Where are all the butterflies coming from?
THOUSANDS, if not hundreds of thousands, of Yellow Migrant butterflies have been streaming across roads and paddocks on the Northern Rivers and South East Queensland.
ANU College of Science Associate Professor Michael F Braby said they are Yellow Migrant butterflies but there is also the chance of the presence of Grass Yellow butterflies.
Assoc Prof Braby said the Yellow Migrant was a tenacious butterfly, with large wings, distinctive yellow colour and could fly large distances.
He said the wing patterns would change from season to season and in winter the females stop breeding.
“They respond rapidly to wet conditions,” he said.
“But often after we have big rains there are a couple of species which seem to have these boom-and-bust life cycles.
“They breed on the new growth of their food plants which proliferate after the rains.”
He said it was not unusual at this time of year to see such activity, but he added that the prolonged drought had, from an anecdotal perspective, influenced butterfly numbers.
“There seems to be a big crash in numbers.
“Some species are just not present, or if they are present, they are just present in small numbers, whereas in good years you would find a lot more species and you find them to be quite abundant.
“We have had three or four years of continuous lack of rainfall and I think that is having quiet a big effect.”
Assoc Prof Braby said the fires would almost certainly have been detrimental to butterfly populations but they hadn’t been able to access burnt areas to do a survey.
“Myself and my colleagues certainly have a lot of concern because the nature of these fires were so expansive and so catastrophic, we are moving into a new paradigm.”
He said some butterflies were like orchids and could only be found in very specific areas and habitats in the landscapes.
He said in those areas hit by fire there was all likelihood the butterflies wouldn’t have survived as the fires were pretty hot and catastrophic.
“So they only areas they can recolonise from are from unburnt patches in the landscape,” he said.
”So those unburnt areas become really important for the long term survival of a species because they are the source areas from which populations would recolonise.”
Assoc Prof Braby said they were particularly worried about the Montane Heath Blue and Flame Hairstreak who’s only known habitats in the mountains of SE Australia had all been hit by fire.
He said doing a survey may have to wait until next year as access and the seasonality of the butterfly populations meant patience was key.
He said in the meantime, three things that were vital were; keeping fires out critical source areas for repatriation; in the medium term start targeting areas for survey and assessing damage; and mitigating the effects of climate change.