Zuniga’s Dark Rice Rat inhabits a desert-dryland habitat known as the coastal Lomas ecosystem, where it has been found in areas of mesic vegetation along stream banks and on hilltops, where the plants retain moisture from sporadic bouts of winter fog. This Peruvian rodent is Critically Endangered, and has not been seen since the former half of the 20th century, when it was described and individuals were collected from the low-lying hills of the Lomas de Atocongo, between elevations of 600 and 800 meters. We know very little about this species as more recent efforts have failed to relocate it. However, biologists believe it is terrestrial and probably nocturnal. As it was never recorded in modified habitats or protected areas, and the coastal Lomas ecosystem in which it dwells has been almost entirely converted for human uses such as livestock grazing and mining, its population is believed to have declined by more than 80 percent in a single decade. It remains severely threatened by extensive ongoing habitat loss within its remaining restricted range – estimated to be less than 100 km2. Further field studies are desperately needed if any remaining Zuniga’s Dark Rice Rats are to be rediscovered and reclaimed from the looming void of extinction.
The yellow-nosed cotton rat (Sigmodon ochrognathus) is a species of rodent in the family Cricetidae. It is native to Mexico and to the states of Arizona, New Mexico, and Texas in the United States, where it inhabits mountain grassland, scrub, and pinyon-juniper woodland. It is common over much of its wide range and the IUCN considers it to be of "least concern".
The head is short and broad and the tail is hairy, with many small scales. The fur on the head, back, and sides is a dull gray color, apart from the snout and a ring round the eye which are ochre, features that distinguish this species from other members of the genus Sigmodon. The underparts are grayish-white, the feet grayish-buff, the upper side of the tail blackish and the underside gray.
Nests of the yellow-nosed cotton rat are often hidden inside tussocks of grass or other dense vegetation. They are made of grass and are 7 to 16 inches in diameter. The gestation period is about 34 days and usually two to six young are born in a litter. They are precocial and able to leave the nest soon after birth, their eyes open during the first day, they grow rapidly, and are weaned at around 15 days.
The yellow-nosed cotton rat does not compete well with other species of cotton rats, and where their ranges overlap, it occupies thinly vegetated, rocky slopes with tussocks of grass. Where it is the only cotton rat in a locality, the yellow-nosed cotton rat inhabits grassy meadows and alluvial fans where the soil is deeper. In these habitats, it makes runs between the clumps of grass, but in sparsely vegetated areas, these runways are difficult to discern. It is primarily active during the day, moving fast along its runways so as to be exposed to predation for as little time as possible. It feeds primarily on blue grama grass, but also the green parts of other plants, and less frequently on seeds and fruits. It cuts sections of grasses and forms small piles of grass blades on the surface and caches further piles of dried foliage underground.
The Magdalena rat (Xenomys nelsoni) is a species of rodent in the family Cricetidae which is found only in a small region of western Mexico.It is the only species in the genus Xenomys. The common name comes from the village where the first specimen was collected.
The species is endemic to Colima and southwest Jalisco, along the Pacific coast of Mexico. It is estimated to inhabit an area of no more than 4,600 km2 (1,800 sq mi). Within this region, it is found in dense tropical forests. at elevations up to 450 m (1,480 ft).
The Magdalena rat is a relatively large member of its family, measuring 12 to 13 inches in length, including the 5.5 to 6.7 inch tail. Adults weigh an average of 113 g (4.0 oz). The general body color is cinnamon to yellowish brown, being paler on the head and fading to creamy white on the underparts. It can be distinguished from other local rat-like species by the presence of white spots above the eyes and behind the ears; the cheeks are also marked with white fur. The tail is both hairy and scaly, and is dark brown in colour.
The species is arboreal and nocturnal. They use branches and vines in dense vegetation to travel from tree to tree, and mostly remain between 3-13 feet above the ground. They spend the day sleeping in spherical nests constructed in tree hollows. The nests are lined with grass and kapok fruit fibres. They also use specific latrines, either in tree hollows or at the forks of branches. They breed between late May and November, and give birth to one or two young at a time.
