Brown rats thrive best in temperate climates and reproduce sexually.  They will normally produce offspring throughout Spring, Summer, and Autumn, but they can reproduce in winter as long as  the living conditions are suitable.  According to a study done in Buenos Aires, the Rattus norvegicus had the highest abundance of population in the park side during the summer.  The reserachers also concluded the highest abundance for the shanty town habit was in Autumn. [13]  This could be associated with the warmth that towns can provide as the temperature begins to dhroughout Arop tutumn.  A litter roughly consist of about 8 offspring that are parented about 3 to 4 weeks before gradually becoming independent.   The Rattus norvegicus anually has about 5 liters of offspring which in  return become sexually mature in about 10 weeks give or take a week or two. [4] .  So throughout their typical   1 1/2 to 3 year life span, the brown rat can have about 15 liters in a perfect reality.  Take this multiplied by 8 offspring for each liter gives you 120 offspring.  The high reproductive rate allows for increased survival against natures unknown catastrophes.  Something unique is the Rattus norvegicus can potentially have over a 1,000 offspring if not disturbed by any external forces throughout the year.   Also being a mammal, it almost seems overwhelming comparing how many offspring humans have in contrast with the Rattus norvegicus. 










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The graph is expressing various survivorship curves in relation to the number of offspring produced along with survival rate.  For example, humans are larger mammals that produce few offspring, but they provide excessive care for teaching their young throughout developmental stages of life.  These characteristics define a type 1 curve.   A squirrel, like the Rattus norvegicus, is small and has continuous growing incisors; however they produce more off spring than humans to make up for the death rate early on.  The death rate is linear or constant throughout the life span.  The number of survivors will meet that of humans.  This is known as the type 2 survivorship curve.  Now the oyster produces an even higher abundance of offspring, though they provide minimal care for their young.  So many of the offspring die in the larval stage, but the survivors tend to live for a long time after the development of particular defenses mechanisms such as a shell.  This survivorship curve is known as type 3.  [2]



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