Reproduction in Cottontails
By John Gibble
In order to maintain a good population of cottontail rabbits for our club grounds and running areas, we need to think a bit about population dynamics. Managing a population is much like managing a bank account. You have deposits (reproduction, immigration, and individuals added through trap and release). You also have withdrawals (death through predation or disease, and emigration or escapes). Reproduction is an important key to balancing or increasing your account.
April is the start of the peak in cottontail reproduction so this seemed like a good month to give some thought to it. But before we talk about April, we need to go a few months back to January when breeding season for cottontails begins. A number of researchers attribute the start of breeding season to the increase in daylight length, while others cite an increase in average daily temperatures. The temperature argument relies on observed periods of unusually cold weather in late winter causing delays in the onset of cottontail breeding.
As hours of daylight increase and/or daily average temperatures increase, both male and female cottontails react. In late summer or early fall the testes in the male rabbits shrank and shut down to save metabolic energy. At the end of January, the testes are reactivated and return to functioning. In the females the changes in daylight and temperature cause a release of hormones, revitalizing their reproductive system, creating a state of “pre-estrus”. This state continues until breeding actually takes place.
As I’m writing this in February, the onset of the breeding season is quite apparent. Where I haven’t seen a rabbit killed on the road for several months, I just started seeing two or three killed most every morning on my way to work. At sunrise, as I’m drinking coffee and staring out the window at my pen I enjoy watching the rabbits chase each other, face off, jumping straight up in the air or leap-frogging over each other. Classic mating behavior.
Don’t miss the rest of this article starting on page 14 of our April 2018 issue!