284 research outputs found
Camera trap arrays improve detection probability of wildlife: Investigating study design considerations using an empirical dataset.
Camera trapping is a standard tool in ecological research and wildlife conservation. Study designs, particularly for small-bodied or cryptic wildlife species often attempt to boost low detection probabilities by using non-random camera placement or baited cameras, which may bias data, or incorrectly estimate detection and occupancy. We investigated the ability of non-baited, multi-camera arrays to increase detection probabilities of wildlife. Study design components were evaluated for their influence on wildlife detectability by iteratively parsing an empirical dataset (1) by different sizes of camera arrays deployed (1-10 cameras), and (2) by total season length (1-365 days). Four species from our dataset that represented a range of body sizes and differing degrees of presumed detectability based on life history traits were investigated: white-tailed deer (Odocoileus virginianus), bobcat (Lynx rufus), raccoon (Procyon lotor), and Virginia opossum (Didelphis virginiana). For all species, increasing from a single camera to a multi-camera array significantly improved detection probability across the range of season lengths and number of study sites evaluated. The use of a two camera array increased survey detection an average of 80% (range 40-128%) from the detection probability of a single camera across the four species. Species that were detected infrequently benefited most from a multiple-camera array, where the addition of up to eight cameras produced significant increases in detectability. However, for species detected at high frequencies, single cameras produced a season-long (i.e, the length of time over which cameras are deployed and actively monitored) detectability greater than 0.75. These results highlight the need for researchers to be critical about camera trap study designs based on their intended target species, as detectability for each focal species responded differently to array size and season length. We suggest that researchers a priori identify target species for which inference will be made, and then design camera trapping studies around the most difficult to detect of those species
Departure from the constant-period ephemeris for the transiting exoplanet WASP-12 b
Most hot Jupiters are expected to spiral in towards their host stars due to
transfering of the angular momentum of the orbital motion to the stellar spin.
Their orbits can also precess due to planet-star interactions. Calculations
show that both effects could be detected for the very-hot exoplanet WASP-12 b
using the method of precise transit timing over a timespan of the order of 10
yr. We acquired new precise light curves for 29 transits of WASP-12 b,
spannning 4 observing seasons from November 2012 to February 2016. New
mid-transit times, together with literature ones, were used to refine the
transit ephemeris and analyse the timing residuals. We find that the transit
times of WASP-12 b do not follow a linear ephemeris with a 5 sigma confidence
level. They may be approximated with a quadratic ephemeris that gives a rate of
change in the orbital period of -2.56 +/- 0.40 x 10^{-2} s/yr. The tidal
quality parameter of the host star was found to be equal to 2.5 x 10^5 that is
comparable to theoretical predictions for Sun-like stars. We also consider a
model, in which the observed timing residuals are interpreted as a result of
the apsidal precession. We find, however, that this model is statistically less
probable than the orbital decay.Comment: Accepted for publication in A&A Letter
High angular resolution imaging and infrared spectroscopy of CoRoT candidates
Studies of transiting extrasolar planets are of key importance for
understanding the nature of planets outside our solar system because their
masses, diameters, and bulk densities can be measured. An important part of
transit-search programmes is the removal of false-positives. The critical
question is how many of the candidates that passed all previous tests are false
positives. For our study we selected 25 CoRoT candidates that have already been
screened against false-positives using detailed analysis of the light curves
and seeing-limited imaging, which has transits that are between 0.7 and 0.05%
deep. We observed 20 candidates with the adaptive optics imager NaCo and 18
with the high-resolution infrared spectrograph CRIRES. We found previously
unknown stars within 2 arcsec of the targets in seven of the candidates. All of
these are too faint and too close to the targets to have been previously
detected with seeing-limited telescopes in the optical. Our study thus leads to
the surprising results that if we remove all candidates excluded by the
sophisticated analysis of the light-curve, as well as carrying out deep imaging
with seeing-limited telescopes, still 28-35% of the remaining candidates are
found to possess companions that are bright enough to be false-positives. Given
that the companion-candidates cluster around the targets and that the J-K
colours are consistent with physical companions, we conclude that the
companion-candidates are more likely to be physical companions rather than
unrelated field stars.Comment: 12 pages, 12 figures, A&A in pres
Co-occurrence of invasive and native carnivorans affects occupancy patterns across environmental gradients
