Raiders of the fox scat

Student Spotlight - Benjamin Rozier

Master's research carried out at the University of Wolverhampton

Email: benrozier1@gmail.com  

Introduction

Red foxes are nowadays known for their presence in our cities. This once rural mammal is increasingly present in our everyday lives because of different factors. Firstly, cities are growing, and with this comes an expansion onto land that was once forest or farm. Secondly, food is relatively difficult to come by for a predator in the wild, whereas the scraps in our bins typically don’t run away. However, the effects on the health of foxes of heavily processed food coming from potentially unclean bins, is not well understood. Therefore, we led an investigation into the quantities of potentially hazardous chemicals and metals in the diet of foxes. For this, the faeces of foxes both from rural areas and urban areas had to be collected and analysed. To understand the levels of chemicals in the scat, a Gas Chromatography Mass Spectrometry (GC-MS) analysis was undertaken. Though this technique only reveals volatile chemicals, a complementary analysis through Liquid Chromatography Mass Spectrometry (LC-MS) could not be undertaken due to time constraints. Volatile chemicals are, as their name suggests, chemicals with high volatility. This means that they are likely to exist as a vapour under normal temperature and atmospheric pressure. Water boils and turns into vapour at 100°C under normal atmospheric pressure, whereas a volatile chemical would vaporise at a very low temperature under the same conditions. Following the first GC-MS analysis, the scat samples were subsequently analysed through Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), to assess the levels of heavy metals.

Sample collection

Being based at the University of Wolverhampton, we centred our study around the West Midlands. To collect as many samples as possible in a relatively short time, it was necessary to recruit volunteers. Social media and local environmental groups were instrumental in finding willing volunteers. The collection of fox scat comes with a certain amount of risk, due to the parasites and bacteria it may contain. Because of this, a collection kit including gloves, tweezers, and a protocol to follow, was distributed to every volunteer in order to ensure their safety. This was also necessary as the scats needed to be collected in GC-MS glass vials. These vials don’t need to be opened for the GC-MS analysis to be undertaken as the lid is perforated. This allows for the least amount of chemicals to be lost. In addition, if the scats were collected in plastic bags, the phthalates contained in many plastic products could mask other chemicals during the analysis. The collection kits containing scats then had to be stored in a cold environment, ideally a freezer, to limit the volatilisation of chemicals.

Sample analysis

The samples first underwent the GC-MS analysis, with the objective of not losing volatile chemicals through previous opening of the vials. The ICP analysis was consecutively undertaken. However, the quantities of mercury could not be analysed due to the need of an additional method, which would have taken too much time. In addition, the results were correlated to an urbanisation index. This index was created on QGIS to quantify how close to a potential source of pollution the scat was found. The map was divided into squares of 300x300 meters. Each square was attributed an “urbanisation” score, calculated in 3 steps. Firstly, the score is primarily based on how much buildings or roads cover it (Table 1). Secondly, to this first score, points are added if “additional contamination features” are contained within the square. Additional contamination features were fast food restaurants, sewage sites, bins, scrapyards, factories, and petrol stations.

Table 1: primary and secondary urbanisation score grading system for each square of the grid.

Attribute	Points toward complete score
Building cover is 0%	0
Building cover is 1-50%	1
Building cover is 51-100%	2
Road cover is 0%	0
Road cover is 1-50%	1
Road cover is 51-100%	2
Additional contamination feature	+1 for each feature inside the square

Thirdly and finally, as foxes are mobile and have a variable territory size. The final score of each square is influenced by the secondary scores of the squares around it (Figure 2). Thus the final score calculation for the central square will be: “secondary score central square” + ((ssq1 + ssq2 + ssq3 + ssq4 + ssq5 + ssq6 + ssq7 + ssq8)/16) = final score central square, with ssq meaning secondary score square.

Results

In total, we managed to get the help of 21 volunteers and collect a total of 18 samples. This is evidently a very limited sample size, however, as this is novel research, it mostly serves as the indication that further and more precise research is needed in this area. All the chemicals found from the GC-MS analysis were classed by source and hazard to health. Sources could be natural, artificial, or both, as many chemicals are nowadays produced artificially in large quantities but were originally present in nature. For hazards, they were classed as safe or dangerous. Most chemicals are irritant in large quantities or concentrations, thus irritants were not classed as dangerous. Chemicals classed as dangerous were usually tagged as poisonous, corrosive, toxic, or a health hazard on PubChem. Other chemicals had tags such as environmental hazard or hazard to aquatic life, however this was not counted as dangerous as they did not necessarily pertain to red foxes. One of the 18 samples was lost during the laboratory analysis but from the 17 remaining samples, 493 chemicals were found of natural origin, 288 of artificial origin, 202 chemicals were classed as safe and 200 as dangerous.

A total of 135 dangerous artificial chemicals were found in 17 samples of fox scat.

Amongst these dangerous artificial chemicals, many had uses in food and perfumes as additives. Thus we, as humans, would also be exposed to them frequently.

For the heavy metal analysis, potassium concentration was found to have a correlation with the urbanisation score. Based on a simple linear regression, it was found that the concentration of potassium in fox scats decreases as the urbanisation score increases (Figure 3).

This can be interpreted as a lower intake of potassium. If we compare this to humans, potassium is known as a “shortfall nutrient” which can reduce blood pressure, thus reducing risks of stroke and heart disease and can also help prevent bone loss with age (Weaver, 2013). This study also acknowledges the fact that many humans in the United States of America have low levels of potassium due to a heavily processed diet and little fruit and vegetables. This reduction in dietary potassium for humans can also be attributed to foxes. Indeed, urban foxes are known to scavenge in disposed waste and can have a heavily processed diet (Chartered Institute of Environmental Health, 2013; The Mammal Society, 2022). It is, therefore, possible that urban foxes, or any other urban animal with a similar diet, could be potassium-deficient, and could be exposed to a multitude of cardiovascular related health risks.

Alarmingly, some samples also contained several chemicals that had likely sources in petrol and cigarettes. It is therefore likely that these foxes had consumed discarded cigarette buds and petrol.