Hedgehogs: Endangered Species or Prickly Pest?

The British love hedgehogs. They are associated with the UK and are considered to be a national species. In 2013, the Hedgehog even won the UK natural emblem poll. However the once common hedgehog is now under threat from various factors including development and habitat loss.

In the last 10 years, numbers have fallen by 30% and there are now thought to be fewer than 1 million left in the UK compared to the 36 million estimated in the 1950s.  

The UK's favourite cute and prickly animal.
Photo: Michael Gäbler.

There could be many factors that are contributing to the decline of hedgehog populations in the UK. The increasing use of impenetrable fencing around gardens, which reduces movement of hedgehogs between gardens, has led to fragmentation of urban populations and is likely to have contributed to declining numbers. Pesticides have reduced amounts of invertebrates available for hedgehogs to eat in gardens. Furthermore, slug pellets are also thought to impact directly, causing mortalities. Herbicide use on lawns also reduces the availability
of earthworms, a main prey species.

Due to agricultural intensification, there has been around a 50% decline in hedgerows in rural Britain since 1945. Hedgerows provide ideal locations for hedgehog nesting sites as well as being important movement corridors. Another issue is with the way hedges are managed. Mechanical flailing has replaced traditional coppicing in many places resulting in hedgerows that are increasingly gappy and lack a dense base. This makes them far less suitable as places to shelter from predators and for nesting or hibernation.

In the UK it has been estimated that up to 15,000 hedgehogs are killed annually on roads. Roads also act as barriers to the movement of hedgehogs, causing fragmentation of populations. 

Numerous campaigns, charities and societies have been set up to raise awareness and protect this much loved animal and save it from going extinct.

But meanwhile in New Zealand..

Hedgehogs are thriving. They are viewed as a pest and are an invasive species, being a threat to native wildlife.

The hedgehogs were brought to New Zealand by British colonists in the 1870s to remind them of home. The first recorded introductions were in 1870, with subsequent introductions in 1871, 1885, 1890 and 1894. Aside from acclimatisation, hedgehogs were also introduced to control garden pests such as slugs, snails and grass grubs. Hedgehogs are now present in almost all New Zealand habitats, including urban, rural, braided river and forests areas.  

  

Their foreign diet includes the eggs and chicks of ground-nesting birds and they are already believed to have contributed to the decline and extinction of up to fifteen bird species and are a threat to those that remain.

Hedgehog preying on ground-nesting bird eggs.
Photo: Martin H. Smith.

Species they impact include riverbed breeding birds such as banded dotterel and black-fronted tern, of which they predate on their eggs and chicks. They are known to predate upon the rare giant native centipede and the critically endangered Cromwell chafer beetle. Lowland populations of Powelliphanta snails are also affected, and although only smaller juvenile snails are eaten, this severely affects recruitment and population recovery. Hedgehogs also prey upon lizards, particularly in cooler periods when lizard activity slows and Skinks are particularly at risk from them.

New Zealanders are encouraged to trap and control hedgehog numbers to protect native birds during their breeding seasons in particular. This is a huge leap from the intense campaigning going on in the UK to protect them, considering they are at risk of dying out!

It is amazing how different species adapt and react to different environments. Even in their natural home they are worse off than in a location with a very different climate and environment. The invasive, introduced population in New Zealand is now higher than the native population in the UK. 

It is an important lesson, animals should not be moved and introduced to countries where they don't belong, as you can never fully predict the impact they may have and the problems they could cause in the future.