Wildlife hair as bioindicators of metal exposure

Direct and Indirect Linkages Between Trace Element Status and Health Indicators - a Multi-tissue Case-Study of Two Deer Species in Denmark

Measuring trace element concentrations in tissue can be a valuable approach to monitor animal health status. Temporal variation in the absorption, transport, and storage of elements between different tissues can, however, complicate the assessment of element-health relationships. Here, we measured concentrations of selected essential (copper (Cu), zinc (Zn), selenium (Se)) and non-essential (arsenic (As), cadmium (Cd), lead (Pb)) trace elements within blood, liver, kidney, and hair of fallow deer (Dama dama; N=20) and red deer (Cervus elaphus; N=21). Using multivariate regression and structural equation models, we estimated direct and indirect linkages between tissue-specific trace element profiles and long- (body condition) and short-term (serum protein biomarkers for acute inflammation, infection, and malnutrition) health indicators. Trace element concentrations varied markedly and were weakly correlated among tissues, with the exception of Se. After accounting for sex- and site-differences in trace element concentrations, body condition of red deer was directly, and positively, associated to trace element status in liver and hair, but not in kidney. For both deer species, trace element status in blood was directly linked to serum protein status with an indirect positive association to deer body condition. For fallow deer, no direct association between trace element status and body condition was detected in any of the tissues, possibly because of elemental homeostasis, and because all individuals were in good clinical health. This study shows that hair can serve as an effective, non-invasive, biomarker in deer health assessments, yet, to fully uncover trace element-health relationships a variety of sample matrices is preferred.

Variability of the Ionome of Wild Boar (Sus scrofa) and Red Deer (Cervus elaphus) in a Dutch National Park, with Implications for Biomonitoring

The ionome-an important expression of the physiological state of organisms-is poorly known for mammals. The focus on particular tissues-such as liver, kidney, and bones-in biomonitoring of environmental pollution and potential deficiencies is based on widely held assumptions rather than solid knowledge of full mammalian ionomes. We examined the full ionome of Red deer (Cervus elaphus) and Wild boar (Sus scrofa), two commonly used mammals for biomonitoring, in a Dutch protected nature reserve (Veluwezoom). We used four individuals per species. We dissected 13 tissues and organs from each individuals (eight in total) of each species and measured 22 elemental concentrations in each. We assessed, for each element, how concentrations varied across tissues within and between individuals. Based on existing literature, we put our findings in the context of their function in the mammalian body. We found that the ionome was highly variable between as well as within the two species. For most elements, tissues containing the highest and lowest concentration differed between individuals. No single tissue accurately represented the accumulation of toxic elements or potential deficiencies in the bodies. Our assessment of the element's biological roles revealed a serious lack of reference values. Our findings imply that analyses of commonly used tissues in biomonitoring do not necessarily capture bioaccumulation of toxins or potential deficiencies. We recommend establishing a centralized database of mammalian ionomes to derive reference values in future. To our knowledge, our study is one of the most complete assessments of mammalian ionomes to date.

Fecal thyroid hormone metabolites in wild ungulates: a mini-review

This review aims to analyse the fluctuations of fecal thyroid hormone metabolites (FTMs) related to environmental and individual variables in different species of wild ungulates and provide a collection of assay methods. The great advantage of fecal sampling is being completely non-invasive. A systemic search was conducted from 2019 to 2024, using data sources PubMed, Scopus, Web of Science, and the World Wide Web, and ten studies were found on this topic. Three studies used the radioimmunoassay method for FTMs analysis, while the others used a less expensive enzyme-linked immunosorbent assay. Most of these papers validated the method for the species-specific matrix. Related to the studied variables, some authors analysed FTM fluctuations only concerning individual variables, and others in response to both. Temperature and fecal cortisol metabolites (FCMs) were the most studied environmental and individual variables, respectively. Since FTMs are an integrative measure of plasma thyroid hormones, the information obtained from a non-invasive-assay method regarding wild ungulate physiology is becoming of great interest to the scientific community.

Passive surveillance of wild fauna in northwestern Italy: a possible cognitive approach through geographical district study and fur elementary analysis

The analysis of animal hair is a useful and non-invasive investigation method for monitoring metal content, whose beginning dates to a few decades ago. This study addresses the issue of wildlife mortality in Piedmont and Aosta Valley by linking the evidence to the characteristics of the territories and to hair elemental profile. The considered animal species were badger, fox, marten, and wolf. The quantitative data for 11 trace metals and 16 lanthanides were evaluated considering animal location and death causes regarding impacts, whose relevant number was confined to the Turin province and to the badger and fox species. The evaluation of the analytical results was performed after the out of bounds sample identification by mean of statistics. For trace metals, some areas have thus been identified, mainly in Turin province, in which the large excess of As, Cd, and Pb was related to district pollution. Moreover, the lower contents of Fe, Mn, and Al in Aosta Valley badgers' hair seem influenced by the different characteristics of the subsoil, in comparison to Piedmont, and a relationship with the living environment and the habits was suggested. Regarding lanthanides, Biella province represents an area in which environmental contamination and abundance of rare-earth elements was recorded.

