1138

Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

Effectiveness of aerial wildlife crossings: Do wildlife use rope bridges more

than hazardous structures to cross roads?

Katra Laidlaw

; https://orcid.org/0000-0002-7782-1339

Eben Broadbent

; https://orcid.org/0000-0002-4488-4237

Stephanie Eby

; https://orcid.org/0000-0001-7047-7101

1. Department of Marine and Environmental Sciences, Northeastern University, 02115, Boston, Massachusetts, United

States of America; katra.laidlaw@gmail.com (Correspondence*)

2. School of Forest, Fisheries, and Geomatics Sciences, University of Florida, 32611, Gainsville, Florida, United States

of America; eben@ufl.edu

3. Department of Marine and Environmental Sciences, Northeastern University, 02115, Boston, Massachusetts, United

States of America; s.eby@northeastern.edu

Received 23-V-2021. Corrected 09-IX-2021. Accepted 30-IX-2021.

ABSTRACT

Introduction: Although wildlife crossing structures have proven successful at reducing wildlife-vehicle col-

lisions and linking fragmented habitat, their ability to prevent electrocutions of arboreal wildlife has not been

closely examined.

Objective: To evaluate the effectiveness of aerial rope bridges in restoring habitat connectivity for arboreal spe-

cies in Manuel Antonio, Costa Rica, while preventing electrocutions by determining 1) what species are using

the rope bridges and 2) whether wildlife prefer to use rope bridges instead of other hazardous structures that

cross the roads (such as telephone cables, which are often in close proximity to electric wires).

Methods: From January to May 2016, nine rope bridges along the highly-trafficked main road that extends from

Quepos to Manuel Antonio, Costa Rica, were monitored using camera traps, and ten rope bridges were observed

directly along a paved side road off the main road.

Results: A total of 11 species were seen using the bridges, and 1 540 crossings were witnessed via camera traps

and observations (1 234 via camera traps, 306 during observations). Results from a paired t-test showed no

significant difference in the average number of individuals crossing the road via rope bridges versus telephone

cables (t(8) = 1.027, P = 0.334).

Conclusions: Rope bridges are used by a variety of arboreal wildlife species with a high degree of frequency;

however, due to the equally high usage of telephone cables by arboreal wildlife, they are insufficient to prevent

wildlife electrocutions on their own. Rope bridges should be installed in tandem with other methods to prevent

electrocutions, such as insulating electric wires, to facilitate the safe passage of wildlife over roads.

Key words: electrocution mitigation; telephone cables; anthropogenic impacts; habitat modification; behavioral

ecology; wildlife management; endangered species; Costa Rica.

Laidlaw, K., Broadbent. E., & Eby, S. (2021). Effectiveness

of aerial wildlife crossings: Do wildlife use rope bridges

more than hazardous structures to cross roads?. Revista

de Biología Tropical, 69(3), 1138-1148. https://doi.

org/10.15517/rbt.v69i3.47098

https://doi.org/10.15517/rbt.v69i3.47098

Habitat loss and fragmentation lead to

a variety of negative consequences for eco-

systems (Broadbent et al., 2008; Chape et

al., 2005; Haddad et al., 2015). Long-term

studies have indicated that habitat fragmen-

tation degrades ecosystems, reduces species

richness and persistence, impedes nutrient

retention, alters trophic dynamics, and hinders

1139

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

wildlife movement among isolated habitat frag-

ments (Haddad et al., 2015; Turner, 1996).

Roads are one of the main causes of habi-

tat fragmentation (Coffin, 2007; Spellerberg,

1998; van der Ree et al., 2011).

In addition to fragmenting habitats, roads

also cause the death of wildlife due to colli-

sions with vehicles (Artavia, 2015; Caceres,

2011; Coffin, 2007; Laurance et al., 2009).

Although arboreal species generally experi-

ence fewer vehicle-related deaths than terres-

trial species, they still experience a significant

amount of vehicular mortality (Artavia, 2015;

Caceres, 2011; Rodrigues & Martinez, 2014).

Powerlines, which often run along roads, also

kill wildlife, particularly arboreal wildlife, via

electrocutions (Cunneyworth & Slade, 2021;

Kumar & Kumar, 2015; Lindshield, 2016;

Lokschin et al., 2007; Moore et al., 2010;

Rodrigues & Martinez, 2014; Teixeira et al.,

2013). For example, in Ilhéus, Bahia, Brazil,

electrocutions are the leading cause of injury

and/or death of Wied’s Marmosets (Callithrix

kuhlii) due to human infrastructure (Rodrigues

& Martinez, 2014).

If wildlife is unable to safely access habitat

on the other side of the road, then roads even-

tually lead to the genetic isolation of wildlife

populations, thereby increasing the risk of

inbreeding and local species extinctions (Cace-

res, 2011; Forman et al., 2003; Glista et al.,

2009; Haddad et al., 2015; Rybicki & Hanski,

2013). Local extinctions could cause changes

in community structure, which may ultimately

lead to further extinctions (Larsen et al., 2005).

