That they have. First couple of reports of them being in the Mary are from about 5 years ago (annoyingly just after I moved to Brisbane from the area for uni). What makes this sighting particularly interesting is not that it's in the Mary, but how far upstream it was sighted and how this now represents the most southern sighting since culling. Until now most people have thought that the crocs are restricted to the lower sections, with most of the previous sightings being around Maryborough and River heads. One outlier to this was a similar sized animal photographed via camera trap in Tiaro a year or two ago. It's certainly not surprising that one was spotted where it was. Considering that crocodiles can travel 60 km in a day, it was never a question of if but when would one be spotted there.
You're correct Scutellatus, the Logan river represents the most southern extent that estuarine crocodiles have been recorded. Historically though the populations in these areas have never been high and it is generally considered that below the Fitzroy river is outside of their breeding niche. Although with how the climate is warming it will be interesting to see if this is still the case. I'm not to sure if that policy is honestly having to much of an impact on the potential southern population. Since the first sightings in the Mary 5 years ago only two have been removed south of the Boyne. If the population is really low this may have a major impact, but we just don't know how large of a population it currently is so it's hard to tell. Will be interesting to see what happens and how much more frequently sightings become now that more are potentially emigrating down and people are becoming more aware of the potential for them to be present. I'm particularly interested in seeing what happens with this as I would love to track these southern animals and compare them against the FNQ population I am currently researching. Could potentially be some interesting behavioural and movement differences present.
Cheers, Cameron