Action

Create or restore rock outcrops

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Five studies evaluated the effects of creating or restoring rock outcrops on reptile populations. All five studies were in Australia.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

  • Abundance (1 study): One replicated, paired sites, controlled study in Australia found that areas restored with artificial rocks had a higher abundance of adult velvet geckos and similar numbers of juveniles compared to unrestored areas.
  • Survival (1 study): One replicated, paired sites, controlled study in Australia found that in areas restored with artificial rocks, juvenile velvet geckos had higher survival rates than in unrestored areas.

BEHAVIOUR (4 STUDIES)

  • Use (4 studies): One replicated, randomized, controlled study in Australia found that some restored rocky outcrops were recolonized by pink-tailed worm-lizards. One replicated, controlled study in Australia found that constructed rock outcrops were used by two snake and six lizard species at least as often as natural outcrops. Two replicated studies (including one randomized study) in Australia found that artificial rock outcrops were used by two lizard and one snake species and six lizard and two snake species. One study also found that unshaded artificial rocks were used more frequently by velvet geckos than shaded ones.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, randomized study in 1994–1995 on a sand plateau in New South Wales, Australia (Webb & Shine 2000) found that reptiles used artificial rocks (concrete pavers/paving stones) and tended to be found more often under unshaded artificial rocks with narrow crevices. Velvet geckos Oedura lesueurii used 28 unshaded pavers (45 individuals recorded) and nine shaded pavers (11 individuals recorded), of which 26 pavers were narrow-creviced (44 individuals recorded) and 12 were wide-creviced (12 individuals recorded). One skink Cryptoblepharus virgatus and one broad-headed snake Hoplocephalus bungaroides were recorded in one unshaded, narrow-creviced paver each. In November 1994–January 1995, artificial rocks (square concrete pavers: 19 cm wide, 5 cm thick) were placed in groups of four (20 cm apart in a square formation) at three undisturbed rock outcrops (sites >1 km apart, 32–52 total pavers/site). Rocks were modified with either 4 mm or 8 mm crevices (created by gluing wood to the underside of the pavers) and unshaded or shaded (90 x 50 cm steel frame covered with two layers of shade cloth; unshaded pavers had only steel frames). Surveys were attempted six times/site in April–November 1995 (18 total surveys) with reptiles marked with a toe clip. Human disturbance of artificial rocks prevented seven of 18 surveys from being carried out.

    Study and other actions tested
  2. A replicated study in 2007–2008 on two sandstone plateaus in New South Wales, Australia (Croak et al. 2010) found that most artificial rocks were colonized by reptiles within 40 weeks. Artificial rocks started to be colonised by reptiles after six weeks. After 14 weeks, 50% of rocks were used and after 40 weeks, 82% were used. Lizards began using rocks after six weeks and snakes by 28 weeks (six lizard and two snake species were recorded in total). Rock spacing (either placed > 3 m from other rocks, or in pairs separated by < 0.5 m) did not affect colonisation rates (data reported as model outputs). The daily thermal characteristics (maximum, minimum and range of temperatures) of artificial rocks were similar to natural rock (see paper for details). In July–August 2007 artificial rocks (198 fibre-reinforced cement 55 x 39 x 4 cm with crevices constructed on the bottom) were placed at five sites (20 at each of two sites with no natural rock removal in a national park, and 40–72 at three sites with rock removal). Reptiles were surveyed on artificial and natural rocks 14 times in July 2007–May 2008 by turning rocks by hand.