This would be especially true if the species that

go locally extinct are important pollinators or

seed dispersers (Anderson et al., 2011; Mem-

mott et al., 2004; Van Wieren & Worm, 2001).

Many types of arboreal rainforest wildlife,

such as primates, play an important role in

the seed dispersal of rainforest plants (Bond,

1994; Chapman & Russo, 2005). If seed-dis-

persing wildlife becomes locally extinct, then

plants that have developed reproductive depen-

dence on this mutualism could also become

extinct (Memmott et al., 2004). This would

decrease plant diversity and regeneration in

the rainforest, which may, in turn, negatively

impact other wildlife species (Bond, 1994;

Cordeiro & Howe, 2003).

To reduce road-related deaths of wildlife

and mitigate the effects of habitat fragmenta-

tion, a variety of approaches have been used.

These approaches generally aim to modify

the behavior of motorists and/or to modify the

behavior of wildlife. To change the behavior of

motorists, speed limits, lights, and signs have

been established to warn drivers of the pres-

ence of crossing wildlife (Forman et al., 2003).

To change the behavior of wildlife, crossing

structures and habitat modifications have been

implemented (Glista et al., 2009). Although

the effectiveness of wildlife crossing signs

is questionable, wildlife-crossing structures

have proven successful at reducing roadkill

and restoring habitat connectivity (Dodd et

al., 2004; Glista et al., 2009; Van Wieren &

Worm, 2001).

Rope bridges have been shown to be effec-

tive wildlife crossing structures for a variety

of arboreal species (e.g., Lindshield, 2016;

Lokschin et al., 2007; Teixeira et al., 2013;

Weston & Goosem, 2011). However, despite

their usage, wildlife also attempts to cross

roads using telephone cables and electric wires

(Lokschin et al., 2007; Teixeira et al., 2013).

Although telephone cables do not directly

pose a threat to wildlife, they are usually con-

nected to the same poles as electric wires and,

therefore, can inadvertently bring wildlife in

close proximity to dangerous structures such

as uncovered electric wires and transformers.

When wildlife uses telephone cables to cross

the road, they are at a higher risk of electrocu-

tion than if they choose to cross the road on

rope bridges, which are not connected to the

electric poles.

This study aims to evaluate the effective-

ness of rope bridges in reconnecting fragmented

habitats while preventing the electrocution of

arboreal wildlife. Specifically, this study aims

to determine what species of wildlife are using

the rope bridges in the Quepos/Manuel Antonio

area of Costa Rica, how frequently they use the

rope bridges, and whether they use the bridges

1140

Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

more than hazardous structures (such as tele-

phone cables that are adjacent to electric wires)

to cross roads. Although other studies have

noted the use of telephone cables by arboreal

wildlife (Lokschin et al., 2007; Moore et al.,

2010; Rodrigues & Martinez, 2014), this is the

first study to quantitatively compare the usage

of telephone cables by wildlife with the usage

of crossing structures intentionally installed for

wildlife (i.e., rope bridges). We hypothesize

that arboreal wildlife will use rope bridges

more than telephone cables or electric wires

to cross the road due to frequent sightings of

wildlife using rope bridges by local residents.

We tested this hypothesis by conducting daily

observations at a series of ten rope bridges

along a road with telephone cables and uncov-

ered electric wires and installing camera traps

on an additional nine rope bridges distributed

throughout the study area.

MATERIALS AND METHODS

Study site: The study area is located South

of Quepos and North of Manuel Antonio, Costa

Rica (9°25’55.2”-9°23’33.3” N & 84°09’41.6-

84°08’13.2” W). Costa Rica is an ideal location

to conduct this study because electrocutions

from power lines and transformers and vehicu-

lar mortalities are the primary causes of death

for wildlife in the country (Lindshield, 2016;

Monge-Nájera, 2018). The study was conduct-

ed in a mixed-use area that consists primarily

of hotels and restaurants with some residential

housing (Fig. 1). Extending from Quepos to

Manuel Antonio, there is a highly-trafficked

two-lane road (approximately 6 m wide) that is

frequented by charter bus companies, taxis, and

local buses that run every 20 min. Stemming

from the main road are less trafficked roads, the

majority of which are gravel. The speed limit

Fig. 1. Map of the study area in Costa Rica with vegetation types overlaid with the locations of rope bridges (vegetation

data from Broadbent et al., 2012).

1141

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

for the main road is 40 kph, although vehicles

regularly exceed this speed limit. Amidst the

buildings and roads are patches of primary

and secondary forest which are inhabited by a

variety of wildlife.

