Cetacean diversity and distribution off Tenerife (Canary Islands)

Abstract

Dedicated surveys were conducted along the south-west and north-east coasts of Tenerife (Canary Islands), between 1997 and 2006, to gather baseline information on cetacean diversity, abundance, spatial and temporal distribution. A total of 1016 sightings of sixteen cetacean species was recorded during the study period. Sightings were recorded throughout the year although the period in which the highest number of species were sighted was in spring and summer (from May through to August). The most frequently sighted species were bottlenose dolphin (Tursiops truncatus) and short-finned pilot whale (Globicephala macrorhynchus), which together comprised 82% of the total sightings. These were followed by common dolphin (Delphinus delphis), Atlantic spotted dolphin (Stenella frontalis) and dense beaked whale (Mesoplodon densirostris) which represented 9% of the total sightings. Most sightings were recorded along the south-west coast of Tenerife, where the distribution of the different species seemed to be influenced by water depth. Calves were present during sightings of almost every recorded species, especially in toothed whales. Two mother–calf pairs of fin whales (Balaenoptera physalus) were also observed. This suggests that the surveyed area, or at least the south-west sub-area, might play an important role as a calving ground for the four most frequently sighted species. The information acquired in this study indicates that the waters around Tenerife constitute an important habitat for cetaceans.

Full text

Cetacean diversity and distribution off
Tenerife (Canary Islands)
manuel carrillo
1
, claudia pe
’rez-vallazza
2
and rosana a
’lvarez-va
’zquez
2
1
Tenerife Conservacio
´n, C/Maya No. 8, La Laguna, Tenerife, Canary Islands, Spain,
2
Elittoral S.L.N.E. (Coastal and Oceanographic
Engineering Studies), Edificio Polivalente II, Parque cientı
´fico tecnolo
´gico, Planta baja, oficina 19, Campus de Tafira, Gran Canaria,
Canary Islands, Spain
Dedicated surveys were conducted along the south-west and north-east coasts of Tenerife (Canary Islands), between 1997 and
2006, to gather baseline information on cetacean diversity, abundance, spatial and temporal distribution. A total of 1016
sightings of sixteen cetacean species was recorded during the study period. Sightings were recorded throughout the year
although the period in which the highest number of species were sighted was in spring and summer (from May through to
August). The most frequently sighted species were bottlenose dolphin (Tursiops truncatus) and short-finned pilot whale
(Globicephala macrorhynchus), which together comprised 82% of the total sightings. These were followed by common
dolphin (Delphinus delphis), Atlantic spotted dolphin (Stenella frontalis) and dense beaked whale (Mesoplodon densirostris)
which represented 9% of the total sightings. Most sightings were recorded along the south-west coast of Tenerife, where the
distribution of the different species seemed to be influenced by water depth. Calves were present during sightings of almost
every recorded species, especially in toothed whales. Two mother–calf pairs of fin whales (Balaenoptera physalus) were
also observed. This suggests that the surveyed area, or at least the south-west sub-area, might play an important role as a
calving ground for the four most frequently sighted species. The information acquired in this study indicates that the
waters around Tenerife constitute an important habitat for cetaceans.
Keywords: cetacean, diversity, abundance, distribution, calves, Canary Islands, Tenerife
Submitted 1 July 2009; accepted 1 May 2010
INTRODUCTION
Cetacean research usually begins with the study of occurrence
and diversity. In the case of the Atlantic Islands, 62 cetacean
species have been identified (Hoyt, 2005) and, to date, 28 of
them have already been recorded in the Canary Archipelago
(Arbelo, 2007). Of these, 24 have been sighted in Tenerife
(Carrillo, personal communication), which represents more
than 85% of all cetacean species present in the Canaries.
