DOI: 10.5061/dryad.z8w9ghxbd
title: Peaceful coexistence between people and deadly wildlife: why are recreational users of the ocean so rarely bitten by sea snakes?

description: 1) Research on interactions between humans and deadly snakes has
 focused on situations that result in high rates of snakebite; but we can
 also learn from cases where snakes and people coexist peacefully. For
 example, coastal bays near Noumea, in the Pacific archipelago of New
 Caledonia, are used by thousands of tourists and snakes, but bites are
 rare. 2) Our long-term studies clarify reasons for this coexistence.
 Although 97% of snakes encountered in standardized snorkel surveys were a
 harmless species (Emydocephalus annulatus), we recorded dangerously
 venomous taxa often enough (one snake per eight hours snorkelling) that we
 would expect many risky human- snake interactions in these crowded bays.
 However, the risk is reduced by low overlap between humans and snakes in
 the timing of activity, both seasonally and on the diel cycle.
 Mate-searching male snakes, the group most likely to approach divers,
 enter the bays only in cooler months of the year when few beach users are
 present. Also, snakes tend to be active by night whereas people are not.
 3) Risk is further reduced by spatial divergence: bare-footed beach users
 stay in sandy areas rather than the adjacent coral-reef areas that are
 preferred by snakes. The response of snakes to disturbance is important
 also: most sea snakes are reluctant to bite even when harassed. Water
 currents frequently push sea snakes against hard objects, perhaps
 explaining why the snakes do not interpret brief contact with a human as
 an attack. The ability of snakes to flee is increased by uniformly high
 body temperature, and a complex three-dimensional aquatic environment. 4)
 Thus, the danger of snakebite for recreational users of these popular
 beaches is reduced by aspects of human and snake behaviour that (i)
 decrease encounter rates, and (ii) render snakes unlikely to bite even if
 contacted. The risk to snakes is also reduced, because snakes are more
 difficult to detect and kill underwater than on land. As a result,
 thousands of snakes and people coexist harmoniously within these
 small bays.
description: This repository has two sets of
 data:  1) Beach survey data of usage and behaviour of
 beachgoers at two tourist beaches in Noumea, New Caledonia
 On five days in January 2019, four days in October 2019, and four
 days in January 2020 we walked along the beachfront of both bays at hourly
 intervals (daylight hours only during good weather) to record numbers of
 people in areas where the substrate was dominated by sand versus by
 fringing coral reef. These months represented seasonal periods where we
 expect high human-snake interactions, when numbers of recreational users
 are high (December-February) and when snake movements are at their peak
 during the winter mating season (August-October). The numbers of people in
 each ~200 m section of that transect were scored, as were their locations
 (in water vs on the beach), and on some surveys we also estimated age
 groups (children &lt; ~10 years old, vs older people) and clothing
 (barefoot or not) as a function of activity (walking, swimming,
 snorkelling, etc.) and substrate type (sand vs coral). Our surveys
 encompassed the entire diel period of human use of the water, with no
 people recorded in the water at night during occasional nocturnal surveys
 on foot (as above) nor during 24 nocturnal observations (hourly, 1800 h to
 0600 h over two nights) from a hotel balcony overlooking one of the
 bay (to verify absence of people in the water). 2)
 Acoustic telemetry data from telemetered sea snakes monitored within two
 bays in Noumea, New Caledonia We hand-captured
 4 <em>Aipysurus duboisii</em>, 2 <em>A.
 laevis</em> and 16 <em>Hydrophis major</em> in the Baie
 des Citrons and Anse Vata in January and October 2017, and a qualified
 veterinarian surgically implanted acoustic transmitters (V9P-2H; Vemco
 Ltd., Bedford, Nova Scotia) into the snakes under gaseous anesthesia.
 Transmitters weighed &lt;1% (mean ± SE; 0.65 ± 0.17%) of snake body
 mass and were neutrally buoyant; snake behavior and locomotor ability were
 assessed during a 24-hour post-surgery recovery period and appeared to be
 unaffected by the implantation. The animals were released at their sites
 of capture the day after surgery, and their movements over the following
 349 days were monitored with an array of 18 acoustic receivers that
 recorded detections of individuals when they were within detection range
 of each receiver. The detection range of receivers within the array was
 tested by comparing the expected and observed number of detections from
 range-testing tags placed at multiple locations within the array over a
 period of 1 week at the start of the study, and was measured to be on
 average 150 m. Receiver stations were arranged ~300 m apart through
 relatively shallow (&lt;3 m depth) areas of the two bays, with all
 receivers remaining fully submerged and active across the full tidal range
 within the study site. We also obtained hourly data on tidal height (data
 from Service Hydrographique de la Marine Nationale) from which change in
 tidal height (henceforth hourly tidal range) and direction of flow (i.e.,
 rising vs. falling tide) was calculated for each 60-minute observation
 period coinciding with movement records of telemetered snakes.
description: Beach survey dataset is an excel spreadsheet with two worksheets
 a) Number of beach users; and b) beach users habits.
 Acoustic telemetry data is in a R data object in the .RDS format
 that can be opened and accessed in the R statistical environemnt. The R
 object contained within is an ATT object to be used with the Animal
 Tracking Toolbox in the VTrack packge
 (https://github.com/rossdwyer/VTrack). The ATT object is a list object
 containing three components a) Raw tag detection data from the acoustic
 array in Noumea, b) tag metadata from animals tracked in this study, and
 c) receiver array metadata for the array used to monitor the telemetered
 snakes. See the following vignette on how movement metrics and activity
 space metrics can be obtained using this ATT
 object: https://vinayudyawer.github.io/ATT/docs/ATT_Vignette.html