dawn and twilight. Various environmental conditions and the effects of nearby humans may cause species to alternate between nocturnal, diurnal, and crepuscular activities.

Pikas have several types of social structures. Those that live in rocky areas of North America are unsocial, with males and females having separate territories and rarely interacting except to mate. Pikas in rocky areas of Asia live in pairs within a communal territory. Burrowing pikas, in contrast, are extremely social animals. Families of up to thirty individuals live within burrows and there are about ten family groups within a territory. There is a lot of interaction between family members, including grooming, playing, and sleeping together.

Rabbits and hares have similar differences in social organization. Most rabbits and hares in the wild live solitary lives, although they will often graze together, and are not territorial. The European rabbit is very social. They live in "warrens" or groups of six to twelve adults controlled by a dominant male. The warren consists of a maze of burrows and chambers.

Pikas breed in the spring, with peak breeding occurring in May and early June. Female pikas reach sexual maturity at about one year of age. The gestation period, the time the females carry their young in the womb, is about thirty days. Litters consist of two to six babies and are cared for exclusively by the mother. Females breed for a second time shortly after the first litter is born and usually produce a second litter before the end of summer. Babies are born blind and nearly hairless but grow quickly, reaching adult size in forty to fifty days.

Rabbits breed throughout the year, depending on climate. Generally the breeding season in the wild is spring and summer. Females have multiple litters per year with litter sizes of two to eight babies on average, although it can be as high as fifteen babies. The gestation period is twenty-five to fifty days, with the longer periods occurring in hares.

There is extremely limited parental care of babies in lagomorphs. Most mothers visit the young in their nest once a day, usually between midnight and 5:00 a.m. for a short period of nursing. In rabbits and hares, the young are weaned, stop feeding on their mother's milk, at about one or two months of age. They reach sexual maturity, able to reproduce, in four to six months.

FROM RODENTS TO PRIMATES

Lagomorphs were originally classified in the order rodentia, or rodents, until 1912, when researchers recognized that they had several distinct features lacking in rodents.

These features are:

Lagomorphs have four, rather than two, incisors in the upper jaw.
The male's scrotum is in front of the penis.
The penis has no bone as it does with a rodent.
Lagomorphs re-digest certain soft feces to obtain nutrients.

In the early twentieth century, the order Lagomorpha was established with two families, Leporidae (rabbits and hares) and Ochotonidae (pikas). There are about 91 living species of lagomorphs. Genetic testing done in the 1990s show lagomorphs are more closely related to primates, such as apes, and tree shrews than they are to rodents.

LAGOMORPHS AND PEOPLE

Pikas have little economic importance to humans. They are too small to be used as food, although they are sometimes hunted for their fur, particularly in China. Pikas are sometimes considered agricultural pests and killed by farmers. Rabbits and hares are hunted worldwide for sport and for their meat and fur. They are also raised commercially for their fur and meat. Several species are used extensively by humans as experimental subjects in laboratories. Rabbits are also raised as pets, primarily in the United States, Canada, and Western Europe. They are sometimes considered agricultural and horticultural pests and killed by farmers and other humans.

CONSERVATION STATUS

Six species of lagomorphs are listed by the World Conservation Union (IUCN) as Critically Endangered, facing an extremely high risk of extinction. Twelve species are listed as Endangered, facing a very high risk of extinction; fourteen species are listed as Vulnerable, facing a high risk of extinction; and one species, the Sardinian pika is listed as Extinct, died out. Eight species are listed as Near Threatened, not currently threatened, but could become so.

The primary reason for declining populations of lagomorphs are loss of habitat, disease, especially the pox virus myxomatosis (mix-oh-mah-TOE-sus), and conversion of habitats to agricultural use by humans.

FOR MORE INFORMATION

Books:

Macdonald, David. The New Encyclopedia of Mammals. Oxford, U.K.: Oxford University Press, 2001.

Miller, Sara Swan. Rabbits, Pikas, and Hares. New York: Franklin Watts, Inc., 2002.

Morris, Ting. Rabbit (Animal Families.) Mankato, MN: Smart Apple Media, 2004.

National Research Council. "Rabbits." In Microlivestock: Little-Known Small Animals with a Promising Economic Future. Washington, DC: National Academies Press, 1991. Online at http://books.nap.edu/books/030904295X/html/179.html (accessed on July 12, 2004).

National Research Council. "Domestic Rabbit." In Microlivestock: Little-Known Small Animals with a Promising Economic Future. Washington, DC: National Academies Press, 1991. Online at http://books.nap.edu/books/030904295X/html/183.html (accessed on July 12, 2004).

Nowak, Ronald M. Walker's Mammals of the World, 6th ed. Baltimore: Johns Hopkins University Press, 1999.

Swanson, Diane. Welcome to the World of Rabbits and Hares. Portland, OR: Graphic Arts Center Publishing Co., 2000.

Swanson, Diane. Rabbits and Hares (Welcome to the World of Animals). Milwaukee: Gareth Stevens, 2002.

Periodicals:

Chapman, Joseph A., et al. "Sylvilagus floridanus." Mammalian Species (April 15, 1980): 1–8.

Cohen, Philip. "Rabbit-Human Stem Cell Claims Provoke Controversy and Doubt: Scientists in China Say Stem Cell Capable of Forming Muscle or Nerve Tissue can be Derived by Interspecies Cloning, Overcoming the Shortage of Human Eggs." New Scientist (August 23, 2003): 14.

Graur, Dan, et al. "Phylogenetic Position of the Order Lagomorpha (Rabbits, Hares, and Allies.)" Nature January 25, 1996): 333–335.

Hacklander, Klaus, et al. "The Effect of Dietary Fat Content on Lactation Energetics in the European Hare (Lepus europaeus)." Physiological and Biochemical Zoology (January 2002): 19–28.

Krebs, Charles J., et al. "What Drives the 10-Year Cycle of Snowshoe Hares?" BioScience (January 2001): 25.

Roach, John. "Rabbit Woes: Easter Icons Face Survival Struggles." National Geographic News (April 17, 2003). Online at http://news. nationalgeographic.com/news/2003/04/0417_030417_rabbits.html (accessed on July 12, 2004).

Smith, Andrew T., and Marla L. Weston. "Ochotona princeps." Mammalian Species (April 26, 1990): 1–8.

Sohn, Emily. "Now Mammals are Feeling the Heat." New Scientist (October 5, 2002): 9.