Tuesday, June 23, 2015

Bunny Boom

Eastern Cottontail Rabbit

     People may have noticed quite an increase in the number of rabbits they are seeing in certain places this year. This is due to a couple of factors. First of all, many of our native Eastern Cottontail (Sylvilagnus floridanus) rabbits have just completed weaning and are heading off on their own to find new places to live. Many of these rookie rabbits do not make it very far, ending up hit by cars, picking poor locations to live, or eaten by predators, but many at least temporarily do.
     I also suspect that there may be more rabbits about because of a decline in one of their main predators. Red foxes suffered from an outbreak of sarcoptic mange over the last year. This caused numerous fatalities and thus less predatory pressure on cottontails, allowing their numbers to expand. Rabbits can make up to 50% of the diet of foxes and they are their most important predator. For more on the red fox, who weren't originally part of our landscape, check out this previous Blog entry on them:             http://capitalnaturalist.blogspot.com/2013/12/red-fox_26.html

     The Eastern Cottontail is quite common throughout our region, and indeed throughout the East. Having 3-4 (up to 7) litters a year of 3-6 bunnies each (after about a month's gestation), they can reproduce quite quickly. But since they're a favorite meal for many hawks, owls, foxes, cats, bobcats, dogs, large snakes, coyotes, possums, mink, skunks, weasels, and even crows, mortality rate is close to 80% of the adults a year. Even fewer rabbits even make it to adulthood. Fifteen months is a good average old age in the wild, while in captivity they can live to 5 years. Injured rabbits give quite an eerie scream. This often attracts predators, a trick learned by hunters using artificial game calls to lure them in.
     Young are born in a depression usually hidden in the brush or grass. This is sometimes called a "form" and is lined with leaves and fur. Baby rabbits are born naked and with eyes closed (unlike Hares which are born haired and with their eyes open, and who also have longer ears). Two to four weeks later, they're hopping off on their own, often themselves ready to mate at 2-3 months of age. Males rabbits are called "bucks" while females are called "does."
     Rabbits (along with hares and pikas) are called "lagomorphs," differing from rodents by having long back legs, often large ears, short tails, and most especially an unusual tooth arrangement. Lagomorphs have a double set of upper incisors, one set right in front of the other. Cottontails are herbivores and are coprophagous (eating their own green fecal pellets the first time it goes through their system to get the most of what they've eaten).

Two rabbit skulls, with the double incisors visible on the left one.

     Many people think that all rabbits live in holes (called "warrens" in Europe where their rabbits do live in burrows), but our native cottontails do not do so. They may "hole up" in a groundhog hole if being chased or in extreme weather, but they actually live above ground. Most maintain a home range that's about 100 yards or so, though this varies, with males especially having larger ranges. They do not like to venture out of this small territory, running in zig zags, flashing their tails, but usually circling around at some point rather than leave their familiar territory.
     Cottontails have actually increased their distribution, living now in New England and some parts of Canada where they did not do so before. They've also been introduced to several islands and have bred, well, like rabbits, now being numerous in those places.
   So enjoy the cottontails while they're around. Though they may eat some of our garden plants, they will not be around for long. Something will end their lives shortly, be it cars, diseases like tularemia, or predators. Bunny booms are short lived.

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