Seed predation may be an important ecosystem service for controlling glyphosate-resistant crop volunteers, which are a growing management concern in conventional cropping systems that rely heavily on pesticide based management. In the Midwest USA, prairie deer mice (Peromyscus maniculatus) are important seed predators, removing unwanted weed seeds and waste grain from the soil surface all year round. In this study, we examined how the spatial distribution of experimental maize (Zea mays) seed patches influenced overwinter foraging, mouse populations and waste grain removal in conventional crop fields. We predicted that (1) individual mice will increase foraging on maize waste grain in fields with many small maize seed patches compared to fields with a few large maize seed patches (functional response) and (2) more mice will forage in fields with many small seed patches than. in fields with a few large seed patches (numerical response). We found mouse functional responses were not influenced by the spatial distribution of maize seed patches nor did mice respond numerically to seed addition in general. Mice did, however, remove 59-66% (94-106 kg ha(-1)) of the maize seeds, providing a valuable ecosystem service. Our work shows that prairie deer mice are able to remove large amounts of waste grain from the soil surface over winter, supporting the hypothesis that overwinter seed predation by mice can drastically reduce volunteer maize densities in conventional crop fields. Future research should further examine what management practices (such as practicing no-till) increase mouse abundance and foraging efficacy, so that management strategies that maximize seed predation can be developed.

OBJECTIVES We evaluated risk-sensitive foraging in adult male western chimpanzees (Pan troglodytes verus) occupying a savanna environment at Fongoli, Senegal. The aim of this study was to determine how the risks of predation and heat stress influenced their behavior while feeding on a key food, fruit of the baobab tree (Adansonia digitata). MATERIALS AND METHODS Proximity of fruiting baobab trees to anthropogenic landmarks were compared to food intake, feeding rate, and behavioral indicators of fear in adult males (N = 11) at Fongoli. Additionally, we compared foraging to vegetative habitats, baobab ripe fruit nutritive quality, surface water availability, and foraging party composition. RESULTS Fruit abundance increased with proximity to anthropogenic landmarks, and chimpanzees exhibited higher frequencies of antipredator behaviors as they approached these risky areas. However, predation risk did not deter adult males from visiting these fruiting trees; instead, risky foraging bouts were associated with higher food intakes and longer feeding times. Additionally, higher feeding rates were observed in open-canopy habitats, and this behavior may have minimized their risk of heat stress. CONCLUSIONS Adaptations that minimize predation risk are widespread in mammalian prey species, but these traits are poorly understood in chimpanzees. Great apes encounter few nonhuman predators capable of successfully capturing and killing them; thus, such events are rarely observed. Although people rarely hunt chimpanzees in Senegal, we found that adult males perceived humans as predators and adjusted their behavior while foraging in risky habitats. From an applied perspective, risk-taking behavior is important for understanding and mitigating the problem of crop-feeding in locations where chimpanzees and humans live in sympatry.

Reductions in community evenness can lead to local extinctions as dominant species exclude subordinate species; however, herbivores can prevent competitive exclusion by consuming otherwise dominant plant species, thus increasing evenness. While these predictions logically result from chronic, gradual reductions in evenness, rapid, temporary pulses of dominance may also reduce species richness. Short pulses of dominance can occur as biotic or abiotic conditions temporarily favour one or a few species, manifested as increased temporal variability (the inverse of temporal stability) in community evenness. Here, we tested whether consumers help maintain plant diversity by reducing the temporal variability in community evenness. We tested our hypothesis by reducing herbivore abundance in a detailed study of a developing, tallgrass prairie restoration. To assess the broader implications of the importance of herbivory on community evenness as well as potential mechanisms, we paired this study with a global herbivore reduction experiment. We found that herbivores maintained plant richness in a tallgrass prairie restoration by limiting temporary pulses in dominance by a single species. Dominance by an annual species in a single year was negatively associated with species richness, suggesting that short pulses of dominance may be sufficient to exclude subordinate species. The generality of this site‐level relationship was supported by the global experiment in which inter‐annual variability in evenness declined in the presence of vertebrate herbivores over timeframes ranging in length from 2 to 5 years, preventing declines in species richness. Furthermore, inter‐annual variability of community evenness was also negatively associated with pre‐treatment species richness. Synthesis. A loss or reduction of herbivores can destabilize plant communities by allowing brief periods of dominance by one or a few species, potentially triggering a feedback cycle of dominance and extinction. Such cycles may not occur immediately following the loss of herbivores, being delayed until conditions allow temporary periods of dominance by a subset of plant species.

