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Rabies is an acute viral infection that is typically fatal. Most rabies modeling has focused on disease dynamics and control within terrestrial mammals (e.g., raccoons and foxes). As such, rabies in bats has been largely neglected until recently. Because bats have been implicated as natural reservoirs for several emerging zoonotic viruses, including SARS-like corona viruses, henipaviruses, and lyssaviruses, understanding how pathogens are maintained within a population becomes vital. Unfortunately, little is known about maintenance mechanisms for any pathogen in bat populations. We present a mathematical model parameterized with unique data from an extensive study of rabies in a Colorado population of big brown bats (Eptesicus fuscus) to elucidate general maintenance mechanisms. We propose that life history patterns of many species of temperate-zone bats, coupled with sufficiently long incubation periods, allows for rabies virus maintenance. Seasonal variability in bat mortality rates, specifically low mortality during hibernation, allows long-term bat population viability. Within viable bat populations, sufficiently long incubation periods allow enough infected individuals to enter hibernation and survive until the following year, and hence avoid an epizootic fadeout of rabies virus. We hypothesize that the slowing effects of hibernation on metabolic and viral activity maintains infected individuals and their pathogens until susceptibles from the annual birth pulse become infected and continue the cycle. This research provides a context to explore similar host ecology and viral dynamics that may explain seasonal patterns and maintenance of other bat-borne diseases.

Ecologists have long hypothesized that fragmentation of tropical landscapes reduces avian nest success. However, this hypothesis has not been rigorously assessed because of the difficulty of finding large numbers of well-hidden nests in tropical forests. Here we report that in the East Usambara Mountains in Tanzania, which are part of the Eastern Arc Mountains, a global biodiversity hotspot, that daily nest survival rate and nest success for seven of eight common understory bird species that we examined over a single breeding season were significantly lower in fragmented than in continuous forest, with the odds of nest failure for these seven species ranging from 1.9 to 196.8 times higher in fragmented than continuous forest. Cup-shaped nests were particularly vulnerable in fragments. We then examined over six breeding seasons and 14 study sites in a multivariable survival analysis the influence of landscape structure and nest location on daily nest survival for 13 common species representing 1,272 nests and four nest types (plate, cup, dome, and pouch). Across species and nest types, area, distance of nest to edge, and nest height had a dominant influence on daily nest survival, with area being positively related to nest survival and distance of nest to edge and nest height being both positively and negatively associated with daily nest survival. Our results indicate that multiple environmental factors contribute to reduce nest survival within a tropical understory bird community in a fragmented landscape and that maintaining large continuous forest is important for enhancing nest survival for Afrotropical understory birds.

In 2001-2005 we sampled permanently marked big brown bats (Eptesicus fuscus) at summer roosts in buildings at Fort Collins, Colorado, for rabies virus neutralizing antibodies (RVNA). Seroprevalence was higher in adult females (17.9%, n = 2,332) than males (9.4%, n = 128; P = 0.007) or volant juveniles (10.2%, n = 738; P<0.0001). Seroprevalence was lowest in a drought year with local insecticide use and highest in the year with normal conditions, suggesting that environmental stress may suppress RVNA production in big brown bats. Seroprevalence also increased with age of bat, and varied from 6.2 to 26.7% among adult females at five roosts sampled each year for five years. Seroprevalence of adult females at 17 other roosts sampled for 1 to 4 years ranged from 0.0 to 47.1%. Using logistic regression, the only ranking model in our candidate set of explanatory variables for serological status at first sampling included year, day of season, and a year by day of season interaction that varied with relative drought conditions. The presence or absence of antibodies in individual bats showed temporal variability. Year alone provided the best model to explain the likelihood of adult female bats showing a transition to seronegative from a previously seropositive state. Day of the season was the only competitive model to explain the likelihood of a transition from seronegative to seropositive, which increased as the season progressed. We found no rabies viral RNA in oropharyngeal secretions of 261 seropositive bats or in organs of 13 euthanized seropositive bats. Survival of seropositive and seronegative bats did not differ. The presence of RVNA in serum of bats should not be interpreted as evidence for ongoing rabies infection.

