Acorn tannins may affect food preferences and foraging strategies of squirrels through effects on acorn palatability and digestibility and squirrel physiology. Captive eastern gray squirrels (Sciurus carolinensis) were fed 100% red oak (Quercus rubra) or white oak (Quercus alba) acorn diets to determine effects on intake, digestion, and detoxification activity. Red oak acorns had higher phenol and tannin levels, which may explain the lower dry matter intakes and apparent protein digestibilities and the higher glucuronidation activities observed in squirrels. Although the white oak acorn diet had lower apparent protein digestibilities than the reference diet, it did not suppress dry matter intake for a prolonged period or stimulate glucuronidation. Negative physiological effects of a 100% red oak acorn diet suggest gray squirrels may require other foods to dilute tannin intake and provide additional nutrients. To distinguish the roles of different tannin types in the observed effects of acorn diets on squirrels, squirrels were fed rat chow containing no tannins, 4% or 8% tannic acid (hydrolyzable tannin), or 3% or 6% quebracho (condensed tannin). Apparent protein digestibilities were reduced by tannic acid and quebracho diets. Only the 8% tannic acid diet tended to increase glucuronidation. Specific effects of tannins may largely depend on tannin type, composition, and source and on other nutritional and physiological factors.

Many natural processes in the riparian cottonwood (Populus deltoides) forest of the Middle Rio Grande (MRG) in the southwestern United States have been disrupted or altered, allowing non-native plants such as saltcedar (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) to establish. We investigated reptilian responses to restoration efforts by sampling communities of lizards at 12 study sites invaded by non-native plants along the MRG in New Mexico for 7 years (2000)(2001)(2002)(2003)(2004)(2005)(2006). Sites within three regions were randomly assigned to one of the three treatments to remove non-native plants and woody debris, or as untreated controls. We used pitfall and funnel traps to capture, mark, and release lizards from June to September. Principal components analysis of 15 vegetation variables identified five factors that best explained variation among sites before and after removal of non-native plants. Relative abundances for four of six common species of lizards were associated with vegetation characteristics that significantly changed after plant removal. Species were either positively associated with the more open, park-like understory found in treated sites or negatively associated with debris heaps and thickets of non-native plants found in untreated sites. Eastern fence lizards (Sceloporus consobrinus) and New Mexico whiptails (Aspidoscelis neomexicana) increased in relative abundance after nonnative plants were removed. Overall, removal of nonnative plants seems beneficial, or at least is non-damaging, to lizard communities of the MRG forest. Providing information on habitat associations of lizard communities will help land managers balance management objectives with other considerations, such as providing important wildlife habitat.

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