Providing evidence to improve practice

The journal, Conservation Evidence

Our online journal publishes research, monitoring results and case studies on the effects of conservation interventions. All papers include some monitoring of the effects of the intervention and are written by, or in partnership with, those who did the conservation work. It includes interventions such as habitat creation, habitat restoration, translocations, reintroductions, invasive species control, and education or integrated conservation development programmes, from anywhere around the world.

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Volume 8



In the UK, shrubby sea-blite Suaeda vera is a Nationally Scarce species restricted to coastal localities in eastern and southern England. It is locally common on the tidal face of sea wall flood defences in Essex. However, its dense bushy growth makes the engineering inspection of these important defences by the Environment Agency (the government agency responsible for flood defence maintenance) difficult. In consultation with Natural England it was agreed that S. vera could be flailed (cut) to a height of 30 cm along a 2.8 km length of sea wall in Essex to ease inspection, and as a trial to assess S. vera response to such cutting.  The response three months after cutting was encouraging with 94% of cut plants showing signs of regrowth. Eight months after cutting the mean height of the cut shrubs (79.7 cm) was about equivalent to that of uncut S. vera (82.1 cm) in a nearby uncut area (of similar height prior to cutting), indicating good vertical growth after flailing. However, the mean width of the cut shrubs (115.8 cm) was less than that of the uncut plants (177.4 cm). This is attributed to the cutting method (using a side-arm flail which reduced plant width in places, as well as removing the often broader, mid-crown growth), which coincidentally further eased inspection. These short-term results suggest that a one-off cut of S. vera can be used to allow sea wall inspection without detrimental damage to S. vera populations.

European badgers Meles meles and their setts are legally protected in the UK. If setts are to be damaged or destroyed as part of development, humane exclusion of badgers is usually required in advance of works. Exclusion can be achieved by erecting one-way gates over sett entrances which allow badgers to exit but not regain entry. Natural England (the governmental conservation advisory body in England) recommends that exclusion is maintained for 21 days before construction work begins to ensure that the sett has been vacated. In this study, a large diameter (400 mm) water main was installed through a badger sett without exclusion of animals due to discovery of the sett only after construction work had commenced. The sett location and the presence of numerous European rabbit Oryctolagus cuniculus burrows interspersed with sett entrances would have made exclusion difficult. As an emergency mitigation measure, a 1.4 m deep, 40 cm wide trench was excavated 6 m from the sett entrances (located mostly in a lapsed field boundary using a combination of hand augering (to detect badger tunnels and chambers; these were then excavated by hand), followed by mechanical excavation. Subsequent to this, work to excavate the trench, lay the pipe through the sett and back-fill the trench took one week. Despite the disturbance caused by this approach, badgers were not excluded from the entire sett and the risk of killing badgers which may have been present below ground was significantly reduced; no badger or other large mammal activity was evident during the mitigation works.

All works were carried out under Natural England licence and under the supervision of an ecologist and a Natural England Wildlife Management Adviser.

Lemur bridges provide crossing structures over roads within a forested mining concession near Moramanga, Toamasina Province, Madagascar
Mass V., Rakotomanga B., Rakotondratsimba G., Razafindramisa S., Andrianaivomahefa P., Dickinson S., Berner P.O. & Cooke A. (2011), 8, 11-18

The Ambatovy Project includes a large, open-pit nickel mine located in Madagascar's eastern humid forest, and an associated pipeline to remove laterite slurry off site. The area is recognized for its high biodiversity exemplified by the presence of at least 13 lemur species in forests surrounding the mine site. In order to reduce potential habitat fragmentation impacts on the lemur populations as a consequence of recent access road construction, seven crossing structures (referred to as 'lemur bridges') were erected within the mine footprint area and along the slurry pipeline that will remain in place until rehabilitated forest allows for movement over roads via the forest canopy. Two bridge designs were used due to differences in road width and vehicle traffic type. Lemur bridges have been monitored since their construction in January-February 2009. To date (10 August 2010), bridges have been used by six lemur species. Mine footprint type bridges (suspension bridge design) have been used more frequently than slurry pipeline bridges (plank bridge design) and, overall, there has been an increase in bridge use in 2010 when compared to 2009 (from 8 % to 24 % of total observations where lemurs are present in proximity to bridges). These results suggest that although a certain time period may be required for lemurs to locate and habituate to bridges, these crossing structures offer an effective mitigation measure to assist in reducing the impacts of habitat fragmentation.