Sea turtles in the Gulf of Mexico, which are listed as either threatened or endangered under the US Endangered Species Act, face numerous threats but are particularly susceptible to the negative effects of light pollution on nesting beaches. Light pollution affects the distribution, density, and placement of nests on beaches, and disrupts seafinding in hatchlings emerging from nests; often leading to their death. Rapid urban growth near Gulf Islands National Seashore (GUIS), Florida, USA, over the last century has contributed to increased light pollution on its beaches. There is concern that light pollution is causing females to lay nests in at-risk locations subject to erosion and flooding, and is causing the observed high rates of hatchling misorientation. From 2015-2016, we measured brightness of the night sky, horizon profile, and lunar variables at GUIS at loggerhead (Caretta caretta) nests to assess the effects of brightness on laying of at-risk nests and hatchling misorientation. In addition, we quantified the effects of relocating at-risk nests on nest success. We found that contrast in brightness between the landward and seaward directions at GUIS was partially responsible for high rates of hatchling misorientation, and there was a strong moderating influence of lunar fraction and lunar altitude on hatchling misorientation: larger lunar fractions and lower lunar altitudes reduced misorientation. We did not document an effect of artificial light, horizon profile, or lunar fraction on the propensity of loggerheads to lay nests in at-risk locations, and found no evidence that relocating nests at GUIS reduced loggerhead nest success. Rather, we found nest success was improved and hatchling misorientation rates were reduced for relocated loggerhead nests.

Long‐term ecological monitoring provides valuable and objective scientific information to inform management and decision‐making. In this article, we analyze 22 years of herpetofauna monitoring data from the Point Loma Ecological Conservation Area (PLECA), an insular urban reserve near San Diego, CA. Our analysis showed that counts of individuals for one of the four most common terrestrial vertebrates declined, whereas counts for other common species increased or remained stable. Two species exhibited declines in adult body length, whereas biomass pooled over the five most common species increased over time and was associated with higher wet season precipitation. Although the habitat and vegetation at PLECA have remained protected and intact, we suspect that changes in arthropod communities may be driving changes in the abundance, growth, and development of insectivorous lizards. This study underscores the value of long‐term monitoring for establishing quantitative baselines to assess biological changes that would otherwise go undetected. Species‐specific capture rate patterns for adults and juveniles over a calendar year. The x‐axis is the month (1 = January, …, 12 = December) and the y‐axis is capture rate (captures in month i/array‐nights in month i). Monthly captures were the monthly count data pooled over the years 1995–2016; monthly array‐nights were from Table S2.

Most approaches for assessing species vulnerability to climate change have focused on direct impacts via abiotic changes rather than indirect impacts mediated by changes in species interactions. Changes in rainfall regimes may influence species interactions from the bottom-up by increasing primary productivity in arid environments, but subsequently lead to less predictable top-down effects. Our study demonstrates how the effects of an EL Niño/Southern Oscillation (ENSO)-driven rainfall pulse ricochets along a chain of interactions between marine and terrestrial food webs, leading to enhanced predation of a vulnerable marine predator on its island breeding grounds. On Santa Barbara Island, barn owls ( Tyto alba ) are the main predator of a nocturnal seabird, the Scripps's murrelet ( Synthliboramphus scrippsi ), as well as an endemic deer mouse. We followed the links between rainfall, normalized difference vegetation index and subsequent peaks in mouse and owl abundance. After the mouse population declined steeply, there was approximately 15-fold increase in the number of murrelets killed by owls. We also simulated these dynamics with a mathematical model and demonstrate that bottom-up resource pulses can lead to subsequent declines in alternative prey. Our study highlights the need for understanding how species interactions will change with shifting rainfall patterns through the effects of ENSO under global change.

We studied associations with winter habitat for seven species of birds, one species-group (eastern and western meadowlarks combined), and total sparrows at seven sites in the semidesert and plains grasslands of southeastern Arizona from 1999–2001, sampling with mist-nets and survey-transects. We measured structure and composition of vegetation, assessing vegetative differences among sites, and modeled associations between indices of avian abundance and six vegetative variables using generalized linear models. For all vegetative variables, there were significant differences among sites. Numbers of northern harriers (Circus cyaneus) were positively associated with total number of sparrows. Indices of abundance for individual species of birds were statistically correlated with various measures of structure and composition of vegetation. In particular, grasshopper (Ammodramus savannarum) and vesper (Pooecetes gramineus) sparrows were negatively associated with amount of bare ground; horned larks (Eremophila alpestris) were negatively associated with vertical grass density; Baird's sparrows (A. bairdii) were negatively associated with shrub density; meadowlarks (Sturnella magna and S. neglecta combined) were positively associated with native grass. Our results suggest that these species would benefit from management of habitat that affects the vegetative characteristics associated with their abundance.

