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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(Suppl. 2): S297-S303, October 2021 (Published Oct. 30, 2021)

The yellow-bellied sea snake, Hydrophis platurus (Squamata: Elapidae),

off the Southwestern Pacific coast of Nicaragua, Central America

Joëlle De Weerdt1,2; https://orcid.org/0000-0003-4054-6609

Carla Patulny1; https://orcid.org/0000-0001-7232-3341

Phillip Clapham3; https://orcid.org/0000-0002-2776-5746

1. Association ELI-S, 39 Allée de Verdalle, 33470 Gujan-Mestras, France; eliscientific@gmail.com

2. Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium

3. Seastar Scientific, 27605 Hake Road SW, Vashon WA 98070, USA; phillip.clapham@gmail.com

Received 12-XI-2020. Corrected 30-I-2021. Accepted 28-II-2021.

ABSTRACT

Introduction: The yellow-bellied sea snake (Hydrophis platurus, formerly Pelamis platurus) is known to occur

along the Pacific coast of Central America. However, there are no marine records of this species off the coast

of Nicaragua.

Objective: Report the first in situ marine observations of the yellow-bellied sea snake observed on three occa-

sions in 2020 during cetacean surveys off the southwestern Pacific coast of Nicaragua.

Methods: During the sightings, photographs were taken which allowed the identification of the species based

on morphology. Sea surface temperature, sea state, and distance to the coast are presented as descriptors of the

habitat of the records.

Results: Three field observations of yellow-bellied sea snakes were recorded on separate occasions. Sightings

occurred within 30 km of each other and 3.3 km from the coast. Average sea surface temperature was 26.6 °C

with low swell and sea state.

Conclusions: The present information offers new knowledge about the presence of the yellow-bellied sea snake

on the Pacific coast of Central America, contributing to the biodiversity record in Nicaragua.

Key words: Pelamis platurus; sea snakes; reptiles; Eastern Tropical Pacific; San Juan del Sur; distribution.

De Weerdt, J., Patulny, C., & Clapham, P. (2021). The yellow-

bellied sea snake, Hydrophis platurus (Squamata:

Elapidae), off the Southwestern Pacific coast of Nicaragua,

Central America. Revista de Biología Tropical, 69(Suppl.

2), S297-S303. https://doi.org/10.15517/rbt.v69iS2.48324

https://doi.org/10.15517/rbt.v69iS2.48324

Marine reptiles such as sea snakes play an

important trophic role in marine ecosystems

(Brischoux & Lillywhite, 2013; Voris, 1972)

and their distribution encompasses mainly

tropical waters (Tu, 1988). The yellow-bellied

sea snake, Hydrophis platurus (previously:

Pelamis platurus), is the most widely distrib-

uted hydrophiid snake in the world (Hernán-

dez-Camacho et al., 2005; Lomonte et al.,

2014; Quiñones et al., 2014) and is the only

pelagic species (Brischoux & Lillywhite, 2011;

Heatwole, 1999; Sheehy et al., 2012). The

presence of this species has been confirmed in

the Eastern Tropical Pacific, from the coasts

of Mexico to northern Peru (Brischoux & Lil-

lywhite, 2011; Graham, Rubinoff, & Hecht,

1971; Quiñones et al., 2014).

The movement patterns of H. platurus

remain largely unknown. Marine currents (Kro-

pach, 1971) and sea surface temperature (SST)

(Quiñones et al., 2014) are environmental

parameters related to their distribution patterns,

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with ocean currents playing an important role

in the the movement of H. platurus (Brichoux

et al., 2016). Slicks are formed when surface

currents converge and snakes passively drift

within these slicks (Kropach, 1971). The abun-

dance of snakes on a slick can be influenced

by the quantity of flotsam found within the

slick (Brischoux & Lillywhite, 2011). The

yellow-bellied sea snake is a ‘passive surface

drifter’ and is often transported by currents to

locations where it is not considered resident

(Dunson & Ehlert, 1971).

As an ectotherm, sea surface temperature

(SST) limits the species’ distribution to a mini-

mum of 18 °C, since locomotor abilities and

feeding are inhibited or cease at lower SSTs

(Heatwole, Grech, Monahan, King, & Marsh,

2012); and to a maximum of 33 °C (Dunson

& Ehlert, 1971). These SST ranges prevent the

species from colonising regions such as the

Atlantic Ocean ( Lillywhite et al., 2018; Quiño-

nes et al., 2014) and the Pacific coast of South

America, where strong upwelling of cold water

limits their distribution (Dunson & Ehlert,

1971). Waters off Central America represent

optimal thermal conditions for the yellow-

bellied sea snake, since mean monthly tem-

peratures of > 25 °C are the minimum required

for feeding (Hecht, Kropach, & Hecht, 1974).

Although H. platurus has a natural preference

for offshore waters, the species has been also

recorded in shallow coastal waters (Heatwole,

1999; Hecht et al., 1974). Its dependence on

freshwater to avoid water deficits due to dehy-

dration during dry season may explain their

coastal distribution in Costa Rica (Lillywhite et

al., 2010), but its still controversed (Lillywhite

et al., 2014; Lillywhite et al., 2019).

