Loss and/or degradation of sites used for hill-topping by butterflies was listed as a KEY THREATENING PROCESS on Schedule 3 of the Threatened Species Conservation Act 1995 [20 April 2001].
Hill-topping in butterflies is a complex behaviour that often facilitates meeting of the sexes (Shields, 1967; Atkins, 1975; Common and Waterhouse, 1981; Baughman and Murphy, 1988; Sands, 1993; New, 1997; Newland, 1997). Hill-tops act as a focus for mating. Many butterfly species, especially in the families Hesperiidae, Papilionidae and Lycaenidae appear to be obligatory hill-toppers and tend to congregate on hill or ridge tops that are usually higher than the surrounding countryside. Well known examples of butterfly hill-topping sites are Mt Warning, Razorback Lookout, Lions Lookout, Peates Mountain Mt Ramornie (all in northern NSW), Mt Sugarloaf, near Newcastle and Cook Trig in Wahroonga.
Disturbance of plants on, or topography of, the hill-top, or to its slopes and immediate surroundings, may render it unsuitable to butterflies as a hill-topping site. In the absence of other hill-topping sites, butterflies may disappear entirely from a district. Loss of hill-top habitats throughout NSW would affect butterfly species which rely on such sites and some local extinctions have occurred due to hill-top alteration.
Loss of hill-topping sites due to habitat alteration (e.g. loss of vegetation for agriculture, urban development, forestry, tourist development, communication towers or power transmission lines), may lead to loss of resting sites for male butterflies, loss of focal points for mating and thus local extinctions.
Butterflies which hill-top in NSW and whose populations could become threatened if hilltopping sites were lost include: Hesperiidae such as Neohesperilla xanthomera and Hesperilla crypsigramma; Lycaenidae such as Acrodipsas arcana, Acrodipsas brisbanensis, Acrodipsas cuprea, Acrodipsas mortoni, Acrodipsas myrmecophila, Ogyris genoveva, Ogyris olane, Ogyris oretes, Deudorix epijarbas and Candalides cyprotus; and Theclinae such as Hypochrysops ignitus and Hypochrysops delica.