This association with water could be due the increased number of available food sources in wetter areas or to the softer soil conditions, making digging and burrowing easier. Nine-banded armadillos are not often found in arid regions they thrive especially in riparian habitats or areas with a sufficient amount of water and/or at least 38 cm of rain annually. They are also found in grasslands and savanna regions around woody areas, but much prefer forests over grasslands because they forage in forest litter for small invertebrates. Nine-banded armadillos most often inhabit forest and scrub-brush areas in tropical and temperate regions. ( Chapman and Feldhamer, 1982 Talmage, 1954 Taulman and Robbins, 1996) Further, human activities have caused a decline in many natural predators of North American nine-banded armadillos. Even so, they do not readily cross large bodies of water. Nine-banded armadillos are able swimmers due to their ability to hold air in their digestive tract, increasing buoyancy they are also able to walk along river bottoms as a result of their ability to maintain a large oxygen debt. The construction of roads and bridges have both facilitated human introduction of nine-banded armadillos into new areas, as well as provided a means for wild nine-banded armadillos to move across the wide waterways and other natural obstacles that would had previously prevented their expansion. Increasing human populations and development of transportation routes are thought to help rather than hinder the geographic expansion of nine-banded armadillos. ( Chapman and Feldhamer, 1982 Macdonald, 1984 Van Deelen, et al., 2002 Wilson and Ruff, 1999) For this reason, nine-banded armadillos have not migrated into the arid, desert regions of New Mexico and other western states. Another factor that has limited their migration westward is dependence on rainfall or other sources of water. They can survive short periods of severe cold by remaining in a burrow for days at a time. However, if winter seasons become milder, nine-banded armadillos may continue their migration northward. Migration and establishment of populations northward is likely limited by the severity of cold, winter weather, for which the species does not have a strong tolerance. In 2000, the dead body of a nine-banded armadillo was discovered in central Illinois. They have been spotted as far east as Florida and are common as far north as Missouri. Beginning in the late 19th century, they gradually expanded their range to the northeast. As early as 1850, nine-banded armadillos were found no further north than Texas. Saper CB, Lu J, Chou TC, Gooley J (2005) The hypothalamic integrator for circadian rhythms.Nine-banded armadillos are found in South, Central, and North America, and have the largest range of any extant species of armadillo, from Argentina and Uruguay, through Central America and into the southern United States. PhD thesis, Michigan State University, East Lansing, MIįuller PM, Gooley JJ, Saper CB (2006) Neurobiology of the sleep-wake cycle: sleep architecture, circadian regulation, and regulatory feedback. Mahoney M (2003) Sex, surges and circadian rhythms: The timing of reproductive events in a diurnal rodent. PhD thesis, Michigan State University, East Lansing, MI Schwartz MD (2006) Neural substrates of diurnality in the Nile grass rat, Arvicanthis niloticus. Smale L, Lee TM, Nunez AA (2003) Mammalian diurnality: Some facts and gaps. Klein D, Moore RY, Reppert SM (1991) Suprachiasmatic Nucleus: the mind's clock. Stephan FK (2002) The “other” circadian system: food as a zeitgeber, J Biol Rhythms 17:284–292 In: Knobil E, Neill JD (eds) The physiology of reproduction, Raven Press, New York, pp 487–540 Turrek FW, van Cauter E (1994) Rhythms in reproduction. Moore-Ede M, Sulzman F, Fuller C (1983) The clocks that time us.
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