Hi Ray,
My friend I am familiar with the above mentioned paper having read it many years ago. Hops are and have been my thing for a very long time and I have to admit that you make some very valid points (especially regarding the motivation for the study in the first place and the correlation of subsequent papers published later on). Likewise there are a number of points brought forward that I disagree with.
I actually authored an unpublished species profile on them for the NSW NPWS in 1993. In fact it was me who was called upon by Rick and John to assist John with his original paper on the subject and through personal communication at the time and prior to the original study, Rick admitted to me he had only ever collected one specimen and John had never had anything to do with them at all let alone collect any.
Personally I was very disappointed in the end result of Webb and Shine's original publication as I knew for a fact that a lot of the data was not actually verified during the study period. I also questioned on going publications ie; Substitute rock replacement and population predation by Lyre Birds. I can tell you know that the substitute rock replacement was a dismal failure and a total waist of time and considering the nature of the prefered exfoliates I doubt very much that Lyre Birds had/have a significant affect on populations, like wise I question their assumption regarding inbreeding and the alleged low fedundancy rate of wild populations.
I know for a fact that you can walk onto a ridge and walk past 90% of assumed micro habitat and go to a particular rock or rocks to find your hops, simply because of the location, shape, size, thickness and nature of the exfoliate against the parent rock. So even though there maybe an abundance of assumed micro habitat, it is actually limited due to preference for one type over another. Due to the vulnerability of their habitat to summer fires, other than finding refuge in hollows of large gums (which are limited a top sandstone ridges) I don't see what advantage they would have finding refuge in shrubs and accompanying coastal heath and believe they are a lot less arboreal than first believed. They are built for climbing rocks and through personal observation believe they prefer to find refuge in crevices on the face of the sandstone escarpment during the daytime periods over the hotter months and scour the tops of the outcrops in search of prey at night. This activity makes them all the less likely to be discovered by collectors during this time of the year. I have a theory why they emerge from these crevices during winter and spring but I won't go into that here.
As with several species of reptiles that inhabit the Sydney Sandstone Region, there colouring and patterns make them ideal for utilising sandstone crevices as a means of concealment and I'll add that I've found plenty in these situations during the winter and spring periods.
It is obvious to anyone who has anything to do with them that individual specimens do utilise the same rocks as shelter sites, over and over again, on different occasions over periods that extend to years (personal obs & communication with a well know hop man of the 60's, 70's and 80's, Mr Mick Van der Straten)...who incidentally was very successful breeding them during this same period) I also have a theory for this but again I won't go into it here.
Most certainly habitat destruction is a contributing factor that affects population densities however if you care to delve further you'll discover that there are plenty being held in collections illegally at the moment. The populations are no doubt sustainable and secure in isolated and inaccessible habitat, but those that are currently being held illegally have been removed from wild populations in restricted areas. I'll add they they still are valued by collectors and you only have to visit some of the reptile facebook pages to see how many people are out there actively searching for them still. There might only be a limited number of people removing them in numbers, but they are a marketable commodity. I believe another major reasons that people are taking them from the wild is due to the restrictions and conditions placed on having them and the current price. On top of that I hear they are also prized by international collectors and fetching sums in the tens of thousands of dollars. Surely, these points alone are incentive enough for some to get out and get there hands on them.
I think I've said enough for now and besides I have to go off and prepare for this week's work commitments.
Again, all the best to you
George.