Install rope or pole (canopy) bridges

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study in Brazil found that black lion tamarins and capuchins used a pole bridge to cross a road.
  • One before-and-after study in Belize found that a black howler monkey population increased after the construction of pole bridges over man-made gaps.
  • One before-and-after study in Madagascar found that all six monitored lemur species used bridges to cross roads and pipelines.

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 study in 1991-1994 in an Atlantic coastal forest in São Paulo State, Brazil found that black lion tamarins Leontopithecus chrysopygus and tufted capuchins Cebus apella used a pole bridge to cross a service road on at least 40 occasions over 3.5 years. From the installation of the bridge in 1991 to the end of 1994, two groups of black lion tamarins and one large group of capuchins were recorded using the bridge on at least 40 occasions. The authors suggested that the groups may have used the bridge regularly, possibly daily. The bridge was installed exactly where black lion tamarins had been observed crossing the road during a long-term primate study that was conducted in the area before. The bridge was 8 m wide and 6 m high and connected naturally forested habitat on both sides of the road.

    Study and other actions tested
  2. A before-and-after trial in 1985-1998 in secondary riparian forest in the Community Baboon Sanctuary, Belize found black howler monkey Alouatta pigra numbers increased by 138% over 13 years after the construction of pole bridges over man-made gaps, alongside ten other interventions. The population increased from 840 to more than 2,000 individuals (138% increase). No statistical tests were carried out to determine whether this difference was significant. Additional interventions included the protection of the sanctuary by the communities surrounding it, preserving forest buffer strips along property boundaries, preserving a forest corridor along the river, preserving important howler monkey food trees in large clearings, involving local communities in the management of the sanctuary, creating a museum for education purposes, implementing an eco-tourism and research programme, presence of permanent staff, and monetary (income from employment, tourism and craft industries) benefits to local communities for sustainably managing their forest and its wildlife communities. The study does not distinguish between the effects of the different interventions mentioned above.

    Study and other actions tested
  3. A before-and-after trial in 2009-2010 at the Ambatovy mine in humid forest in Toamasina, Madagascar found that all six lemur species (Lemuroidea) monitored used canopy bridges to cross roads and pipelines around the mining area. Observed road crossings on the ground decreased from 69 during two weeks before bridge construction to six crossings during the 1.5 years after construction. Furthermore, bridges were used 63 times during the first 1.5 years. Lemurs preferred to use the mine area bridge, which the authors assumed was due to the shorter distance needed to be crossed without the shelter of the canopy. Three bridges (8–15 m in length) in the mine area and four (22-25 m in length) along the pipelines were constructed from January to February 2009. Lemur (eastern woolly lemur Avahi laniger, greater dwarf lemur Cheirogaleus major, grey bamboo lemur Hapalemur griseus, diademed sifaka Propithecus diadema, brown lemur Eulemur fulvus, red-bellied lemur Eulemur rubriventer) use of bridges was monitored 10 hours/day during four to six days/week from March 2009 until August 2010. Prior to bridge construction, mine area roads and pipelines were monitored for 14 days to detect potential crossing points.

    Study and other actions tested
Please cite as:

Junker, J., Kühl, H.S., Orth, L., Smith, R.K., Petrovan, S.O. & Sutherland, W.J. (2020) Primate Conservation. Pages 431-482 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Primate Conservation

This Action forms part of the Action Synopsis:

Primate Conservation
Primate Conservation

Primate Conservation - Published 2017

Primate Synopsis

What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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