Protecting Native Invertebrates

ZSL Releasing red barbed ants at Chobham Commin

Some of the UK’s insects and spiders are highly endangered. The red barbed ant, for example, is the rarest creature in the UK. ZSL has been involved in a number of conservation projects aimed specifically at the UK’s smaller inhabitants, including the red barbed ant, fen raft spider, and field cricket. Because they are small, these species can potentially be bred in large numbers in captivity for release, which means that this kind of conservation intervention can be extremely effective. 

Fen Raft Spider

In 2011 and 2012 ZSL became involved in the captive rearing programme for the fen raft spider, which is listed as Vulnerable to Extinction in the IUCN Red List. As part of a BIAZA zoo collaborative project with Natural England, newly hatched spiderlings were reared to a larger size to give them a better chance of survival when translocated. The spiderlings were released at selected sites to boost wild populations. The captive rearing project has now finished as so many spiders were successfully reared, however we will be involved in fieldwork to monitor the progress of the released spiders. 

Red Barbed Ant

The red-barbed ant is probably the rarest animal in Britain. The ant can only be found in two sites in the UK, making the population extremely vulnerable, so a conservation programme was set up in 2006 to help stabilise and increase the red-barbed ants chances of survival. ZSL kept some translocated red-barbed ant colonies from the Isles of Scilly at ZSL London Zoo in a purpose-built insect rearing facility, whilst The Surrey Wildlife Trust prepared ideal habitat conditions for their release.

Field Cricket

In the 1980’s, a single population of less than 100 field crickets existed in Sussex, so ZSL joined forces with English Nature and other partners in the 1990’s to try to help save this cricket from extinction in Britain. A captive breeding programme was established for the field cricket at ZSL London Zoo, and over 15000 crickets have been released in carefully selected sites since the project began. The wild population is now self-sustaining and this species has been saved from extinction due to the rearing project.

Wart-biter cricket 

The wart-biter cricket has suffered a similar fate to the field cricket, with particularly loss of habitat restricting its range to a few sites in southern Britain. A significantly more challenging species to rear, we were still able to release over 600 nymphs at two sites between 1994 and 2000 and established new wild populations.



Project information

Key species

  • Fen raft spider (Dolomedes plantarius)
  • Red barbed ant (Formica rufibarbus)
  • British Field cricket (Gryllus campestris)
  • Wart-biter cricket (Decticus verrucivorus)

People involved

  • Paul Pearce Kelly managed the red barbed ant and field cricket conservation projects for ZSL
  • Dave Clarke ran the fen raft spider breeding project for ZSL.


  • Natural England
  • Surrey Wildlife Trust
  • Isles of Scilly Wildlife Trust 

Kindly funded by: Heritage Lottery Fund, Natural England