Action

Manage vegetation by cutting or mowing

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

Study locations

Key messages

  • Seven studies evaluated the effects of managing vegetation by cutting or mowing on reptile populations. Five studies were in the USA, one was in Australia, and one was in Spain.

COMMUNITY RESPONSE (3 STUDIES)

  • Richness/diversity (3 studies): Three replicated, randomized, controlled studies (including one before-and-after study) in the USA found that areas where vegetation was managed by cutting had similar reptile species richness compared to areas with no cutting.

POPULATION RESPONSE (5 STUDIES)

  • Abundance (4 studies): Three of four replicated, controlled studies (including three randomized studies) in the USA found that areas where vegetation was managed by cutting had similar reptile abundance compared to areas with no cutting. The other study found that densities of eastern Massassauga rattlesnakes were higher after cutting during the first three years, but similar after four years.
  • Condition (1 study): One replicated, randomized, controlled, before-and-after study in Spain found that an adapted brush cutter caused less damage to tortoise carcasses than a conventional brush cutter.

BEHAVIOUR (1 STUDIES)

  • Use (2 studies): One replicated, randomized, controlled study in Australia found that after cutting back canopy vegetation, reptiles used unshaded rocks more often than shaded rocks in winter but not spring. One randomized study in the USA found that mown areas were used for nesting by Blanding’s turtles less frequently than tilled areas.

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, controlled study in 2002–2003 of rock outcrops on a sandstone plateau in New South Wales, Australia (Webb et al. 2005) found that after removing overhanging canopy, reptiles used unshaded rocks more often in winter, but not in spring, than shaded rocks. After canopy removal, reptile use of unshaded rocks was similar to shaded rocks in spring (unshaded: 38% of rocks used, shaded: 12%) but higher in winter (unshaded: 88%, shaded: 0%). Two broad-headed snakes Hoplocephalus bungaroides, four Lesueur’s velvet gecko Oedura lesueurii, and one red-throated skink Acritoscincus platynotum were recorded under unshaded rocks and one Lesueur’s velvet gecko under a shaded rock. In May 2002, sixteen rocks in three sites shaded by emerging shrubs and saplings were managed either by increasing canopy openness by 15% (‘unshaded’) or unmanaged (‘shaded’, 8 rocks/management type). Reptiles were sampled in June and August 2003 by searching under rocks and individually marking captured reptiles.

    Study and other actions tested
  2. A replicated, randomized, controlled, before-and-after study in 2001–2004 in an upland hardwood forest in North Carolina, USA (Greenberg & Waldrop 2008; same experimental set-up as Greenberg et al. 2018) found that mechanically cutting understory vegetation did not increase overall reptile abundance or species richness. Total reptile relative abundance and species richness were both similar after mechanical understory removal (abundance in 2002: 8–13 reptiles/100 nights; richness in 2002: 4–6 species) compared to the year before it took place (abundance in 2001: 4–8 reptiles/100 nights; richness in 2001: 2 species). Reptile abundance increased 40% in all sites (including those with no management) between the two years, but this was not related to understory removal (see original paper for details). Three forest segments were divided into management zones (14 ha each): mechanical vegetation removal and no management. Chainsaws were used to remove understory vegetation in winter 2001–2002. Reptiles were surveyed using drift fences with pitfall and funnel traps before any management took place in August–October 2001 and after management in May–September 2002–2004. In total 13 reptile species were caught.

    Study and other actions tested
  3. A randomized study in 2006–2008 in wetlands in New York, USA (Dowling et al. 2012) found fewer female Blanding’s turtle Emydoidea blandingii nested in mown plots than in tilled plots. Overall, fewer turtles nested in mowed plots (two turtles in 2006) that in tilled plots (7 turtles in 2006; 5 turtles in 2008). In 2006, nine of 10 monitored female turtles nested, and in 2008, six turtles nested. Two turtles nested in the same physical plot each year, in spite of a change in management. In 2006, thread trailing revealed that all female turtles explored or had been placed on each plot type before choosing where to nest. Eight sites around the edge of a fenced 12 ha wetland were monitored for turtle nesting activity. Two plots (5 x 7 m each) were established at each site, and one/site was either mowed to 5 cm height or tilled to a depth of 15 cm (treatment randomly applied in 2006 and 2008). Nesting activity was monitored by visual searches and radio tracking or by attaching a bobbin and thread to female turtles in May and June 2006 and 2008 (10 turtles monitored in total).

