Two significant records of mammals from the Tamaulipan biotic province of Texas.
Most of the province is characterized by a semiarid, megathermal climate that allows for some plant growth throughout the year. However, there is a marked deficiency of moisture for plant growth throughout much of the region (Blair 1950). Riparian vegetation, including elm (Ulmus crassifolia), black willow (Salix nigra), Texas ebony (Chloroleucon flexicaulis) and retama (Parkinsonia aculeta), is found along the margins of the Nueces, Frio, and Rio Grande rivers and their immediate tributaries. Many of the remaining habitats are dominated by thorny brush (Blair 1950). Mesquite (Prosopis glandnlosa), acacias (Acacia spp.), granjeno (Celtis pallida), cenizo (Leucophyllum frutescens), white brush (Aloysia texana), prickly pear (Opuntia lindheimeri), tasajillo (Opuntia leptocaulis), and Condalia are dominant plants in most of these communities.
Blair (1950) remarked that at least 61 species of mammals have been reported from the Tamaulipan province of Texas. Schmidly (2004) noted approximately 63 species of mammals were found (or had occurred in the past) in what he defined as the South Texas Plains region of Texas, which corresponds with Blair's Tamaulipan biotic province. According to Schmidly (2004), the region supports 11 unique mammalian species. Most of the unique species found in the Tamaulipan province (South Texas Plains) are of neotropical origin and reach northern distribution limits in southern Texas (Schmidly 2004). This manuscript reports two species of mammals not previously documented from the Tamaulipan biotic province of Texas.
Specimens of the American porcupine (Erethizon dorsatum) and American black bear (Ursus americanus) have been obtained in Webb County, Texas. Both species often are poorly represented in natural history museum collections, therefore information on their biogeographic distributions and status within Texas is incomplete. The specimens are first records for Webb County, Texas and represent the first reported occurrences of the species within the Tamaulipan province of Texas. The specimens are deposited in the Mammal Collections of Midwestern State University (MWSU), Wichita Falls, Texas and the Lamar Bruni Vergara Environmental Science Center (LBVESC), Laredo Community College, Laredo, Texas.
The American porcupine (MWSU 23240) was obtained from the City of Laredo Animal Control Department in Spring 2005 (approximate locality: 27.62634N, 99.54314W). The animal was a young, adult female and was held as an educational specimen by the LBVESC until her death on 5 December 2010. Measurements of the specimen are as follows: total length, 690; tail length, 215; hind foot, 95; ear, 12. Because she was a captive animal, the porcupine was non-reproductive.
Schmidly (2004) noted that E. dorsatum is found in a wide variety of habitats and has expanded its range in Texas. Brand et al. (2009) remarked upon the expansion of the American porcupine's range on the Edwards Plateau of Texas and reported southernmost occurrences of E. dorsatum from Mason and Kerr counties. Brand et al. (2009) hypothesized that the American porcupine could potentially expand its range into the Blackland Prairie region of Texas. Within Mexico, Baker (1956) and Anderson (1972) reported only a few scattered records of E. dorsatum from the states of Coahuila and Chihuahua. The American porcupine is listed as an endangered species in northern Mexico (Roze & Ilse 2003).
Porcupines are herbaceous browsers and feed upon a wide variety of trees, shrubs, and other vegetation (Woods 1973). The animals are often confined to vegetated riparian areas when occurring away from forested regions. The Webb County animal was captured in a Laredo subdivision adjacent to the Rio Grande River, thus riparian vegetation and potential sources of food were nearby.
Local land owners have reported sightings of porcupines from the vicinity of the Rio Grande and other pastureland areas within Webb County, and Laredo veterinarians have reported removing porcupine quills from dogs owned by Webb County residents (Dr. Phyllis Voltz-Creamer, DVM 2011, personal communication).
The nearest documented records of E. dorsatum are from Val Verde and Kerr counties to the north (Schmidly 2004). Although the range of E. dorsatum is diagrammed as extending southward to Webb, Duval, and Jim Wells counties, no specimens exist from these counties (Schmidly 2004). Therefore, the specimen reported herein represents the southernmost record of the American porcupine within Texas and extends the known range of the species approximately 273 km south of previously documented records into a new biogeographic region.