Adult male big brown bats (Eptesicus fuscus) sometimes occur within maternity roosts. We investigated male attendance at big brown bat maternity roosts in a Colorado study area that shows a pattern of sexual segregation by elevation. We tested multiple predictions of three nonmutually exclusive hypotheses to explain male attendance patterns: 1) sex-specific differences in energetic strategies of males and females are maintained at the lower elevation; 2) natal philopatry of inexperienced young males accounts for most attendants; 3) males gain a reproductive advantage for late summer mating at maternity roosts. We tested predictions based on captures of bats at emergence, automated monitoring of annual, seasonal, and daily roost attendance by known-age bats tagged with passive integrated transponders, and anatomical evidence for mating. Findings were most consistent with the first two hypotheses. Adult males accounted for just 3.1% of 8,192 captures of bats at 285 evening emergences from 46 roosts during 2001–2005. Daily attendance rates of males during each active season (0.10 detections/day at age 1 year and 0.20 detections/day at ≥ 2 years old) were lower than in females (0.34 at age 1 year and 0.45 at ≥ 2 years old). Only 92 of 299 males tagged as volant juveniles were detected as adults at five maternity roosts monitored 2002–2005, far fewer than female returns in every age category. We detected known-age adult males almost exclusively at their natal roosts and most males that returned (91 of 92) in years after tagging as juveniles were first detected as 1-year-olds; 20 of 21 individuals that returned at 2–4 years of age were previously detected as 1-year-olds. One-year-old males were re-encountered at annual rates 5–16 times higher than 2- to 4-year-old males, and 1-year-old males and females had lower daily attendance rates than older bats. The male reproductive advantage hypothesis was not well supported. None of 80 females examined in late summer had evidence of insemination, and not all males showed distended scrota. Daily attendance rates of tagged adult males (n = 155) and females (n = 788) were lowest during late summer, suggesting that little reproductive advantage was accrued by males utilizing maternity roosts. Attendance of male big brown bats at maternity roosts at our study area is consistent with the sex-specific energetic strategies and natal philopatry hypotheses, and mating probably occurs at higher elevation autumn roosts and hibernacula.

Disease, predation, and genetic isolation resulted in 4 of 6 island fox (Urocyon littoralis) subspecies being listed as endangered in 2004. Potential for disease outbreaks continues to pose a major threat to the persistence of these isolated, endemic populations. We examined how roads influence the spatial ecology of San Clemente Island foxes (U. l. clementae), particularly in regard to spread of disease, to provide management recommendations for preventing or minimizing a disease outbreak on San Clemente Island, California, USA. Home range areas (x̄ = 0.75 km²) and core areas (x̄ = 0.19 km²) of foxes on San Clemente Island were 0.36–1.23 and 2.17 times larger, respectively, than estimates from Santa Cruz Island foxes (U. l. santacruzae). Home ranges and core areas were 78% larger and 73% larger, respectively, for foxes near roads than for foxes away from roads. Home ranges were also largest when foxes were not caring for offspring (i.e., seasons of pup-independence and breeding). We did not detect any dispersal movements, but foxes living near roads moved 33% farther in 2-hour periods than foxes not living near roads. Foxes near roads move faster, range more widely, and could more rapidly spread a pathogen throughout the island; therefore, roads might serve as transmission corridors. We recommend reducing this risk by increasing widths of vaccination firewalls (areas where vaccination is used to induce a disease-resistant or immune population of foxes), ensuring these areas deliberately intersect roads, and vaccinating a higher proportion of foxes living near roads. Disease risk models incorporating these strategies could inform the lowest risk scenarios.

We studied adult survival and population growth at multiple maternity colonies of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado. We investigated hypotheses about survival using information-theoretic methods and mark–recapture analyses based on passive detection of adult females tagged with passive integrated transponders. We constructed a 3-stage life-history matrix model to estimate population growth rate (λ) and assessed the relative importance of adult survival and other life-history parameters to population growth through elasticity and sensitivity analysis. Annual adult survival at 5 maternity colonies monitored from 2001 to 2005 was estimated at 0.79 (95% confidence interval [95% CI] = 0.77–0.82). Adult survival varied by year and roost, with low survival during an extreme drought year, a finding with negative implications for bat populations because of the likelihood of increasing drought in western North America due to global climate change. Adult survival during winter was higher than in summer, and mean life expectancies calculated from survival estimates were lower than maximum longevity records. We modeled adult survival with recruitment parameter estimates from the same population. The study population was growing (λ = 1.096; 95% CI = 1.057–1.135). Adult survival was the most important demographic parameter for population growth. Growth clearly had the highest elasticity to adult survival, followed by juvenile survival and adult fecundity (approximately equivalent in rank). Elasticity was lowest for fecundity of yearlings. The relative importances of the various life-history parameters for population growth rate are similar to those of large mammals.