Twenty-one species have been identified off the coast of La
Gomera (Ritter, 2001) and 14 off La Palma (Pe
´rez-Vallazza
et al., 2008). This suggests that Tenerife’s cetacean diversity
is the highest known in the occidental part of the Canary
Archipelago. Mention should be made also of the sightings
of the highly endangered Atlantic northern right whale
Eubalaena glacialis Mu¨ller, 1776 (Martı
´net al., 1998;
Aguilar Soto, 1999) and of the blue whale Balaenoptera mus-
culus Linnaeus, 1758 (Carrillo, personal communication) in
these waters. Both species have also been sighted off the
island of La Gomera (Ritter & Brederlau, 1998; Brederlau, per-
sonal communication) and can be considered rare in the
archipelago. In addition, cetaceans in this region contribute
to the general economy (Urquiola et al., 1998) as whale watch-
ing in the Canary Archipelago attracts more than 700,000
people every year (Aguilar Soto et al., 2001; Plasencia et al,
2001) and generates more than $62000,000 (Hoyt, 2001;
2005). The south-west (SW) coast of Tenerife, one of the sur-
veyed sub-areas, is the location within the archipelago where
whale-watching operations have shown most development
in the past few years (Urquiola, 1998).
Information on cetacean presence in these islands arises
mainly from stranding records registered by the Canary
Stranding Network (Canary Government, Las Palmas de
Gran Canaria University, Tenerife Conservacio
´n and
SECAC) and some studies published in reports and sym-
posium proceedings (Vonk & Martı
´n, 1988; Martı
´net al.,
1992; Carrillo, 1996; Arbelo, 2007).
So far, only a few studies have carried out further analysis
of cetacean distribution and its relationships with environ-
mental variables in this area (Aguilar Soto, 1999; Arranz
et al., 2008; Pe
´rez-Vallazza et al., 2008). Nevertheless, infor-
mation on spatial and temporal variation in cetacean abun-
dance is essential for conservation and management (Evans
& Hammond, 2004).
In the SW sub-area of Tenerife, studies focusing on
the short-finned pilot whales (Globicephala macrorhynchus
Gray, 1864) and the bottlenose dolphin (Tursiops truncatus
Montagu, 1821), have shown the stable presence of these
species (Escorza et al., 1992; Heimlich-Boran & Heimlich-
Boran, 1992; Heimlich-Boran, 1993; Montero & Arechavaleta,
1996). Nevertheless, very little is still known about spatial and
temporal patterns of cetacean distribution along this coast, or
about their occurrence in other areas of Tenerife.
This paper describes data obtained from sightings between
1997 and 2006; it indicates the occurrence, diversity and
Corresponding author:
M. Carrillo
Email: canariasconservacion@yahoo.es
1
Marine Biodiversity Records, page 1 of 9. #Marine Biological Association of the United Kingdom, 2010
doi:10.1017/S1755267210000801; Vol. 3; e97; 2010 Published online

distribution of the cetacean community off the coast of
Tenerife. The aim of this study was to provide baseline infor-
mation on the principal cetacean species sighted around the
island and on the spatial and temporal distribution of this com-
munity. In addition, we also ascertained whether the island
could function as a breeding area for any of these species.
Survey area
The Canary Archipelago lies about 115 km off the West
African mainland, in the Atlantic Ocean. It is composed of
seven islands and four islets, most of them independent volca-
nic edifices with a subsequent narrow shelf (Anguita &
Herna
´n, 2000) and, consistently, very deep waters (2000 –
4000 m) quite close to the coast. These characteristics deter-
mine some of the main oceanographic features of the area
(Violette, 1974; Herna
´ndez-Leo
´n, 1986; Arı
´stegui et al., 1994).
Our survey area covers mainly two zones off the coast of
Tenerife (Figure 1). The SW sub-area is the marine strip
from Punta de Teno to Punta de Rasca; traditionally, research
effort in this leeward area has been more intense due to good
weather conditions. The second sub-area, the north-east (NE)
coast, is poorly known as survey efforts have been less impor-
tant due to the unfavourable cetacean watch conditions.
Usually, sea states on the windward coast of the Canary
Islands are above Beaufort scale 3 which represents unfavour-
able conditions to perform cetacean abundance and distri-
bution surveys (Evans & Hammond, 2004).
In biological terms, both areas enjoy an outstanding
natural status. Different portions of the surveyed area, such
as the ‘Sebadal de San Andre
´s’ and the ‘Franja Marina de
Teno-Rasca’, are catalogued by the European Union as Sites
of Community Importance (SCI) and are included in the
Natura 2000 Network (Council Directive 92/43/EEC). In par-
ticular, the ‘Franja Marina de Teno-Rasca’ has been included
due to the presence of Tursiops truncatus, as well as for other
ecological findings.