Geochemical landscapes as drivers of wildlife reproductive success: Insights from a high-Arctic ecosystem

The bioavailability of essential and non-essential elements in vegetation is expected to influence the performance of free-ranging terrestrial herbivores. However, attempts to relate the use of geochemical landscapes by animal populations directly to reproductive output are currently lacking. Here we measured concentrations of 14 essential and non-essential elements in soil and vegetation samples collected in the Zackenberg valley, northeast Greenland, and linked these to environmental conditions to spatially predict and map geochemical landscapes. We then used long-term (1996-2021) survey data of muskoxen (Ovibos moschatus) to quantify annual variation in the relative use of essential and non-essential elements in vegetated sites and their relationship to calf recruitment the following year. Results showed that the relative use of the geochemical landscape by muskoxen varied substantially between years and differed among elements. Selection for vegetated sites with higher levels of the essential elements N, Cu, Se, and Mo was positively linked to annual calf recruitment. In contrast, selection for vegetated sites with higher concentrations of the non-essential elements As and Pb was negatively correlated to annual calf recruitment. Based on the concentrations measured in our study, we found no apparent associations between annual calf recruitment and levels of C, Mn, Co, Zn, Cd, Ba, Hg, and C:N ratio in the vegetation. We conclude that the spatial distribution and access to essential and non-essential elements are important drivers of reproductive output in muskoxen, which may also apply to other wildlife populations. The value of geochemical landscapes to assess habitat-performance relationships is likely to increase under future environmental change.

A heavy burden: Metal exposure across the land-ocean continuum in an adaptable carnivore

Urbanisation and associated anthropogenic activities release large quantities of toxic metals and metalloids into the environment, where they may bioaccumulate and threaten both wildlife and human health. In highly transformed landscapes, terrestrial carnivores may be at increased risk of exposure through biomagnification. We quantified metallic element and metalloid exposure in blood of caracals (Caracal caracal), an adaptable felid inhabiting the rapidly urbanising, coastal metropole of Cape Town, South Africa. Using redundancy analysis and mixed-effect models, we explored the influence of demography, landscape use, and diet on the concentration of 11 metals and metalloids. Although species-specific toxic thresholds are lacking, arsenic (As) and chromium (Cr) were present at potentially sublethal levels in several individuals. Increased use of human-transformed landscapes, particularly urban areas, roads, and vineyards, was significantly associated with increased exposure to aluminium (Al), cobalt (Co) and lead (Pb). Foraging closer to the coast and within aquatic food webs was associated with increased levels of mercury (Hg), selenium (Se) and arsenic, where regular predation on seabirds and waterbirds likely facilitates transfer of metals from aquatic to terrestrial food webs. Further, several elements were linked to lower haemoglobin levels (chromium, mercury, manganese, and zinc) and elevated levels of infection-fighting cells (mercury and selenium). Our results highlight the importance of anthropogenic activities as major environmental sources of metal contamination in terrestrial wildlife, including exposure across the land-ocean continuum. These findings contribute towards the growing evidence suggesting cities are particularly toxic areas for wildlife. Co-exposure to a suite of metal pollutants may threaten the long-term health and persistence of Cape Town's caracal population in unexpected ways, particularly when interacting with additional known pollutant and pathogen exposure. The caracal is a valuable sentinel for assessing metal exposure and can be used in pollution monitoring programmes to mitigate exposure and promote biodiversity conservation in human-dominated landscapes.

Red fox as a potential bioindicator of metal contamination in a European environment

In times of widespread environmental pollution with heavy metals of anthropogenic origin and the increasing dynamics of this process, it is justified to collect as much data as possible on the concentration of metals in terrestial mammals from unpolluted areas. The purpose of this research was to present the concentration of essential (chromium, copper, iron, manganese, molybdenum, and zinc), probably essential (nickel, vanadium) and non-esential element (cadmium, lead, silver, strontium, and tin) in the liver, kidneys, muscles and brain of red fox (Vulpes vulpes) inhabiting north-western Poland. We revealed that the concentration of all metals, apart from Ni, was different between studied tissues. Sn and Mo have the highest affinity to the liver, whereas Ag, Sr, Cr had higher concentrations in the brain than in other organs. Various positive relationship between the concentrations of metals were observed in the tissues. Moreover, we noted negative correlations between Ag and Sn in the kidneys and brain, and between Cu and Ag in the liver. In our study the red fox was used as biomonitor for the assessment of exposure of carnivores to metals, in the generally unpolluted areas of Central Europe. Data presented in the report may be used as comparative values in similar ecotoxicological studies.

Roe Deer (Capreolus capreolus) Hair as a Bioindicator for the Environmental Presence of Toxic and Trace Elements

The return to pasture use as an alternative to intensive livestock farming implies some risks with the lack or the excessive presence of potentially toxic elements; in this regard, wild animals have been used as bioindicators for decades. Thus, the purpose of this study is quantifying Cu, Cr, Mn, Zn, Se, As, Cd, Ni, Pb, Al, Fe, and Mg in fur from roe deer and understanding if it is a valid bioindicator tool. Hair was collected from 39 hunted roe deer and divided by age (<36 months old/≥36 months old), sex (male/female), and area of origin (urbanized/rural area). The mean concentrations of Fe, Mg, Mn, Al, Cr, and Pb were higher (p < 0.05) in the urbanized group; the mean levels of Mg and Cr were higher (p < 0.05) in older animals; and Cu, Fe, Mg, Cd, and Cr showed a higher accumulation in females. Our findings showed an age-related variation of elements, with higher concentrations in adult animals and females. In conclusion, our findings prove that hair is a valid matrix for this type of survey, and wild animals are good bioindicators for monitoring the presence of trace elements in pastures.