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- Identification of mammal species preyed upon by urban foxes (Vulpes vulpes) in Sapporo, Japan, determined by fecal DNA analysis
Overview
This study focuses on investigating the diet composition of red foxes (Vulpes vulpes) living in urban areas in northern Japan. Red foxes rely on varying food sources, including several types of small mammals and fruits. This study suggests that the home range of urban foxes can be around 30 hectares, so they have a large area to forage for food in. This paper looked at the types of small mammals that the urban foxes were consuming by analyzing scat samples. The species of animals being consumed by urban foxes was determined by extracting DNA from the scat samples that were collected. The advantages of fecal DNA analysis include non-invasiveness, ease of collection, and high accuracy. The goal of this analysis is to understand the diet of urban red foxes in northern Japan, specifically what animals they are consuming.
Methods:
The ‘urban areas’ that were included in this study had to be considered densely inhabited districts by the Statistics Bureau of Japan. The ‘suburban areas’ in this study were areas that were in the city but outside of densely inhabited districts. One challenge for sample collection was distinguishing the scat of urban foxes from that of other species such as dogs. This was solved by using polymerase chain reaction (PCR) to test for primers that were specific to red foxes. This allowed the researchers to ensure that their samples were actually coming from urban foxes. The researchers also had to develop PCR primers for the species they were testing for in the red fox scat. The wild species that had PCR primers developed for them were gray red-backed vole, Hokkaido red-backed vole, northern red-backed vole, large Japanese field mouse, small Japanese field mouse, brown rat, house mouse, Eurasian red squirrel, Siberian chipmunk, mountain hare, and sika deer. Additionally, the researchers also used PCR primers to test for the presence of livestock species in the urban fox scat (cattle, pig, and chicken). The development of the PCR primers for prey species was essential for allowing the researchers to analyze the scat samples from the urban foxes.
Results:
In total there were 110 scat samples collected, and 78 of them were determined to come from red foxes (these 78 were used for the analysis). The wild mammals that were tested for were found in 47.4% of the samples. The gray red-backed vole was the most commonly detected wild mammal species, and it was found in both urban and suburban samples. Other commonly detected species were the brown rat and the large Japanese field mouse. Interestingly, the mountain hare, house mouse, Hokkaido red-backed vole, northern red-backed vole, and small Japanese field mouse were not found in any of the samples that were collected. When looking at the dietary composition of livestock, chicken was most commonly found in the scat samples (56% of samples contained chicken). Pig was also commonly found in the samples (29% of samples contained pig). Although cattle were not found as commonly, the total frequency of livestock in the urban fox scat samples was 61.5%. Additionally, multiple prey species were found in 38% of the samples.
Reflection/Critiques:
Wild mammals play an important role in the diet of urban red foxes in the study area. The primary wild mammal prey species for urban foxes in this area was determined to be the gray red-backed vole. This was supported through wild mammals being found in 47.4% of samples and the gray red-backed vole being found in 30.2% of samples. Although it is possible that the urban foxes were feeding in different areas than where they were dropping feces, the researchers concluded that this was unlikely due to the home range size of the red foxes. The brown rat was also found to be an important dietary component for the urban foxes. This was likely due to the high abundance of this species in cities (brown rats can take advantage of the urban environment). Sitka deer was only found in one scat sample. This was likely from a scavenged carcass since sitka deer are a much larger mammal species. Overall, wild mammal species are an integral part of the diets of urban red foxes in the study area.
Livestock species were found in a larger percentage of the fecal samples for urban red foxes when compared to wild mammal species. According to this study, livestock species were found in 61.5% of the collected scat samples. This suggests that livestock species play a crucial role in supporting the diet of urban foxes. It is likely that this dietary component was primarily sourced from human garbage due to the urban location. The livestock species that was most commonly found in urban fox diets was chicken. This is likely due to it being frequently discarded in garbage. This area of Japan has higher average pork consumption when compared to cattle. This explains why pork was found more frequently in urban fox scat when compared to cattle. Overall, anthropogenic food sources are very important to the diets of urban red foxes in the study area.
The primary critique I have for this study is the relatively small sample size of urban red fox scat. The researchers only analyzed 78 scat samples. If the number of samples were increased, then the conclusions that the study found would be more reliable. The researchers could have greater confidence in the new discoveries regarding the dietary composition of urban red foxes in the study area. Although this would have required more input, the researchers had a reliable method to distinguish the red fox scat from other species.