Understanding species interactions and their effects on distributions is crucial for assessing the impacts of global change, particularly for invasive species. Co-occurrence models can help investigate these effects when interactions are likely given shared traits. For such an assemblage of invasive and native carnivorans, we examined how patterns of co-occurrence change across space and environmental gradients using a static multispecies occupancy model that accounts for imperfect detectability and models co-occurrence as a function of environmental variables, and also extended it to be temporally dynamic. We focused on invasive raccoons, which pose threats to humans and wildlife globally. In Japan, raccoons prey on many native taxa, but little is known about interactions with sympatric carnivorans. We searched for signals of competitive exclusion of native raccoon dogs (tanuki) and invasive masked palm civets by applying the model to detection data from a broad-scale trapping effort over 6 years. Forest cover was the strongest predictor of occupancy for individual species and raccoon co-occurrences, and raccoon occupancy probability increased with forest cover conditionally depending on the co-occurring carnivoran: only tanuki absence or civet presence had positive responses. However, tanuki occupancy probability increased with forest cover despite any co-occurrence. Thus, we found no evidence of competitive exclusion by raccoons, contrary to our expectations. As parts of the world with invasive raccoons can also have invasive tanuki, our findings may have broad management implications. The model we present should be useful for inferring signals of biotic interactions between species with low detectability over multi-year time frames
Measuring the cityscape : a pipeline from street-level capture to urban quantification
Any solution to achieving climate targets must be performed at scale. Data driven methods allow expert modelling to be emulated over a large scope. In the UK, there are nearly 30 million residential properties, contributing to over 30% of the national energy consumption. As part of the UK Government's requirement to meet net-zero emissions by 2050, retrofitting residential buildings forms a significant part of the national strategy. This work addresses the problem of identifying, characterising and quantifying urban features at scale. A pipeline incorporating photogrammetry, automatic labelling using machine learning, and 3-D geometry has been developed to automatically reconstruct and extract dimensional and spatial features of a building from street-level mobile sensing
Is the Insect Apocalypse upon us? How to Find Out
In recent decades, entomologists have documented alarming declines in occurrence, taxonomic richness, and geographic range of insects around the world. Additionally, some recent studies have reported that insect abundance and biomass, often of common species, are rapidly declining, which has led some to dub the phenomenon an “Insect Apocalypse”. Recent reports are sufficiently robust to justify immediate actions to protect insect biodiversity worldwide. We caution, however, that we do not yet have the data to assess large-scale spatial patterns in the severity of insect trends. Most documented collapses are from geographically restricted studies and, alone, do not allow us to draw conclusions about insect declines on continental or global scales, especially with regards to future projections of total insect biomass, abundance, and extinction. There are many challenges to understanding insect declines: only a small fraction of insect species have had any substantial population monitoring, millions of species remain unstudied, and most of the long-term population data for insects come from human-dominated landscapes in western and northern Europe. But there are still concrete steps we can take to improve our understanding of potential declines. Here, we review the challenges scientists face in documenting insect population and diversity trends, including communicating their findings, and recommend research approaches needed to address these challenges
The Lupus Transit Survey For Hot Jupiters: Results and Lessons
We present the results of a deep, wide-field transit survey targeting Hot
Jupiter planets in the Lupus region of the Galactic plane conducted over 53
nights concentrated in two epochs separated by a year. Using the Australian
National University 40-inch telescope at Siding Spring Observatory (SSO), the
survey covered a 0.66 sq. deg. region close to the Galactic Plane (b=11 deg.)
and monitored a total of 110,372 stars (15.0<V<22.0). Using difference imaging
photometry, 16,134 light curves with a photometric precision of sigma<0.025 mag
were obtained. These light curves were searched for transits, and four
candidates were detected that displayed low-amplitude variability consistent
with a transiting giant planet. Further investigations, including spectral
typing and radial velocity measurements for some candidates, revealed that of
the four, one is a true planetary companion (Lupus-TR-3), two are blended
systems (Lupus-TR-1 and 4), and one is a binary (Lupus-TR-2). The results of
this successful survey are instructive for optimizing the observational
strategy and follow-up procedure for deep searches for transiting planets,
including an upcoming survey using the SkyMapper telescope at SSO.Comment: 27 pages, 9 figures, 4 tables. Accepted for publication in A
Multi-object spectroscopy of stars in the CoRoT fields II: The stellar population of the CoRoT fields IRa01, LRa01, LRa02, and LRa06
With now more than 20 exoplanets discovered by CoRoT, it has often been
considered strange that so many of them are orbiting F-stars, and so few of
them K or M-stars. Although transit search programs are mostly sensitive to
short-period planets, they are ideal for verifying these results. To determine
the frequency of planets as a function of stellar mass, we also have to
characterize the sample of stars that was observed. We study the stellar
content of the CoRoT-fields IRa01, LRa01 (=LRa06), and LRa02 by determining the
spectral types of 11466 stars. We used spectra obtained with the multi-object
spectrograph AAOmega and derived the spectral types by using template spectra
with well-known parameters. We find that 34.8+/-0.7% of the stars observed by
CoRoT in these fields are F-dwarfs, 15.1+/-0.5% G-dwarfs, and 5.0+/-0.3%
K-dwarfs. We conclude that the apparent lack of exoplanets of K- and M-stars is
explained by the relatively small number of these stars in the observed sample.