Throughout the study area, 75 rope bridges

for wildlife extend across the main and side

roads, installed at an average distance of 90.48

m (+ 8.56 SE) from one another. These bridges

were installed by the wildlife rehabilitation

center, Kids Saving the Rainforest, with the

help of the local electric company, ICE, start-

ing in 2000. The majority of the bridges

were installed from 2001-2002. The wildlife

bridges consist of a blue, 25 mm, electricity-

proof, nylon rope that is fastened to trees on

either side of the road, typically in the space

between the electric wires and the telephone

cables (Fig. 2).

Observations: Ten rope bridges were

observed along a paved side road (approxi-

mately 5-6 m wide) off of the main road that

runs between Quepos and Manuel Antonio

(Fig. 1). At each bridge location, an aver-

age of three electric wires and six telephone

cables crossed the road (≤ 15 m from the rope

bridge) (Fig. 2). This area was chosen because

the electric wires along this road are not insu-

lated; therefore, they pose an electrocution

risk to wildlife.

Animal counts were conducted, from 7:00-

9:00 a.m., and from 3:30-5:30 p.m., for a total

of five morning and five afternoon sessions at

each bridge location between 2/28/2016 and

5/13/2016. During observation sessions, the

observer sat in a folding chair at the side of

the road a minimum of 5 m away from the

rope bridge because, at this distance, wildlife

did not hesitate to approach the observer. In

fact, many times, the wildlife would climb

on the telephone cables that extended above

the observer’s head. Moreover, since Manuel

Antonio is a main tourist area, wildlife is accus-

tomed to seeing people. During observation

sessions, when and what types of wildlife were

seen and how they crossed the road (i.e., on the

ground, jumping across the canopy, using the

rope bridge, using the electric wires, or using

the telephone cables) was noted.

Camera traps: Camera traps were placed

on nine bridges, all located in similar habitat

(primary forest), along the main road that

Fig. 2. Illustration of a typical rope bridge site with telephone cables and electric wires crossing the road within < 15 m of

the bridge.

1142

Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

extends from Quepos to Manuel Antonio (Fig.

1). The main road was chosen because it is

highly trafficked and therefore poses a high

risk of fatal wildlife-vehicle collisions. At each

of the bridge locations, there was an average

of three electric wires and a cluster of six tele-

phone cables that crossed the road < 15 m from

the rope bridge (Fig. 2).

PC800 Hyperfire Professional Semi-

Covert Camera traps were installed above the

rope bridges with one RAM® Short Double

Socket Arm (part number RAM-B-201U-A),

and two RAM® 2.4 cm (1”) balls (part number

RAP-B-366U) connected to an 8.5 × 19.5 cm

portion of PVC pipe (with four slits carved for

Nylon webbing straps). Prior to attaching the

ball joints and double socket arm, the research-

er painted the piece of PVC pipe brown and

green using acrylic paint (to aid in camouflag-

ing the camera). The first ball joint was con-

nected to the piece of PVC by drilling a hole

into the middle of the PVC and then securing it

with a wing nut on the other side. The first ball

joint was then connected to the double socket

arm, and the second ball joint was connected

to the opposite side of the double socket arm

and then screwed into the back of the camera.

Finally, the piece of PVC (with the double

socket arm and ball joint attached to the cam-

era) was secured to the tree using Nylon web-

bing straps and 2.4 cm (1”) plastic buckles that

were threaded through the slits of the portion

of PVC pipe (Gregory et al., 2014). Bicycle

cables were threaded through the hole in the

side of the cameras in order to discourage theft.

In order to provide additional support, heavy-

duty 60 cm (24”) cable ties were also threaded

through the hole in the camera and secured

to the tree using 1 cm (¼”) fence staples at a

45-degree angle above the camera (Fig. 3).

The cameras were set to record 24 h a

day, take three photographs per trigger, with

one second between photographs and no ‘quiet

period’ between triggers. The cameras were

positioned about 30 cm or less above the rope

bridge so that the photographs showed most

of the bridge extending across the road. It was

not always possible to capture the entirety of

the bridge within the camera’s frame because

the passing cars would trigger the camera and

Fig. 3. Front and side view of the PC800 Hyperfire Professional Semi-Covert Camera trap mounted above a rope bridge.

1143

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

quickly cause the camera’s SD card to fill up

and the batteries to run out. Therefore, the

length of the bridges that was not captured by

the cameras ranged from 0.6 to 2.4 m. Cameras

were installed from 1/29/16 to 5/21/16 for an

average of 459.49 h each (± SE 80.21).

