Animals / Mammal Facts / Rodents - Most Populous Group of Mammals

Rodents - Most Populous Group of Mammals

rodents playing


The rodent family are an order of mammals with over 2000 different living species within it. They are the largest order of mammals in existence and are thought to account for around 40% of all mammals on the planet. This is probably due to their small size, short breeding cycle and of course they can survive on many different foods.



rodent body size lifespan


Rodents range grossly in size from the smallest pygmy mice being as little as 2.5 inches (6 cm) and weighing less than 0.25 oz (7 g). The largest species is the capybara which can weigh up to 180 lb (80 kg) and there are extinct species who are said to have weighed over 2200 lb (1000 kg), imagine coming across that creature! Some common rodent species include: squirrels, gerbils, voles, beavers and rats.

All rodents are characterized by their teeth: two incisors in both their lower and upper jaw. These incisors are unique as they grow continuously and need to be consistently worn down by gnawing. The majority of species use their teeth for a range of purposes from cutting wood to defending their young. The majority of rodents feed solely on plants, with seeds being particularly prominent in their diets. However, some species of squirrel are known to eat small birds and there are a few species that will eat fish and insects.


guinea pig brown black


There are two main groups in the rodent family:
Squirrel-like rodents and mouse-like rodents (Sciurognathi) - members include the grey squirrel, dormouse and golden hamster.
Cavy-like rodents (Hystricognathi) - members include the guinea-pig, porcupines and capybara.

The majority of the species are social animals and live in large colonies, although a small number prefer a “family-like” group which is much more intimate. There are also solitary species such as porcupines and pocket mice who live in their own self-dug intricate burrow system.




Doing what they have to do to survive – crawling around in dirty places, rodents have acquired a bad reputation for spreading disease. For health reasons humans have to keep a watchful eye on the populations of wild rodents and their presence among us. Natural predators like owls, coyotes, cats and snakes may contain their populations in a way that is cleaner and safer than chemical pest control.


long eared squirrel snow


Rodents are famous for their reproduction rates and the large number of offspring they produce. This is one of the key reasons that make them the largest order of mammals. The reasons behind this include a brief pregnancy period which means they produce many litters per year and each litter is likely to produce a large number of young. Some species have gestational periods as short as forty-five days and each litter contain be up to four young.




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