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The morphology and function of the digestive tract of the largely arboreal porcupine (Erethizon dorsatum) and the semiaquatic beaver (Castor canadensis) were compared in relation to the similarly woody winter diet of these animals. Digesta particle sizes and Ca concentrations were consistently greater along the digestive tract of the beaver than along that of the porcupine. The small intestine of the beaver is 70% longer than that of the porcupine (P < 0.05 by ANCOVA). Both rodents are hind-gut fermenters and there was selective retention of small digesta particles (< 45 μm) in the cecum of both species. Hind-gut fermentation is confined to the cecum in the porcupine, but in the beaver the cecum and proximal colon function together as a fermentation chamber; the two anatomies appear to yield similar amounts of energy from the volatile fatty acids produced by fermentation, equivalent to 18–19% of the basal metabolic rate. A longer distal colon in the porcupine (P < 0.01 by ANCOVA) is related to greater resorption of water than in the beaver; dry matter content of the digesta increased from 13% in the cecum to 40% in the distal colon of the porcupine (P < 0.001 by ANOVA), but only from 20 to 33% in the beaver (P < 0.01 by ANOVA). High levels of Na accumulate in the porcupine cecum, presumably as a result of effective Na-conservation mechanisms.

We examined the relation between surface activity and the surface microclimate in thirteen—lined ground squirrels. We statistically isolated the effects of thermal conditions on squirrel activity and tested the suitability of two optimization models for predicting thermoregulatory behavior. Metabolic and microclimatic data were used to represent thermal conditions as standard operative temperature. The proportion of time spent on the surface was highest at standard operative temperatures between 30° and 40°C. This range approximately matched the squirrel's physiological thermal neutral zone. This pattern was not qualitatively altered by using a multiple—regression model to remove the effects of potential confounding variables (e.g., time of day or time of year). At low temperature, the observed reduction in surface activity resulted in lost foraging benefits °6 times as great as the energy savings in thermoregulatory and activity costs. Therefore, we believe that these squirrels cannot be considered daily energy maximizers. Rather, optimization must be considered in the context of longer time periods. At high temperatures, the observed reduction in surface activity was described by a constrained thermal model of shuttling thermoregulation, which assumed squirrels maximized surface feeding time. The model also explained a systematic decline in body temperature when exiting and entering the burrow as surface operative temperatures increased.

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1. Understanding the breadth and complexity of changes in phenology is limited by the availability of long-term historical data sets with broad geographic range.2. We compare a recently discovered historical data set of plant phenology observations collected across the state of New York (1826-1872) to contemporary volunteer-contributed observations (2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) to evaluate changes in plant phenology between time periods. These multi-site, multi-taxa phenology data matched with temperature data uniquely extend historical observations back in time prior to the major atmospheric effects of the Industrial Revolution. 3. The majority of the 36 trees, shrubs and forbs that comprised our analysable data set flowered and leafed out earlier in contemporary years than in the early to mid-19th century. This shift is associated with a warming trend in mean January-to-April temperatures, with flowering and leafing advancing on average 3 days/°C earlier. On average, plants flowered 10.5 days earlier and leafed out 19 days earlier in the contemporary period. Urban areas exhibit more advanced phenology than their rural counterparts overall, and insect-pollinated trees show more advanced phenology than wind-pollinated trees and seasonality and growth form explain significant variation in flowering phenology. The greatest rates of temperature sensitivity and change between time periods for flowering are seen in early-season species, particularly trees. Changes in the timing of leaf out are the most advanced for trees and shrubs in urban areas. 4. Synthesis. Citizen science observations across two centuries reveal a dramatic, climate-driven shift to earlier leaf out and flowering. The magnitude of advancement varies across settings, species and functional groups, and illustrates how long-term monitoring and citizen science efforts are invaluable for ecological forecasting and discovery.