MATERIALS AND METHODS
Fieldwork
Cetacean surveys were carried out in both sub-areas off
Tenerife, with variable effort, from March 1997 to October
2006, with two gaps in 2000 and 2005. Weather permitting
(sea state below Beaufort scale 3) dedicated cruises were con-
ducted along the island shelf edge in a 13 m motorboat yacht
with a flying bridge located 7 m above sea level. A total of 9713
nautical miles (17989 km) were covered at a mean survey
speed of 6 knots.
With the aim of establishing standard and repeatable pro-
tocols for these zone conditions, sighting data were collected
following standard line-transect methods of surveying
(Buckland et al., 1993; Heimlich-Boran, 1993; Dudzinski,
1999; Schwarz & Seber, 1999) together with the model pre-
viously designed by Carrillo et al. (2002) for the southern
study sub-area.
In each survey, four experienced observers were onboard.
Two of them watched by naked-eye from a platform 4.20 m
above sea level while a third person observed from the
flying bridge with 7 ×50 binoculars and the fourth person
worked as data recorder. They all changed positions every
hour.
In the data for each sighting, records included species, pres-
ence of calves in the group, time and position, weather and
water depth, among others. Animals were identified to the
lowest taxonomic level possible, which in almost every sight-
ing was the species.
Analysis
Once the information was collected, it was processed to
characterize the cetacean community of Tenerife. Records
were analysed to compare cetacean diversity, average
number of sightings, temporal and spatial distribution and
calves occurrence.
Firstly, the number of sightings of every species during the
research period was calculated. Then, the relative abundance
of the different species was examined by calculating the
number of sightings per effort unit (SPEU) (Evans &
Hammond, 2004), using as the effort unit the total km of
transect-line covered with Beaufort sea state lower than 3.
Mean cetacean sighting rates (number of sightings per 100
km surveyed) were compared between species. Sightings
from each species were separated by month in order to
analyse seasonal changes in cetacean diversity. Sightings
during each month were pooled for several years to investigate
seasonal distribution of the species.
Further analyses were carried out over the five most fre-
quent species (those with more than 15 sightings during the
study period). The distribution of these five species was
studied monthly, using the number of surveyed days as the
effort. Therefore, sighting frequencies were calculated by
dividing the number of sightings by the number of total sur-
veyed days each month.
In addition, sightings of the most common species were
located on an island map to represent the cetacean spatial dis-
tribution and to examine geographical differences using the
software Autodesk Map 2006. Maximum, minimum and
mean depths of the sightings of these species were calculated
together with the standard deviation of the mean depth.
Fig. 1. Location of the Canary Archipelago and the two study sub-areas off
Tenerife.
2 manuel carrillo et al.

Finally, the temporal occurrence and the number of sight-
ings from groups with calves and/or newborns were compared
with the total number of sightings for each species, to deter-
mine which cetacean species bred in the area and when.
RESULTS
Diversity
From 1997 to 2006, cetaceans were sighted 1016 times in both
study sub-areas, across 9713.41 nautical miles (17989.24 km)
on survey (sea state 3 or less), with a mean sighting success of
5.65 sightings per 100 km. Sixteen species were identified,
twelve Odontoceti (Flower, 1869) and four Mysticeti (Cope,
1891). The species could not however be determined in 13
sightings, and were therefore attributed to the ‘whale’,
‘beaked whale’ and ‘unidentified’ general groups.
The species observed and their sighting frequencies are
shown in Table 1.
Odontoceti species represent the largest amount of sight-
ings (994 sightings, 97.83%) with a frequency of 5.52 sight-
ings/100 km, while Mysticeti species correspond to 0.12
sightings/100 km (22 sightings, 2.17%).
Tursiops truncatus was the most frequently seen species
(2.74 sightings/100 km), followed by Globicephala macro-
rhynchus (1.92 sightings/100 km), Delphinus delphis (0.20
sightings/100 km), Stenella frontalis (0.18 sightings/100 km)
and Mesoplodon densirostris (0.15 sightings/100 km). These
are the five species for which further analyses were performed.
Temporal distribution of cetaceans
Regarding cetacean diversity, Table 2 shows cetacean sightings
off Tenerife by month. According to this table, the number of
species sighted does not seem to follow a seasonal pattern.
Although an upward trend can be observed in spring and
summer, the months with the highest diversity are January
and October (10 different species sighted). The months with
lowest cetacean diversity are November and December (5
species sighted each month) (Table 2).
