Use irrigation systems

Overall effectiveness category Awaiting assessment
Number of studies: 2
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Background information and definitions

Conservation of some species may require intensive management such as the redistribution of water resources. This could be achieved by using irrigation systems.

Study locations

Key messages

Two studies evaluated the effects of using irrigation systems on reptile populations. Both studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Reproductive success (1 study): One replicated, controlled study in the USA found that hatching success of Agassiz’s desert tortoises was similar in irrigated and non-irrigated enclosures.
Survival (1 study): One replicated, controlled study in the USA found that survival of juvenile Agassiz’s desert tortoises was similar in irrigated and non-irrigated enclosures.
Condition (2 studies): Two replicated, controlled studies (including one paired study) in the USA found that irrigating nests had mixed effects on growth of Agassiz’s desert tortoises and loggerhead turtles. One of the studies also found that loggerhead turtle hatchlings from nests that were irrigated were larger than those from non-irrigated nests.

BEHAVIOUR (0 STUDIES)

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

A replicated, controlled study in 2003–2008 in a desert scrub site in California, USA (Nagy et al. 2015) found that irrigating the enclosures of Agassiz’s desert tortoises Gopherus agassizii during a head-starting programme resulted in similar hatching success and juvenile survival but higher growth rate compared to tortoises with no supplementary water. Tortoises in irrigated and non-irrigated enclosures had similar hatching success (irrigated: 67% across 5 nests; non-irrigated: 77% across 7 nests) and juvenile survival (90% of 15 tortoises). Growth rate was higher in the first year in irrigated enclosures (15% increase/year) than in non-irrigated enclosures (4% increase/year). For tortoises hatched in 2003, those from irrigated enclosures were larger than those from non-irrigated enclosures after four years (irrigated: 81 cm; non-irrigated: 55 cm; 3 from each treatment; data from other years not provided). Enclosures were constructed in a natural habitat setting, of which six were irrigated (25–38 mm of water delivered through a sprinkler system three times in late winter-spring) and nine received only natural rain. Wild, adult females (number not given) were brought into the pens to lay eggs before being re-released. Hatching success was determined by counting hatchlings and un-hatched eggs, and hatchlings were marked, measured and re-measured after a year.
Study and other actions tested
Referenced paper
Nagy K.A., Hillard S., Dickson S. & Morafka D.J. (2015) Effects of artificial rain on survivorship, body condition, and growth of head-started desert tortoises (Gopherus agassizii) released to the open desert. Herpetological Conservation and Biology, 10, 535-549.
A replicated, controlled, paired study (year not given) on a sandy beach in Florida, USA (Erb et al. 2018) found that watering loggerhead turtle Caretta caretta nests lead to larger hatchlings that grew more in captivity over 10 weeks in one of three measures compared to hatchlings from un-watered nests. Hatchlings from watered nests had higher mass (watered: 17 g; un-watered: 16 g), straight carapace length (watered: 42 mm; un-watered: 40 mm) and straight carapace width (watered: 33 mm; un-watered: 32 mm) compared to those from un-watered nests. Growth in straight carapace width over 10 weeks was higher for hatchlings from watered compared to un-watered nests (watered: 65 mm; un-watered 62 mm after 10 weeks), though there was no significant difference in growth in mass (watered: 89 mm; not watered: 79 mm after 10 weeks) and straight carapace length (watered: 76 mm; not watered: 72 mm after 10 weeks). In one nesting season, eggs from 10 nests were divided in half and reburied 1 m apart (10 pairs of nests, buried 60 cm deep). One received 45 minutes of daily watering, while the other received no additional watering. Hatchlings (67 from watered, 55 from un-watered nests) were transferred to tanks supplied with fresh seawater, and measurements of mass, straight carapace length and width were taken weekly for 10 weeks.
Study and other actions tested
Referenced paper
Erb V., Lolavar A. & Wyneken J. (2018) The Role of Sand Moisture in Shaping Loggerhead Sea Turtle (Caretta caretta) Neonate Growth in Southeast Florida. Chelonian Conservation and Biology, 17, 245-251.

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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This Action forms part of the Action Synopsis:

Reptile Conservation

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