# On the Brink, a Population of Hedgehogs in Central London

## TL;DR

A once-thriving hedgehog population in London's Regent's Park has sharply declined over a decade due to low breeding and high predation, now facing extinction without action.

## Contribution

A 10-year detailed survey of a small, isolated hedgehog population in central London reveals critical insights into its decline and survival challenges.

## Key findings

- Hedgehog numbers dropped from an average of 28 to just six in spring 2023.
- Predation, especially by foxes, caused 59% of hedgehog deaths, with nearly all juvenile deaths attributed to predators.
- The population is now confined to the park's northeast quadrant, showing a significant shift in distribution.

## Abstract

Numbers of the West European hedgehog (
Erinaceus europaeus
) have significantly declined in Britain and Europe over the past 50 years. In central London, they were once common in the Royal Parks but are now confined to The Regent's Park (166 ha), where they are isolated from other populations. Between 2014 and 2023, hedgehog numbers and spatial distribution were studied through twice‐yearly nocturnal searches in spring and autumn by volunteers using torches and thermal cameras, supported by ZSL Veterinary Services and the Garden Wildlife Health Project. Hedgehogs were tagged, examined and released. During the first 6 years, the population averaged 28 individuals (range: 13–38), with seasonal peaks in autumn. However, from 2020, numbers dropped, reaching just six in spring 2023 and slightly recovering to 10 by autumn. Breeding success was moderate to low and survival rates poor, raising concerns about long‐term viability. Of the 88 dead or fatally injured hedgehogs found, 59% showed signs of predation—mainly by foxes. Nearly all juvenile deaths (96%) were caused by predators. Other causes included road accidents, infections and drowning. Hedgehog distribution shifted over time. Initially widespread across the park, they began vanishing from the south and west in 2015, coincident with a population drop in 2016. Since then, they have mostly been found in the park's northeast quadrant. Factors likely to have contributed to the population's decline are considered. After a decade of monitoring, the remaining hedgehog population is critically small and faces extinction without urgent conservation action.

A small breeding population of hedgehogs survives in central London's Regent's Park (166 ha). A 10‐year survey (2014–2023) revealed a decline from an average of 28 individuals to just six in spring 2023, driven by low breeding success and high mortality. Once widespread, hedgehogs are now confined to the park's northeast quadrant and face extinction without urgent conservation efforts.