Figure 2 shows the number of sightings per number of days
surveyed each month for the five most common species.
Regarding this sighting frequency some peaks are shown by
month. These peaks are significantly high in August and
November for Tursiops truncatus and in September and
December for Globicephala macrorhynchus.
Tursiops truncatus and Globicephala macrorhynchus occur
all through the year with more than one sighting per day (1.57
and 1.10 sightings/day respectively). Tursiops truncatus shows
a higher sighting frequency in August (2.35 sightings/day) and
December (2.07 sightings/day), and Globicephala macro-
rhynchus in September (1.85 sightings/day) and December
(2.40 sightings/day), which corresponds to the highest fre-
quency of all species and months.
Delphinus delphis has not been seen in June, or from
August to November, although it is present the rest of the
year with a mean frequency of 0.12 sightings/day. On the
other hand, Stenella frontalis was sighted every month
except for August. Its occurrence remains constant through
the year, excluding a peak in July where it was seen 0.39
times per day. Mesoplodon densirostris was seen every
month except in February, May and December with a mean
frequency of 0.086 sightings/day and two sharp peaks in its
relative frequency of occurrence in August (0.26 sightings/
day) and November (0.22 sightings/day).
Spatial distribution of cetaceans
Figures 3 and 4 show the distribution of the five most fre-
quently sighted species in Tenerife. Distribution for Tursiops
truncatus and Globicephala macrorhynchus remains very
different; the first one concentrates its locations in the
coastal area, especially close to Punta de Teno; and the
second one clearly distributes itself around the 1000 m bathy-
metric. Sighting locations in Delphinus delphis,Stenella fron-
talis and Mesoplodon densirostris seem to appear randomly.
Regarding spatial distribution, differences among species in
water depth at the sighting locations are summarized in
Table 3. Most sightings were concentrated in the SW
sub-area, between Punta de Teno and Punta de Rasca.
Differences in mean depths were found between species
(from almost 300 m to 1000 m approximately). The deepest
average depth is shown by Tursiops truncatus and the shallow-
est one by Globicephala macrorhynchus, the two most sighted
species of both sub-areas.
Presence of calves and newborns
Calves and neonates were observed in several groups of differ-
ent species. Only one Mysticeti species was observed with
calves: two mother–calf pairs of Balaenoptera physalus.
Nine Odontoceti species were seen with calves and/or neo-
nates. Pseudorca crassidens was seen in December both with
a calf and a newborn. Physeter macrocephalus was observed
in March and May with one and two calves respectively.
Table 1. Summary of cetacean sightings in Tenerife (1997 –2006).
Species N % Sightings/
100 km
Odontoceti 994 97.83 5.5255
Tursiops truncatus Montagu, 1821 492 48.43 2.7350
Globicephala macrorhynchus Gray, 1864 346 34.06 1.9234
Delphinus delphis Linnaeus, 1758 36 3.54 0.2001
Stenella frontalis Cuvier, 1829 33 3.25 0.1834
Mesoplodon densirostris Blainville, 1817 27 2.66 0.1501
Steno bredanensis Lesson, 1828 19 1.87 0.1056
Stenella coeruleoalba Meyen, 1833 16 1.57 0.0889
Physeter macrocephalus Linnaeus, 1758 7 0.69 0.0389
Ziphius cavirostris Cuvier, 1823 5 0.49 0.0278
Pseudorca crassidens Owen, 1846 3 0.30 0.0167
Lagenodelphis hosei Fraser, 1956 1 0.10 0.0056
Mesoplodon europaeus Gervais, 1855 1 0.10 0.0056
Beaked whales 5 0.49 0.0278
Unidentified 3 0.30 0.0167
Mysticeti 22 2.17 0.1223
Balaenoptera edeni Anderson, 1879 9 0.89 0.0500
Balaenoptera physalus Linnaeus, 1758 5 0.49 0.0278
Balaenoptera borealis Lesson, 1828 2 0.20 0.0111
Megaptera novaeangliae Borowski, 1781 1 0.10 0.0056
Whale 5 0.49 0.0278
Total 1016 100.00 5.6478
N, number of sightings; %, percentage from the total number of sightings.
cetacean diversity and distribution off tenerife (canary islands)3

Steno bredanensis was seen five times in groups with calves; on
one of these occasions, in August, there was also a neonate in
the group. Stenella coeruleoalba groups were observed with
calves on nearly half of the occasions (43.75%), five of
which also included newborns (in January and March).
