Cottontail rabbits (Sylvilagus) are widespread lagomorphs across North America, recognizable by their bushy white tail. They inhabit diverse environments, from deserts and swamps to suburban parks. Determining their size is complex because the term covers approximately 13 distinct species, each with unique characteristics. This overview provides factual data on the general physical dimensions of adult cottontail rabbits.
Standard Adult Dimensions
The average adult size is best represented by the common Eastern Cottontail (Sylvilagus floridanus), the most abundant species. These medium-sized rabbits typically measure between 14 and 19 inches (36 to 48 centimeters) in total length, including the head and body. Their weight usually falls within a range of 1.8 to 4.4 pounds (0.8 to 2.0 kilograms).
Body mass exhibits slight variation between the sexes, known as sexual dimorphism. In the Eastern Cottontail, females tend to be marginally heavier and larger than males, which is common among cottontails. This size advantage is often associated with the high energy demands of reproduction. Total size is also influenced by geographic location, with individuals in northern latitudes sometimes growing larger than their southern counterparts.
Species-Specific Size Differences
The overall size of a cottontail rabbit varies significantly across the species within the Sylvilagus genus. The smallest North American rabbit is the Pygmy Rabbit (Brachylagus idahoensis), which is sometimes discussed alongside cottontails. An adult Pygmy Rabbit is strikingly smaller, weighing 0.8 to 1.1 pounds (375 to 500 grams) and reaching a body length of only 9.3 to 11.6 inches.
Conversely, the largest cottontail is the Swamp Rabbit (Sylvilagus aquaticus), found in the southeastern United States. These rabbits are robust, with adults commonly weighing between 2.5 and 6 pounds (1.1 to 2.7 kilograms). Swamp Rabbits also have a longer body length, measuring 16 to 22 inches (41 to 56 centimeters). The largest species can be nearly six times the mass of the smallest.
The Mountain Cottontail (Sylvilagus nuttallii) occupies a moderate size range. It typically weighs 1.5 to 2.6 pounds (0.7 to 1.2 kilograms), with a length generally between 13.8 and 15.4 inches.
Growth and Maturity
Cottontail rabbits are born highly altricial, meaning the young are blind, hairless, and completely dependent on maternal care. A newborn Eastern Cottontail kit typically weighs only 0.8 to 1.1 ounces (25 to 30 grams) at birth. This small starting size necessitates a rapid growth timeline for survivability.
The young develop quickly, opening their eyes within the first week and becoming mobile enough to leave the nest site around two weeks of age. Weaning usually occurs at four to five weeks, after which the young become independent. This rapid development is an adaptation to their short average lifespan in the wild.
Cottontails reach their full adult size and weight surprisingly swiftly. Many individuals attain sexual maturity at just two to three months of age, often coinciding with reaching maximum adult dimensions. For example, the Swamp Rabbit reaches sexual maturity around 23 weeks. By the end of their first summer, most spring-born cottontails are indistinguishable in size from mature adults.