Epimeletic behaviour in free-ranging rough-toothed dolphins
(Steno bredanensis) in the Canary Islands
BE-03
Yzoard, Chloe 1,2 ; Gil, Marcel³; Aguilar de Soto, Natacha 4
Chloe Yzoard
[email protected]
¹ Dpto. Biología Animal, Edafología y Geología, Universidad de la Laguna, Canary Islands, Spain. Grupo de Investigación de Cetáceos, Canary Islands, Spain
² GIC Grupo de Investigación de Cetáceos, Canary Islands, Spain
³ Cory´s, Barcelona, Spain
4 Instituto Español de Oceanografía, Canary Islands, Spain
BACKGROUND
Epimeletic behaviour refers to altruistic and care-giving actions exhibited by a healthy
individual toward a distressed, injured, or dead conspecific (Scott, 1958). This behaviour is
considered nurturing when directed toward a juvenile but can also be displayed toward
adults or even individuals of different species. It has been observed both in the wild and in
captivity in at least 21 cetacean species. Associated behavioural patterns include standingby, carrying, pushing, and supporting the corpse.
Here, we describe a case of epimeletic behaviour by rough-toothed dolphins (Steno
bredanensis) toward a dead adult of the same species, observed off El Hierro, Canary
Islands (Spain. The recording of this behaviour is valuable for understanding this poorly
known and understudied oceanic delphinid species. It provides insight into the complex
social behaviours of highly mobile top marine predators.
a
(Photo Marcel Gil/ULL)
c
b
METHODOLOGY
Fig. 1 Study area in El Mar de las Calmas
and Mar de Las Playas in El Hierro, Canary
Islands.
Fig. 2 Rough-toothed behavioural patterns observed in the presence of a dead adult conspecific. a. Group
surfacing next to the carcass; b. Individual surfacing by the carcass, c. Physical contact of rostrum with the carcass;
d. Push from behind by one individual, e. Spy-hopping, f. Lateral push, g. Righting of the body with an impulse; h.
and i. Interaction with a yellow-legged sea gull Larus michaellis
In 2013, researchers from the University of
La Laguna conducted four seasonal
scientific surveys as part of a long-term
cetacean monitoring program focused on
beaked whales in El Hierro, Canary Islands
(Fig.1). A total of 45 days of land and sea
based survey effort gathered 906 sightings
of eight odontocete and one mysticete
species. For each land-based sighting, data
on date, time, location, species, group size,
composition, and behaviour were recorded
using Logtool (MATLAB). During boat-based
surveys, photographs and videos were
collected using digital single-lens reflex
cameras for photo-identification and
behavioural analysis.
The winter survey was conducted from the 3rd to the 16th of February 2013, off El Hierro.
Sea and weather conditions allowed 9 days of effort with 186 sightings of 6 species:
Ziphius cavirostris, Physeter macrocephalus, Globicephala macrorhynchus, Tursiops
truncatus, Stenella frontalis and Steno bredanensis
(Photo Patricia Montagas/ULL)
(Photo Patricia Montagas/ULL)
d
e
(Photo Marcel Gil/ULL)
(Photo Patricia Montagas/ULL)
g
f
RESULTS
During the winter survey in February 2013, 7 sightings of free-ranging rough-toothed
dolphins Steno bredanensis were recorded. Groups were encountered from the boatbased platform on the 7th, 9th, 13th , 14th, 15th and 16th. Group size varied from 5 to 25
individuals (median: 15). On February 9th, a small group of 5-10 individuals was
observed SW off the island (27.688.958, -18.094.261). The group included a deceased
individual floating laterally at the surface exhibiting signs of moderate decomposition
(Díaz-Delgado, 2015). The animal displayed an open mouth and second-degree
autolysis characterized by circular red patches of skin with depigmentation and
peeling (Fig. 2). Social interactions indicative of care-giving behaviour were
documented with five video recordings (88 seconds) and 180 photographs.
Four members of the group exhibited epimeletic behaviour toward the deceased
individual during the observation period from 14:42 to 14:52 UTC. The individuals
displayed a wide range of behavioural patterns in proximity to the carcass with or
without physical contact (Fig. 2). Behaviours included synchronized surfacing near the
carcass and individual standy-by, spy-hopping and surfacing by the carcass. Physical
contacts with the deceased animal included touching with the rostrum, lateral
pushing, pushing from behind, sinking the body by swimming over it, and later
righting the carcass. One individual interacted with a yellow sea-gull Larus michahellis
attempting to scavenge the body. Breaches in the area of the sighting were also
recorded.
The activity exhibited by individuals interacting with the carcass is consistent with
epimeletic behaviour as described in the literature (Bearzi et al., 2018). The actions
displayed by group members toward the deceased individual appeared to be attempts
to assist and care this dead animal, including righting the body to a normal horizontal
dorso-ventral position to facilitate breathing. The interaction with scavengers further
demonstrates care-giving behaviour, as the dolphins defended the body from
potential attacks and injuries. This epimeletic behaviour displayed by the caregiver
dolphins underscores the strong social bond with the deceased individual, which
might be genetically related. It can be considered an altruistic behaviour, as the
actions undertaken to assist their conspecific involved a notable expenditure of
energy from the individuals involved.
(Photo Marcel Gil/ULL)
(Photo Patricia Montagas/ULL)
h
i
(Photo Patricia Montagas/ULL)
(Photo Patricia Montagas/ULL)
CONCLUSIONS
First report of a case of epimeletic behaviour directed toward an adult by rough-toothed dolphins in Europe.
This new record documents a wide range of individual and group behaviours, including physical interactions with the body of the
deceased conspecific.
Epimeletic behaviour also extends to interspecific interactions, as the dolphins displayed defensive and protective behaviours
toward the corpse in response to scavengers (Larus michahellis).
This complex social behaviour underscores the advanced social structure of rough-toothed dolphins and the need to gather
further knowledge on this poorly known delphinid species seen all-year long in the Canary Islands.
REFERENCES
ACKNOWLEDGEMENTS
Bearzi G, Eddy L, Piwetz S, Reggente MA, Cozzi B (2017) Cetacean behavior toward the dead and dying. In: Encyclopedia of animal cognition and behaviour. 1-30
Bearzi G, Kerem D, Furey NB, Pitman RL, Rendell L, Reeves RR (2018) Whale and dolphin behavioural responses to dead conspecifics. Zoology 128:1-5
Díaz-Delgado, J (2015) Patología y causas de la muerte de los cetáceos varados en las Islas Canarias (2006-2012), Tesis doctoral, Universidad de Las Palmas.
Lodi L (1992) Epimeletic behaviour of free-ranging rough-toothed dolphins, Steno bredanensis, from Brazil, Marine Mammal Science, 8(3):284-287
Reggente MA, Alves F, Nicolau C, Freitas L, Cagnazzi D, Baird RW, Galii P (2016) Nurturant behaviour toward dead conspecifics in free-ranging mammals: new
records for odontocetes and a general review. J Mammal 97(5):1428-1434
Ritter, F. 2007. Behavioural responses of rough-toothed dolphins to a dead newborn calf, Marine Mammal Science, 23 (2),429
Scott JP (1958) Animal behaviour. University of Chicago Press
This study was funded by the Office of Naval Research
GRANT11027853 as a part of the research project entitled
“Population parameters of beaked whales” Grant number
GRANT11027853 of the University of La Laguna. Many
thanks are due to all members of the field teams who
made the collection of the data possible.
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