Tursiops truncatus has been observed 114 times with calves
(22.15% of its sightings), in some cases even with 10 calves in
the same group. Newborn bottlenose dolphins were seen from
May to October. Calves were observed every month of the
year, with a peak in October. Calves were seen in variable
numbers in more than half of the encounters with
Globicephala macrorhynchus (209 times, 63.87% of its
sightings, 31 sightings of neonates). Calves and neonates
of this species were seen every month of the year with the
exception of January and November. Delphinus delphis
calves were seen in February, April, May and December and
only one neonate was seen in March. Stenella frontalis
showed a high percentage of sightings with calves and/or neo-
nates (60.61%). Calves of this species were not seen in January,
May, or from August to November; nevertheless a marked
peak of neonates was observed in November. Mesoplodon den-
sirostris calves were observed three times, in March, August
and November respectively; neonates of this species were
not detected.
Table 2. Cetacean species sighted off Tenerife per month, summing the full study period. Months in which each species was sighted are represented by
cells in black.
Fig. 2. Number of sightings/number of days surveyed each month from the five most sighted species.
4 manuel carrillo et al.

Graphs of the monthly occurrence of calves and neonates,
corrected with the total number of sightings per month for
each of the most sighted species, are shown in Figures 5 & 6.
DISCUSSION
The present study recorded 1016 sightings of 16 cetacean
species during 9713 nautical miles (17989 km) of visual
survey in the study sub-areas off Tenerife. These results,
together with previous sightings of the Atlantic northern
right whale (Martı
´net al., 1998; Aguilar Soto, 1999) and of
the blue whale (Carrillo, personal communication) sum up
to 18 cetacean species sighted off Tenerife, corroborating the
high cetacean diversity around the island. As observed on
other islands in the Canaries group (Pe
´rez-Vallazza et al.,
2008), spring and summer are the periods when more ceta-
cean species are observed. This probably responds to the
occurrence of sporadic and occasional species, such as
mysticetes.
The overall high sighting rate in the study (5.64 sightings/
100 km), similar but higher to rates obtained in other
Macaronesian islands (Silva et al., 2003), demonstrates the
high cetacean presence in the survey area. In the Azorean
Archipelago a SPEU of 4.13 sightings/100 km was estimated,
and 11 cetacean species were identified. The same number of
species was observed in Lanzarote (Canary Islands), where the
Fig. 3. Locations of the two most frequently sighted species off Tenerife.
(A) Tursiops truncatus; (B) Globicephala macrorhynchus.
Fig. 4. Locations of the sightings of (C) Delphinus delphis; (D) Stenella
frontalis; (E) Mesoplodon densirostris.
Table 3. Descriptive statistics for water depth (m) at sighting locations for
the five most sighted cetacean species in Tenerife.
Species N Range xSD
Tursiops truncatus 469 17–1728 293 378
Globicephala macrorhynchus 294 325–1740 1031 242
Delphinus delphis 31 45–1100 508 351
Stenella frontalis 29 97–1500 735 295
Mesoplodon densirostris 17 25–1000 448 310
N, total number of groups sighted; x, mean water depth; SD, standard
deviation.
cetacean diversity and distribution off tenerife (canary islands)5

SPEU was estimated as 2.5 sightings/100 km (Politi et al.,
1997).
In the present study, sightings were dominated by two
Odontoceti; species, together comprising 82% of the total
sightings: Tursiops truncatus and Globicephala macro-
rhynchus. The occurrence of these species in Tenerife is well
known (Escorza et al., 1992; Heimlich-Boran &
Heimlich-Boran, 1992; Carrillo et al., 2006) as both are con-
sidered to be residents (with occasional transient individuals).
The bottlenose dolphin has a population size estimated at 122
individuals (Carrillo et al., 2002), with the highest number of
sightings registered in the SW study sub-area. The population
of short-finned pilot whales includes approximately 362 speci-
mens (Carrillo et al., 2002) and was frequently found in the
south of Tenerife (Los Cristianos – Caleta de Adeje). There
are few places in the world with a cetacean group showing a
high fidelity to such a small area (Carrillo et al., 2006).
Nevertheless, the species was also unexpectedly common in
the NE study sub-area where seventeen groups were sighted
in total.