Daylight is a determining factor in the

surfacing behavior of H. platurus; it shows a

preference for high light levels (Brischoux &

Lillywhite, 2011) and is not often observed at

the sea surface at night (Brischoux & Lilly-

white, 2011); however the latter needs further

investigation due to a lack of samples. In Cen-

tral America, H. platurus has been reported in

the Gulf of Fonseca, Honduras (McCranie &

Gutsche, 2016; Solis et al., 2014), the Pacific

coast of Costa Rica (Bolaños et al., 1974; Tu,

1976; Tu & Salafranca, 1974), the Pacific coast

of El Salvador (Hidalgo, 1980) and the Gulf of

Panama (Guinea et al., 2017; Kropach, 1971;

Vallarino & Weldon, 1996). Yellow-bellied sea

snakes have been frequently reported in the

Pacific coast of Nicaragua between the Gulf

of Fonseca (Chinandega) and San Juan del Sur

(Rivas) (HerpetoNica, 2015), however, obser-

vations are limited to beach strandings and no

data is available on the marine occurrence of

this species. To date, no marine records have

been published on the presence of the yellow-

bellied sea snake in Nicaragua. Here, we report,

for the first time, the presence of H. platurus in

the southwestern Pacific waters of Nicaragua,

offering additional insights into distribution

and behavioral patterns of this marine snake in

the Eastern Tropical Pacific.

MATERIALS AND METHODS

Data were gathered during systemat-

ic boat-based surveys from January to mid-

March 2020. Surveys were conducted using

a 6 m length fiberglass boat, between 0800

and 1700 h daily. When the yellow-bellied sea

snake was found, the following data were col-

lected: date, time, Global Positioning System

location, sea surface temperature (SST, Hecht

thermometer), sea state (using the Beaufort

scale), and swell categorized as either Low (L),

less than one meter; Medium (M) 1-2 m; and

High (H) more than two meters (Table 1). Pho-

tographs were taken using a DSLR camera with

a 55-300 mm lens, and were used for specimen

identification based upon standard morphologi-

cal characteristics (see below). Maps indicating

sighting locations were generated with ArcGIS.

Distance from the nearest point on the coast

was measured for each sighting location using

the line tool in ArcGIS.

RESULTS

Three field observations of yellow-bellied

sea snakes were made on 28 and 29 January

2020 (photographed) and 04 March 2020 (pho-

tographed) (Fig. 1). Based on photographic

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TABLE 1

Overview of field records of the yellow-bellied sea snake (Hydrophis platurus) off the South-West Pacific coast

of Nicaragua, including sighting date and time, latitude and longitude, SST, Beaufort scale and swell,

and distance from the coast

Date Time Latitude Longitude SST

(°C) Picture Sex Beaufort Swell Distance from

coast (km)

28 Jan 2020 12:04 11°7’21.698” N 85°50’29.198” W 27 No Uk 1 L 4.6

29 Jan 2020 16:24 11°18’39.802” N 85°58’54.199” W 28 Fig. 1a Uk 1 L 3.8

04 Mar 2020 16:05 11°20’30.699” N 85°00’27.698” W 25 Fig. 1b Uk 4 L 1.4

SST = Sea Surface Temperature, Uk = unknown.

Fig. 1. Location of the yellow-bellied sea snake (Hydrophis platurus) observations with reference to the date of observation,

south Pacific of Nicaragua.

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observations, the following morphological fea-

tures confirmed the identification of the spe-

cies: 1) Black dorsal side extending from the

head to the tail with variations in the dorsal

band pattern; 2) Yellow ventral side extending

from the head to the tail; 3) Dark spots on the

tail; 4) Paddle-shaped tail. Both photographed

individuals were bi-colored and displayed two

distinct color patterns (Fig. 2). Sex and size

could not be inferred or measured from the

photographs. On the three occasions, the yel-

low-bellied sea snake was swimming alone

at the surface and moved southwards. Each

individual dived after traveling at the surface

for a few minutes. Sightings occurred in a

range of 30 km from each other and 3.3 km

from the coast. The average SST was 26.6 °C

(± 1.25 SD, N = 3) (Table 1). Swell was low on

all occasions and the Beaufort sea state ranged

between 1 and 4 (Table 1).

DISCUSSION

Our observations confirm the presence of

yellow-bellied sea snakes in shallow coastal

waters off the southwestern coast of Nicara-

gua. Extensive variation in color patterns of

this species has been documented, with almost

completely black and entirely yellow speci-

mens represented at each end of the spectrum

Fig. 2. Morphological features for identification of the yellow-bellied sea snake include: 1) Black dorsal side 2) yellow

ventral side 3) Dark tail spots 4) Paddle-shaped tail. A) Individual photographed on 29 January 2020 with a partially straight

dorsal band; B) Individual photographed on 04 March 2020 with a straight dorsal band with the exception of subcaudal

portion. Color pattern as described by Tu (1976).