Trait‐based theories of biodiversity consider interspecific tradeoffs among species‐specific traits as prerequisites to maintaining community evenness, a component of species diversity. Such tradeoffs are commonly observed in plant communities, particularly in relation to traits associated with resistance to herbivory. Indeed, global experiments show that interspecific tradeoffs are common between plant defense and growth or competitive ability; however, the positive effects of herbivory on plant diversity predicted by theories with trait‐based tradeoffs are far less commonly observed. Moreover, both the overall and relative importance of these tradeoffs in promoting plant diversity are not well known. To disentangle the relationships among growth, competition, and defense in relation to plant community evenness, we built a model that describes the effects of a shared herbivore on two plant species with the potential to differ in each of these traits. While tradeoffs between plant defense and growth or competitive ability can increase plant diversity via evenness, this is not always the case nor is it a requirement for increased diversity. Herbivores may increase plant diversity even in the absence of defensive tradeoffs, preferentially consuming apparently maladapted species, by limiting the negative effects of interspecific interactions. Therefore, the importance of defensive tradeoffs in increasing diversity may not be as important, or as straightforward, as previously hypothesized.

Prairie deer mice (Peromyscus maniculatus bairdii) are permanent residents of row-crop fields in the Midwestern United Sates, and may provide ecosystem services by regulating weed seed and waste grain populations. Seed predation is especially critical in the months of highest seed availability following crop harvest, and is dictated by population density and individual patterns of diet choice. We used a combination of spatial mark-recapture demographic and stable isotope dietary analyses to investigate the ecology of prairie deer mice during this critical over-winter period within corn and soybean agro-ecosystems of west-central Indiana. Winter prairie deer mouse populations were robust in the row-crop habitats we sampled, with densities typically >13 individuals/ha but variable among trapping grids and throughout winter. Apparent survival of individuals also varied throughout winter (57-79% monthly survival rate), and mean over-winter (December April) survival of adults was 21%. Winter diets were dominated by waste grain, with corn and soybean contributing 55% and 77% of diet for mice sampled in corn and soybean fields, respectively. Weed seeds contributed less (2-27%) to winter diets. Based on our results and published field metabolic rates, we estimate that prairie deer mice consume 6.3 kg/ha of waste corn and 7.1 kg/ha of waste soybean seeds during the non-growing season. Collectively, our results suggest that prairie deer mice make meaningful contributions to reducing waste-grain populations during winter in post-harvest row-crop fields, during a time of year when most other seed predators are inactive.

Plant-herbivore interactions influence the establishment context of plant species, as herbivores alter the community context in which individual species establish, and the spatial relationship between individuals and their source population as plants invade. This relationship can be described using an establishment kernel, which takes into account movement through seed dispersal, and subsequent establishment of adults. Mammalian herbivores are hypothesized to influence plant population growth and establishment through a combination of consumption of seeds and seedlings, and movement of seeds. While the movement abilities of plants are well known, we have very few empirical mechanistic tests of how biotic factors like mammalian herbivores influence this spread potential. As herbivores of all sizes are abundant on the landscape, we asked the question, how do mammalian herbivores influence the population growth, spatial establishment, and the community establishment context of an early-recruiting native prairie legume, Chamaecrista fasciculata? We planted C. fasciculata in source populations within a four-acre tallgrass prairie restoration in plots with and without herbivores, and monitored its establishment with respect to distance from the source populations. We found that herbivores decreased population growth, and decreased the mean and range establishment distance. Additionally, C. fasciculata established more often without herbivores, and when surrounded by weedy, annual species. Our results provide insight into how the interactions between plants and herbivores can alter the spatial dynamics of developing plant communities, which is vital for colonization and range spread with fragmentation and climate change. Mammalian herbivores have the potential to both slow rates of establishment, but also determine the types of plant communities that surround invading species. Therefore, it is essential to consider the herbivore community when attempting to restore functioning plant communities.

Prairie deer mice are important predators in many agricultural systems, and through their diet they can help to regulate pest insect and weed populations. Our objective was to test whether fecal material is an effective means of detailing the foraging ecology of small mammals. We conducted three studies to evaluate the efficacy of this technique: 1) field-collected fecal material from unknown deer mice from late winter to early spring, 2) fecal material collected in an enclosure with mice fed a mix of C3 and C4 plant seeds, and 3) fecal material from tagged female mice in the field. We detected significant shifts in δ 13C in one study and δ15N in another relative to spring thaw (δ13C: –13.34 vs. –10.72, P = 0.01, δ15N: 4.92 vs. 4.09, P = 0.03), a significant correlation between the relative amounts of two seed types and δ13C (slope = 5.46, SE = 1.82, P < 0.01), and a significant decrease in δ15N due to nursing (4.57 ± 0.19 vs 3.28 ± 0.47, P = 0.02). Use of this technique will help to clarify foraging of this economically important species in agroecosystems.