The next most abundant species of the survey area, total-
ling 9% of all sightings, were Delphinus delphis,Stenella fron-
talis and Mesoplodon densirostris. The latter two species
tended to occur almost every month of the year. Presence of
Delphinus delphis, on the contrary, follows a marked seasonal
pattern from December to May, as reported in other sites of
the north-east Atlantic in general (Lo
´pez et al., 2004), and
in other Canary Islands in particular (Politi et al., 1997;
Aguilar Soto, 1999; Pe
´rez-Vallazza et al., 2008). Although
Stenella frontalis occurs the whole year round in the archipe-
lago, it is most common in winter and spring. In the present
paper sightings were registered in waters of depths from 100
to 1500 m, in contrast to previous studies where the depth
distribution-range was established at 600 to 900 m depth
(Carrillo et al., 2002).
Steno bredanensis is a rare species in other regions of the
world, but relatively common in Tenerife with 0.11 sight-
ings/100 km. This species might be resident in these waters,
at least seasonally, as it was recorded every month of the
year except in October, November and December. Further
photo ID data are needed to assess this possibility.
Although it was not observed during several months
(February, April, July and December), this could be due to a
more offshore distribution or to low relative abundance in
the survey area. It is thought that Stenella coeruleoalba is
present all year-round.
Lagenodelphis hosei can usually be found in tropical habi-
tats (Reeves et al., 2005), which is not the case in the
Canaries. However, general tropicalization of the waters
(Stergiou, 2002) or anomalous environmental conditions,
could favour its presence in the Canary Islands. Over the
past few years its occurrence in these waters has become
more frequent, with it being sighted in La Gomera (Ritter,
2001) and Tenerife. Pseudorca crassidens is also typically
Fig. 5. Presence of calves/number of sightings within each species per month.
Fig. 6. Presence of neonates/number of sightings within each species per month.
6 manuel carrillo et al.

distributed over tropical and temperate waters. The present
study shows it to be present in the entire archipelago in
winter and springtime (Carrillo, personal communication).
The family Ziphiidae is represented in the Canaries by five
species; two of them (Mesoplodon densirostris and Ziphius
cavirostris) are known to be resident in the most western
island of the archipelago, El Hierro (Aguilar Soto 2006;
Aparicio et al., 2009). These two species and another one
from the five Ziphiidae inhabiting the archipelago, were ident-
ified in the present study off Tenerife. Mesoplodon densirostris
is the beaked species most frequently sighted around the
island (Carrillo et al., 1998), and in the present study
(almost every month). Autumn was the time with a higher fre-
quency of sightings for this species, in agreement with pre-
vious results in this sub-area (Carrillo et al., 1998).
Mesoplodon europaeus and Ziphius cavirostris were rarely
observed in the study area. Mesoplodon europaeus has been
seen occasionally in the Atlantic Ocean (Carrillo & Martı
´n,
1999) and in the present paper it was once seen in January
at a depth of 1700 m. Ziphius cavirostris was registered five
times, in June, August and October. These data and previous
results in the area (Carrillo, 2003), suggest that the species is a
summer and autumn resident in these waters. Its depth-range
is from 509 to 1808 m, with an average of 953 m, which con-
stitutes a similar estimate to the one reported in previous
studies of the Canaries (Carrillo, 2003; Arranz et al., 2008).
Regarding Physeter macrocephalus, it was registered seven
times in the survey area, all of them in the SW zone. This
species seems to be frequent in the channel between
Tenerife and Gran Canaria (Andre
´, 2000). However, in the
present study, no sightings were recorded in the NE area of
Tenerife.
Despite the huge effort invested and the fact that both
species have been stranded on the island (Canary Stranding
Network), the occurrence of Kogia breviceps Blainville, 1838
(pygmy sperm whale) and Kogia sima Owen, 1866 (dwarf
sperm whale) off Tenerife, was not confirmed.
