The rock pocket mouse (''Chaetodipus intermedius'') is one of 19

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of pocket mice in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''Chaetodipus''. It is sometimes grouped in the genus ''

Perognathus ''Perognathus'' is a genus of pocket mouse. Like other members of their family they are more closely related to pocket gophers than to true mice. Characteristics The silky pocket mice are small animals with soft pelage, long tails, and small ...

''.

Description

Found mainly in rocky outcrops in the deserts of the southwestern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

and

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, the rock pocket mouse is medium-sized (length ~18 cm, weight ~12–18g) and nocturnal. It eats mainly plant seeds and makes small burrows in soil close to or under rocks to evade

owl Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...

s, its main

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. The breeding season spans a few months, starting in February or March, and the litter size is typically between three and six. As with most pocket mice, the tail is longer than the body (~10 cm).

Taxonomy

Historically, rock pocket mice have been subdivided into as many as ten subspecies (Benson 1933; Dice and Blossom 1937) based on geographical distribution and coat colour. Most rock pocket mouse populations have light, tawny fur consistent with the colour of the desert rocks on which they live. However, darker coloured rock pocket mice are found living amid black,

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

ic rock formations.

Example of natural selection

In 2003, scientists sampled DNA from both light- and dark-coloured rock pocket mice from areas in Pinacate Peaks, Mexico and

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ke ...

, USA. In the Pinacate mice, they discovered a perfect association between different versions of the Melanocortin-1 receptor (''Mc41r6'')

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

and coat colour . Subsequent studies demonstrated that there is strong selective pressure maintaining ''Mc1r''

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

and coat colour frequencies across the short geographic distances between the light- and dark-coloured rock islands. Thus

melanism The term melanism refers to black pigment and is derived from the gr, μελανός. Melanism is the increased development of the dark-colored pigment melanin in the skin or hair. Pseudomelanism, also called abundism, is another variant of ...

in rock pocket mice is considered a fabulous example of adaptation by

natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...

. Changes in the ''Mc1r'' gene sequence are not responsible for the colour difference in the mice sampled from New Mexico, however, leading the researchers to conclude that the almost identical dark coat colours developed multiple times in rock pocket mice, an example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

Description

Taxonomy

Example of natural selection

See also

References

Further reading