Hedgehogs - Are they really hogging all the hedges?

article written by Josh Deakins 

Regarded with affection in England and referred to as ‘gainneog’ (‘ugly little things’) in Ireland, we can all agree however that populations of European hedgehogs (Erinaceus europaeus) are declining. A journal article published in 2020 highlights this decline, showing a decrease in abundance of 40.6% between 1992 and 2018 in urban areas. Needless to say therefore that hedgehogs are classified as ‘vulnerable to extinction’ on the International Union for Conservation of Nature (IUCN) Red List for British Mammals.

In this project, I aimed to explore the distribution of hedgehogs against protected areas within the counties of Oxfordshire and Berkshire, a style of investigation termed a ‘gap analysis’. TVERC currently has 1331 hedgehog records and has mapped 2075 protected areas. The records are classed as ‘citizen science data’ and are particularly beneficial because the data is more precise when over a large time period (1964 to 2020 in this case) and a large area (3867 km2 for my purposes).

Studying Figure 1, it is clear that a larger proportion is red (87.7%) than green (12.3%) and a statistical test indicated that this difference was not due to chance. This alone would imply that hedgehogs are not well represented within protected areas in Oxfordshire and Berkshire. However, other factors, primarily related to the assumptions I made about the records, may have influenced the results.

Figure 2 exhibits a slight recorder bias with high densities of hedgehog records in urban areas such as Newbury, Wantage, Abingdon-on-Thames, Earley and Maidenhead, all outside of protected areas. Furthermore, scrutinising Figure 1 in more detail, we see that numerous hedgehog records are bisected by the border of protected areas, such as between Broadmoor to Bagshot Woods and Heaths SSSI and Bracknell and Crowthorne.

Returning to the assumptions, I assumed firstly that the coordinates of the record were the centre of the home range. But if a hedgehog was recorded on the edge of a protected area and an urban area, it may have been on the edge of its home range and a larger proportion was actually within the protected area. Secondly, I assumed that the records were obtained using unbiased, randomised sampling. Rather, opportunistic sampling was utilised, and thereby places that are more convenient to access received the most attention - for example, a person’s garden or alongside a road.

These kinds of limitations accompany the vast majority of scientific research, and in reality are not hindrances but provide the foundation for further, vital study. A journal article published in 2004 concluded with a poignant reminder and a rousing call to action: “if the planet is to conserve its living biodiversity heritage, ... investment in establishing new protected areas must be made as soon as possible.”

Therefore, I am optimistic that this mini-placement has paved the way for better understanding the environmental, social, economic and political factors influencing the protection of declining species such as hedgehogs, and has provided a starting point for identifying new sites suitable for designation.

Posted: December 29, 2020