As one of the most commercially valuable and commonly used rattan palms in the furniture- making industry, populations of manau rattan Calamus manan have severely declined throughout their Southeast Asian range due to unsustainable harvest of wild plants, exacerbated by habitat loss due to deforestation. Surveys conducted in Sumatra in forest in 2003 and 2004 highlighted how rare the species had become. In March 2006, a total of 670 nursery-grown seedlings (1.5 and 2.5 years old) were planted out in formerly occupied areas of Bukit Duabelas National Park (Sumatra). Three sites were chosen representing three habitat types: hill forest, riverside forest, and a rubber Hevea brasiliensis plantation within a valley. Survival after 16 months was highest in the plantation (44%), followed by the hill forest site (33%) and riverside site (22%). Seedling growth (height increase) was somewhat variable but overall, was best for those planted in the plantation (average initial height 45 cm, increasing to 100 cm at 16 months). Longer term monitoring of survival and growth is required to assess if transplanting into the wild is a viable conservation management intervention.

In order to design a micropropagation protocol for Caracas walnut Juglans venezuelensis (a critically endangered Venezuelan endemic), morphogenesis studies were performed based on different explants. The explants were cultivated in mediums with different combinations of growth regulators under various conditions of light and darkness. Using nodal and apical segments, aerial sprouts developed when using Thidiazuron (TDZ) with concentrations of 0.3, 1.2 and 3.0 mg/l, and Benzilamine Purine (BA) with concentrations ranging from 0.2 to 1.5 mg/l. Microshoots with a lateral bud, cultivated in a medium complemented with Indole Butyric acid (IBA) (0.01 and 0.05 mg/l) + BA (1.0 mg/l) and TDZ (0.01 and 0.02 mg/l), also developed aerial sprouts (later transferred to another cultivation medium to promote root growth). In addition, starting from foliar explants in a medium complemented with Kinetin (Kin) (1.0 mg/l) combined with Naphthaleneacetic acid (NAA) (0.1 mg/l), somatic embryos were developed in globular and torpedo stages, as well as thick radical structures and several radical hairs. The formation of new sprouts, followed by rooting and the conversion from embryos to plants is a key factor yet to be achieved in order to produce stock for incorporation into reforestation programmes.


Grasshopper strips (alternate, 1-m wide strips of uncut and cut grassland) are a novel conservation feature in a rural churchyard in the village of Rivenhall (Essex), southeast England.  The effectiveness of these strips in enhancing the abundance of grasshoppers (Acrididae) was investigated during the summer of 2010 using sweep-net surveys.  Two grasshopper species were recorded.  The meadow grasshopper Chorthippus parallelus was significantly more abundant in the cut grasshopper strips than in nearby short grassland (control) plots regularly mown throughout the summer.  The field grasshopper Chorthippus brunneus was contrastingly more abundant in the uncut grasshopper strips than in the controls. The grasshopper strips appear to provide a mosaic of short and tall grassland in close proximity which is required for nymphs and adults of both C. parallelus and C. brunneus.

Campaigns to eradicate introduced rats (Rattus spp.) from small islands are very successful; however, reinvasions on rat-free islands continue to be a major concern. In New Zealand, rodent sniffing dogs are employed to detect suspected rat incursions. The ability to detect and catch a known free-ranging rat on a rat-free island has previously been proven only once and never been experimentally tested. This study tested the ability of a rodent sniffing dog to detect a free-ranging Norway rat R. norvegicus and four caged albino laboratory rats (R. norvegicus) on rodent-free Browns Island. A male Norway rat fitted with a GPS/VHF transmitter was released on the island as part of a trial to test the ability to detect its presence using caged 'lure' rats. A failure to detect any signal from the transmitter forced us to bring in a trained rodent sniffing dog to locate the rat. In a systematic search of the island, the dog found three of the four caged rats, and through air sniffing downwind it was able to track and catch the wild rat from a distance of approximately 170 m. This is one of the very few times that a rodent sniffing dog has been tested in a realistic scenario in which there was a confirmed free-ranging rat on an otherwise rodent-free island. The successful detection and capture indicates that trained sniffing dogs can contribute to the detection of rat incursions on island sanctuaries and assist in rat control.

