One of South Africa’s most famous butterfly species is missing and possibly extinct — a victim of the 2017 wildfire that destroyed more than 1,000 homes in Knysna.
Not a single Brenton blue has been seen since November 2017 despite years of searching by the butterfly’s “custodian”, who fears the worst. “It does seem to be a distinct possibility [that the species is extinct],” said Dave Edge, who with his wife, has been scouring stretches of the southern Cape coast for signs of the rare insect.
“We haven’t exhausted all possibilities yet, and so are not yet in a position to declare it extinct.”
A species needs to have been missing for 30 years to be declared officially extinct by the International Union for Conservation of Nature.
The Brenton blue has beaten the odds before. First discovered in Knysna in 1858, it was thought for many years to be extinct before reappearing in Natures Valley in 1977, only to disappear again in the 1980s. It re-emerged in 1991 on a small patch of land in Brenton-on-Sea that was due to be developed, prompting a court showdown that resulted in its last-known homeland being declared a nature reserve.
This refuge was obliterated in the wildfire that swept through the Knysna area, burning 20,000ha of fynbos and alien vegetation, including the patch of indigofera plants the butterfly needs to survive.
Initially Edge and his fellow butterfly monitors were relieved to see it appeared to have survived the fire. Though the butterfly reserve was burnt, several were spotted at the site a few months after the fire.
“We were most excited because we did find some — not many, less than 10, but there were males and females and we really thought, wow, fantastic, the Brenton blue has survived,” Edge said.
But by February there was no trace of the butterfly. None have been seen since.
Follow-up studies and surveys suggest its disappearance is linked to the loss of a particular ant species, camponotus baynei, which protects Brenton blues in their caterpillar phase in return for a sweet nectar-like substance produced by the caterpillar.
Unlike the indigofera plants, which have recovered well since the fire, camponotus baynei vanished, along with most other ant species.
“We discovered that at the site there was basically only one active ant still alive, and it wasn’t camponotus baynei,” Edge said. “It was an indigenous ant called the brown sugar ant, very commonly found in human households.”
“We kept monitoring the ant over several years and we are still finding it is the only ant found in the reserve.”
Unfortunately for the Brenton blue, the brown sugar ant is notoriously aggressive and unlikely to form an alliance with the butterfly.
“The worst news is that the brown sugar ant is known for forming super colonies, not just small nests. They can inhabit a whole area of several hectares and even more,” said Edge, appointed custodian of the Brenton blue by the Lepidopterists' Society, which protects local butterflies and moths. Countrywide, it has appointed 20 custodians to look after 60 critically endangered species as part of a conservation project supported by government and wildlife organisations.
Other wildlife stakeholders said the potential loss of the Brenton blue was indicative of broader ecosystem strain brought about by human activity. It is also a sign that more resources are needed to conserve threatened species.
“The loss of the Brenton blue tells us that the broader system is collapsing,” said Ian Little of the Endangered Wildlife Trust.
“At the end of the day the reality with these highly localised species is that we need to secure the landscapes and not just that particular area. The Brenton blue is kind of like the straw that broke the camel’s back in terms of the sign of what is happening in the broader environment.”
System stress factors such as water catchment loss, ground cover disturbance and the spread of invasive alien vegetation all combined to upset the balance of natural ecosystems.
“It would never have happened [loss of the Brenton-on-Sea butterfly colony] if that broader landscape had been better managed.”
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