Ecosphere最新文献

Urbanization is a significant pressure affecting wildlife and has the potential to greatly alter behavioral responses in animal communities. A behavioral response that is potentially affected by urbanization is the mobbing of predators by potential avian prey species. We tested three hypotheses concerning the effects of various abiotic and biotic factors in influencing avian mobbing responses along an urban–rural gradient. We conducted predator simulations by using playback of the vocalizations of the Western Screech-owl, Megascops kennicottii, which is a predatory species that elicits a mobbing response from other birds. These vocalizations, accompanied by stuffed models of the screech-owls, were broadcast at a variety of points along an urban–rural gradient in Los Angeles and Orange Counties in Southern California. We used an experimental approach using playback, that is, vocalization and models, to investigate whether mobbing responses of birds change in areas where predators may be naturally present (high vegetation density) or absent (high impervious cover). We recorded the number of individual birds and species that exhibited mobbing behavior at experimental sites, as well as various biotic and abiotic factors that may influence avian mobbing, including noise level, impervious surface cover, avian community turnover across the urban-to-rural gradient, and the structure of local vegetation, which we assumed may be important for either hosting roosting screech-owls or providing cover for mobbing bird species. For both the number of mobbing individuals and species, we showed that mobbing responses decreased with increasing noise levels and percentage of impervious surfaces and increased with increasing woody vegetation. There was some evidence that predator presence influenced mobbing responses. Our results show that the changes associated with urbanization can significantly alter antipredator behavior in birds, and that these changes can alter avian social eavesdropping networks.

Wild prey can reduce predation risk by avoiding areas used by their predators. As they get older, individuals should be able to fine-tune this avoidance based on their increased experience with predation risk. Such learning mechanisms are expected to play a key role in how individuals cope with risk during their life, particularly in altered landscapes where human disturbances have created habitat conditions distinct from those of the past. We studied the role of experience on the avoidance of risky areas by boreal caribou (Rangifer tarandus caribou) in a system where they are under high predation pressure from gray wolves (Canis lupus) and black bears (Ursus americanus). Using telemetry data collected on 28 caribou, 31 wolves, and 12 bears, we investigated whether caribou adjusted their level of predator avoidance with passing monitoring years, a proxy of increasing experience. We observed an increase in the avoidance of areas suitable to wolves (during two study periods) and bears (during all study periods) with passing years. Periods during which caribou did not adjust their behavior toward wolves (winter and calving) were characterized by persistent—potentially innate—avoidance. Our results suggest that, in most circumstances, caribou became more efficient at avoiding areas selected by their predators as they gained experience. Future work should attempt to demonstrate whether such tactics are heritable; if so, our results would suggest that, given time, caribou living in disturbed environments would have the potential to adapt to changing levels of risk. This would give hope for the conservation of caribou, a species at risk in Canada, provided levels of risk do not surpass the limits of their behavioral plasticity.

In the past decade, studies have demonstrated that urban and nonurban wildlife populations exhibit differences in foraging behavior and diet. However, little is known about how environmental heterogeneity shapes dietary variation of organisms within cities. We examined the vertebrate prey components of diets of coyotes (Canis latrans) in San Francisco to quantify territory- and individual-level dietary differences and determine how within-city variation in land cover and land use affects coyote diet. We genotyped fecal samples for individual coyote identification and used DNA metabarcoding to quantify diet composition and individual niche differentiation. The highest contributor to coyote diet overall was anthropogenic food followed by small mammals. The most frequently detected species were domestic chicken, pocket gopher (Thomomys bottae), domestic pig, and raccoon (Procyon lotor). Diet composition varied significantly across territories and among individuals, with territories explaining most of the variation. Within territories (i.e., family groups), the amount of dietary variation attributed to among-individual differences increased with green space and decreased with impervious surface cover. The quantity of anthropogenic food in scats also was positively correlated with impervious surface cover, suggesting that coyotes consumed more human food in more urbanized territories. The quantity of invasive, human-commensal rodents in the diet was positively correlated with the number of food services in a territory. Overall, our results revealed substantial intraspecific variation in coyote diet associated with urban landscape heterogeneity and point to a diversifying effect of urbanization on population diet.

