Invertebrate of the Month: Frégate Island Giant Tenebrionid Beetle

This month our star invertebrate is the Frégate Island Giant Tenebrionid Beetle!

Hi, I’m Fluer the Frégate Island Giant Tenebrionid beetle - I’m three years old and have been living at Bristol Zoo Gardens

Guess where I’m from! Hint: it’s in my name. I hope you guessed it - Frégate Island, which is in the Seychelles off the coast of East Africa. We live in a very specific habitat, so you won’t find us in the wild anywhere else - we were only discovered 172 years ago in 1848. We are large brown or black flightless beetles that are 2-3cm in body length, with long legs and a large round abdomen. You’ll most likely find us on rotting logs and palm fronds - including sandragon and cashew trees. Being nocturnal, we are mostly active at night (our favourite time), usually searching for leaves, fruit, fungi and seeds to eat.

Flynn, my son, is currently a larva and he lives under the surface of the ground close to his food source: decaying leaves and wood; he also gets treated to some buried vegetables! He started his life in a pale-yellow egg about 2mm in diameter, which I safely laid into a rotten log. It then took two weeks for him to hatch from the egg. He is currently 4-5cm long and a yellow sandy colour and loves burrowing underground. Soon he will create a chamber around himself in the soil; this will protect him as he metamorphoses into a pupa. After about 34 days, he will emerge as an adult beetle and then be able to explore the world for himself (however, this could take a while as he can only crawl, so he’d better hurry up as he’s only got an average life expectancy of three and half years).

Being eaten is not a desirable outcome for us, so we have two tricks under our wing cases. When we feel threatened, we secrete a special chemical that smells musky and stains your skin purple - but it won’t harm you. Our second trick to escape being eaten is playing dead; we are so good at this we can remain motionless for up to fifteen minutes - you try staying dead still for that long.

When the zookeepers at Bristol Zoo Gardens spray us with a fine mist of water, we stick our abdomens in the air, lower our heads and sway quickly from side to side. We are keeping the reason for this - and whether we do it in the wild - a secret. Scientists think that is possibly either to help us deflect water in heavy rain or to help us get a better grip with our feet. Who knows if they are right – we do!

We are categorised as Vulnerable on the IUCN Red List of Threatened SpeciesTM, so we are not as endangered as other fellow residents in Bug World - like Louisa the Lord Howe Island stick insect or Diego the Desertas wolf spider (who are both Critically Endangered) but we do still need help to thrive. The main threat to our existence is habitat destruction; in the 1800s, the island was almost cleared of its native vegetation and replaced with non-native trees - we didn’t recover until the mid-1900s. In addition, the introduction of black rats contributed to our decline as they really relished the way we taste.

Conservation plans were set in motion to help my species thrive. Habitat restoration programmes have re-planted native plants and trees to combat the lack of habitat available to us. Rats have also been eradicated from Frégate Island which has significantly helped with our survival. Captive breeding populations were also started in many zoos around the world, including Bristol Zoo Gardens, to ensure the long-term survival of our species.

Zoos that are keeping Frégate beetles aim to improve knowledge on captive care, research our life history and investigate how disease affects us. So far, they have discovered the best way to care for us in zoos along with some of our life cycle and health secrets. They also hope to move some of our ancestors from Frégate Island to other islands we used to occupy, such as Round Island in Mauritius. Before they are able to help our species in this way, they have to make sure that the island they are moving us to has a suitable habitat - and is not home to any of our predators.

All of this hard work has changed our IUCN category from ‘Critically Endangered’ to ‘Vulnerable’ and we are so grateful.

Thank you, Bristol Zoo Gardens!

To help support the continued success of the Zoo, and all of the society's breeding programmes, visit: https://uk.virginmoneygiving.com/fund/covid19appeal

Blog post written by Laura Thomas, placement student in Bug World. Image taken by Nicola Cooke.

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