Very little is known about the stocks of Mysticeti that
inhabit the Canary Islands. Nevertheless, results from the
present study confirm a certain level of seasonal migration
for these species. Balaenoptera physalus and Balaenoptera
edeni have been sighted in every island of the archipelago,
during spring and summertime respectively (Politi et al.,
1997; Ritter, 2001; Carrillo et al., 2002; Pe
´rez-Vallazza &
Haroun, 2005; Pe
´rez-Vallazza et al., 2008), in agreement
with our results. The temporal distribution of Balaenoptera
borealis in the archipelago remains unclear. To date, its pres-
ence is confirmed in Gran Canaria (Carrillo et al., 2006),
Lanzarote (Politi et al., 1997), La Gomera (Ritter, 2001), La
Palma (Pe
´rez-Vallazza et al., 2008) and Tenerife (Carrillo
et al., 2006) from the end of autumn to the beginning of
spring. The present study reinforces this seasonal pattern,
which suggests that Balaenoptera borealis is present only sea-
sonally in the Canaries. When visiting the Canary Islands,
Megaptera novaeangliae is thought to be on its migratory
route (April–June) from its breeding area in Cabo Verde
(February–March), to its feeding area in Europe or America
(July–August). Nevertheless, recent records, such as the
January sightings recorded in this study, do not follow this
pattern.
From the Mysticeti suborder, only Balaenoptera physalus
was observed with a calf, which happened twice from a total
of five sightings. In both cases records were from the month
of May (of different years), coinciding with their seasonal
visit to our waters.
As far as the Odontoceti suborder is concerned, almost
every species was observed with a calf, at least once (except
for Lagenodelphis hosei, Mesoplodon europaeus and Ziphius
cavirostris). Furthermore, some groups of the four most
sighted species (Tursiops truncatus, Globicephala macro-
rhynchus, Delphinus delphis and Stenella frontalis) included
neonates. This fact suggests that Tenerife may be a calving
ground for these four species. Despite the absence of new-
borns in the dense beaked whale, three groups of this
species (registered in March, August and November) included
calves. The use of the study area as a breeding ground by this
species requires further study.
We should note the highest frequency of calves in both sur-
veyed sub-areas, revealed by Globicephala macrorhynchus
(0.60 sightings with newborns/total species sightings), with
more than half of the encounters containing calves and/or
neonates within the group (63.9% from the total sightings
within this species). In particular, in most of the NE encoun-
ters (76.5%) calves and neonates were part of the group.
Considering these statistics and the fact that the presence of
calves and neonates of this species was detected almost
every month of the year, the survey area could act as an
important calving ground for the short-finned pilot whale.
Summer seems to be the most important birth period for
this species in our study area, as higher neonate frequencies
were observed from June to October. Tursiops truncatus also
seems to use the survey area as a breeding ground, mainly
during the summer, as neonates were only observed from
May to October.
Stenella frontalis showed the highest frequency of sightings
of neonates in the survey area (0.18 sightings with newborns/
total species sightings) and the second highest percentage of
sightings with calves and/or neonates after Globicephala
macrorhynchus. In one of these sightings, four adults
showed mating and evasive behaviour, which together with
the presence of calves and newborns indicates that the study
area is being used as a breeding ground for this species.
Delphinus delphis appeared with calves in almost every
month that the species was sighted, which indicates that the
study area may be used as a calving ground for this species.
This paper highlights the high cetacean diversity and
occurrence found off the island of Tenerife. Most of the
recorded cetacean species occur all throughout the year.
However, Balaenoptera physalus, Balaenoptera edeni,
Megaptera novaeangliae, Delphinus delphis and Ziphius cavir-
ostris can be classified as occasional or seasonal species present
in the study area. In addition, the area is being used as a
breeding ground for several species, which emphasizes the
biological and ecological importance of these waters. The
information acquired enables a better understanding of the
Canary cetacean community and can be useful in future man-
agement and conservation measures.
ACKNOWLEDGEMENTS
We would like to thank to the numerous field assistants who
helped us with the collection of data. We are also very grateful
to Natacha Aguilar, Ciro Pe
´rez, Ruth Ferna
´ndez and Noelia
Arto for their valuable comments. The cruises were carried
out thanks to the financial support of different projects
cetacean diversity and distribution off tenerife (canary islands)7

(principally from the Canary Government), managed by
Tenerife conservacio
´n, a non-profit association which works
for cetacean conservation in the Canary Archipelago. The
‘Monachus’ yacht is a cession from Las Palmas de Gran
Canaria University to the Tenerife conservacio
´n Association.
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Correspondence should be addressed to:
Manuel Carrillo
Tenerife Conservacio
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La Laguna
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email: canariasconservacion@yahoo.es
cetacean diversity and distribution off tenerife (canary islands)9