The American black bear (Ursus americanus) formally was widespread within Texas, but was listed as a state endangered species in 1987 (Doan-Crider & Hellgren 1996). Schmidly (2004) reported that a small, resident population of U. americanus was thought to occur in the Chisos Mountains of Trans-Pecos Texas. Subsequent researchers have confirmed the existence of this population within the state (Hellgren et al. 2005). A small population of U. americanus also is found in the Black Gap Wildlife Management Area of Texas (Stangl et al. 2011). The Texas Parks and Wildlife Department (TPWD 2009) reported that sightings of U. americanus in Texas have increased, and at least one sighting per year is reported from the Central Texas region. Schmidly (2004) mentioned sightings of the American black bear from the Edwards Plateau region, but none have been previously reported from the Tamaulipan province of Texas.
Historically, U. americanus ranged throughout much of Northern Mexico (Medellin et al. 2005). Van Den Bussche et al. (2009) conducted a study on the phylogeography of U. americanus in southern North America and ascertained that black bears may have colonized Louisiana, Texas, and northern Mexico from the eastern United States during the Pleistocene and Recent eras. However, factors such as hunting, trapping, land reform practices, and livestock ranching contributed to the black bear's decline and extirpation over much of its original range within Texas and northern Mexico (Baker 1956; Schmidly 2004; Medellin et al. 2005).
However, because of changing public attitudes, conservation efforts, revised hunting regulations, and other factors, reproductively active populations of U. americanus have been documented from central and western Chihuahua, northeastern Sonora, northern Coahuila, central Tamaulipas, and Nuevo Leon (Medellin et al. 2005). Researchers of the American black bear have ascertained that animals dispersing from the mountains of northern Mexico are recolonizing their historical habitats in the Trans-Pecos region of Texas (Onorato et al. 2003; Onorato et al. 2004). Montane areas of northern Mexico act as a series of "sky islands" to support a metapopulation of U. americanus within a surrounding, inhospitable desert and savannah region (Onorato et al. 2003).
The Webb County specimen (LBVESC 021) was collected by a hunter in the Lall of 2002 from an unspecified locality north of Laredo, Texas. The animal was a young male measuring 167.64 cm in total length. Because the black bear was obtained without proper permits, it was subsequently confiscated by TPWD and prepared as a taxidermy specimen. The specimen was placed on public display as an educational exhibit at the LBVESC. This specimen represents the first record of U. americanus from Webb County and the Tamaulipan biotic province of Texas.
Dispersal distances of U. americanus may be quite extensive, ranging up to 219 km (Lariviere 2001). Populations of U. americanus have been reported from the Carmen Mountains, Serranias del Burro Mountans, Sierra Madre near Monterrey, and Sierra Picachos Mountains, Mexico (Onorato et al. 2004; Medellin et al. 2005). Respective distances from Laredo are approximately 292, 234, 233, and 160 km. The Webb County specimen was taken from an unspecified locality to the northwest of Laredo, so dispersal distances from the Serranias del Burro, Sierra Madre, and Sierra Picachos would have been within documented dispersal ranges for U. americanus. Additionally, young, adult males are reported to disperse greater distances than females (Onorato et al. 2004; Hellgren et al. 2005). Long-distance migrations from and to the resident populations in Mexico have been reported (Hellgren et al. 2005).
The Webb County bear demonstrates U. americanus' ability to disperse and survive within the region's arid, lowland habitats. A staple food of black bears within the southwestern United States and northern Mexico is acorns (Onorato et al. 2003). Oaks (Quercus spp.) are not native to Webb County and are not found in high numbers in the surrounding area. However, Onorato et al. (2003) reported that black bear in Black Gap Wildlife Management Area fed upon mesquite beans (Prosopis glandulosa) and Spanish dagger (Yucca torreyi) fruits; both of which are readily available in Webb County. An additional food source for U. americanus in the southwestern United States is prickly pear (Opuntia spp.) cactus (Pelton 2003). These cacti are abundant in Webb County and surrounding areas.
It has been noted that future dispersals of U. americanus from metapopulations in Mexico and Texas may be impeded by construction of a border fence between the United States and Mexico (Varas 2007). An iron fence 3 m high with pickets 10 cm apart was constructed by the United States Army Corps of Engineers on the campus of Laredo Community College in April, 2005. If a similar fence is placed contiguously along the border of Texas and Mexico, dispersals and migrations of black bears into western Texas might potentially be prevented. If recolonization and establishment of viable resident populations of the American black bear in western Texas is desired, such ecological impacts must be carefully considered before political actions are undertaken.
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J. R. Goetze and T. D. Miller
Natural Sciences Department, Laredo Community College, Laredo, Texas 78040
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|Title Annotation:||GENERAL NOTES|
|Author:||Goetze, J.R.; Miller, T.D.|
|Publication:||The Texas Journal of Science|
|Date:||Feb 1, 2012|
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