The Bonneville Estates Rockshelter rodent fauna and changes in Late Pleistocene–Middle Holocene climates and biogeography in the Northern Bonneville Basin, USA

Excavations at Bonneville Estates Rockshelter, Nevada recovered rodent remains from stratified deposits spanning the past ca. 12,500 14C yr BP (14,800 cal yr BP). Specimens from horizons dating to the late Pleistocene and early Holocene include species adapted to montane and moist and cool habitats, including yellow-bellied marmot (Marmota flaviventris) and bushy-tailed woodrat (Neotoma cinerea). Shortly after 9000 14C BP (10,200 cal yr BP) these mammals became locally extinct, or nearly so, taxonomic diversity declined, and the region became dominated by desert woodrats (Neotoma lepida) and other species well-adapted to xeric, low-elevation settings. The timing and nature of changes in the Bonneville Estates rodent fauna are similar to records reported from nearby Homestead and Camels Back caves and provide corroborative data on terminal Pleistocene–early Holocene environments and mammalian responses to middle Holocene desertification. Moreover, the presence of northern pocket gopher (Thomomys talpoides) at Bonneville Estates adds to a sparse regional record for that species and similar to Homestead Cave, it appears that the ca. 9500 14C yr BP (10,800 cal yr BP) replacement of the northern pocket gopher by Botta's pocket gopher in the Great Salt Lake Desert vicinity was also in response to climate change.

Long-Term Response of Small Mammal Communities to the 1988 Huckleberry Mountain Fire

Biologists have long been interested in the response of small mammals and their habitat following natural disturbances. The Greater Yellowstone Area (GYA) fires of 1988 have provided opportunities to study short and long term responses. This study continues investigations conducted in the 1990’s following identical methodology at the same sites now 21 years post-fire. We live trapped 256 Clethrionomys gapperi (Red-backed Vole), 116 Peromyscus maniculatus (Deer Mouse), 44 Tamius minimus (Least Chipmunk), 28 Zapus princeps (Western Jumping Mouse), two Microtus montanus (Montane Vole), 1 Thomomys talpoides (Northern Pocket Gopher) and 37 shrews (Sorex ssp.). These results support findings from other investigations regarding the initial early dominance of P. maniculatus in burn areas and C. gapperi in control or non-burn areas, and as time has progressed since the burn, differences between burn and control sites (as measured by community diversity indices) has decreased. As expected calculated Shannon diversity indices (H’) in 2009 are higher for at least one of the burn sites than in previous years as the habitat recovers to pre-burn conditions.

Body Weights of Adult and Juvenile Northern Pocket Gophers, Thomomys talpoides, in Central Alberta Alfalfa Fields

In an effort to recognize adults from juveniles in late summer and early fall, carcasses of Northern Pocket Gophers (Thomomys talpoides) captured from April to October 1994 in a pure alfalfa (Medicago spp.) field in Camrose and a mixed alfalfa-orchard grass (Dactylis glomerata)-dandelion (Taraxacum spp.) field in Lacombe, in central Alberta were analyzed. Mean weights of adult males and females were significantly (P < 0.05) larger than those of juveniles with near-adult body sizes in late summer and early fall. On the basis of the limits of 95% confidence intervals for individual values in Camrose and Lacombe, live-captured males weighing < 130 g could be classified as juveniles; those that are > 180 g would be adults. Males weighing between 130 and 180 g could be either juveniles or adults. Live-captured females weighing < 110 g would likely be juveniles. With larger animals, the pubic symphysis should be used to distinguish young females from adults. Given the variability of body weight in Northern Pocket Gophers, it is suggested that criteria for aging based on weight be derived for local populations in specific habitat types. On average, Northern Pocket Gopher males and females from Camrose were significantly (P < 0.05) heavier than those of Lacombe. Animals from both fields were, on average, heavier than those previously studied in natural-vegetation communities. Differences in the food nutritional quality may explain the observed variation in body weights among populations.