SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe

Mammal responses to global changes in human activity vary by trophic group and landscape

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.Peer reviewe

The influence of sulfur and hair growth on stable isotope diet estimates for grizzly bears

<div><p>Stable isotope ratios of grizzly bear (<i>Ursus arctos</i>) guard hair collected from bears on the lower Stikine River, British Columbia (BC) were analyzed to: 1) test whether measuring δ³⁴S values improved the precision of the salmon (<i>Oncorhynchus</i> spp.) diet fraction estimate relative to δ¹⁵N as is conventionally done, 2) investigate whether measuring δ³⁴S values improves the separation of diet contributions of moose (<i>Alces alces</i>), marmot (<i>Marmota caligata</i>), and mountain goat (<i>Oreamnos americanus</i>) and, 3) examine the relationship between collection date and length of hair and stable isotope values. Variation in isotope signatures among hair samples from the same bear and year were not trivial. The addition of δ³⁴S values to mixing models used to estimate diet fractions generated small improvement in the precision of salmon and terrestrial prey diet fractions. Although the δ³⁴S value for salmon is precise and appears general among species and areas, sulfur ratios were strongly correlated with nitrogen ratios and therefore added little new information to the mixing model regarding the consumption of salmon. Mean δ³⁴S values for the three terrestrial herbivores of interest were similar and imprecise, so these data also added little new information to the mixing model. The addition of sulfur data did confirm that at least some bears in this system ate marmots during summer and fall. We show that there are bears with short hair that assimilate >20% salmon in their diet and bears with longer hair that eat no salmon living within a few kilometers of one another in a coastal ecosystem. Grizzly bears are thought to re-grow hair between June and October however our analysis of sectioned hair suggested at least some hairs begin growing in July or August, not June and, that hair of wild bears may grow faster than observed in captive bears. Our hair samples may have been from the year of sampling or the previous year because samples were collected in summer when bears were growing new hair. The salmon diet fraction increased with later hair collection dates, as expected if samples were from the year of sampling because salmon began to arrive in mid-summer. Bears that ate salmon had shorter hair and δ¹⁵N and δ³⁴S values declined with hair length, also suggesting some hair samples were grown the year of sampling. To be sure to capture an entire hair growth period, samples must be collected in late fall. Early spring samples are also likely to be from the previous year but the date when hair begins to grow appears to vary. Choosing the longest hair available should increase the chance the hair was grown during the previous year and, maximize the period for which diet is measured.</p></div

A comparison of mean isotope ratios of various tissue types for four potential grizzly bear prey species from the lower Stikine valley of northeast British Columbia.

<p>A comparison of mean isotope ratios of various tissue types for four potential grizzly bear prey species from the lower Stikine valley of northeast British Columbia.</p

Stable isotope values vs hair length.

<p>Isotope signatures were based on analysis of the longest guard hairs available in each sample. Hair length was the average of all hairs when more than one hair was included in the isotope analysis. Some of these hairs were sectioned in thirds by length to analyze seasonal diet, the average of the 3 values is presented here. Grizzly bears detected in drainages with spawning salmon are shown in red symbols (n = 54). Green symbols indicate bears were detected in drainages without spawning salmon (n = 40). Filled symbols indicate the hair was likely from an entire season of growth, lighter fill means the period of growth is less certain though still likely from an entire season of growth and, unfilled symbols indicate the hair were likely grown the year of sampling and hence represent a partial year’s growth.</p

Chum salmon selective foraging.

<p>This photo shows how grizzly bears may eat only the brains of salmon when they are abundant, which was commonly observed in our study area. They also preferred the eggs of female salmon and at times choose the skin while leaving other body parts.</p

The mean difference between isotope ratios of muscle and hair or skin for three potential grizzly bear foods.

<p>Delta values are the average difference compared to muscle. A single sample of coho eggs was compared to the mean coho muscle values because this sample was taken from a unique fish.</p

Diet of individual bears by season.

<p>Guard hairs for each sample (n = 40) were cut into 3 equal lengths. We assumed hair began growing June 1 and finished Oct 31. Each point depicts the diet between it and the previous x-value which was June 1 for the first segment of all samples. For hair samples that we believed came from the year the sample was collected, the last day of growth was the collection date. Observation date was calculated by dividing the difference between the beginning and end of hair growth into thirds. Grizzly bears detected in drainages with spawning salmon are shown in red symbols (n = 23). Green symbols indicate bears detected in drainages without spawning salmon (n = 17).</p

Mean isotope ratios for seven potential grizzly bear foods from the lower Stikine valley of northeast British Columbia.

<p>δ¹³C values for marmot hair samples were reduced by 1.5. ^b<i>n</i> = 1 for sulfur in this category.</p