Thread: Multiplicity of infants taking birth at a time

My question is this - why does a cow give birth to one calf while goats give birth to 3 at a time? I mean what is the factor that decides the number of infants taking birth at a time. Please enlighten me.

I would assume that the size of the fetus during develpment would be the limiting factor in regards to the number of offspring...calves are quite large at birth and carrying more than one calf would put too much stress on the mothers system!

Well if we think in terms of fitness, we have to think of a few parameters.

Cost of fitness per offspring for the mother.

Likelihood of offspring surviving to reproductive age.

Degree and cost of parental care.

Within these broad categories you can think of ways that number of offspring can effect fitness. Typically, what you observe in nature is two trends: low number of offspring, high level of parental care and high individual survival of offspring; and high number of offspring, low parental care and high mortality rates amongst the offspring. Which model is more beneficial depends on the environment.

The evolutionary history also has to be taken into account. For the ancestors of cows a single offspring at the time may have been more obviously beneficial than it is to us today, it takes a long time for reproductive systems to change.