804 E. Flatt et al.


TABLE 1 Summary of all domestic and wild animal species detected by camera traps at five bridges monitored by camera traps in Osa Peninsula, Costa Rica (Fig. 1).


Bridge RCT1


Domestic species


RCT2 Dog RCT7


RCT9 Dog


RCT15 Dog, cattle, horse


Mammal species


Northern raccoon Procyon lotor pumilus


Northern raccoon Northern raccoon


Northern raccoon, White-nosed coati Nasua narica


Bird species


Bare-throated tiger heron Tigrisoma mexicanum, great-tailed grackle Quiscalus mexicanus


Black vulture Coragyps atratus, great-tailed grackle


Little blue heron Egretta caerulea


Bare-throated tiger heron, great-tailed grackle, little blue heron, snowy egret Egretta thula, white ibis Eudocimus albus


Bare-throated tiger heron, black vulture, cattle egret Bubulcus ibis, great-tailed grackle, grey-necked wood-rail Aramides cajaneus


to record 13 s videos, with 30 s resting periods) underneath 17 bridges along two paved highways in the Osa Peninsula for 4 months (February–May 2019) during the dry season, before the heavy rains caused the rivers to rise, which can make the underpasses inaccessible to people and wild- life (Fig. 1). The rivers were 13.5–21.6 m wide and bridge heights 4.95–7.54 m. We installed locks and informative signs on all camera traps to reduce the potential for theft (Plate 1). Of the 17 camera traps, five obtained data, 11 were stolen


and one broke, probably because of humidity or an electrical fault. The five working camera traps accumulated a total of 167 trap-nights (open habitat caused a high number of false triggers by quick-growing vegetation, and exposure to high temperatures and heavy rain resulted in short battery life). The camera traps detected two wild mammal species, eight bird species, one reptile species, three domestic species and people (Table 1). The two wild mammal species were habitat-generalist omnivores: the northern raccoon Procyon lotor pumilus and the white-nosed coati Nasua narica. The northern raccoon was detected under four of the bridges and was observed moving through these struc- tures and foraging. The white-nosed coati was detected moving beneath just one of the bridges. Dogs were detected at three bridges, horses and cattle at one bridge and human activity (passing through and socializing) was detected at all five bridges from which we retrieved data. We detected only two of the 23 wild terrestrial mammal


species recorded in the region. This was surprising for two reasons: firstly, we conducted the study during the dry sea- son, which is when the rivers are at their lowest, facilitating wildlife movements, and secondly, a similar study in the Guanacaste region of Costa Rica detected 14 mammal spe- cies using six drainage culverts (Monge-Velázquez & Saenz, 2022). Furthermore, the culverts in the Guanacaste region, just like the potential multiple-use structures surveyed in our study, were not built specifically for wildlife use, with no techniques being adopted to encourage wildlife


movements (Monge-Velázquez &Saenz, 2022). The reasons for the low number of species detected in our study could be the surrounding land uses (cattle farming, agriculture and small towns) and the fact that the bridges are not established wildlife crossings. It is possible that species might risk crossing the roads in preference to using underpasses. Strategically placed fencing or tree planting, which are pro- ven techniques for funnelling wildlife (Littlewood et al., 2020), could help promote wildlife use of these underpasses. However, the principal reason for the low number of species detected is the limited number of cameras and trap-nights because of the theft of 65% of the camera traps. Theft was significant despite the installation of security


cases, locks and signs. Even with these security measures, this study resulted in a financial loss of USD 2,970 (the total material cost of the study was USD 4,590,withUSD 1,020 of this invested specifically in theft protection). There was also a cost in terms of the missed opportunity to contribute knowl- edge on wildlife movement and to use this to improve under- passes to facilitate their use by wildlife. To reduce camera-trap theft, some studies have installed camera traps at greater heights than usual, to avoid their detection by people, but this has resulted in a dramatic decrease in wildlife detections (Meek et al., 2016). Studies that focus on nocturnal species have collected the deployed camera traps each day to limit their theft (Athreya et al., 2013), but this is not a suitable or sustainable solution for large-scale studies assessing multiple species. However, a security post for camera traps, installed in a bollard-style housing to limit theft, has been developed and is proving successful (Meek et al., 2022). Perhaps the best potential solution to combat camera-trap theft is the de- velopmentofsmall andcryptic camera traps thatcan evade detection by people but still detect wildlife. Conservation or- ganizations are making advances in camera-trap technology to develop improved camera traps (Meek & Pittet, 2012), but there is still work to be done tomake these solutions accessible and scalable (Curnick et al., 2022; Westworth et al., 2022). These improvements will limit resource losses and fill data


Oryx, 2024, 58(6), 802–805 © The Author(s), 2025. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000097


Green iguana Iguana iguana


Reptile species


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