“I See You”: Na’vigating the Bridge between Scientific Observation and Religious Apprehension in Avatar

This is a review of Avatar (2009)

Factors influencing survival and reproduction of Virginia opossums (Didelphis virginiana) at their northern distributional limit

To understand how species\u27 distributions vary with landscape and climatic changes, we must first understand the proximate mechanisms responsible for distributional boundaries. A direct physiological link between the Virginia opossum\u27s (Didelphis virginiana) winter energetics and its northern geographical range limit has been hypothesized. However, opossums now occur well beyond the predicted limit. Though opossums commonly occur in the Connecticut River Valley of central Massachusetts, I found in a road-kill survey that opossums are rare in undeveloped areas. These findings suggest that the region is a local distributional edge. Demographic models indicated that northern population persistence depends upon high (0.67–0.81) over-winter survival of subadult females. Revisiting winter energetics, I found that average-weight subadult females should not, under natural conditions, survive most Amherst, Massachusetts winters at these rates. This model explains the failure of opossums in natural areas but not their presence in developed areas. I compared winter temperatures across the region; while urbanized areas had the warmest winter nights (and hence the environment in which opossums have the highest chance of survival), urban temperatures should still have been too cold for sufficient subadult female survival. Radio-monitoring free-ranging opossums, I found that use of anthropogenic resources allowed subadult females to obtain the necessary extra energy required to survive winter. The actual winter survival estimate for subadult urban female opossums was 0.697. This survival rate was high enough to contribute to a growing urban population, because both reproduction and juvenile pre-winter survival were higher than expected. “Rural” animals, which did not use anthropogenic resources, did not persist through the winter. Many individuals shifted to using urban resources before the onset of winter, and the remainder died, primarily of predation in autumn or starvation in winter. Though the demographics for the total sample population indicate a declining population, the opossums in Massachusetts actually could be in a stable “source-sink” dynamic, with populations in urbanized areas growing and supporting declining populations in rural areas. By exploiting anthropogenic resources, Virginia opossums already occur in northeastern North America where they otherwise would not persist, and further northward expansion through an increasingly urbanized landscape is thus expected

I See You’: Na’vigating the Bridge Between Scientific Observation and Religious Apprehension in Avatar

This is a review of Avatar (2009)

Winter Energetics of Virginia Opossums (Didelphis Virginiana) and Implications for the Species’ Northern Distributional Limit

While climatic limitations are widely recognized as primary factors determining the distributions of many species, the physiological link between climate and species\u27 persistence is poorly understood. The Virginia opossum Didelphis virginiana is a species for which winter energetics have been evaluated and a northern geographical limit has been hypothesized. Expansion of opossum populations beyond this limit, however, suggests that a previous winter energetics model requires modification. I update this energetics model by incorporating random foraging success to estimate the probability of opossum survival under varying winter temperature regimes. Estimation of opossum success for winters in Amherst, Massachusetts, since 1926 showed that juvenile females, the key breeding component of the population, would survive at a rate high enough to maintain a stable population in only 4 of the 77 yr. The model correctly predicted the fate of 13 of 14 opossums monitored in the Amherst area during the winters of 2000-2003. The current energetics model does not correctly predict autumn weight gain, but it does accurately estimate opossum winter survival. However, the model predicts that opossums should be winter-limited in areas such as Amherst, Massachusetts, where in fact they are well established. This discrepancy may be explained in three ways: weather station data do not adequately reflect available microclimates, opossums show high levels of flexibility in cold-weather foraging behavior, and most likely, humans provide food and shelter that mitigate the effect of winter

Individual Differences in a Novel Environment Do not Reflect Field Measures in Muskrat (Ondatra zibethicus)