Another critique for this study is the choice to collect samples without any way of identifying which individual fox they came from. This could have an impact on the data if multiple samples were collected from the same individual fox. It would be beneficial to have a method of quantifying the number of different individual foxes that contributed samples to the study. It would also be beneficial to know the number of samples that came from each individual fox. This would improve the analysis since the diet of each individual is variable and unique. Although this would improve the study, it is likely not practical. Monitoring individual foxes would be difficult, time consuming, and costly. It would also be difficult to attribute particular scat samples to individual foxes.
Reference:
Waga, D., Amaike, Y., Nonaka, N., & Masuda, R. (2025). Identification of mammal species preyed upon by urban foxes (Vulpes vulpes) in Sapporo, Japan, determined by fecal DNA analysis. The Journal of veterinary medical science, 87(8), 960–965. https://doi.org/10.1292/jvms.25-0199
- Critical Review of “Urbanization Effects on Spotted Salamander and Wood Frog Presence and Abundance”
Overview
This study by J.M. Reed and colleagues, published in Urban Ecosystems, explores how urban development influences the presence and abundance of two amphibian species: the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). Both species rely on temporary woodland pools, known as vernal pools, for breeding. Because amphibians are highly sensitive to environmental changes, they serve as indicators of ecosystem health. The researchers aimed to determine how surrounding land cover, such as forest area, impervious surfaces, and road proximity, affects amphibian occurrence and breeding success in human-altered landscapes.
Methods
Reed and his team surveyed 41 vernal pools in central Massachusetts that represented a range of surrounding land uses, from heavily forested to highly urbanized areas. They measured egg mass counts to estimate breeding abundance and recorded environmental factors including forest cover within 100–300 meters, hydroperiod, road density, and impervious surface area. To evaluate which factors most influenced amphibian presence, the researchers used logistic regression and stepwise model selection.
A key strength of the study was its use of GIS data to quantify the surrounding landscape, offering more precision than visual observation alone. However, one limitation was that data collection occurred during a single breeding season. The authors noted that year-to-year differences in rainfall and hydroperiod could influence amphibian breeding success, meaning a longer-term study might reveal additional trends or variability.
Results
The study found a clear negative relationship between urbanization and amphibian presence. Spotted salamanders were observed in 69 percent of pools with over 75 percent surrounding forest, but in fewer than 20 percent of pools where forest cover was below 25 percent. Wood frogs showed a similar pattern, though they appeared somewhat more tolerant of moderate development.
Road density within 100 meters of pools was one of the most consistent predictors of absence. Roads not only fragment habitats but also increase adult mortality as salamanders and frogs migrate to breeding sites. In addition, the amount of impervious surface near pools was strongly linked to lower abundance, likely due to disrupted hydrology and reduced water quality. The authors pointed out that even small increases in pavement or built infrastructure can lead to disproportionate ecological effects, illustrating how sensitive amphibians are to habitat loss and fragmentation.
Reflection / Critique
This study presents convincing evidence that urbanization substantially reduces amphibian populations, but there are several aspects that could have been expanded upon. While the authors recommend maintaining at least 30 to 50 meters of forest buffer around vernal pools, they do not provide practical guidance on how these recommendations might be implemented through zoning or conservation policy. Including examples of towns or municipalities that have successfully integrated amphibian habitat protection into land-use planning would have made the research more applied and actionable.
Another limitation is the lack of direct water quality data. The authors mention that pollution from runoff could influence amphibian populations, but they did not measure chemical variables such as nitrogen, phosphorus, or heavy metals. Without this information, it remains uncertain whether declines were driven primarily by habitat fragmentation or by contamination of breeding pools. Future studies combining both land-use and water chemistry analyses could paint a fuller picture of how urbanization impacts amphibians.
Even with these limitations, the study makes a valuable contribution to urban ecology. The finding that spotted salamanders virtually disappear when impervious cover exceeds 25 to 30 percent provides an important threshold for conservation planning. The authors also highlight how both landscape connectivity and small-scale features like forest buffers can make a major difference in sustaining amphibian populations.
Overall, this research offers a strong reminder that sustainable development must consider the needs of species that rely on small, seasonal, and easily overlooked habitats. Amphibians like the wood frog and spotted salamander are not just victims of habitat loss but also indicators of how human choices shape the health of entire ecosystems.
Reference:
Reed, J. M., et al. (2005). Urbanization Effects on Spotted Salamander and Wood Frog Presence and Abundance. Urban Ecosystems - What can we learn from wildlife sightings during the COVID-19 global shutdown?
Introduction
The global lockdown beginning in 2020 allowed some wildlife to venture into cities, like foxes, coyotes, and birds. The paper “What can we learn from wildlife sightings during the COVID-19 global shutdown?” by Zeller et al. (2020) in Ecosphere encompasses both an ecological and social study. The author uses citizen science data to explore changes in wildlife observations during the pandemic. This paper caught my attention due to the discussion in class about the pause in human activity during the pandemic and how urban wildlife behavior is intertwined with our presence.
