New World Mice
The division of living beings into systematics is a continuous subject of research. Different systematic classifications exist side by side and one after the other. The taxon treated here has become obsolete due to new research or is not part of the group systematics presented in the German-language Wikipedia.
The New World mice are a group of mouse-like rodents from the family of the burrowers (Cricetidae). It is a group that is rich in shape and species (around 500 species) and is distributed across the entire American continent. The New World mice have no scientific name and no systematic rank, but are divided into three subfamilies, Neotominae , Sigmodontinae and Tylomyinae . It is unclear whether the New World mice form a monophyletic group (that is, more closely related to each other than to any other animal).
features
The New World mice are a diverse group that have occupied a wide variety of ecological niches and accordingly have different body shapes. Many species resemble mice or rats , but there are also vole , mole , gerbil and shrew- like representatives. The length of the head body varies depending on the species from 5 to 35 centimeters and the weight between 6 and 450 grams. The South American giant rats ( Kunsia ) are among the largest representatives, while the American harvest mice ( Baiomys ) are among the smallest . The texture of the fur varies as well as the color, but most species are kept in brown, gray or black tones, whereby the underside and often the feet are lighter. The length of the tail is variable depending on the way of life, as is the structure of the limbs. The individual subfamilies differ in the morphology of the penis .
The tooth formula for almost all types is I 1/1 - C 0/0 - P 0/0 - M 3/3, so a total of 16 teeth. Only the genus Neusticomys has only 2 molars and a total of 12 teeth per half of the jaw. The molars have roots, the arrangement of the chewing cusps is variable, the rearmost molar is usually smaller.
distribution and habitat
New World mice are native to the entire American continent, their range extends from Alaska and northern Canada to Tierra del Fuego . There they have populated almost every habitat, they can be found in grasslands and steppes as well as in deserts and tropical rainforests and also in mountain regions up to over 5000 meters above sea level. Some species have adapted to the proximity of humans as cultural followers and also inhabit fields and plantations.
Way of life
As diverse as the body shapes and habitats, the ways of life of the New World mice are just as diverse. Most species are ground-dwellers, but many are good climbers and some have specialized in a tree-dwelling way of life. There are also species that lead an underground, burrowing way of life and also semi-aquatic forms (some of which live in water). They can be active at night, at dusk or during the day, they do not hibernate , but during the cool season they sometimes go into a cold rigor ( torpor ). Social behavior is also variable; in addition to solitary species, there are also species that live in groups.
nutrition
Many species are herbivores that eat grass, seeds, fruits, nuts, mushrooms, tubers and other parts of plants. In addition, there are also a number of omnivorous species that supplement their diet with animal food (insects, spiders, scorpions, crabs, earthworms, small vertebrates, eggs and others). Some groups such as the grasshopper mice and the fish rats have even completely adapted to a carnivorous diet, which is rather untypical for rodents.
Reproduction
New World mice are generally very fertile animals with a high rate of reproduction. In warmer areas, mating can usually take place all year round, with the females having several litters each year. The gestation periods are usually very short with 20 to 40 days, the litter sizes are typically two to five young animals (in individual cases it can be over ten). The newborns are nestled , but grow quickly. After about one to two weeks, their eyes open, after two to four weeks they are weaned. Sexual maturity occurs at one to four months.
Life expectancy is low. Numerous predators such as predators , snakes , birds of prey , owls and others ensure that animals rarely live more than a year in the wild. In human care, however, ages of up to 5 years are possible.
New World mice and humans
Some species have adapted to humans as cultural followers and already show in their names their preference for plantation fruits ( cotton rats , rice rats or sugar mice ). In some places they are considered a plague and are persecuted. Some species are also feared as carriers of viruses (such as hantaviruses ).
A number of species are among the most common mammals in their range, others have only a small habitat and are endangered. Island endemics - species that only occur on individual islands - are particularly threatened . Several of these species are already extinct, such as the Caribbean giant rice rats, the bush rat Neotoma bryanti bunkeri , the Fernando de Noronha rat , the Galápagos giant rat , and others. The reasons for their extinction are mostly due to the introduction of rats , cats or mongooses .
Systematics
The New world together with the voles (Arvicolinae) and hamsters (Cricetinae) the family of agitators (Cricetidae). However , they are more distantly related to the Old World mice , which often occupy the same ecological niches and lead a similar way of life.
Today the New World mice are divided into three subfamilies:
- The Neotominae comprise around 125 species and are common in North and Central America.
- The Tylomyinae are a species-poor group (10 species) of tree-dwelling animals from Central America.
- The Sigmodontinae are approximately 375 species, the most species-rich group have their main distribution in South America - only a few representatives live in North and Central America.
Traditionally, all New World mice were grouped together in a common subfamily, Sigmodontinae, the division into the three present-day subfamilies is based on differences in the structure of the penis and hind feet and has also been confirmed by molecular genetic studies. Whether or not the three subfamilies form a monophyletic group is controversial. The study by Jansa and Weksler (2004) could indicate that the Sigmodontinae are more closely related to the voles than to the other New World mice. These correspondences are only weakly pronounced, the molecular findings are unclear, so that the question of monophyly in New World mice cannot be answered at present. What is certain is that the three subfamilies separated from each other at about the same time as the other subfamilies.
literature
- Sharon A. Jansa, Marcelo Weksler: Phylogeny of Muroid Rodents: Relationships Within and Among Major Lineages as Determined by IRBP Gene Sequences. In: Molecular Phylogenetics and Evolution. Vol. 31, No. 1, April 2004, ISSN 1055-7903 , pp. 256-276, doi : 10.1016 / j.ympev.2003.07.002 , (online: PDF , 755 kB).
- Ronald M. Nowak: Walker's Mammals of the World. 2 volumes. 6th edition. Johns Hopkins University Press, Baltimore MD et al. 1999, ISBN 0-8018-5789-9 .
- Don E. Wilson , DeeAnn M. Reeder (Eds.): Mammal Species of the World. A taxonomic and geographic Reference. 2 volumes. 3. Edition. Johns Hopkins University Press, Baltimore MD 2005, ISBN 0-8018-8221-4 .
Web links
- Sigmodontinae , Neotominae and Tylomyinae on Animal Diversity Web