An endangered species, it is threatened by habitat destruction and fragmentation due to deforestation and development. It is known from only three localities, and is believed to have a very low, and declining, population.
The white-throated woodrat (Neotoma albigula) is a species of rodent in the family Cricetidae. It is found from central Mexico north to Utah and Colorado in the United States.The animal lives mostly in the Upper and Lower Sonoran life zones, occurring from pinyon-juniper woodland in higher country to desert habitats at lower elevations.
As with other species of woodrats, the white-throated woodrat constructs middens of a variety of materials such as sticks, cactus parts, and miscellaneous debris. An above-ground chamber within the midden contains a nest lined with grasses and kept free of feces. In non-rocky areas, the den usually is several feet in diameter and most commonly built around the base of a shrub that gives additional cover. In areas of rocky outcrops, crevices often are utilized, with sticks and other materials preventing free access to the nesting chamber.
The white-throated woodrat is generally associated with creosotebush, mesquite, cacti (particularly prickly-pear and cholla), catclaw acacia, and paloverde. These plants provide cover and succulent plant food (>50% water by weight), the 2 most critical habitat requirements for white-throated woodrat. White-throated woodrats prefer habitat with low tree canopy cover, high shrub and rock cover, and coarse woody debris. When available, natural and human constructed riparian habitat may be used by white-throated woodrats.
As the only marked standard not to specifically dictate where the markings of the rat must be, variegated rats probably get away with much more than many others in the marked section. The front of the rat is very distinctly described, but once we’re beyond the shoulders we’re simply told that the back, sides, and tail should have even flecks and patches of colour rather than told exactly the size of these flecks and where they should be.
Commonly, variegateds end up with not much colour on their sides (and all of the flecks concentrated in a wide stripe on their back), or patches of colour that merge into blocks, giving a very solid look rather than the flecky and patchy look that’s desired.
The unexpected cotton rat only lives very high in mountains in Ecuador, 3500 to 4000 m above sea level, in a few locations. It’s habitat is threatened by agriculture and deforestation and its population is declining – it is listed as Vulnerable.And because it is so inacessible, not much else is known about it.
Cotton rat is really a misnomer as it is only the species living in the U.S. that lives in cotton fields and it is in fact much more widely distributed and occurring far further north than does cotton. Now all species in the genus Sigmodon have cotton rat as part of their common name.
The unexpected cotton rat’s Latin name is Sigmodon inopinatus. It will have been classed in this genus because of physical features and behaviour it shares with other Sigmodon species. This southern most species of Sigmodon most likely has the common name unexpected because it wasn’t originally believed that this genus occurred that far south.
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Full disclosure, I was only able to find one picture of this species, but the name was too good to pass up including in the alphabet. The other three are actually the similar-looking Hispid Cotton Rat.
Taillessness is a true mutation that causes a severe alteration of the rat’s normal body structure. Tailless rats, also called manx rats, may be shown in any recognized color, marking, or Variety. The distinct feature is the complete absence of a tail. Tailless rats may have a cobbier body and will have a rounded rump.
Ideally it results in a totally Tailless rat with a rounded rump. Unfortunately, this mutation often does not produce consistent results, and the animals can show a number of different physical results. Some of these are benign; others can cause a drastic negative impact on the animal’s life.
Stub tails are a natural by-product of breeding Tailless rats. Some Tailless litters will contain babies with a little piece of tail. Stub tails can range from a lump where the rat’s tail would normally start, to a thin, stiff, string-like tail an inch or two long. These tails are typically very thin, simply vertebrae covered with skin. When these stub tails are very short they seldom cause the rat problems, however, longer (sometimes curled) ones can get caught and break.