Star cactus Astrophytum asterias is listed endangered in the USA.  The few known extant populations are located in Starr County, Texas and adjacent north Mexican states. According to the United States Fish and Wildlife Service A. asterias recovery plan, reintroduction is an acceptable step in recovery of this species.  This paper reports on a pilot A. asterias reintroduction program.  Seeds and seedlings (2¼ and 2¾ years of age) were planted in the spring and autumn of 2007.  Of the seeds sown (120 each in spring and autumn), less than 4% grew to produce seedlings (five from the spring planting and four from the autumn planting).  After a monitoring period of 14 months, spring- and autumn-planted seedling survival was 55.0% and 72.5%, respectively. Mean diameter of the surviving spring-planted seedlings (n = 66) increased from 8.9 (± 1.6) mm at planting to 10.4 (± 2.0) mm. Mean diameter of surviving autumn-planted seedlings (n = 87) increased from 9.4 (± 2.0) mm to 11.3 (± 2.6) mm. Based upon these results, for A. asterias reintroduction purposes transplanting nursery reared seedlings appears a better strategy than sowing of seeds directly into the wild.

Monitoring of badger tunnels using clay mats on nine Highways Agency road schemes was undertaken to establish their effectiveness in terms of use by large mammals (primarily European badger Meles meles), as well as the efficacy of tunnel design advice provided by the agency.  The results indicate that tunnels are an effective means of mitigating the effects of all types of new road schemes on badgers; 89% of the tunnels monitored were used.  The results suggest that no one factor is of over-riding importance in tunnel design; however, design features that appeared to be associated with the use of tunnels were good vegetation cover, habitat connectivity, good drainage and a tunnel width of at least 600 mm.

In March 2009, 79 hihi (stitchbird) Notiomystis cincta were translocated from Tiritiri Matangi and Little Barrier (Hauturu) Islands to Maungatautari, a 3,255 ha New Zealand mainland reserve with a predator (exotic mammals) exclusion fence. Genetic management, by mixing founders from both a reintroduced and highly productive site (Tiritiri Matangi) and the only naturally occurring extant population (Little Barrier), appears successful with at least one mixed pairing producing fledglings in the first breeding season after release. Monitoring this population is challenging due to the large area and rugged terrain of the reserve.  However, closed mark-recapture analysis based on a 15-day survey about 1 year after release indicated that between 15 and 41 (19 - 52%) of the translocated hihi had survived.  Unringed hihi were also observed during this survey (25 observations but it is unknown how many of these were the same individuals), indicating successful breeding in the first year. If they persist and thrive in the longer term, this translocation will provide an important hihi population at a large mainland site and will contribute to the ongoing ecological restoration of Maungatautari.

A protocol for micropropagation of the medicinally important plant Premna serratifolia was developed due to its increasing rarity as a result of over-exploitation and poor natural regeneration within its range of occurrence in the Indian sub-continent. Plantlets were regenerated through shoot tip explants. Shoot tip explants were cultured on different media (MS, SH, Y3 and B5). Anti-oxidants (activated charcoal, citric acid, polyvinylpyrrolidone) and the effect of seasonal changes (through out the year) were analyzed for reducing explant browning and better shoot multiplication. The highest number of shoots was developed from MS medium supplemented with BAP (3.0 mg/l), IAA (0.5 mg/l) and activated charcoal (10.0 mg/l) between November and March. Best rooting was achieved from the medium supplemented with NAA (1.0 mg/l). Complete regeneration was achieved in about 21 days. The plantlets, thus developed were maintained under controlled conditions in the green house for 40 days. They were then planted out into a nursery where growth has been good and survival, up to 1 year, has been high (95%).

Managing competition between birds and bats for roost boxes in small woodlands, north-east England
Meddings A., Taylor S., Batty L., Knowles M. & Latham D. (2011), 8, 74-80

A total of 196 bat boxes were installed between 2005 and 2009 across 21 sites throughout the Highways Agency's (HA) 'soft estate' woodland in north-east England in support of the HA's Biodiversity Action Plan. The woodlands are typically small linear blocks (<3 ha) with trees mostly less than 40 years of age. Suitable natural cavity sites are thus very limited, hence the attractiveness of bat boxes as a conservation measure to enhance these woodland habitats. Monitoring in 2006-2007 had shown that in some areas (seven woodland sites) over 40% of bat boxes were being used by nesting passerine birds. Bird boxes were installed in an attempt to reduce bird occupancy of bat boxes. Provision of bird boxes significantly reduced bird use of bat boxes (a 50% overall reduction in occupancy) thus potentially making more bat boxes available for bat use. We also assessed if there was any relationship between the number/density of available bat boxes and level of bat occupancy to assess if there was a limit to the occupancy levels that could be achieved, thus determining an approach that could maximise benefits and cost effectiveness of box installation. Occupancy of bat boxes by bats appears not to increase above 30% utilisation with an increasing number of boxes on site after eight boxes. This suggests that, as bat boxes are installed three boxes per tree (as per best practice guidelines), the optimal number to install would generally be between nine to 12 boxes in these small woodland areas.