Data analysis: For the observation data, a

paired t-test was used to compare the average

number of crossings that occurred via the rope

bridges versus the telephone cables. All statis-

tics were conducted in Microsoft Excel

RESULTS

A total of 11 species were seen using the

bridges, and 1 540 crossings were witnessed

via camera traps and observations (1 234 via

camera traps, 306 during observations) (Table

1). An average of 8.44 (± SE 3.69) crossings

per bridge were captured by the camera traps

per day, and an average of 6.12 (± SE 3.77)

crossings per bridge were seen during obser-

vations per day. The following species were

seen: common opossum (Didelphis marsu-

pialis); Derby’s woolly opossum (Caluromys

derbianus); kinkajou (Potos flavus); Mexican

tree porcupine (Coendou mexicanus); two-fin-

gered sloth (Choloepus hoffmanni); Northern

tamandua (Tamandua mexicana); white-faced

monkey (Cebus capucinus); grey-crowned

Central American squirrel monkey (Saimiri

oerstedii citrinellus); mantled howler mon-

key (Alouatta palliata); three-fingered sloth

(Bradypus variegatus); and variegated squirrel

(Sciurus variegatoides) (Table 1).

During observations only one squirrel

monkey (Saimiri oerstedii citrinellus) was seen

using an electric wire to get across the road.

Therefore, electric wires were excluded from

all statistical analyses. Results from a paired

t-test showed no significant difference in the

average number of crossings that occurred via

rope bridges versus telephone cables (t(8) =

1.027, P = 0.334) (Fig. 4).

TABLE 1

Total number of crossings of each species seen using bridges

Species observed

using bridges

Number of crossings seen

during observations

Number of crossings seen

via camera traps

Saimiri oerstedii citrinellus

199 402

Cebus capucinus

65 337

Alouatta palliata

39 179

Sciurus variegatoides

2 79

Bradypus variegatus

1 -

Potos flavus

- 125

Coendou mexicanus

- 55

Caluromys derbianus

- 27

Choleopus hoffmanni

- 12

Didelphis marsupialis

- 9

Tamandua mexicana

- 9

Total 306 1 234

Fig. 4. There was no significant difference in the average

number of road crossings (+ SE) that occurred via the

bridges or telephone cables (P = 0.3).

1144

Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

DISCUSSION

Wildlife crossing structures have proven

successful at reducing roadkill and restoring

habitat connectivity in a variety of contexts and

are an essential tool in mitigating the negative

effects of roads on wildlife (e.g., Dodd et al.,

2004; Glista et al., 2009; Van Wieren & Worm,

2001). However, the relationship between rope

bridges and electrocutions has largely been

unexamined. Over the course of this study,

rope bridges in Manuel Antonio, Costa Rica,

were frequently used by a variety of arbo-

real wildlife with average crossing frequencies

comparable to the high usage of rope bridges

by the endangered Western ringtail possums

(Pseudocheirus occidentalis) in Australia (8.87

± 0.59 complete crossings per night) (Yokochi

& Bencini, 2015). However, despite their high

usage, there was not a significant difference in

usage between the rope bridges and the tele-

phone cables, which were in close proximity to

uncovered electric wires. It seems that wildlife

will use any infrastructure that allows them to

move throughout the landscape.

Electrocution risk: Only one individual

was seen crossing the road using an electric

wire during observations of the ten rope bridg-

es along the side road. However, local residents

witnessed the electrocutions of two mantled

howler monkeys and one grey-crowned Central

American squirrel monkey, and we saw a dead

two-fingered sloth showing signs of electrocu-

tion along that same road. It is possible that

wildlife in the area does not typically choose

electric wires to cross the road because they

are thinner and therefore more difficult to walk

across than the thicker clusters of telephone

cables. Alternatively, it is possible that wildlife

accustomed to using telephone cables may not

perceive electric wires as a threat and may

eventually get electrocuted when attempting to

use them in the future (Lindshield, 2016).

These findings are consistent with the

incidences of electrocutions of arboreal wild-

life in other locations (Cunneyworth & Slade,

2021; Kumar & Kumar, 2015; Lindshield,

2016; Lokschin et al., 2007; Moore et al.,

2010; Rodrigues & Martinez, 2014; Saavedra-

Rodríguez et al., 2013; Teixeira et al., 2013).

According to a study conducted in the rural

areas of the city of Cali, Colombia, over the

course of 14 months, two electrocuted Derby’s

woolly opossums (Caluromys derbianus) and

two gray-bellied night monkeys (Aotus lemu-

rinus) were found dead on the electric wires

(Saavedra-Rodríguez et al., 2013). Given the

substantially smaller area evaluated in this

study, the three electrocutions that were wit-

nessed firsthand along the same road, over the

course of five months, constitutes a notably

high rate of electrocutions.