Humans have altered the biotic and abiotic environmental conditions of most organisms. In some cases, such as intensive agriculture, an organism's entire ecosystem is converted to novel conditions. Thus, it is striking that some species continue to thrive under such conditions. The prairie deer mouse (Peromyscus maniculatus bairdii) is an example of such an organism, and so we sought to understand what role evolutionary adaptation played in the success of this species, with particular interest in adaptations to novel foods. In order to understand the evolutionary history of this species' masticatory structures, we examined the maxilla, zygomatic plate, and mandible of historic specimens collected prior to 1910 to specimens collected in 2012 and 2013. We found that mandibles, zygomatic plates, and maxilla have all changed significantly since 1910, and that morphological development has shifted significantly. We present compelling evidence that these differences are due to natural selection as a response to a novel and ubiquitous food source, waste grain (corn, Zea mays and soybean, Glycine max).

The spatial configuration of habitat and the frequency of disturbances through time could have interacting effects on population viability. With this in mind, we assessed the rate of post-hurricane recovery and long term viability of the Alabama beach mouse (Peromyscus polionotus ammobates). We collected detection/nondetection data across the range of the Alabama beach mouse for four years subsequent to hurricanes Ivan and Katrina, and then fit a dynamic patch occupancy model to these data using hierarchical Bayesian methods. We converted remotely sensed data into habitat classes, and then mapped site survival probability over the entire range of the species. These estimates were then used to parameterize a spatially-explicit population viability analysis. Our occupancy modeling demonstrates that the probability of patch occupancy increased from 0.16 to 0.67, with occupancy in the surveyed patches approaching an asymptote by the third post-hurricane summer. The viability analysis suggests that extinction probability increases nonlinearly with monotonic increases in both habitat loss and hurricane frequency. Extinction risk is sensitive to the regularity of catastrophic hurricanes; consecutive hurricanes dramatically increase extinction risk, further suggesting that the effect of global climate change on hurricane regimes may have a large effect on the probability of long-term persistence. A mild interaction between habitat loss and hurricane frequency occurs when extinction probability is relatively low, but disappears as extinction probability increases. Our results indicate that extinction risk is a complex function of multiple interacting drivers.

Most animal species forage with risk from an ensemble of predators, wherein some predators are themselves prey to the others. A forager's behavior should reflect a synthesis of the effect of environmental conditions on both marginal predation risk and rates of energy accumulation. Here, a forager's giving-up density [GUD] is analyzed for signs of these complex signals. Specifically, we hypothesized that temperature can reverse the effect of moonlight intensity on Alabama beach mouse (Peromyscus polionotus ammobates) GUD because changes in temperature change the ensemble of predators from homeothermic taxa with better vision than the mouse to ectothermic taxa with worse vision than the mouse. We fit several models to GUD measurements taken over a broad range of temperatures and nocturnal luminosities. We obtained strong information-theoretic support for a model that is consistent with our hypothesis of temperature-dependent reversal of the effect of nocturnal illumination on mouse GUD. Signals in GUDs can reveal complex effects of optimal foraging at multiple trophic levels, which is especially informative when direct measurement of taxonomic sources of predation is not feasible.

Motivated by conservation concerns, we assessed whether Sigmodon hispidus (hispid cotton rat) affects the realized niche of Peromyscus polionotus ammobates (Alabama beach mouse). After experimentally removing S. hispidus and accounting for spatial autocorrelation in our data, we found weak evidence for an increase in habitat use by P. p. ammobates at locations previously occupied by S. hispidus. This pattern is consistent with a niche-constriction hypothesis, and was not observed on 2 control grids where removals were not conducted. Our results suggest that removal of S. hispidus from habitat remnants immediately following catastrophic hurricanes ameliorates extinction risk of P. p. ammobates, but we also stress the inferential limitations of our data and the need for further investigation of competitive interactions between these species.

Deer-vehicle crashes are a growing problem in Iowa where deer-vehicle crashes represent 13% of all crashes reported. In 2009, these crashes resulted in nine fatalities and 451 injuries in the state. Deer-vehicle crashes are a problem even in urban areas of Iowa. It is known that deer-vehicle crashes are typically underreported. To address this underreporting, deer carcass salvage reports may be used to augment deer-vehicle crash reports. The objective of this paper is to exploit two sources of deer-vehicle crash data using a statistically reliable assessment methodology, empirical Bayes, to assess the potential for safety improvement of 150 urban highway sections in Iowa. Reconciliation of records to reduce double counting is discussed and a negative binomial regression model of deer-vehicle crash frequency as a function of roadway and environmental factors is estimated. The 25 most promising segments for deer-vehicle crash countermeasures are identified, mostly located on high-speed roadways, roadway segments with gravel right shoulders, and segments adjacent to grasslands. The methodology facilitates the identification of locations for countermeasure implementation as well as monitoring deer-vehicle crash trends.