    Study and other actions tested
  4. A replicated, randomized, controlled study in 2006–2007 in hardwood forests in North Carolina, USA (Matthews et al. 2010) found overall reptile species richness and capture rates were similar in areas with vegetation cutting compared to areas with no cutting. Overall reptile richness and overall reptile, snake, lizard and turtle captures were similar after vegetation cutting (richness: 6–7 species/100 trapping nights, overall captures: 6 individuals/100 trapping nights, snakes: 1–2 individuals/100 trapping nights, lizards: 4–5 individuals/100 trapping nights, turtles: 0 individuals/100 trapping nights) and no cutting (richness: 6 species, overall captures: 7–7 individuals, snakes: 3–5 individuals, lizards: 4 individuals, turtles: 0 individuals).  Three blocks of four sets of 10 ha sites were either managed by cutting vegetation (using chainsaws to cut trees and understory, 2001–2002) or were left uncut. Reptiles were surveyed in May–August 2006 and 2007 using a group of drift fences with pitfall traps (3 groups/site).

    Study and other actions tested
  5. A replicated, randomized, controlled study in 2013 in abandoned vineyards, pine and oak forest in Catalonia, Spain (Vilardell-Bartino et al. 2015) found that a specially adapted brush cutter accessory minimised tortoise cutting injuries during vegetation cutting. When an adapted brush cutter was used, no tortoise carcasses were damaged, but when a conventional brush cutter was used, the majority of tortoise carcasses sustained what would have been fatal injuries (yearlings: 40% no damage, 60% fatal wounds; juveniles: 60% serious damage, 40% fatal wounds; subadults and adults: 100% fatal wounds). In February 2013, eight plots (100m2 each) were cleared of shrub cover using either a modified brush cutter (6 plots) or conventional cutter (2 plots). One-hundred and four frozen tortoises (5 yearlings, 5 juveniles and 3 adults/plot) were randomly distributed under shrubs and the impact on tortoise carcasses was assessed immediately after cutting.

    Study and other actions tested
  6. A replicated, controlled study in 2008–2012 in swamp forest and shrubland in New York State, USA (Johnson et al. 2016) found that where shrubs and canopy cover were reduced, densities of eastern Massassauga rattlesnakes Sistrurus catenatus were higher in the first three years after cutting, but densities in cut and uncut plots were similar after four years. The effect of removing canopy or shrubs cannot be separated. Estimated rattlesnake densities were greater in 0-year-old (0.072–0.141 snakes/100 m2), 1-year-old (0.045 snakes/100 m2) and 3-year-old (0.133 snakes/100 m2) cut plots than uncut plots (0.003–0.009 snakes/100 m2). Rattlesnake densities in 4-year-old cut plots (0.013 snakes/100 m2) were similar to uncut plots. Canopy was reduced by cutting shrubs to <0.25 m high in 50 plots in two known rattlesnake breeding areas in 2008 (six 28 m2 plots), 2011 (thirty-two 100 m2 plots) and 2012 (twelve 28 m2 plots). In addition, 4 ha of adjacent forest was mechanically cleared in 2011. Snakes were monitored using visual encounter surveys in 66 locations with canopy removal (50 plots of cut vegetation in breeding areas and sixteen 36 m2 plots within the forest areas cleared in 2011), and 44 areas with no vegetation removal (twenty-eight 28 m2 plots of uncut vegetation in breeding areas and sixteen 36 m2 plots in uncut forest). In 2011 and 2012, the number of snakes caught in canopy removal areas (removal having occurred 0–4 years previously) was compared to the number of snakes in uncut plots. It is unclear whether the results reported are based on the breeding areas only or include the cut and uncut forest plots. Surveys were carried out once a week in June–August 2011 and May–August 2012. Snakes were captured, sexed and individually marked with PIT tags.

    Study and other actions tested
  7. A replicated, randomized, controlled study in 2001–2016 in upland forest in North Carolina, USA (Greenberg et al. 2018; same experimental set-up as Greenberg & Waldrop 2008) found that cutting vegetation did not increase overall reptile species richness or the abundance of different species compared to areas with no cutting. Overall reptile species richness was similar in areas with vegetation cutting and in areas with no cutting (data reported as statistical model outputs, see original paper for details). Eastern fence lizard Sceloporus undulatus and five-lined skink Plestiodon fasciatus abundance was similar in cut (1–3 individuals/100 trapping nights) and uncut (0–2 individuals/100 trapping nights) plots, and all other reptile species were excluded from analysis due to small sample sizes (20 species total, see paper for details). Three similar study sites were selected within a 5,841ha mixed oak-hickory forest. Within each site, one plot each (10 ha core areas with 20 m wide buffers) was managed by cutting understorey vegetation (in winters 2001–2002 and 2011–2012) or was left uncut. Reptiles were surveyed after management using drift fences with pitfall and funnel traps (‘arrays’) in May–August of 2003–2004, 2006–2007, and 2014–2016 (158–341 array nights/plot/year).

    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.

Where has this evidence come from?

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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