A project undertaken from 2003 to 2009 evaluated the efficacy of cattle exclosures to enhance breeding whinchat Saxicola rubetra numbers in a 65 ha study area comprising sub-alpine cattle-grazed pasture (42 ha) and hay meadows in the Southern Alps of Switzerland. Potentially suitable nesting sites were created in the pasture by erecting fences to exclude cattle, and this made available additional perches (providing hunting and song posts in territories) where previously mostly lacking. One 0.9 ha plot was excluded from grazing cattle with a wooden fence, and five smaller 0.1 ha plots with electric fences. Whinchats used the plots as parts of their territories and the fence posts as song posts and perches. The 0.9 ha plot secured whinchat territories until 2009. For the five 0.1 ha plots there was no clear effect on whinchat territory occupancy. Over the study period the whinchat population declined (following a general regional trend) from a high of 27 pairs in 1990 to a low of six pairs in 2009.

The endemic plant Impatiens gordonii (Balsaminaceae) is one of the most threatened plants in the Seychelles; it is known from a small number of localities on the islands of Mah© and Silhouette. There have been a number of attempts to establish a new population on Silhouette. Between 2001 and 2005, five seedlings and 54 rooting stems were planted at several points in one main field site. Although 11 plantings survived for over three months, all but one died within 2 years. That single plant has now survived for 10 years and has produced two seedlings. Problems with establishment were identified as being vulnerable to desiccation and rot, requiring high light levels but not full exposure to sunlight, and vulnerability to invertebrate herbivory (snails, caterpillars and crickets).

Control of giant reed Arundo donax on Vila Franca do Campo Islet, Azores, Portugal
Silva C.M.N., Silva L., Oliveira N., Geraldes P. & Hervías S. (2011), 8, 93-99

The non-native, invasive giant reed Arundo donax covers an estimated 30% of Vila Franca do Campo Islet (Azores). It blocks the entrance of Cory's shearwater Calonetris diomedea borealis nest burrows and out-competes threatened Azorean endemic flora. Three A. donax control methods were tested in 90, 1m2 plots, and cost-effectiveness of each determined using a Simple Additive Weighting Model. The most effective control method was cutting and removal of reed stems followed by two glyphosate-based foliar herbicide applications (one in May and another in late October i.e. corresponding to before and after the Cory's shearwater breeding cycle). After one year, 92% of giant reed was eradicated at an estimated cost of €8,000 per hectare.

Two types of anticoagulant rodenticides have proven successful at eradicating invasive rats and mice from islands. Brodifacoum is the most commonly used and has a low failure rate both when delivered from the air and from ground-based systems. It does, however, present a risk to non-target animals such as birds. When such risk is not acceptable or cannot be mitigated, diphacinone has been favoured by some managers because it is less toxic to birds and less persistent in rodents. However, unlike brodifacoum, diphacinone requires a rodent to eat several baits over several days to ingest a lethal dose. This increases the risk that not all rodents will be killed. When data on attempts to eradicate rats and mice for both aerial and ground-based methods are combined, brodifacoum has a significantly lower failure rate at 17% (54 of 322 attempts) than diphacinone at 33% (13 of 39 attempts). The difference is more significant when just rats are considered. Ground-based methods show similar failure rates for both rodenticides, but to date the very few attempts using aerially sown diphacinone baits have had a high failure rate compared with that for brodifacoum.

During electricity substation upgrading works at a site in Suffolk (England), five Eurasian badger Meles meles setts were closed (under licence) in 2009 as they were directly under the footprint of the works. As part of the licence agreement, mitigation included provision of three artificial setts. After completion of construction, monitoring indicated that all three setts displayed signs of occupancy and increased badger commuting and foraging evidence around their vicinity. In 2011, a remote motion-activated  infra-red camera was used to determine badger occupancy at a three-entrance outlier sett that also required closure during the badger breeding season. Previous extensive monitoring showed that badgers were unlikely to be present. However, a monitoring program using the remote camera was implemented to ensure that this was the case. When evident that badgers were not using the sett, it was destroyed under supervision of an ecologist. Being a novel, non-invasive monitoring technique this was done in liaison with the governmental statutory body, Natural England, but without the need for a licence. Remote monitoring techniques like this could be applied in similar situations where work is required during the badger breeding season (December to June) when licences are not normally issued.