Swamp hamster - Reithrodontomys raviventris is endangered. Total abundance unknown. Probably, it amounts to no more than a few thousand during the summer peak in numbers.
The southern subspecies are especially small. Its reduction is associated with the use by a person of the territory occupied by swamp hamsters for development, crops, salt production, as well as with irrigation. Protected by law.
How to find out
The length of the body and tail is 12.5-16.2 cm. The length of the tail is 5.6-9.5 cm. Outwardly similar to mice. The ears are rather large, almost bare. Paws are narrow. The hair is thick and soft. The dorsal side of the body is pinkish-light brown with scattered black hair, especially numerous along the midline of the back.
The abdominal surface is pinkish-light brown or whitish. The tail is dark brown or black on top, pale, sometimes almost white below. Hind limbs are dark brown or whitish.
They were distributed in the USA, in California throughout the Petalum-Napa region, as well as in Gallinas, Corte Madera and Petalum. A creek near San Pablo Bay and in the marshes of the northern and southern shores of Suisun Bay and most of the shores of San Francisco Bay. At present, they are found only in saline bogs adjacent to the bays of San Francisco, San Pablo and Suisun.
Lifestyle and Biology
Two subspecies are distinguished: R. G. raviventris in the southern part of the range and R. G. halicoetes in the north. It is inhabited by salty and brackish swamps. Salt marshes are characterized by the predominance of Salicornia with Spartina fohosa in the lower areas and Grindelia cuneifolia in the highlands. Typha latifolia and Scirpus with Salicornia and Distichlis dominate in brackish bogs.
Both types of swamps have a dense vegetation cover from 0.2 to 1 m high. Active at night. Spherical nests are built, where they spend the day (R. g. Halicoetes). R. g. Reviver tris, apparently, builds nests only during the breeding season
They feed on leaves and stems of plants, as well as, in much smaller quantities, seeds and insects. Reproduction lasts from March to November at R. G. raviventris and from May to November at R. G. halicoetes. There are four cubs in a litter. Females of R. g. Halicoetes bring one litter per year. Life expectancy, apparently, no more than a year.
With two exceptional pairs whose arms are highly unequal, all other autosomes are more or less equal-armed. Secondary constriction can be found on some autosomes near the centromeres. Identification of the sex chromosomes is unequivocal. In female cells, the two X chromosomes usually display a difference in morphology.
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