Use of telephone cables: The lack of

difference between rope bridge and telephone

cable usage may indicate that arboreal spe-

cies do not have a preference for the type of

crossing structure and simply seek to cross the

road however possible. In addition to witness-

ing wildlife using telephone cables to cross

the roads, we also witnessed wildlife using

telephone cables to travel alongside the road to

gain access to the rope bridges. This could be

problematic in cases where using the telephone

cables puts the individual at a higher risk of

electrocution by bringing them in close prox-

imity to uncovered electric wires and trans-

formers. On the other hand, if electrocution

risk is low, for example, because the electric

wires are covered, telephone cables might actu-

ally benefit arboreal species by providing safe

passage away from traffic and other threats on

the ground. However, ideally, canopy bridges

should be installed above the powerlines with

sufficient distance between them to prevent the

electrocution of wildlife.

Alternatively, it could be that the lack of

a difference in use has to do with site-specific

factors. On average, there were more crossings

via the bridges (34 ± 21) than the telephone

cables (12 ± 5). However, there was large

variability in site-specific bridge use with use

ranging from 0-183 crossings at a specific

bridge site. This variability was also observed

in preference between crossing structures at

1145

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

the site level. At five of the observation sites,

wildlife used bridges more than the telephone

cables. While at four of the sites, wildlife used

the telephone cables more than bridges. Future

studies should focus on trying to determine

how use varies depending on site charac-

teristics. Furthermore, how species-specific

preferences affect the frequency of rope bridge

use should also be evaluated in future studies.

For example, Northern tamanduas (Tamandua

mexicana) and common opossums (Didelphis

marsupialis) are the species most frequently hit

by cars in Costa Rica (Monge-Nájera, 2018).

The degree of arboreality varies widely among

Tamandua mexicana, and therefore, to effec-

tively prevent road-related deaths of Northern

tamanduas, terrestrial and arboreal crossing

structures should be installed and monitored

(Brown, 2011).

Other electrocution mitigation methods:

Nevertheless, the fact that our data suggests

that wildlife do not appear to prefer rope bridg-

es over the telephone cables is a noteworthy

finding. If wildlife does not prefer the bridges

over the telephone cables, then rope bridges are

insufficient to prevent wildlife electrocutions

on their own. This suggests that other methods,

aside from installing rope bridges, need to be

employed in order to prevent wildlife electro-

cutions. Unfortunately, according to ICE, the

costs of insulating powerlines are substantial;

it would cost $ 250 to insulate a transformer,

$ 18 462 to insulate a km of secondary electric

wires, $ 21 538-$ 46 154 to insulate a km of

semi-isolated electric wires, and $ 141 129 to

bury a km of electric wires. Therefore, further

studies should focus on assessing the success

and cost-effectiveness of less expensive meth-

ods to prevent electrocutions, such as trimming

branches that touch powerlines while main-

taining natural canopy crossings and installing

structures that successfully deter wildlife from

accessing the electric wires. In Diani, Kenya,

a combination of short-term and long-term

solutions were implemented to prevent wildlife

electrocutions, from trimming trees to relocat-

ing transformers and isolating electric cables,

and despite the expansion of electricity infra-

structure throughout the study period, primate

electrocutions did not increase (Cunneyworth

& Slade, 2021). If less expensive methods do

not prove sufficient or cost-effective in the

long term, covering the wires in locations with

high amounts of electrocutions may be the only

viable permanent solution. There is evidence,

in some localities, that electrocutions occur in

hotspots, meaning that the strategic insulation

of these zones could greatly reduce the number

of electrocutions overall (Katsis et al., 2018;

Ram et al., 2015).

Conclusion: Where electric wires are cov-

ered, telephone cables provide a relatively safe

way for wildlife to cross the roads and navigate

modified habitats. However, in areas where

electric wires are uncovered, rope bridges

should be installed along with other electrocu-

tion mitigation methods, such as insulating the

electric wires, to effectively facilitate the safe

passage of wildlife across roads while prevent-

ing wildlife electrocutions. Further research is

needed to determine the most cost-effective

combination of strategies to mitigate arboreal

wildlife electrocutions while taking into account

the site-specific conditions and species-specific

preferences. Additional studies are also needed

in the Manuel Antonio area to determine the

effect of the rope bridges in maintaining the

genetic diversity of local populations of wild-

life, particularly the endangered grey-crowned

Central American squirrel monkey.

Ethical statement: the authors declare

that they all agree with this publication and

made significant contributions; that there is

no conflict of interest of any kind; and that we

followed all pertinent ethical and legal proce-

dures and requirements. All financial sources

are fully and clearly stated in the acknowled-

gements section. A signed document has been

filed in the journal archives.

1146

Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

ACKNOWLEDGMENTS

First and foremost, we would like to

thank Rocío Pérez for her unyielding support

and incredibly useful knowledge of the rope

bridges and their history. Additionally, we

would like to thank Grupo ICE (specifically

José Ricardo Carvajal Rodríguez) for support-

ing this project by helping to install the camera

traps and maintaining the rope bridges. We

would also like to thank, Kids Saving the

Rainforest, for establishing the Monkey Bridge

Project and for helping to facilitate this project.