Summary
Zellmer and colleagues analyzed citizen reported wildlife sightings from platforms like iNaturalist and eBird, comparing data from the early months of the pandemic to previous years. The purpose was to figure out whether wildlife actually became more abundant in cities during lockdown or if people only noticed a greater abundance of animals because they were at home and actually paying attention.
Results
They found mixed evidence. Reports increased of wildlife sightings in many urban areas, but this does not mean that there were necessarily more animals. Species that appeared more frequently in urban environments were coyotes, deer, and foxes. These were species that typically avoid dense human spaces. The paper emphasized that changes in behavior varied by species, city, and the degree of lockdown strictness. They ultimately, highlighted, that human movement can drastically alter the visibility and distribution of urban wildlife. A big portion of the paper is dedicated to acknowledging what the data cannot prove due to observer effort bias, detection vs. abundance, and heterogeneity among cities. The article never comes to an exact conclusion that wildlife increased in urban areas during lockdowns, but rather raises possibilities and promotes cautious interpretation.
Critical Reflection
This study is strong in that it used this rare global event as a large-scale natural experiment. The use of citizen science allowed for fast data collection and broad spatial coverage during a difficult time. The article is also rightfully cautious in not claiming “nature reclaimed cities” and instead acknowledging biases in observation and sampling. This underlines that this study is more of an analysis of human behavior rather than animal abundance. All in all this reflects on their credibility, making it a more reliable source. However, the authors could have gone further in correcting biases, rather than simply acknowledging it. For example they could have implemented observation models and categorization, which could have helped them separate real life wildlife increases from high detection rates. Furthermore, the study focuses on the early stages of lockdown in 2020, when in reality animals responses to the lockdown evolved over time. A study comparing all years of lockdown would test whether behavioral flexibility persists. Further studies could combine citizen science with automates monitoring, such as camera traps, sensors or tracking collars. Additionally, comparing results across continents could reveal cultural or infrastructural influences on how wildlife adapted depending on the density of buildings, size of city, noise pollution etc.
Work Cited
Zellmer, A. J., Wood, E. M., Surasinghe, T., Putman, B. J., Pauly, G. B., Magle, S. B., Lewis, J. S., Kay, C. A. M., & Fidino, M. (2020). What can we learn from wildlife sightings during the COVID-19 global shutdown? Ecosphere, 11(8), e03215. https://doi.org/10.1002/ecs2.3215
- Microbial diversity and community respiration in freshwater sediments influenced by artificial light at night
Background: The purpose of this study was an analysis of the impacts of light pollution on benthic microbial populations. The researchers state how these kinds of microbial populations are populous all over the planet and are highly diverse. They hypothesized that artificial light pollution will affect the composition and behavior of these populations and therefore will change ecosystem dynamics, affecting the global carbon cycle. The study was designed to take two similar benthic microbial populations and expose one to artificial light at night for six months and have the other in natural conditions to see whether this was true, and what effects this artificial light would have on the communities and their processes.
Methods: The study was conducted by identifying two sites of benthic microbial organisms, two agricultural drainage ditches. The team verified that moisture levels were near identical for both sites, and also established that the species and populations were biologically similar enough for their study. They did this through DNA metabarcoding and included these results in the study to verify that their two populations were suitable for experimentation. These sites were located in a verified Dark Sky zone to confirm that the control would not experience any artificial light at night. One site was therefore chosen as a control and would receive no treatment, and the other site had artificial lamps installed over it. The lumens of the treatment for this site were also measured and controlled to be similar to the average lumens experienced in other urban settings that experienced artificial light at night. This data was also included in the study to verify that treatment levels were significantly similar to actual experienced light levels. Then, the light was maintained over the treatment site for six months. At the end of this time period, biological information about population composition, cellular respiration, and carbon sinking were recorded.
Results: The study returned results that photosynthetic autotrophic organisms saw statistically significant population growth and comprised a larger percentage of the benthic ecosystem in the site that received treatment than in the one that didn’t. They also detected that cellular respiration levels had decreased. Overall this indicates a decrease in species diversity as the benthic communities were made to shift towards auto phototrophic majority populations, however they did anticipate that this could eventually lead to net positive NEP in these kinds of communities as light levels at night increase over time. This answers one major question of the experiment, which was whether or not light levels at night, significantly lower in intensity than sunlight, would be enough to stimulate photosynthesis for these benthic autotrophic organisms.