Global biodiversity is declining at an alarming rate. Consequently, there is a pivotal need to determine the occurrences and distributions of threatened species. Monitoring and detection approaches are traditionally reliant on capture (traps and cameras), as well as observations. However, these approaches are time-consuming and skewed toward the detection of large and/or common species. Invertebrate ingested DNA (iDNA) is being increasingly used as a novel approach for indirectly monitoring terrestrial vertebrates via their DNA in invertebrates with hematophagous, coprophagous, or saprophagous feeding strategies. This study aimed to examine the vertebrate diversity which could be retrieved using mosquito-derived iDNA in a peri-urban setting. Furthermore, the study also examined the influence of a human blocking primer and the application of multiple primers on the detection of the targeted taxa. Sampling was performed in Sydney, Australia, in a peri-urban environment adjacent to both urbanized and protected environments. As a means of ensuring that sampling could be performed by nonscientists, domestically available light traps were used. In total, 118 mosquitoes were captured. DNA was extracted from individual mosquitoes and amplified using four different primers, targeting vertebrates, mammals, and birds, with and without a human blocking primer (except for the bird polymerase chain reactions). The overall diversity retrieved reveals a broad diversity of species with 10 avian taxa and six mammalian taxa, including both native and non-native species of varying body sizes and behavioral characteristics. Both the multi-locus approach and the use of a human blocking primer revealed additional diversity. The use of iDNA offers the potential as an important tool for local land managers and citizen science projects for the monitoring of vertebrates.

Butterflies are important bioindicators that can be used to monitor the effects of climate change, particularly in montane environments. Changes in butterfly population size over time, reflective of indicator life stages, can signal changes that have occurred or are occurring in their environment indicating ecosystem health. From the perspective of understanding butterflies as bioindicators in these systems, it is essential to identify influential environmental variables at each life stage that have the greatest effect on population dynamics. Life stage hypothesis modeling was used to assess the effects of multiple temperature and precipitation metrics on the population growth rate of a Parnassius clodius butterfly population from 2009 to 2018. Extreme maximum temperatures during the larval-pupal life stages were identified to have a significant negative effect on population growth rate. We speculate that higher temperatures during the spring ephemeral host plant's flowering, and P. clodius' larval stage, may lead to earlier plant senescence and lower P. clodius growth. Because Parnassius butterflies are well studied from a global perspective, results may aid in understanding the potential indicator life stages of other insect species in montane environments to climatic changes. Findings from this study demonstrate the value in assessing a butterfly species' response to short-term weather variation or long-term climatic changes at each life stage in order to protect and conserve insects and their interactions with other organisms.

Plant phenology is affected by both abiotic conditions (i.e., temperature, nitrogen enrichment, and drought) and biotic conditions (i.e., species diversity). The degree of spatial heterogeneity in soil resources is known to influence community assembly and dynamics, but the relationship between resource heterogeneity and phenology or the potentially interactive effects of soil resources on phenology are less understood. We leveraged a tallgrass prairie restoration experiment that has manipulated soil nitrogen availability and soil depth over 20 years to test the effects of environmental heterogeneity, nutrient enrichment, and potentially interactive effects of global change drivers (nutrient enrichment and a drought manipulation) on the phenology of a highly dominant prairie grass (Andropogon gerardii). We recorded the timing of major developmental stages of A. gerardii in plots containing four soil heterogeneity treatments (control, soil depth heterogeneity, nutrient/depth heterogeneity, and nutrient/precipitation heterogeneity). We found that the boot, first spikelet, and emerged spikelet stages of A. gerardii occurred earlier in treatments with greater heterogeneity of soil nitrogen, and this effect was driven by the accelerative effect of nitrogen enrichment on phenology. Reduced precipitation increased the flowering length of A. gerardii but did not otherwise affect developmental phenology. There were no interactive effects among any soil resource treatments on phenology. These results advance our understanding of the relationship between plant phenology and global change drivers, which is important for understanding and predicting the timing of plant resource use and the provision of resources to higher trophic levels by plants under varying levels of resource availability.

Ecoacoustic methods provide opportunities for ecological studies of vocalizing species within the context of the natural habitats and communities in which they occur. Continuous acoustic monitoring of species assemblages can reveal patterns in breeding phenology, behavior, and interactions. We used long-duration false-color spectrograms derived from acoustic indices to detect the nightly chorusing of a community of anurans in a tropical savanna in north Queensland. We described the chorusing patterns of each species over two wet seasons at three breeding sites, and used conditional random forest analysis to investigate the influence of various environmental factors. Frogs in these habitats form multispecies aggregations at water bodies during breeding periods when males form large choruses to attract females. The chorusing patterns revealed the species have different breeding periods, which could be broadly categorized as explosive or prolonged. While rain events were often a trigger for the commencement of the breeding period, species responded differently to environmental conditions. Choruses of explosive breeding species occurred only on the night of, or night after, the first high rainfall event of the wet season. The prolonged breeding species showed idiosyncratic patterns of chorusing, which were generally consistent across sites. Fine-grained nightly data on patterns of chorusing and the relationship with environmental conditions allow us to understand the detectability of the presence, or absence, of the frog species in these habitats, and provide baseline data for monitoring and management programs.