We would also like to express our gratitude to

Tremaine Gregory, for helping to troubleshoot

during the installation of the camera traps and

assisting during the launching of the study.

Thank you to Northeastern University for pro-

viding scholarship funding to pay for supplies

and living costs.

RESUMEN

Eficacia de los pasos aéreos sobre carretera:

¿Cruza la fauna más por puentes de cuerda que

por otras estructuras peligrosas?

Introducción: Aunque los pasos de fauna han demostrado

ser exitosos para reducir las colisiones entre vehículos y

vida silvestre y vincular el hábitat fragmentado, su capa-

cidad para prevenir electrocuciones de la vida silvestre

arbórea no se ha examinado a fondo.

Objetivo: Evaluar la efectividad de los puentes aéreos

de cuerdas para restaurar la conectividad del hábitat de

las especies arbóreas en Manuel Antonio, Costa Rica y al

mismo tiempo prevenir las electrocuciones al determinar

1) qué especies están usando los puentes de cuerda y 2) si

la vida silvestre prefiere usar puentes de cuerda en lugar de

otras estructuras peligrosas que cruzan las carreteras (como

cables telefónicos, que frecuentemente están muy cerca de

cables eléctricos).

Métodos: De enero a mayo de 2016, se monitorearon

nueve puentes de cuerda a lo largo de la carretera princi-

pal altamente transitada que se extiende desde Quepos a

Manuel Antonio, Costa Rica, utilizando cámaras trampa y

la observación directa en diez puentes de cuerda a lo largo

de una carretera pavimentada más pequeña fuera de la

carretera principal.

Resultados: Se observaron un total de 11 especies utili-

zando los puentes y se presenciaron 1 540 cruces mediante

cámaras trampa y observaciones (1 234 mediante cámaras

trampa, 306 durante las observaciones). Los resulta-

dos de una prueba t pareada no mostraron diferencias

significativas en el número promedio de individuos que

cruzan la carretera a través de puentes de cuerda versus

cables telefónicos, t (8) = 1.027, P = 0.334.

Conclusiones: Los puentes de cuerdas son utilizados por

una variedad de especies de vida silvestre arbóreas con

un alto grado de frecuencia; sin embargo, debido al uso

igualmente elevado de cables telefónicos por parte de la

vida silvestre arbórea, se considera que son insuficientes

para prevenir las electrocuciones de la vida silvestre por

sí solas. Los puentes de cuerda deben instalarse junto con

otros métodos para evitar electrocuciones, como cables

eléctricos aislados, para facilitar el paso seguro de la vida

silvestre por las carreteras.

Palabras clave: mitigación de electrocuciones; cables tele-

fónicos; impactos antropogénicos; modificación del hábi-

tat; ecología del comportamiento; manejo de vida silvestre;

especies en peligro de extinción; Costa Rica.

REFERENCES

Anderson, S. H., Kelly, D., Ladley, J. J., Molloy, S., &

Terry, J. (2011). Cascading effects of bird functional

extinction reduce pollination and plant density. Scien-

ce, 331(6020), 1068–1071. https://doi.org/10.1126/

science.1199092

Artavia, A. (2015). Identificación y caracterización de

cruces de fauna silvestre en la sección de la amplia-

ción de la carretera nacional Ruta 32, Limón, Costa

Rica (Master’s Thesis). Centro Agronómico Tropi-

cal de Investigación y Enseñanza (CATIE), Costa

Rica. http://repositorio.bibliotecaorton.catie.ac.cr/

handle/11554/7083

Bond, W. J. (1994). Do mutualisms matter? Assessing the

impact of pollinator and disperser disruption on plant

extinction. Philosophical Transactions of The Royal

Society Series B: Biological Sciences, 334(1307),

83–90. https://doi.org/10.1098/rstb.1994.0055

Broadbent, E. N., Asner, G. P., Keller, M., Knapp, D.

E., Oliveira, P. J. C., & Silva, J. N. (2008) Forest

fragmentation and edge effects from deforestation

and selective logging in the Brazilian Amazon. Bio-

logical Conservation, 141(7), 1745–1757. https://doi.

org/10.1016/j.biocon.2008.04.024

Broadbent, E. N., Almeyda Zambrano, A. M., Dirzo, R.,

Durham, W. H., Driscoll, L., Gallagher, P., Salters,

R., Schultz, J., Colmenares, A., & Randolph, S.

G. (2012). The effect of land use change and eco-

tourism on biodiversity: a case study of Manuel

Antonio, Costa Rica, from 1985 to 2008. Landscape

Ecology, 27(5), 731–744. https://doi.org/10.1007/

s10980-012-9722-7

Brown, D. D. (2011). Activity patterns and space use of

northern tamandua anteaters (Tamandua mexica-

na) on Barro Colorado Island, Panamá (Doctoral

Dissertation). University of California Davis, USA.