Limp tails are tail appendages which lack vertebrae. They can range from a tiny flap of skin at the base of the pelvis, to an entire normal size tail with no vertebrae in it. A rat who has a large tail appendage (1 inch or more) up to an entire tail which is lacking vertebrae can suffer from significant issues. These rats have no way to move or control these “dead” tails and so the tails are in danger of being caught or damaged. They also make it difficult for the rat to get around. These rats are reported to be prone to urinary tract infections and have difficulty keeping their hind end clean.
Some Tailless rats are born with rear leg abnormalities. When this happens, often the back legs fuse to the pelvis. This leads to a rat who cannot walk normally, and often hops like a rabbit. Occasionally, a Tailless will have a leg structure which forces it to only walk on its heals, makes it toe in or out, or simply makes it wobble as it walks. At the far extreme of this condition is the rare cases where there is no attachment of the hind legs to the pelvis or even a complete lack of pelvis, and the rat has to drag its back end. There have been a couple of reports of tailed rats out of Tailless lines who have the same pelvic structure as a Tailless.
Some very normal appearing Tailless rats have a hidden problem. Everywhere they go they leave little dribbles of urine. This goes beyond marking, and is actually a lack of bladder control. Some also experience the same problems with their bowels. Urinary tract infections are not all that uncommon in Tailless, and there has been numerous incidences of bladder stones.
In order to breed Tailless, some inbreeding must be done. This needs to be approached with great caution. Due to the nature of these rats, breeding animals who themselves have problems will lead to babies who have problems. Responsible breeders take great pains NOT to let this happen, and discontinue whole lines if necessary to prevent it!
Nectomys squamipes, also known as the Atlantic Forest nectomys, South American water rat, or scaly-footed water rat, is a semiaquatic insectivorous rodent species. It is from Argentina, Brazil, and Paraguay — found primarily near forest rivers and streams in the Atlantic Forest ecoregion.
Nectomys is derived from Greek words meaning "mouse" and "swimming".
Nectomys squamipes, or the South American water rat can be distinguished from other Sigmodontinae based on their size and morphology of their hindfeet. They are the largest of the family (average of 216g) and have long hind legs with partially webbed feet to aid in swimming and have completely scaled heels. The Nectomys squamipe tends to have relatively longer, less hairy ears and a glossy, long pelage. This pelage is made up of wool hairs and guard hairs and is darker dorsally and tends to be lighter grey on its sides and ventrally. The tail is much less covered in hair, and length is around 75% of the body length.
The South American water rat inhabits elevations from sea level to around 2,000 m. Almost all of these mammals are found a small (2 m) distance from tropical forest streams and rivers. They tend to prefer the moist habitats in forested areas such as swamps or marshes, and are sometimes found inhabiting caves.
Nectomys sqaumipes is an omnivorous mammal with a diet ranging from fruits and leaves to insects and small fish. The South American water rat tends to feed more often after the end of the wet season, when food is in abundance. Many newborn water rats will grow bigger during this time period, because they have access to more food than those born during drier periods.
When swimming and searching for food, the South American water rat is able to detect objects under water and lift them above the surface in order to inspect to see if the object is edible or not using olfaction and sight. When hunting on land it is able to secure prey by pouncing and grasping with its forepaws.
The South American water rat is a polygynous mammal in which males will increase their home range in attempt to mate with many females to produce the most offspring possible. Although males tend to be sexually active all year long, seasonal breeding patterns are suggested since females have a higher pregnancy rate during the wet season, which is August to November in South America. This will produce offspring that have an abundant food source when born, resulting in greater growth and larger populations.
Gestation periods last around 30 days, with litters as small as 1 offspring and as large as 7. Males are generally absent when raising the altricial young, so the female is responsible for feeding and caring for the young.
Nectomys squamipes is a solitary mammal that is active during the night. The males have a much less defined home range and tend to roam, while the females are very territorial.
The South American water rat has mainly one predator, the barn owl (Tyto alba). They are most vulnerable at night when the barn owls are hunting and the nocturnal rat is out of its nest. Nectomys squamipes are very good swimmers and climbers, which act as short-term defenses against predation. Their darkened dorsal pelage may also act as camouflage.
