The rock pocket mouse (''Chaetodipus intermedius'') is one of 19 species of pocket mice in the genus ''Chaetodipus''. It is sometimes grouped in the genus '' Perognathus''.

Description

Found mainly in rocky outcrops in the

desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

s of the southwestern United States and Mexico, the rock pocket mouse is medium-sized (length ~18 cm, weight ~12–18g) and

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

. It eats mainly plant seeds and makes small burrows in soil close to or under rocks to evade owls, its main predator. The

breeding season Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and cha ...

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 In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

(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, basaltic 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 The Pinacate Peaks (Sierra Pinacate, ood, Cuk Doʼag) are a group of volcanic peaks and cinder cones located mostly in the Mexican state of Sonora along the international border adjacent to the U.S. state of Arizona, surrounded by the va ...

, Mexico and

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

, USA. In the Pinacate mice, they discovered a perfect association between different versions of the

Melanocortin-1 receptor The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormones ...

(''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 pi ...

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