Assessing the risks of soil-associated metals to bats in England and Wales


               The scientific interest in chiropteran species has increased in recent years due to the observed declines in populations of these species worldwide. Several factors (e.g. climate change, habitat fragmentation, roost loss, urbanization and agricultural intensification, the increase in wind turbines, the pressure of disease and exposure to chemicals in the environment) have been identified as potential stressors on bat populations. In addition, bats are highly beneficial to ecosystems and agriculture.

        Bats are expected to receive high chemical exposure as they are long-lived organisms and small flying mammals with a high metabolic rate. Only a few studies have focused on the toxic effects of metals to bats whereas the effect of organic compounds have received more interest. These few studies on bats have shown a wide range of symptoms observed in intoxicated bats such as histological lesions in different organs and tissues (kidneys, spleen, lungs,brain) and mortality following exposure to Pb, Cd and Zn.                                                                                                                                                                                                                            

           The project Mammals-2   

                 The overall aim of this project was to explore the risks of soil-associated metals (Cd, Cu, Pb, Zn) to insectivorous bats. The main objectives are presented below.

           1.    How to assess the risks of soil-associated metal to bats ?

        The spatially explicit modelling framework was developed, parameterized and applied to assess the risks of soil-associated metals (Pb, Cu, Zn and Cd) to Pipistrellus sp. bats in England and Wales. The metal uptake route considered in the model is from soils into invertebrates and then into bats. Information on soil metal concentration, uptake into prey items, bat diet, foraging behaviour, the bat distribution and toxicity of metal to bats are integrated into the modelling framework to assess exposure and the exposure predictions are then compared with toxicological data to establish the level of risk.     

       Further reading: “A spatially-based modeling framework for assessing the risks of soil-associated metals to bats”
Environmental Pollution, 2013.

 2.  Does metal exposure pose a risk to the health of British bat species ? What are the key drivers of risk ?

    The modelling framework was extended to assess risks of metals to the health of 14 additional bat species present in the UK. Information on bat ecology: diet, foraging behaviour, bat distribution for the different bat species and the metal uptake into different insect prey items were compiled for different bat species. The relative vulnerability of the different bat species was discussed and the main ecological parameters driving risk were identified through a systematic evaluation of the model.

Further reading: “Interspecies variation in the risks of metals to bats”
Environmental Pollution, 2015, In press.

      3. Is metal exposure contributing to declines in bat populations ? How to verify our model predictions ?

      A large monitoring campaign to assess the level of metals in bat (Pipistrellus sp.) (n=193 individuals) tissues (Kidneys, liver, stomach, fur and bones) was conducted across a gradient of soil metal pollution in England and Wales. The individuals were provided from the Veterinary Laboratory Agency, Surrey, UK. The tissue concentrations were measured with ICP-MS. Tissue concentrations were compared with toxicity data for small mammals to assess the potential concern for bat health. The developed dataset was also used to evaluate our modelling framework predictions to verify whether the individuals identified as “at risk” by the model contained higher metal levels in their tissues than the bats not identified at risk.

Further reading: available on request.

       4. Is fur a valuable less-invasive tool to monitor metal contamination in bat populations ?

        The environmental risk assessment of wildlife species needs monitoring studies, however these are highly time and cost consuming and are highly submitted to ethical constraints. The use of fur samples was assessed as a less-invasive tool to monitor metal contamination in bat population.

Further reading: available on request.

      5.  Is the bioaccessibility varying across different food types ? What are the implications for environmental risk assessment ?

        To assess the metal bioaccessible fraction from insects to bats, an In vitro gastric model was developed. The differences in bioaccessibility across different insect types: Coleoptera, Lepidoptera and Diptera were then investigated using the in vitro system. The insects investigated comprised the major part of the diet of bats living in England and Wales. The implications of the observed differences in bioaccessibility, between insect orders, for environmental risk assessment were explored.

Further reading: “Implications of in vitro bioaccessibility differences for the assessment of risks of metals to bats”,
ET&C, 2015.    