1147

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

https://www.semanticscholar.org/paper/Activity-

Patterns-and-Space-Use-of-Northern-on-Brown/

c8a33690a2385ff978b81d67c4dfd9b69c296e8a

Caceres, N. C. (2011). Biological characteristics influen-

ce mammal road kill in an Atlantic Forest-Cerrado

interface in south-western Brazil. Italian Journal of

Zoology, 78(3), 379–389. https://doi.org/10.1080/112

50003.2011.566226

Chape, S., Harrison, J., Spalding, M., & Lysenko, I. (2005).

Measuring the extent and effectiveness of protected

areas as an indicator for meeting global biodiversity

targets. Philosophical Transactions of The Royal

Society Series B: Biological Sciences, 360(1454),

443–455. https://doi.org/10.1098/rstb.2004.1592

Chapman, C. A., & Russo, S. E. (2005). Primate Seed

Dispersal: Linking Behavioral Ecology with Forest

Community Structure. In C. J. Campbell, A. F.

Fuentes, K. C. MacKinnon, M. Panger, & S. Bear-

der (Eds.), Primates in Perspective (pp. 510–525).

Oxford University Press.

Coffin, A. W. (2007). From roadkill to road ecology: A

review of the ecological effects of roads. Journal of

Transport Geography, 15(5), 396–406. https://doi.

org/10.1016/j.jtrangeo.2006.11.006

Cordeiro, N. J., & Howe, H. F. (2003). Forest fragmenta-

tion severs mutualism between seed dispersers and

an endemic African tree. Proceedings of the National

Academy of Sciences, 100(24), 14052–14056. https://

doi.org/10.1073/pnas.2331023100

Cunneyworth, P. M. K., & Slade, A. M. (2021). Impact

of Electric Shock and Electrocution on Popula-

tions of Four Monkey Species in the Suburban

Town of Diani, Kenya. International Journal of

Primatology, 42, 171–186. https://doi.org/10.1007/

s10764-020-00194-z

Dodd, C. K., Barichivich, W. J., & Smith, L. L. (2004).

Effectiveness of a barrier wall and culverts in redu-

cing wildlife mortality on a heavily traveled highway

in Florida. Biological Conservation, 118(5), 619–631.

https://doi.org/10.1016/j.biocon.2003.10.011

Forman, R. T. T., Sperling, D., Bissonette, J. A., Clevenger,

A. P., Cutshall, C. D., Dale, V. H., Fahrig, L., France,

R. L., Goldman, C. R., Heanue, K., Jones, J., Swan-

son, F., Turrentine, T., & Winter, T. C. (2003). Road

Ecology: Science and Solutions. Island Press.

Glista, D. J., DeVault, T. L., & DeWoody, J. A. (2009).

A review of mitigation measures for reducing wild-

life mortality on roadways. Landscape and Urban

Planning, 91(1), 1–7. https://doi.org/10.1016/j.

landurbplan.2008.11.001

Gregory, T., Rueda, F. C., Deichmann, J., Kolowski, J.,

& Alonso, A. (2014). Arboreal camera trapping:

taking a proven method to new heights. Methods in

Ecology and Evolution, 5(5), 443–451. https://doi.

org/10.1111/2041-210X.12177

Haddad, N. M., Brudvig, L. A., Clobert, J., Davies, K. F.,

Gonzalez, A., Holt, R. D., Lovejoy, T. E., Sexton,

J. O., Austin, M. P., Collins, C. D., Cook, W. M.,

Damschen, E. I., Ewers, R. M., Foster, B. L., Jenkins,

C. N., King, A. J., Laurance, W. F., Levey, D. J.,

Margules, C. R., …Townshend, J. R. (2015). Habi-

tat fragmentation and its lasting impact on Earth’s

ecosystems. Science Advances, 1(2), 1–9. https://doi.

org/10.1126/sciadv.1500052

Katsis, L., Cunneyworth, P. M. K., Turner, K. M. E., &

Presotto, A. (2018). Spatial Patterns of Primate Elec-

trocutions in Diani, Kenya. International Journal of

Primatology, 39, 493–510. https://doi.org/10.1007/

s10764-018-0046-6

Kumar, V., & Kumar, V. (2015). Seasonal electrocution

fatalities in free-range rhesus macaques (Macaca

mulatta) of Shivalik hills area in northern India. Jour-

nal of Medical Primatology, 44(3), 137–142. https://

doi.org/10.1111/jmp.12168

Larsen, T. H., Williams, N. M., & Kremen, C. (2005).

Extinction order and altered community struc-

ture rapidly disrupt ecosystem functioning.

Ecology Letters, 8(5), 538–547. https://doi.

org/10.1111/j.1461-0248.2005.00749.x

Laurance, W. F., Goosem, M., & Laurance, S. G. (2009).

