Artificial shelters
We designed the artificial shelters based on the preferred nesting/sheltering microhabitat of microhylid frogs, as described by Felton et al. (2006) for Cophixalus ornatus (now C. australis ; Hoskin, 2012). Sheltering and nesting microhabitats are essentially small crevices or holes in soil or wood, or under leaf litter, logs or rocks. The objective was to make artificial shelters that contain small spaces and can have a camera inserted to film any of these spaces (i.e., a ‘chamber’) that is in use.
Two artificial shelter types were constructed, one using wood and one using concrete. The wooden shelters were made by splitting logs found at the site (e.g., from a tree fall near a road or path) (Fig. 2A). By splitting the log in half, we produce a flat surface to place against the ground (Fig. 2B). The resulting log size (i.e., surface in contact with the ground) was an average of 60.4 cm in length x 18.5 cm in width. When a frog occupied the shelter and we decided to film, a 42 mm wide hole was drilled through the log to fit the camera. The diameter of the drill hole reflected the size of the end of the camera so that it can be neatly inserted. We also sourced sink plugs of approximately 40 mm diameter and filled these with concrete, so that these could be used to block the hole when the camera was ultimately removed. The concrete was used to add weight to the plug and to add thermal buffering to the chamber.
The concrete artificial shelters are rectangular concrete blocks of (29.5 x 22.5 x 4.5 cm), with six rounded (42 mm diameter) nesting chambers, each with two entrances/exits (Fig. 3B). A plug hole is present above each nesting chamber so that the plug can be lifted to inspect the nesting chamber. The plug sits atop a 40 mm wide and 35 mm long piece of PVC pipe. The plug has concrete packed into it to better buffer the nest chamber. We constructed concrete artificial shelters using a four-two-one concrete mixture (four parts crushed rock; two parts sand; and one part cement). One-third of the concrete was poured in a 4 L Tupperware container, and then six 42 mm-wide plastic-wrapped PVC pipes were equally distributed in the concrete, placed vertically to make chambers and a galvanized 1 x 1 cm mesh hardware cloth was placed around them. The other two-third of the concrete was then poured into the Tupperware container around the PVC pipes. Pieces of garden hoses (each 3 cm) were placed in the concrete where the entrances/exits going to be (Fig. 3A). The whole Tupperware container was then placed on a vibrating plate to remove air bubbles. After drying for at least 48 hours, the PVC pipes and garden hose pieces were taken out of the concrete. The shelters were then soaked in water for 3 days and then dried completely in the sun before being deployed in the field. The cost of making the shelters was AU $20, per mould (4L Tupperware, 42 mm x 100 mm PVC pipe, and 10 pieces of 3 cm garden hose), AU$3 for the concrete shelter (concrete, sand, crushed rock, and galvanized mesh hardware cloth) and about AU$18 for the six lids per shelter (sink plugs, PVC pipe, screws, concrete mixture) (Table 1). So, once you have the moulds, which are reused, the total cost per shelter is around AU$21 (US$14), with potential labour costs not included (Table 1).