    Study and other actions tested
  3. A replicated, paired sites, controlled study in 2009–2010 on a sand plateau in New South Wales, Australia (Croak et al. 2013) found that sites restored with artificial rocks had higher abundances of adult, but not juvenile, velvet geckos Oedura lesueurii compared to unrestored sites, but juveniles had higher survival rates in restored sites. Adult gecko abundances were higher in sites restored by adding artificial rocks (12–23 individuals/site) compared to unrestored sites (2–7), whereas juvenile abundances tended to be similar (restored: 37, unrestored: 18). Juvenile survival rates were higher in restored (90% survival) than unrestored sites (80%), whereas adult survival rates were similar (restored: 92–93%, unrestored: 78–92%). Gecko abundances were similar underneath individual artificial and individual natural rocks (results reported as model outputs). Six rock outcrop sites were restored by adding 50 artificial rocks (fibre-reinforced cement 51 x 35 x 5 cm) to natural rocks (18 natural rocks on average/site). Each restored site was paired with a nearby (average 500 m apart) unrestored site (26 natural rocks). Reptiles were surveyed by turning all artificial and natural rocks and hand-capturing geckos monthly throughout 2009–2010. Geckos were toe clipped before being released.

    Study and other actions tested
  4. A replicated, randomized, controlled study in 2014–2015 in six rock and grassland areas in Australian Capital Territory, Australia (McDougall et al. 2016) found that when rock cover and native grasses were restored, Australian pink-tailed worm-lizards Aprasia parapulchella recolonised rock outcrops within one year, depending on additional management. Results were not statistically tested. Pink-tailed worm-lizards recolonised restored rock cover and grassed plots after nine months (rock and plants restored only: 4 live lizards and 1 shed skin observed; rock and plants restored plus prescribed fire and herbicide application: 4 live lizards; rock and plants restored plus prescribed fire: 2 lizards). There was no evidence of lizards at unrestored sites of poor habitat quality or at sites with rock and plant restored combined with herbicide application only. Four lizards and three shed skins were observed in plots in unrestored, nearby high-quality lizard habitat. In April–May 2014, plots (4 x 4 m) in six sites (150 m apart) were managed by: rock (30% rock cover) and native grass restoration alone; rock and grass restoration with prescribed fire (using a blow torch); rock and grass restoration with herbicide application (Glyphosate, 1:100 glyphosate:water); or rock and grass restoration with prescribed fire and herbicide application. In each site, two additional plots received no rock or plant restoration (one was adjacent to managed plots and the second was in nearby high-quality lizard habitat). In February 2015, all plots were surveyed for lizards (live sightings and skins) including two unmanaged plots/site (one in poor, the other near high-quality lizard habitat).

    Study and other actions tested
  5. A replicated, controlled study in 1998–2013 of rocky outcrops in the southern metropolitan area of Sydney, Australia (Goldingay et al. 2017) found that constructed outcrops were occupied by broad-headed snakes Hoplocephalus bungaroides, small-eyed snakes Cryptophis nigrescens, velvet geckos Oedura lesueurii and five species of skink at least as often as natural outcrops. Broad-headed snakes and small-eyed snakes were recorded in a similar proportion of constructed outcrops (broad-headed: 49%; small-eyed: 27%) as natural outcrops (broad-headed: 48%; small-eyed: 52%). Velvet geckos and skinks (five species grouped together) were more abundant in constructed outcrops (1.6 geckos/10 rocks, 0.6 skinks/10 rocks) than natural outcrops (0.7 geckos/10 rocks, 0.2 skinks/10 rocks). The authors reported that broad-headed snakes were more likely to be recorded in outcrops >500 m from trails or roads (75% probability) than <150 m from trails or roads (41% probability, see original paper for details). In March 1998 and 1999, thirty-three outcrops were constructed in an area of a national park (8 x 10 km) by placing rocks on a rocky platform in a grid (22 small 10-rock/platform outcrops and six pairs of large (12 total) 50-rock/platform outcrops, see original paper for details). In total 33 constructed outcrops (one small outcrop was excluded from analysis) and 31 natural outcrops were surveyed for reptiles during August–September in seven years between 2000–2013 (starting 1–2 years after outcrops were constructed). Reptiles were monitored by lifting rocks to reveal any inhabitants.

    Study and other actions tested
Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

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