The science of goannas

Continuing from Bell’s form observations in Victoria (previous post) …

New science

After some intensive but unsystematic searching I found two relatively recent scientific publications which answered my main questions about how Bell’s form relates to the ‘normal’ goanna. It’s easier to discuss the more recent one first, so that’s what I will do.

(1) Photographic evidence

Farquhar et al (2022) had a double aim, firstly to show that iNaturalist records could assist research and secondly to use them to define (and perhaps explain) the range of Bell’s form. His results on the second point confirm common knowledge, i.e., Bell’s form is more common in drier country. He goes on to analyse, in some detail, likely environmental causes for that pattern of distribution.

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A Bell’s form goanna in Victoria

Occasional posts here on Green Path emerge from readers’ input. This one and its sequel began when Lindsay Muston sent me a comment on my old (2016) post about Dry-country goannas after coming across it while looking for more information about his resident wildlife.

Lindsay: Thought you would be interested – here’s a pair of Bell’s form goannas regularly breeding near my house. Way south! Tallygaroopna, northern Vic, about 50km south of the Murray river. Have sighted this year’s young. Historically we’ve had the standard grey goanna and have one nearby at 7’. I have known of others, similar sizes, still alive 40 years on.

The conversation, lightly edited here for clarity, continued:
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Citizen Science – iNaturalist

The internet and digital photography have opened up wonderful opportunities for ordinary people to get involved in citizen science as observers of the natural world. Online meeting places and forums come and go but the best at the moment seems to be iNaturalist – https://www.inaturalist.org.

It’s a global project and the numbers are huge: 54 million observations by 1.4 million observers from nearly every country in the world when I looked recently. That presents a management problem, of course, which is solved by having countries run independent branches, e.g. https://inaturalist.ala.org.au/

Anyone at all can browse the content of the site but people have to sign up to participate. When that’s done (at no cost and very little trouble) they can upload their observations, help with identifying others’ observations, and join the discussion forums.

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Weevil or beetle?

Let me begin by admitting that my title question is misleading: weevils are different from most beetles in a very recognisable way but they are in fact still beetles, a family within the order Coleoptera which includes longicorns, elephant beetles and all the others.

Wikipedia informs us that Curculionidae, “the “true” weevils (or “snout beetles”) … are one of the largest animal families, with 6,800 genera and 83,000 species described worldwide.” It’s not surprising, then, that, “with so many species, a spirited debate exists about the relationships between subfamilies and genera,” (Wikipedia’s polite way of saying that the experts are still arguing).

CSIRO’s invaluable site says that weevils are, “Highly variable in form, but usually moderately to strongly convex, robust, heavily sclerotised and often clothed with scales or bristles. Head always more or less produced [i.e. extended] in front of eyes to form a rostrum, which is usually much longer than broad; antennae always geniculate [elbowed] with long scape and more or less compact club.” Many of those features can be seen in my photos of an individual I found in my garden recently:

weevil
Weevil on a frangipani branch

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