   6.       Predicting the threats of chemicals to wildlife: What are the challenges?

The main limitations and issues encountered while developing and parameterizing the food chain model to predict the threats of metals to wildlife species are discussed in “Predicting the threats of chemicals to wildlife: What are the challenges?


  • Hernout, B.V., Pietravalle, S., Arnold, K.E., McClean, C.J., Aegerter, J., and Boxall, A.B., 2015.  Interspecies variation in the risks of metals to bats. Environmental Pollution, In press.
  • Hernout, B.V., Bowman, S.R., Weaver, R., Jayasinghe, C.J., and Boxall, A.B.A, 2015. Implications of in vitro bioaccessibility differences for the assessment of risks of metals to bats. Environmental Toxicology and Chemistry, 34(4): pages 898–906.
  • Hernout, B.V., Somerwill, K.E., Arnold, K.E., McClean, C.J., and Boxall, A.B.A. , 2013. A spatially-based modeling framework for assessing the risks of soil-associated metals to bats. Environmental Pollution, 173 :110-116.
  • Hernout, B.V., Arnold, K.E., McClean, C.J., Grimm, V., and Boxall, A.B.A. , 2011. Predicting the Threats of Chemicals to Wildlife: What Are the Challenges? Integrated Environmental Assessment and Management, (3): 499-506.    


  • Hernout, B.V., McClean, C.J., Arnold, K.E., Walls, M., Baxter, M., and Boxall, A.B.A. Fur: a non-invasive approach to monitor metal exposure in bats

Main oral presentation:

·         “Assessing metal bioaccessibility from invertebrates to bats using an In Vitro Gastric Model“, CREAM Open Conference, Leipzig, Germany, June 2013.

·         Predicting exposure of bats to soil-associated metals:  Model evaluation”, SETAC Europe, Glasgow, UK, May 2013.

·         “Predicting exposure of Pipistrellus sp. to soil-associated metals”, SETAC North America, Boston, US, November, 2011.

·         Predicting exposure of Pipistrellus sp. to soil-associated metals”, CREAM Mid-term meeting, Krakow, Poland, September 2011.

·         “Modelling the effects of soil contaminants on bats”, SETAC 2nd Young Environmental Scientists Meeting, Aachen, Germany, March 2011.


Further relevant reading

Boyles, J.G., Cryan, P.M., McCracken, G.F., and Kunz, T.H., 2011. Economic importance of bats in agriculture. Science, 332(6025): 41-42.

Carravieri, A., and Scheifler, R., 2013. Effets des substances chimiques sur les chiroptères: synthèse bibliographique. Le Rhinolophe, 19: 1-46. [Abstract in English]

Hickey, M.B.C., Fenton, M.B., MacDonald, K.C., and Soulliere, C., 2001. Trace elements in the fur of bats (Chiroptera: Vespertilionidae) from Ontario and Quebec, Canada. Bulletin of Environmental Contamination and Toxicology, 66: 699-706.

Kaufman, C.A., Bennett, J. R., Koch, I., and Reimer, K.J. , 2007. Lead bioaccessibility in food web intermediates and the influence on ecological risk characterization. Environmental Science & Technology, 41(16): 5902-5907; DOI 10.1021/es062443u.

Stevens, C.E., and Hume, I.D., 2005. Comparative Physiology of the Vertebrate Digestive System. Cambridge University Press. [Bat digestive system picture]

Walker, L.A., Simpson, V.R., Rockett, L., Wienburg, C.L., and Shore, R.F., 2007. Heavy metal contamination in bats in Britain. Environmental Pollution, 148: 483-490. 


Last update:  July 2015.

Ph.D Fellow : Beatrice Hernout (University of York)

Supervisor : Alistair Boxall (UYork)

Co-supervisors : Volker Grimm (UFZ), Kathryn Arnold (UYork) and Colin McClean (UYork)

Associated partner:CRD

Current : Post-doctoral research associate in the Wildlife Toxicology Laboratory, Department of Environmental Toxicology, The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX, United States of America.

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