Felines, wolves, elephants, apes… We all know big mammals, but what about the smaller ones? Do you know what is a desman or a solenodon? Read on to find out more about small mammals and their importance.
WHAT IS A MICROMAMMAL?
The word “micromammal” has no taxonomical value: it is not a word that biology uses in the classification of mammals. However, this colloquial term, like the word “dinosaur” sometimes it is used in scientific publications to group together several orders of small mammals, although in the same taxonomic group some species can have a large size.
In general, we consider micromammals animals of the following groups:
- Bats
- Rodents (rats, mice, squirrels, marmots, beavers, prairie dogs, hamsters, lemmings, gerbils, voles, chinchillas…)
- Lagomorphs (rabbits, hares and pikas)
- Insectivores (shrews, hedgehogs, moles, desmans …)
BATS
As we learnt in a previous post, bats are essential animals for ecosystems, they also have unique characteristics that make them worthy of several records: they are the only mammals able to fly actively, they are distributed to nearly every continent, they don’t get sick… to find out more about bats, visit What is a bat for?
In the Iberian Peninsula live eight species of bats. Learn more about them in the website Fauna Ibérica.
RODENTS
Rodents are the largest order of mammals, accounting for over 40% of the total and inhabit all continents except Antarctica. Some rodents are not considered micromammals for its large size, such as capybaras or porcupines. Most rodents are quadrupeds with long tail, claws, whiskers and continuously-growing large incisors. This fact forces them to constantly gnaw through its specialized jaws, to wear away the incisors and always keep them sharp. They have a great sense of smell and hearing, and the sense of touch in his whiskers. They communicate by scent and various vocalizations.
Most species are social and form large communities. Their anatomy is not so specialized than other mammals, allowing them to adapt to different habitats. Added to the high birth rate, they can keep populations stable in adverse conditions. The black rat, for example, can have litters every month of more than 10 babys.
Some rodents, especially rats and mice, occupy the same habitats that humans and are considered a plague. In addition to eating human food, they can contaminate it with their urine and feces and they are transmitters of more than 20 diseases, including the typhus and plague.
In the Iberian Peninsula inhabit about 23 species, divided into five categories:
- Cricetidae: voles (8 species), water vole and southern muskrat (non-native).
- Gliridae: Gray dormouse
- Sciuridae: common squirrel
- Muridae: mice and rats
- Myocastoride: Coypu (non-native)
RABBITS, HARES AND PIKAS (LAGOMORPHS)
Contrary to what a lot of people believe, rabbits and hares are not rodents but they belong to the order of lagomorphs. Unlike rodents, lagomorphs have a small, round tail, paws with thick fur and hair in their foot sole that helps grip while running.
All species are terrestrial and are distributed almost worldwide. They are among the most hunted animals, so its body has adapted to elude predators:
- Long ears for good hearing
- Eyes on top of the head with a vision of almost 360º
- Elongated hind legs to reach 56 km/h
Like rodents, the incisors are also continuously-growing, but behind them there is another smaller pair. They have high reproductive rates (some species can conceive a second litter before the first is born), sexual maturity within a few months of life and short gestations.
Lagomorphs are herbivores and practice cecotrophy: substances that can not be diggested, are evacuated through the anus in the shape of soft balls. They eat this balls in order to do a second digestion. If you have a rabbit as a pet ¡this behavior is completely normal!
In the Iberian Peninsula lives a species of rabbit and 4 species of hares (Iberian, European and Cabo del Piornal (non-native).
INSECTIVOROUS MICROMAMMALS
Currently the order Insectivora is no longer used and micromammals that feed on insects (and other animals) can be classified into five Orders:
- Hedgehogs, moonrats or gimnurs (Erinaceomorpha)
- Shrews, moles and solenodons (Soricomorpha).
- Tenrecs and golden moles (Afrosoricida)
- Elephant shrews (Macroscelidea)
- Treeshrews (Scandentia)
They are considered to be the most primitive mammals. Many species are characterized by:
- Elongated, thin and mobile snout. They have a good sense of smell
- Ears and small eyes in some species, like moles
- Five clawed toes on each paw
- They are plantigrades
- Some species, such as hedhehogs and tenrecs have spikes
- The solenodonts, water shrews and shrews are among the few poisonous mammals in the world. Read this post to learn more.
Most of them are nocturnal and their diet is based on insects, spiders and worms, but they also eat plants and other animals. Besides, they are not the only mammals that eat insects.
In the Iberian Peninsula lives the Pyrenean desman, two species of hedgehog, about five species of shrews, two species of water shrews, and the Spanish mole. To learn more about the Pyrenean desman, in the website El Bichólogo you can find more information.
IMPORTANCE OF MICROMAMMALS
- In Paleozoology, the fossils of micromammal provide a lot of information as they tend to be found more often in deposits than other mammals. In addition, many times their bones are accumulated due to the eating habits of their predators. They provide valuable information on the climate of the past (paleoclimatology) and the classification of rocks in layers (biostratigraphy).
- Despite its bad reputation, some rodent species are beneficial, controlling insect populations and destroying weeds, contributing to the health of forests spreading fungus… and are still used in scientific research.
- Many species are responsible for the spread of pollen or seeds.
- They are vital for the conservation and maintenance of their predatory species in decline, as the Pyrenean owl or Iberian Lynx.
- Since some of them live in burrows (rabbits) or they are burrowers (moles), they contribute to the ventilation of the soil and its fertility.
REFERENCES
- Clutton-Brock, Juliet et al. 2002. Animal. Pearson Education
- Diversidad con los micromamíferos de la Sima del Elefante (Atapuerca, Burgos)
- fauna ibérica
- Botanical-online
- Por qué es tan importante el conejo?
- Source of cover image (star-nosed mole)
All you need is Biology 
Muy majo post¡¡