The role of individual behavioral tendencies in wild populations remains largely unstudied, especially in mammals, despite its potential ecological importance. We examined whether individual variation in muskrat (Ondatra zibethicus) behavior in a captive novel environment correlates with other measures of behavior and habitat use. We compared the novel environment assay behavior with handling docility and trap habitat for all animals. We radio-collared subadults to look for correlation between assay behavior, summer space use, trappability and likelihood of autumn dispersal. In the novel environment test, we found many muskrat did not exit the shelter during the test. Muskrat that entered the arena showed activity and boldness/emotionality axes similar to behaviors identified in other taxa in similar tests. Participation in entering the arena appears to be related to boldness rather than activity. Both participation and boldness were lower in subadults and higher in males. Neither activity nor boldness of participants in the novel arena was correlated to handling docility, suggesting that such measures would not be interchangeable for evaluating muskrat behavioral tendencies. None of these behaviors related to fine-scale habitat use as reflected by the capture site. In subadults they did not relate to field measures of home range composition, trappability or autumn dispersal, and there is only a suggestion of a positive correlation between captive activity and home range size, although small sample size limits the power of these subadult analyses. Muskrat vary in their behavioral responses in captivity, but there is no strong indication that this variation reflects differences in space use in the wild

Stability in Activity and Boldness Across Time and Context in Captive Siberian Dwarf Hamsters

Individual personality is an important source of variation in animal behavior. However, few studies have examined the reliability of individual behaviors across both time and context for even common temperament traits such as boldness, especially in mammals. We tested a laboratory colony of Siberian dwarf hamsters ( Phodopus sungorus) in two similar assays, a tunnel maze and an open field, both provisioned with a home nestbox for shelter. Animals were tested in each assay at three ages, beginning at weaning. Principal components analysis on each assay identified an axis of activity level in both tests, boldness and reactivity in the tunnel maze, and nestbox orientation in the open field. All traits were moderately (7-18%) heritable. Individual activity level was the most reliably consistent trait, both within and between tests. Tunnel maze boldness, tunnel maze reactivity, and open field nestbox orientation did not correlate at any age. Correlation between boldness and activity changes from positive to negative as animals age, while reactivity was consistently negatively associated with activity. A negative correlation emerged in adults between open field activity and nestbox orientation. These results suggest that either development or habituation results in different personality trait associations in an individual over time. Individual temperament traits such as general activity level may be quite stable, but caution should be used in generalizing single assays to represent boldness across time and across contexts

Impact of Probiotic Supplements on Microbiome Diversity Following Antibiotic Treatment of Mice

Shifts in microbial populations of the intestinal tract have been associated with a multitude of nutritional, autoimmune, and infectious diseases. The limited diversity following antibiotic treatments creates a window for opportunistic pathogens, diarrhea, and inflammation as the microbiome repopulates. Depending on the antibiotics used, microbial diversity can take weeks to months to recover. To alleviate this loss of diversity in the intestinal microbiota, supplementation with probiotics has become increasingly popular. However, our understanding of the purported health benefits of these probiotic bacteria and their ability to shape the microbiome is significantly lacking. This study examined the impact of probiotics concurrent with antibiotic treatment or during the recovery phase following antibiotic treatment of mice. We found that probiotics did not appear to colonize the intestine themselves or shift the overall diversity of the intestinal microbiota. However, the probiotic supplementation did significantly change the types of bacteria which were present. In particular, during the recovery phase the probiotic caused a suppression of Enterobacteriaceae outgrowth (Shigella and Escherichia) while promoting a blooming of Firmicutes, particularly from the Anaerotruncus genus. These results indicate that probiotics have a significant capacity to remodel the microbiome of an individual recovering from antibiotic therapy

Buffelgrass (Pennisetum ciliare) invades lands surrounding cultivated pastures in Sonora, Mexico

We examined relationships between land disturbance and the extent and abundance of exotic buffelgrass (Pennisetum ciliare) at the interface of cultivated pastures and native desert lands in Sonora, Mexico. Plot and transect surveys of lands inside and outside pasture fences and general linear mixed models revealed complex relationships among buffelgrass, native vegetation, distance from pasture fences, and three categories of land disturbance (undisturbed, moderate, and severe). Results illustrate that buffelgrass invasion is extensive in lands surrounding pastures, and that buffelgrass abundance declines steeply with distance from pasture fences. The role of disturbance is weak but significant in its interaction with distance from the fence. Buffelgrass is more successful at colonizing severely disturbed lands than native vegetation, and its decline in abundance on severely disturbed lands is relatively more gradual than on other disturbance regimes, so landscapes where severely disturbed lands are interspersed with buffelgrass pastures could become centers of extensive buffelgrass invasion. In light of its potential to transform the Sonoran Desert, buffelgrass outside pastures warrants attention in a region-wide control scheme, as well as in future research, which ideally would involve remote sensing. © 2013 Weed Science Society of America