2017 Guest blog: Caribbean

During Invasive Species Week 2017 we heard lots about how invasive non-native species (INNS) are having an impact in Great Britain, but further afield they are also an important issue.

The UK has 14 Overseas Territories (OTs), all of which are islands except for the British Antarctic and Gibraltar. Biodiversity in the OTs is globally significant, supporting unique species and ecosystems and a large number of rare and threatened species.

The impacts of invasive non-native species on small islands is often much worse than elsewhere because the native flora and fauna have evolved in isolation from predators, competitors and diseases. As a result native species are less able to compete and defend themselves in the face of new threats.

Read on for a guest blog from one of the UK OTs.

Iguanas and invasives, and invasive iguanas

Elizabeth Radford leads RSPB’s Caribbean UK Overseas Territories programme and here explores the massive threat presented by invasive species to some of the iconic ancient reptiles of the Caribbean.

It’s not every week that you get to see two of the UK’s most threatened native iguana species. Yes, you did read that correctly, iguanas are alive and.... not quite so well in the UK... the UK Overseas Territories of the Caribbean to be precise.

It’s mid morning in late March and its hot; the kind of day that is common in the tropics but to a temperate human being such as myself is like stepping out into a proverbial wall of heat. “My goodness it’s really blue!” I exclaimed in awe at the incredible rather stately blue lizard sitting on the ground in front of me. He was oblivious; of the heat and of me. He blinked and stared. This was no ordinary lizard but the famous Blue Iguana Cyclura lewisi, and I was in the iguana captive breeding facility the Queen Elizabeth Botanic Park on Grand Cayman. Around twenty years ago this species had been reduced to 12 pairs in the wild, due to massive habitat modification and an influx on invasive alien species that arrived with humans. Rocky open areas in dry forest and open shore are prime habitats for iguanas, and have all but disappeared in Grand Cayman as they are also prime real estate. Now the greatest nemesis of these iguanas are invasive non native feral cats which kill iguana hatchlings. Invasive non native feral dogs and rats are also a great threat. The former will hunt and damage adult iguanas, and rats predate hatchlings and eggs, and compete for food in the form of fruits and seeds of native plants.

This critical situation has been turned around over the last 15 years thanks to the Blue Iguana captive breeding programme, now run by a 4- person team from the National Trust of the Cayman Islands. Paul Watler from the Trust who manages the programme told me Blue Iguana is still threatened but no longer so critical. Around 800 individuals have been released to date, into native forest and salina reserves in the less populated east side of the island, and individuals are breeding in the wild.

Hours after my introduction to the Blue Iguana I was descending in a small plane towards the tiny island of Little Cayman 80 miles north east of ‘Grand’ in the Caribbean Sea. A band of turquoise was clearly visible surrounding the island on the approach, marking a small but exceptionally beautiful reef. Little Cayman is a paradise for nature lovers and famous for its marine and birdlife. I was here however, to find a second endemic Caymanian iguana; the Sister Islands Iguana Cyclura nubila caymanensis. And so I did. Mike Vallee and Ed Houlcroft are enthusiastic and dynamic volunteers for the National Trust on Little Cayman, they took me on a tour of the island and I found that Sister Islands iguanas are hard to miss. I saw them as most tourists do, sunning themselves on the tarmac coastal road – they are often bolder than they should be when it comes to crossing roads. Whilst without the magnificent blue colouring of its relative on Grand, these iguanas are no less stately. Sadly this iguana too is threatened by habitat loss and invasive species (particularly feral cats) and is now critically endangered. Around 2000 live on Little Cayman and less than 80 on the neighbouring island of Cayman Brac. A new insidious threat looms large for these iguanas with the recent arrival of the invasive non native Green iguana (Iguana iguana) from the Americas via Grand Cayman. Green iguanas have already overrun Grand Cayman – they are very fertile and although only arrived on the island in the late 1990s, research by Cayman’s Department of Environment shows the population doubles each year, with around 400,000 present in 2016. Green iguanas do not directly compete with native ones, they are also vegetarian but live and feed in the trees. Their sheer numbers decimate the foliage and change habitats locally. Of massive concern is the recent finds of several hybrid iguanas on Little Cayman (Green-Sister Island hybrids). If these hybrids produce viable offspring that are not controlled the Sister Islands Iguana may well be doomed.

Mike and Ed are at the front line of the battle to keen Green iguanas out of Little Cayman; they have raised awareness through the Iguana B’Gonna programme and are the ‘go to guys’ when locals find Green Iguanas, which are then captured and humanely euthanised. In 2016 two green iguanas were found and captured in a shipping container that came from Grand Cayman. Shipping freight is a classic route by which Green Iguanas (and many other invasive species) can travel, and checks at ports will be crucial to stop them spreading to islands throughout the Caribbean.

As I fly out of Little Cayman with my back to the setting sun I reflect on the sad fact that four of the five UK Overseas territories of the Caribbean possess endemic native iguanas and all are threatened by very similar problems to those in Cayman: the Lesser Antillean iguana of Anguilla (Iguana delicatissima), the Anegada Ground iguana (Cyclura pinguis) in the British Virgin Islands and the Turks and Caicos Rock iguana (Cyclura carinata). All struggling for survival because of predation by invasive species, along with a host of other unique wildlife these incredible islands hold. Many organisations and individuals are working to save them. RSPB, Flora and Fauna International, the Durrell Wildlife Conservation Trust and other UK and internationally based organisations are working in support of herculean efforts of local conservation organisations who are trying to combat the invasive species threat in their islands. Funding provided by the European Union BEST programme and the Darwin Plus fund are central and crucial to these efforts, and the new funding for UK Overseas Territories from the Department of Food and Rural Affairs for biosecurity will provide a further most welcome boost to this work from 2017. Conservation efforts will and must continue – these ancient stately reptiles are most surely worth it.

Article by: Elizabeth Radford, RSPB

Photos (top - bottom):

  • Blue iguana
  • Invasive green iguana
  • Hunting iguanas on Little Cayman
  • Green iguanas found in a container

Thin strip of image show tree trunk and bark