White-nose syndrome is a skin disease of bats caused by the fungus Pseudogymnoascus destructans (Pd). Pd has devastated populations of some bat species in North America, where environmental reservoirs of the fungus are considered a threat to the persistence of bat populations. However, long-term patterns of Pd environmental persistence in North American hibernacula are unknown. We swabbed hibernacula walls 11 years after the invasion of Pd into Maritime Canada in 2011. This is the first study to examine the persistence of Pd in North American hibernacula >7 years after the first documentation of Pd at a site. The proportion of hibernacula wall swabs with viable Pd decreased over time, with 40.6% of wall swabs positive (n = 32) in 2012, 35.0% (n = 40) in 2015, and 1.7% (n = 120) in 2022. In early winter 2022, 41.18% (n = 17) of bats (Myotis lucifugus, M. septentrionalis, and Perimyotis subflavus) were Pd-positive compared to 6.67% (n = 15) in late winter, a low prevalence and the opposite pattern compared to the first 4 years after Pd invasion to sites. Our results suggest that Pd loads in the environment naturally decrease to low or undetectable levels over time in our study region. Since attempts to reduce environmental reservoirs have a high likelihood of negative nontarget effects on hibernacula ecosystems, and a low likelihood of completely eradicating Pd, actions to reduce environmental reservoirs in hibernacula should consider deprioritizing sites where Pd has been present >10 years. We urge the collection of further data across hibernacula sites with varied geochemistry, microclimates, organic matter availability, timing of Pd arrival, and surviving bat colony sizes. This will allow a more comprehensive assessment of this strategy.

Causes, consequences, and potentials for recovery from invasions by the invasive annual grass, cheatgrass (Bromus tectorum), in western North America have been extensively documented. The vast majority of these studies have come from regions where yearly precipitation is dominated by “winter-wet” patterns, but this species has also demonstrated its ability to invade plant communities in “spring/summer-wet” areas as well. In grasslands of the Front Range of Colorado, a region experiencing a “spring/summer-wet” precipitation pattern, cheatgrass can exploit early-season soil moisture, but moderate rainfall continues into the growing season beyond the time of cheatgrass senescence. In this study, we measured how cheatgrass dominance changed over a 13-year interval in a disturbed meadow along the Front Range of Colorado with a “spring/summer-wet” precipitation pattern. Cheatgrass cover declined in absolute abundance by about 50% while total vegetation cover increased over this time period. The site was neither grazed nor burned during this interval. A “spring/summer-wet” precipitation pattern with high interannual variation in amounts occurred during the study, but no relationships between the seasonality or amounts of precipitation and the directional decline in cheatgrass abundance were observed. Rainout shelter manipulations showed that the seasonality of precipitation influenced cheatgrass abundance, with winter drought treatments reducing cheatgrass cover relative to plots that experienced summer drought treatments. The cheatgrass decline corresponded with a lesser decline in native grass cover and no change in native forb cover, while the abundance of non-native perennial grasses and forb species increased over the study interval. Although cheatgrass can invade communities across broad climatic gradients following disturbance, results from this study show that the persistence of cheatgrass within invaded areas may depend on the seasonality of precipitation and plant communities that vary across these gradients.

Migration strategy is a key behavioral characteristic guiding how migratory species time their annual cycles and use habitat. Understanding variation in migration strategy within and among species and individuals can be useful for understanding how birds navigate energetic trade-offs and designing or modifying conservation plans meant to benefit multiple species and life histories. We compared migration strategies among three migratory shorebird species with variable life history traits and short, medium, and long migration distances, respectively: American avocets (Recurvirostra americana), black-bellied plovers (Pluvialis squatarola), and Hudsonian godwits (Limosa haemastica). Avocets (short distance) exhibited the most within-species variation in migration duration, proportion of migration time spent at stopovers, and stopover duration. Plovers (medium distance) and godwits (long distance) showed less variation in these metrics, but godwits showed the most variation in the number of stopovers used. There were significant differences among species in migration distance, number of stopovers used, proportion of time stopped over, departure and arrival dates, and migration duration, but not mean stopover duration. We also found that avocets spent more time stopped over relative to migration distance than plovers or godwits, indicating that avocets showed the most energy-minimizing strategy of the three species. Our findings set the stage for future work assessing the effects of climate change and land use on characteristics associated with different migration strategies for additional migratory species.