Impacts of roads and linear clearings on tropical

forests. Trends in Ecology and Evolution, 24(12),

659–669. https://doi.org/10.1016/j.tree.2009.06.009

Lindshield, S. M. (2016). Protecting nonhuman prima-

tes in peri-urban environments: A case study of

neotropical monkeys, corridor ecology, and coastal

economy in the Caribe Sur of Costa Rica. In M.

T. Waller (Ed.), Ethnoprimatology: Primate Con-

servation in the 21st Century (Developments in

Primatology: Progress and Prospects) (pp. 351–

369). Springer International Publishing. https://doi.

org/10.1007/978-3-319-30469-4

Lokschin, L. X., Printes, R. C., Cabral, J. N., & Buss,

G. (2007). Power lines and howler monkey conser-

vation in Porto Alegre, Rio Grande Do Sul, Bra-

zil. Neotropical Primates, 14(2), 76–80. https://doi.

org/10.1896/044.014.0206

Memmott, J., Waser, N. M., & Price, M. V. (2004). Tole-

rance of pollination networks to species. Proceedings

of the Royal Society Series B: Biological Scien-

ces, 271(1557), 2605–2611. https://doi.org/10.1098/

rspb.2004.2909

Monge-Nájera, J. (2018). Road kills in tropical ecosystems:

a review with recommendations for mitigation and

for new research. Revista de Biología Tropical, 66(2),

722–738. https://doi.org/10.15517/RBT.V66I2.33404

1148

Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(3): 1138-1148, July-September 2021 (Published Sep. 30, 2021)

Moore, R. S., Nekaris, K. A. I., & Eschmann, C. (2010).

Habitat use by western purple-faced langurs Trachy-

pithecus vetulus nestor (Colobinae) in a fragmented

suburban landscape. Endangered Species Research,

12(3), 227–234. https://doi.org/10.3354/esr00307

Ram, C., Sharma, G., & Rajpurohit, L. S. (2015). Morta-

lity and threats to Hanuman langurs Semnopithecus

entellus entellus in and around Jodhpur (Rajasthan).

Indian Forester, 141(10), 1042–1045.

Rodrigues, N. N., & Martinez, R. A. (2014). Wildlife in

our backyard: interactions between Wied’s marmoset

Callithrix kuhlii (Primates: Callithrichidae) and resi-

dents of Ilhéus, Bahia, Brazil. Wildlife Biology, 20(2),

91–96. https://doi.org/10.2981/wlb.13057

Rybicki, J., & Hanski, I. (2013). Species-area relationships

and extinctions caused by habitat loss and fragmen-

tation. Ecology Letters, 16(1), 27–38. https://doi.

org/10.1111/ele.12065

Saavedra-Rodríguez, C. A., Lizcano, A., & Corrales, J.

D. (2013). Incidentes de fauna silvestre en líneas de

energía en zona rural del Valle del Cauca, Colom-

bia. Revista Biodiversidad Neotropical, 3(2), 85–89.

https://doi.org/10.18636/bioneotropical.v3i2.102.g95

Spellerberg, I. F. (1998). Ecological effects of roads and

traffic: a literature review. Global Ecology and

Biogeography Letters, 7(5), 317–333. https://doi.

org/10.1046/j.1466-822x.1998.00308.x

Teixeira, F. Z., Printes, R. C., Fagundes, J. C. G., Alonso,

A. C., & Kindel, A. (2013). Canopy bridges as road

overpasses for wildlife in urban fragmented landsca-

pes. Biota Neotropica, 13(1), 117–123. https://doi.

org/10.1590/S1676-06032013000100013

Turner, I. M. (1996). Species loss in fragments of tro-

pical rain forest: a review of the evidence. Jour-

nal of Applied Ecology, 33(2), 200–209. https://doi.

org/10.2307/2404743

van der Ree, R., Jaeger, J. A., van der Grift, E. A., & Cle-

venger, A. P. (2011). Effects of roads and traffic on

wildlife populations and landscape function: Road

ecology is moving toward larger scales. Ecology

and Society, 16(1), 48–58. https://doi.org/10.5751/

ES-03982-160148

Van Wieren, S. E., & Worm, P. B. (2001). The use of

a motorway wildlife overpass by large mammals.

Netherlands Journal of Zoology, 51(1), 97–105.

https://doi.org/10.1163/156854201X00071

Weston, N., & Goosem, M. (2011). Using canopy bridges

to link habitat for arboreal mammals: successful

trials in the wet tropics of Queensland. Australian

Mammology, 33(1), 93–105. https://doi.org/10.1071/

AM11003

Yokochi, K., & Bencini, R. (2015). A remarkably quick

habituation and high use of a rope bridge by an

endangered marsupial, the western ringtail pos-

sum. Nature Conservation, 11, 79–94. https://doi.

org/10.3897/natureconservation.11.4385