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(Solórzano, 2011). In addition, the patterns

of the black dorsal band vary from straight to

completely curved, and spots may be complete-

ly absent (Tu, 1976). All three of our sighted

individuals were bi-colored, as also observed

in other Central American regions (Hidalgo,

1980; Tu, 1976).

The bi-color pattern is commonly observed

in juvenile yellow-bellied sea snakes, which

develop the tri-color pattern during ontogeny

(Tu & Salafranca, 1974). The observation made

on the 28 January 2020 (Fig. 2A) displayed a

saw-edged dorsal band which matches speci-

mens found in El Salvador and Costa Rica

(Hidalgo, 1980; Tu, 1976), while the observa-

tion made on the 04 March 2020 (Fig. 2B) did

not display the dorsal pattern which is consis-

tent with juvenile descriptions of specimens

found in Costa Rica (Tu, 1976).

The mean measured SST of 26.6 °C falls

within the range of optimal feeding temperatures

(Hecht et al., 1974). Although our observations

of solitary snakes were made in such condi-

tions, the snakes were probably not involved in

feeding behaviors, due to the absence of slicks

with which they tend to associate for feeding

(Dunson & Ehlert, 1971; Kropach, 1971). The

observation of solitary snakes not associated

with slicks is commonly observed in Panama

(Kropach, 1971) and Costa Rica (Brischoux &

Lillywhite, 2011).

Our sightings of yellow-bellied sea snakes

occurred within 5 km of the coast which

coincides with other records in neighboring

countries (Solòrzano, 2004; Tu, 1976). The

underlying factors for the coastal occurrence of

this offshore species remains largely unclear,

even if it was suggested that their reliance on

freshwater could be responsible for the coastal

distribution (Lillywhite et al., 2010) recent

studies did not support this hypothesis (Lil-

lywhite, 2019). All our field observations were

made in the afternoon, which contrasts with

findings in the Papagayo Gulf, Costa Rica,

where snakes were not observed in the after-

noon (Tu, 1976).

Even though yellow-bellied sea snakes

are frequently reported on the beaches of

San Juan del Sur and surrounds, no previous

report on their marine distribution has been

made. The present paper presents, to the best

of our knowledge, the first marine report of

this species in the Pacific waters of Nicaragua.

The presence of non-feeding, lone, bi-colored

individuals in coastal areas can help research-

ers understand the ecology and movement pat-

terns of the species off Central America in the

Eastern Tropical Pacific. Additional research is

needed to understand the correlation between

environmental parameters, such as oceanic

currents, and the distribution patterns of the

yellow-bellied sea snake in Nicaragua.

Ethical statement: authors declare that

they all agree with this publication and made

significant contributions; that there is no con-

flict of interest of any kind; and that we fol-

lowed all pertinent ethical and legal procedures

and requirements. All financial sources are

fully and clearly stated in the acknowledge-

ments section. A signed document has been

filed in the journal archives.

ACKNOWLEDGMENTS

Special thanks to the research team that

helped us gather information in the field:

Sylvain Porrot, Audrey Mazza, Theresa Scha-

backer, Maëline Caradec, Galanne Cestre,

Flordespina Dodds, Pierre Vachaudez, Aurèle

de Thibault, and to Brock Boven for the pro-

duction of the map.

RESUMEN

Observaciones de la serpiente marina

Hydrophis platurus (Squamata: Elapidae) en

el Pacífico sur de Nicaragua, América Central

Introducción: La serpiente marina de vientre amarillo

(Hydrophis platurus, anteriormente Pelamis platurus) se

encuentra distribuida a lo largo de la costa del Pacífico de

América Central. Sin embargo, no existe registros in situ

sobre esta especie en la costa del Pacífico de Nicaragua.

Objetivo: Reportar las primeras observaciones in situ de

la serpiente marina de vientre amarillo en tres ocasiones

durante el 2020 frente a la costa suroeste del Pacífico

de Nicaragua.

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Métodos: Los registros se realizaron de manera oportunis-

ta durante avistamientos de cetáceos en la zona. Las ser-

pientes marinas fueron fotografiadas para su identificación

a nivel de especie en base a su morfología. Durante cada

avistamiento se registró la temperatura de la superficie

del mar, el estado del mar y la distancia a la costa como

descriptores del hábitat.

Resultados: Se registraron tres serpientes marinas de

vientre amarillo en distintas ocasiones. Los avistamientos

ocurrieron a menos de 30 km entre sí y a 3.3 km de la costa.

La temperatura media de la superficie del mar fue de 26.6°

C con oleaje y estado de la mar bajos.

Conclusiones: El presente estudio brinda nuevo cono-

cimiento sobre la distribución de la serpiente de vientre

amarillo en la costa del Pacífico de Centroamérica, contri-

buyendo al registro de biodiversidad en Nicaragua.

Palabras clave: Pelamis platurus; serpientes marinas;

reptiles; Pacífico Tropical Oriental; San Juan del Sur;

distribución.

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