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eBook details

• Title: Status of Red Squirrels in Guadalupe Mountains National Park, Texas (Report)
• Author : Southwestern Naturalist
• Release Date : January 01, 2011
• Genre: Life Sciences,Books,Science & Nature,
• Pages : * pages
• Size : 75 KB

Description

Mountains of the southwestern United States and northwestern Mexico serve as hotspots of biodiversity at an intersection of the Sierra Madre to the south and Rocky Mountains to the north (Turner et al., 1995). Termed sky islands due to mesic conditions relative to surrounding desert (Gehlbach, 1993), species of this terrestrial archipelago, especially boreal forms (Patterson, 1995), have been isolated for 7,000-10,000 years since the Wisconsin glaciation (Van Devender and Spaulding, 1979). During glacial maxima, ranges of northern-boreal-obligate mammals expanded into southern Arizona, New Mexico, and Trans-Pecos Texas as evidenced in the fossil record (Harris, 1990; Gehlbach, 1993; Patterson, 1995). Guadalupe Mountains National Park in Trans-Pecos Texas lies on the eastern boundary of the sky island province and is one of the southernmost locales in which Pleistocene range expansions of boreal mammals occurred. Due to southerly latitude and isolation, the boreal mammalian fauna in the Guadalupe Mountains suffered widespread extirpation at the end of the Pleistocene (Patterson, 1995), as little mesic coniferous forest remained. Despite several surveys conducted within the park (Bailey, 1905, 1931; Davis and Robertson, 1944; Genoways and Baker, 1979), the status of a few mammalian species remains unknown. Red squirrels (Tamiasciurus hudsonicus) are considered boreal obligates and are distributed widely across North America (Steele, 1998). The present patchy distribution of boreal vegetation, especially in southerly latitudes, likely contributes to the existence of 25 subspecies. Currently, the southernmost subspecies is restricted to the Pinalenno Mountains in southeastern Arizona (Steele, 1998). Fossil records indicate that the southern limit of distribution was once as far south as Trans-Pecos Texas, including Guadalupe Mountains National Park (Harris, 1990; Gehlbach, 1993; Patterson, 1995). Whether red squirrels persist in the park is unclear, as their presence is suggested only briefly with little supporting evidence. Davis and Robertson (1944) noted that Tamiasciurus was reported in the region in the late 1800s; however, these authors provided no reference. Early accounts by Bailey (1905, 1931) reported a sighting of a small tree squirrel in 1902 in the southern part of the Guadalupe Mountains, an observation later discounted by Davis (1940) who claimed the squirrel was probably a chipmunk (Tamias). Findley (1961) stated that it would be unlikely for red squirrels to occur within Guadalupe Mountains National Park due to the lack of habitat, and Patterson (1995) listed red squirrels as locally extinct within the park. Recent surveys in Guadalupe Mountains National Park revealed no red squirrel, but reported that it possibly occurs or has occurred (Genoways and Baker, 1979); range maps often include Trans-Pecos Texas (e.g., Hall, 1981). Determining the status of red squirrels in Guadalupe Mountains National Park remains a priority as it would establish the southern distributional limit of red squirrels and highlight a species of special management concern.

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