We also show that the apparently large number of planets orbiting F-stars is
similarly explained by the large number of such stars in these fields. Our
study also shows that the difference between the sample of stars that CoRoT
observes and a sample of randomly selected stars is relatively small, and that
the yield of CoRoT specifically is the detection one hot Jupiter amongst
2100+/-700 stars. We conclude that transit search programs can be used to study
the relation between the frequency of planets and the mass of the host stars,
and that the results obtained so far generally agree with those of radial
velocity programs.Comment: 231 pages with 6 figures, A&A accepte
Component-level residential building material stock characterization using computer vision techniques
Residential building material stock constitutes a significant part of the built environment, providing crucial shelter and habitat services. The hypothesis concerning stock mass and composition has garnered considerable attention over the past decade. While previous research has mainly focused on the spatial analysis of building masses, it often neglected the component-level stock analysis or where heavy labor cost for onsite survey is required. This paper presents a novel approach for efficient component-level residential building stock accounting in the United Kingdom, utilizing drive-by street view images and building footprint data. We assessed four major construction materials: brick, stone, mortar, and glass. Compared to traditional approaches that utilize surveyed material intensity data, the developed method employs automatically extracted physical dimensions of building components incorporating predicted material types to calculate material mass. This not only improves efficiency but also enhances accuracy in managing the heterogeneity of building structures. The results revealed error rates of 5 and 22% for mortar and glass mass estimations and 8 and 7% for brick and stone mass estimations, with known wall types. These findings represent significant advancements in building material stock characterization and suggest that our approach has considerable potential for further research and practical applications. Especially, our method establishes a basis for evaluating the potential of component-level material reuse, serving the objectives of a circular economy
HAT-P-24b: An inflated hot-Jupiter on a 3.36d period transiting a hot, metal-poor star
We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting
the moderately bright V=11.818 F8 dwarf star GSC 0774-01441, with a period P =
3.3552464 +/- 0.0000071 d, transit epoch Tc = 2455216.97669 +/- 0.00024
(BJD_UTC), and transit duration 3.653 +/- 0.025 hours. The host star has a mass
of 1.191 +/- 0.042 Msun, radius of 1.317 +/- 0.068 Rsun, effective temperature
6373 +/- 80 K, and a low metallicity of [Fe/H] = -0.16 +/- 0.08. The planetary
companion has a mass of 0.681 +/- 0.031 MJ, and radius of 1.243 +/- 0.072 RJ
yielding a mean density of 0.439 +/- 0.069 g cm-3 . By repeating our global
fits with different parameter sets, we have performed a critical investigation
of the fitting techniques used for previous HAT planetary discoveries. We find
that the system properties are robust against the choice of priors. The effects
of fixed versus fitted limb darkening are also examined. HAT-P-24b probably
maintains a small eccentricity of e = 0.052 +0.022 -0.017, which is accepted
over the circular orbit model with false alarm probability 5.8%. In the absence
of eccentricity pumping, this result suggests HAT-P-24b experiences less tidal
dissipation than Jupiter. Due to relatively rapid stellar rotation, we estimate
that HAT-P-24b should exhibit one of the largest known Rossiter-McLaughlin
effect amplitudes for an exoplanet (deltaVRM ~ 95 m/s) and thus a precise
measurement of the sky-projected spin-orbit alignment should be possible.Comment: 13 pages with 4 figures and 8 tables in emulateapj format. Minor
changes. Accepted in The Astrophysical Journa
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