Criticisms: I think that this experiment was set up very well. They accounted for many factors that could affect the results of their work and took data measurements to ensure that these factors were mitigated as much as they could be to establish reliable results. The difference in species between locations were accounted for by the DNA metabarcoding to ensure a similarity of species richness. The moisture levels were accounted for by testing to ensure similarity, and the lumen levels of the control site were measured to ensure they met natural dark sky levels to establish significant differences if they appeared. I think that all these precautions show a lot of forethought in the experiment and help to establish credibility of the results. I do think that perhaps they are extrapolating a bit much about the results in the discussion portion. They claim that the results of their experiments are proof that increasing light levels at night in the world will turn benthic organisms into ecosystems of net positive production at night year round, and that this will affect carbon sinking on a global scale. All this experiment really proved is that a long term presence of artificial light at night increased photosynthetic production in this one treatment group. I think these claims they make in their discussion are reasonable hypotheses and absolutely excellent grounds for future experimentation, but not truly establishable from this experiment alone.
https://royalsocietypublishing.org/doi/full/10.1098/rstb.2014.0130
- Decline of the Green Salamander: Corser’s Study on Aneides aeneus
In Corser’s (2001) peer-reviewed article regarding Aneides aeneus, a green salamander species found in the Appalachian Mountains, he found that the species suffered critical population declines during different periods spanning across multiple decades. The first decline was noticed in the 1970s, with another major decline found in the late 1990s. Corser attributed these population losses to habitat destruction, overcollection, climate change, and epidemic diseases.Most amphibian species that have declined in North America are those found in mountainous regions experiencing localized population decreases. These are typically isolated populations, separate from others, representing a localized population decline rather than a species-wide collapse. Additionally, other amphibian species outside of salamanders were found to have even worse population declines due to their (at the time) lack of understanding regarding salamander populations. During the 1990s, following reports of amphibian declines, many researchers were first introduced to the concept of amphibian decline as a present conflict in wildlife ecology (Corser, 2001).
This article focused on a specific species throughout the 1990s when this new issue was brought to the forefront of the wildlife conservation community. Corser chose to study Aneides aeneus, a green salamander found in the “Blue Ridge Escarpment” or BRE. The Blue Ridge Escarpment, according to VisitGreenvilleSC.com, is “the line at which…the Blue Ridge Mountain range plunges down towards the rolling foothills of South Carolina,” which illustrates the interesting ecological niche that these salamanders play a role in. According to Corser (2001), they “occupy one of the most specialized and xeric niches of any eastern salamander.” They live in crevices and short outcroppings along tributaries and gorges of the BRE.
Due to the increased observation of salamander decline apart from the first observed drops in 1970, Corser (2001) chose to observe and collect data to determine the population sizes in the BRE. In areas found along the BRE in Georgia, North Carolina, and South Carolina, Corser located the previous scientist’s survey locations from the 1970 study and attempted to recreate the same observations. Corser found thirteen locations to monitor the green salamander populations, seven of which were exactly from Snyder (1971). This gave Corser both new and previous observational areas to research the rock crevices for brooding females. This method was proven to be significant for Snyder’s (1971) research. Corser surveyed these areas once a year from 1991 to 1999, during the last week of July or the first week in August. This provided a great opportunity to locate brooding females and estimate both population size and fecundity.
By using the MONITOR Monte Carlo linear regression model, Corser (2001) was able to determine that the population decline at the historic sites from Snyder’s (1971) paper remained low and continued to decline. In contrast, the new populations found during the 1991 to 1999 survey period were not significantly declining when compared to the already decimated populations from the 1971 observations.
Finally, Corser (2001) was able to conclude that a myriad of factors—whether that be clear-cutting, habitat loss, increased levels of DDT in salamander systems, or other anthropogenic influences seen in nearby amphibian species—might be contributing to the decline and lack of population rebound. With the limited number of sample sites and a rejection of the null hypothesis for the green salamander populations, one could conclude that there are likely many unknown areas Corser was not able to find, since their ecological niche is so specific and difficult to locate within rock crevices. If more samples were found and observed over longer periods of time, future studies could see more significant results, one way or another. This could further prove that their populations are, in fact, declining and are unable to rebound from ongoing environmental and human-caused stressors.
References: Corser, J. D. (2001). Decline of disjunct green salamander (Aneides aeneus) populations in the southern Appalachian Mountains. Biological Conservation, 97(2), 119–126. https://www.sciencedirect.com/science/article/pii/S0006320700001002?via%3Dihub
Snyder, D. H. (1971). The function and evolution of brooding behavior in the plethodontid salamander Aneides aeneus. Copeia, 1971(2), 385–390. www.visitgreenvillesc.com/listing/blue-ridge-escarpment/6237/