Question: why is it that different species of animals have a different amount of offspring (e.g dogs compared to humans)

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  1. @gannaz: that’s a really great question and the answer lies in our reproductive systems and the way they work – particularly ovulation, or the releasing of the eggs and how resilient they are in the week or so after that.

    In dogs, they adult females have two periods each year when they are ‘in season’ and able to get pregnant. They have several eggs released (as a guide – small breeds typically have 2-4, and larger breeds can have up to 12 pups in a litter) and the eggs stay viable for about a week, so it’s actually possible for a litter to have different dads. Pregnancy lasts around 9 weeks in dogs.

    In humans, there is typically only 1 (sometimes 2) egg/s released each month that can become fertilised (and then become a baby). Pregnancy lasts around 40 (longgggggggggggggggggggg) weeks in humans.

    Different animals have different ‘strategies’ when it comes to offspring. Some (like fish) breed vast quantities (hundreds every fertile period) with minimal after care provided (‘have lots, some will make it’ strategy), while others (like mammals – dogs and humans) produce less numbers and invest more (in terms of time, resources and care). Both strategies (and others that fall in between) are effective and successful from an evolutionary point of view.


  2. Mia’s answer is great.
    My addition to this is to do pigs and their piglets. The sow (mum) is a usually a heavy girl and can find it difficult to move around. The sow builds a nest on the ground for her and her piglets to be comfortable in. Piglets are VERY hungry animals (I guess thats why calling someone a piglet makes sense). So mum is always jumping up and down feeding her piglets or feeding herself without much time in between. It’s common for mum to squash a piglet or 2 before they’re aware enough to get out of the way so her litters are larger than others animals to ‘allow’ for these accidents to happen and not completely wipe out her family in one go.



  1. Thx